Rohde&Schwarz VSE-K18 User Manual

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R&S®VSE-K18 Power Amplifier and Envelope Tracking Measurements User Manual

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1179327302 Version 03

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This manual applies to the following software, version 2.20 and later:

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R&S®VSE Enterprise Edition base software (1345.1105.06)

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R&S®VSE Basic Edition base software (1345.1011.06)

The following firmware options are described:

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R&S®VSE-K18 (1345.1434.02)

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R&S®VSE-K18D (1345.1440.02)

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R&S®VSE-K18F (1345.1457.02)

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R&S®VSE-K18M (1345.1492.02)

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R&S®VSE-KT18 (1345.2060.02)

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R&S®VSE-KT18D (1345.2053.02)

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R&S®VSE-KT18F (1345.2047.02)

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R&S®VSE-KT18M (1345.2030.02)

© 2022 Rohde & Schwarz GmbH & Co. KG Muehldorfstr. 15, 81671 Muenchen, Germany Phone: +49 89 41 29 - 0 Email: info@rohde-schwarz.com Internet: www.rohde-schwarz.com Subject to change – data without tolerance limits is not binding. R&S® is a registered trademark of Rohde & Schwarz GmbH & Co. KG. Trade names are trademarks of the owners.

1179.3273.02 | Version 03 | R&S®VSE-K18

Throughout this manual, products from Rohde & Schwarz are indicated without the ® symbol , e.g. R&S®VSE is indicated as R&S VSE.

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R&S®VSE-K18

1.1 Starting the application................................................................................................ 9

1.2 Understanding the display information.................................................................... 10

3.1 Configuration overview.............................................................................................. 33

3.2 Designing a reference signal..................................................................................... 35

3.3 Configuring inputs and outputs.................................................................................45

3.3.1 Input source settings..................................................................................................... 45

3.3.1.1 Radio frequency input................................................................................................... 46

Contents

1 Welcome to the amplifier measurement application.......................... 9

2 Measurements and result displays.................................................... 12

3 Configuration........................................................................................33

3.3.1.2 I/Q file input................................................................................................................... 50

3.3.2 Configuring the frequency............................................................................................. 52

3.3.3 Defining level characteristics.........................................................................................53

3.3.4 Power sensors.............................................................................................................. 56

3.3.5 Configuring outputs....................................................................................................... 61

3.3.6 Controlling a signal generator....................................................................................... 61

3.3.7 Reference: I/Q file input................................................................................................ 66

3.3.7.1 Basics on input from I/Q data files................................................................................ 66

3.3.7.2 I/Q data file format (iq-tar)............................................................................................. 67

I/Q parameter XML file specification............................................................................. 69

I/Q data binary file......................................................................................................... 78

3.4 Triggering measurements.......................................................................................... 80

3.5 Configuring the data capture..................................................................................... 81

3.6 Sweep configuration...................................................................................................84

3.7 Synchronizing measurement data.............................................................................86

3.8 Evaluating measurement data................................................................................... 88

3.9 Estimating and compensating signal errors............................................................ 90

3.10 Equalizer...................................................................................................................... 91

3.11 Applying system models............................................................................................92

3.12 Applying digital predistortion.................................................................................... 95

3.12.1 Polynomial DPD............................................................................................................ 96

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3.12.2 Direct DPD (R&S VSE-K18D)....................................................................................... 98

3.12.3 Memory polynomial DPD (R&S VSE-K18M)...............................................................103

3.12.4 Hammerstein model (R&S VSE-K18M)...................................................................... 105

3.13 Detailed MSE............................................................................................................. 108

3.14 Configuring power measurements..........................................................................109

3.15 Configuring adjacent channel leakage error (ACLR) measurements.................. 110

3.16 Configuring the parameter sweep........................................................................... 113

3.17 Configuring power servoing.................................................................................... 117

4.1 Configuring traces.................................................................................................... 119

4.1.1 Selecting the trace information....................................................................................119

4.1.2 Exporting traces.......................................................................................................... 122

Contents

4 Analysis...............................................................................................119

4.1.3 Detector settings......................................................................................................... 123

4.2 Using markers........................................................................................................... 124

4.2.1 Configuring markers....................................................................................................124

4.2.2 Configuring individual markers....................................................................................125

4.2.3 Positioning markers.....................................................................................................127

4.3 Customizing numerical result tables...................................................................... 128

4.4 Configuring result display characteristics............................................................. 130

4.5 Scaling the X-Axis.....................................................................................................132

4.6 Scaling the Y-Axis.....................................................................................................134

5 Remote control commands for amplifier measurements...............136

5.1 Introduction............................................................................................................... 136

5.1.1 Conventions used in descriptions............................................................................... 137

5.1.2 Long and short form.................................................................................................... 137

5.1.3 Numeric suffixes..........................................................................................................138

5.1.4 Optional keywords.......................................................................................................138

5.1.5 Alternative keywords................................................................................................... 138

5.1.6 SCPI parameters.........................................................................................................139

5.1.6.1 Numeric values........................................................................................................... 139

5.1.6.2 Boolean....................................................................................................................... 140

5.1.6.3 Character data............................................................................................................ 140

5.1.6.4 Character strings.........................................................................................................141

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5.1.6.5 Block data................................................................................................................... 141

5.2 Common suffixes...................................................................................................... 141

5.3 Selecting the application..........................................................................................141

5.4 Performing amplifier measurements.......................................................................142

5.4.1 Activating Amplifier measurements.............................................................................142

5.4.2 Retrieving graphical measurement results..................................................................142

5.4.3 Retrieving numeric results...........................................................................................145

5.4.3.1 Retrieving general numeric results..............................................................................145

5.4.3.2 Retrieving results of the result summary.....................................................................145

Contents

Retrieving all results....................................................................................................145

Retrieving the modulation accuracy............................................................................ 146

Retrieving power results..............................................................................................150

Retrieving baseband characteristics........................................................................... 157

5.4.3.3 Retrieving results of the parameter sweep table.........................................................160

5.4.3.4 Retrieving results of the statistics table.......................................................................174

Amplitude droop.......................................................................................................... 175

AM/AM curve width..................................................................................................... 175

AM/PM curve width..................................................................................................... 176

Average PAE...............................................................................................................177

Power (Vcc*Icc)...........................................................................................................180

Crest factor input.........................................................................................................183

Crest factor out............................................................................................................184

Frequency error...........................................................................................................185

Gain.............................................................................................................................186

Gain imbalance........................................................................................................... 187

Current (Icc)................................................................................................................ 188

I/Q imbalance.............................................................................................................. 191

I/Q offset......................................................................................................................192

Baseband i input voltage.............................................................................................193

Magnitude error...........................................................................................................196

P1DB input.................................................................................................................. 197

P1DB output................................................................................................................198

P2DB input.................................................................................................................. 199

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Contents

P2DB output................................................................................................................200

P3DB input.................................................................................................................. 201

P3DB output................................................................................................................202

Average power consumption.......................................................................................203

PC based average PAE...............................................................................................204

Phase error................................................................................................................. 205

Power input................................................................................................................. 206

Power output............................................................................................................... 209

Quadrature error......................................................................................................... 212

Baseband q input voltage............................................................................................213

Raw EVM.................................................................................................................... 216

Raw model EVM......................................................................................................... 219

Sample rate error........................................................................................................ 222

Voltage (Vcc)...............................................................................................................223

5.4.4 Retrieving I/Q data...................................................................................................... 226

5.5 Configuring amplifier measurements..................................................................... 227

5.5.1 Designing a reference signal.......................................................................................228

5.5.2 Power sensor measurements..................................................................................... 242

5.5.2.1 Configuring power sensor measurements.................................................................. 242

5.5.2.2 Triggering with power sensors.................................................................................... 251

5.5.3 Configuring data input................................................................................................. 254

5.5.3.1 RF input.......................................................................................................................254

5.5.3.2 Remote commands for external frontend control........................................................ 265

Commands for initial configuration..............................................................................266

Commands for alignment............................................................................................ 272

5.5.4 Configuring the frequency........................................................................................... 275

5.5.5 Defining level characteristics.......................................................................................276

5.5.6 Controlling a signal generator..................................................................................... 282

5.5.7 Configuring the data capture.......................................................................................291

5.5.8 Sweep configuration....................................................................................................296

5.5.9 Synchronizing measurement data...............................................................................298

5.5.10 Defining the evaluation range..................................................................................... 301

5.5.11 Estimating and compensating signal errors................................................................ 303

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5.5.11.1 Error estimation and compensation............................................................................ 303

5.5.11.2 Equalizer..................................................................................................................... 306

5.5.12 Applying a system model............................................................................................ 308

5.5.13 Applying digital predistortion........................................................................................311

5.5.14 Detailed MSE.............................................................................................................. 328

5.5.15 Configuring envelope tracking.....................................................................................329

5.5.16 Configuring ACLR measurements.............................................................................. 330

5.5.17 Configuring power measurements.............................................................................. 336

5.5.18 Configuring parameter sweeps................................................................................... 336

5.5.19 Configuring power servoing........................................................................................ 340

5.6 Analyzing results...................................................................................................... 343

5.6.1 Configuring traces....................................................................................................... 343

5.6.2 Using markers............................................................................................................. 349

Contents

5.6.2.1 General marker settings..............................................................................................349

5.6.2.2 Configuring individual markers....................................................................................350

5.6.2.3 Positioning markers.....................................................................................................356

5.6.3 Configuring numerical result displays......................................................................... 360

5.6.4 Configuring the statistics table.................................................................................... 363

5.6.5 Configuring result display characteristics....................................................................364

5.6.6 Scaling the diagram axes............................................................................................368

5.6.7 Managing measurement data..................................................................................... 374

5.7 Deprecated remote commands for amplifier measurements............................... 375

5.8 Programming example R&S VSE-K18M..................................................................376

List of Commands (Amplifier)...........................................................378

Index....................................................................................................400

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Contents

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1 Welcome to the amplifier measurement

Welcome to the amplifier measurement application

Starting the application

application

The R&S VSE-K18 is a firmware application that adds functionality to measure the efficiency of amplifiers with the R&S VSE signal analyzer. You extend the amplifier application with the R&S VSE-K18D, which adds direct DPD functionality.

This user manual contains a description of the functionality that the application provides, including remote control operation.

Functions that are not discussed in this manual are the same as in the base unit and are described in the R&S VSE user manual. The latest versions of the manuals are available for download at the product homepage.

Installation

Find detailed installing instructions in the getting started or the release notes of the R&S VSE.

● Starting the application..............................................................................................9

● Understanding the display information....................................................................10

1.1 Starting the application

The amplifier measurement application adds a new type of measurement to the R&S VSE.

To activate the amplifier application

Select the "Add Channel" function in the Sequence tool window. A dialog box opens that contains all operating modes and applications currently

available in your R&S VSE.

2. Select the "Amplifier" item.

The R&S VSE opens a new measurement channel for the Amplifier measurement application.

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1.2 Understanding the display information

Welcome to the amplifier measurement application

Understanding the display information

The following figure shows the display as it looks for amplifier measurements. All different information areas are labeled. They are explained in more detail in the following sections.

1 42 3 56

Figure 1-1: Screen layout of the amplifier measurement application

1 = Toolbar 2 = Channel bar 3 = Diagram header 4 = Result display 5 = Status bar 6 = Softkey bar

For a description of the elements not described below, refer to the getting started of the R&S VSE.

Channel bar information

The channel bar contains information about the current measurement setup, progress and results.

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Welcome to the amplifier measurement application

Understanding the display information

Figure 1-2: Channel bar of the amplifier application

Ref Level Current reference level of the analyzer.

Att Current attenuation of the analyzer.

Freq Frequency the signal is transmitted on.

Meas Time Length of the signal capture.

Meas BW Bandwidth with which the signal is recorded.

TTF Time difference between the trigger event and the first sample of the reference

signal (= beginning of a frame).

SRate Sample rate with which the signal is recorded.

SGL Indicates that single sweep mode is active.

Count The current signal count for measurement tasks that involve a specific number

of subsequent sweeps (for example the parameter sweep).

X Axis X-axis value that is currently measured.

Y Axis Y-axis value that is currently measured.

Window title bar information

For each diagram, the header provides the following information:

Figure 1-3: Window title bar information of the amplifier application

1 = Window number 2 = Window type 3 = Trace color and number 4 = Trace mode Blue color = Window is selected

2 3 4

Status bar information

Global instrument settings, the instrument status and any irregularities are indicated in the status bar beneath the diagram. Furthermore, the progress of the current operation is displayed in the status bar.

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2 Measurements and result displays

Measurements and result displays

Note that you can use the R&S VSE-K18 with the sequencer that is available with the R&S VSE. The functionality is the same as in the spectrum application. Refer to the R&S VSE user manual for more information.

Adjacent Channel Leakage Error (ACLR).....................................................................12

AM/AM.......................................................................................................................... 13

AM/PM.......................................................................................................................... 14

DDPD Results (R&S VSE-K18D)..................................................................................15

EVM vs Power...............................................................................................................16

Error Vector Spectrum...................................................................................................17

Gain Compression........................................................................................................ 17

Gain Deviation vs Time.................................................................................................19

Magnitude Capture........................................................................................................19

Memory DPD Coefficients.............................................................................................20

Parameter Sweep......................................................................................................... 20

└ Parameter Sweep: Diagram............................................................................20

└ Parameter Sweep: Table.................................................................................21

Phase Deviation vs Time...............................................................................................22

Raw EVM...................................................................................................................... 22

Numeric Result Summary............................................................................................. 23

└ Results to check modulation accuracy............................................................24

└ Results to check power characteristics...........................................................27

Spectrum FFT............................................................................................................... 29

Time Domain.................................................................................................................30

└ Scale of the x-axis (display settings for the time domain)...............................30

└ Scale of the y-axis (display settings for the time domain)...............................31

Statistics Table.............................................................................................................. 31

Adjacent Channel Leakage Error (ACLR)

The "ACLR" result display shows the power characteristics of the transmission (Tx) channel and its neighboring channel(s).

The ACLR measurement in the R&S VSE-K18 is a measurement based on I/Q data. Thus, its results are calculated by the same I/Q data as the rest of the results (like the EVM). Note that the supported channel bandwidth is limited by the I/Q bandwidth of the analyzer you are using.

The results are provided in numerical form in a table. The table is made up out of two parts, one part containing the characteristics of the Tx channel, the other containing those of the neighboring channels.

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Measurements and result displays

The table contains the following information.

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Channel

Shows the type of channel.

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Bandwidth

Shows the channel's bandwidth.

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Offset (neighboring channels only) Shows the frequency offset between the center frequency of the adjacent (or alternate) channel and the center frequency of the transmission channel.

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Power

Shows the power of the transmission channel, or the power of the upper / lower neighboring channel. The result is calculated over the complete capture buffer, not just the evaluation range.

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Balanced

Shows the difference between the lower and upper adjacent channel power ("Lower Channel" - "Upper Channel").

For more information on configuring the ACP measurement, see Chapter 3.15, "Con-

figuring adjacent channel leakage error (ACLR) measurements", on page 110.

Remote command: Selection: LAY:ADD? '1',LEFT,ACP Result query: CALCulate<n>:MARKer<m>:FUNCtion:POWer:RESult? on page 330

AM/AM

The "AM/AM" result display shows nonlinear effects of the DUT. It shows the amplitude at the DUT input against the amplitude at the DUT output.

The ideal "AM/AM" curve would be a straight line at 45°. However, nonlinear effects result in a measurement curve that does not follow the ideal curve. When you drive the amplifier into saturation, the curve typically flattens at high input levels.

The width of the "AM/AM" trace is an indicator of memory effects: the larger the width of the trace, the more memory effects occur. The "AM/AM" Curve Width is shown in the numerical Result Summary.

Both axes show the power of the signal in dBm. You can analyze the "AM/AM" characteristics of the measured signal and the modeled

signal.

●

Measured signal

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Measurements and result displays

Shows the "AM/AM" characteristics of the DUT. The software uses the reference signal in combination with the synchronized measurement signal to calculate a software model that describes the characteristics of the device under test. The measured signal is represented by a colored cloud of values. The cloud is based on the recorded samples. If samples have the same values (and would thus be superimposed), colors represent the statistical frequency with which a certain input / output level combination occurs. Blue pixels represent low statistical frequencies, red pixels high statistical frequencies. A color map is provided within the result display.

●

Modeled signal Shows the "AM/AM" characteristics of the model that has been calculated. The modeled signal is calculated by applying the DUT model to the reference signal. When the model matches the characteristics of the DUT, the characteristics of the model signal are the same as those of the measured signal (minus noise). The modeled signal is represented by a line trace. When system modeling has been turned off, this trace is not displayed.

All traces include the digital predistortion, when you have turned on that feature.

Remote command: Selection: LAY:ADD? '1',LEFT,AMAM Result query: TRACe<n>[:DATA]? on page 143

AM/PM

The "AM/PM" result display shows nonlinear effects of the DUT. It shows the phase difference between DUT input and output for each sample of the synchronized measurement signal.

The ideal "AM/PM" curve would be a straight line at 0°. However, nonlinear effects result in a measurement curve that does not follow the ideal curve. Typically, the curve drifts from a zero phase shift, especially at high power levels when you drive the amplifier into saturation.

The width of the "AM/PM" trace is an indicator of memory effects: the larger the width of the trace, the more memory effects occur. The "AM/PM" curve width is shown in the numerical Result Summary.

The x-axis shows the levels of all samples of the reference signal (input power) or the measurement signal (output power) in dBm. You can select the reference of the x-axis (input or output power) in the "Result Configuration" dialog box.

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Measurements and result displays

The y-axis shows the phase of the signal for the corresponding power level. The unit is either rad or degree, depending on your phase unit selection in the "Result Configuration" dialog box.

You can analyze the "AM/PM" characteristics of the real DUT or of the modeled DUT.

●

Measured signal Shows the "AM/PM" characteristics of the DUT. The software uses the reference signal together with the synchronized measurement signal to calculate a software model that describes the characteristics of the device under test. The measured signal is represented by a colored cloud of values. The cloud is based on the recorded samples. If samples have the same values (and would thus be superimposed), colors represent the statistical frequency with which a certain input / output level combination occurs. A color map is provided within the result display.

●

Modeled signal Shows the "AM/PM" characteristics of the model that has been calculated. The modeled signal is calculated by applying the DUT model to the reference signal. When the model matches the characteristics of the DUT, the characteristics of the modeled signal are the same as those of the measured signal (minus noise). The modeled signal is represented by a line trace. When system modeling has been turned off, this trace is not displayed.

All traces include the digital predistortion, when you have turned on that feature.

Remote command: Selection: LAY:ADD? '1',LEFT,AMPM Result query: TRACe<n>[:DATA]? on page 143

DDPD Results (R&S VSE-K18D)

The "DDPD Results" result display shows a selectable result (such as EVM or ACLR) over all iterations of the direct DPD. This allows verification of the direct DPD's convergence as well as picking the ideal iteration step for further processing (e.g. in R&S VSE-K18M). It is only available with application R&S VSE-K18D installed.

The display must be placed on screen before starting the direct DPD. The result type is configurable in the "Result Configuration" dialog box.

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Measurements and result displays

Remote command: Selection: LAY:ADD? '1',LEFT,DDPD Configure result type: CONFigure:DDPD:WINDow<n>:RESult on page 316 Result query: TRACe<n>[:DATA]? on page 143

EVM vs Power

The "EVM vs Power" result display shows the EVM against the measured power values.

The ideal EVM vs power curve would be a straight line at 0 %. However, among other effects such as noise, nonlinear effects of the DUT cause an increase of the EVM. Nonlinear effects usually occur on high power levels that drive the power amplifier into saturation.

The y-axis shows the EVM of the signal for the corresponding power level in %. All traces include the digital predistortion, when you have turned on that feature.

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Measurements and result displays

Remote command: Selection: LAY:ADD? '1',LEFT,AMEV Result query: TRACe<n>[:DATA]? on page 143

Error Vector Spectrum

The "Error Vector Spectrum" result display shows the error vector (EV) signal in the spectrum around the center frequency.

The EV is a measure of the modulation accuracy. It compares two signals and shows the distance of the measured constellation points and the ideal constellation points.

The unit is dB. You can compare the measured signal against the reference signal and against the

modeled signal.

●

Measured signal against reference signal Trace 1 compares measured signal and the reference signal. To get useful results, the calculated linear gain is compensated to match both signals. Depending on the DUT, noise and nonlinear effects may have been added to the measurement signal. These effects are visualized by this trace.

●

Measured signal against modeled signal Trace 2 compares measured signal and the modeled signal. The EVM between the measured and modeled signal indicates the quality of the DUT modeling. If the model matches the DUT behavior, the modeling error is zero (or is merely influenced by noise). This result display shows changes in the model and its parameters and thus allows you to optimize the modeling. When system modeling has been turned off, this trace is not displayed.

Remote command: Selection: LAY:ADD? '1',LEFT,SEVM Result query: TRACe<n>[:DATA]? on page 143

Gain Compression

The "Gain Compression" result display shows the gain and error effects of the DUT against the DUT input or output power.

The gain is the ratio of the input and output power of the DUT.

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Measurements and result displays

The y-axis shows the gain in dB. The ideal gain compression curve would be a straight horizontal line. However, nonlin-

ear effects result in a measurement curve that does not follow the ideal curve. In addition, the curve widens at very low input levels due to noise influence.

The width of the gain compression trace is an indicator of memory effects: the larger the width of the trace, the more memory effects occur.

You can analyze the gain characteristics of the measured signal and the modeled signal.

●

Measured signal Shows the gain characteristics of the DUT. The software uses the reference signal in combination with the synchronized measurement signal to calculate a software model that describes the characteristics of the device under test. The measured gain is represented by a colored cloud of values. The cloud is based on the recorded samples. If samples have the same values (and would thus be superimposed), colors represent the statistical frequency with which a certain input / output level combination occurs. Blue pixels represent low statistical frequencies, red pixels high statistical frequencies. A color map is provided within the result display.

●

Modeled signal Shows the gain characteristics of the model that has been calculated. The modeled signal is calculated by applying the DUT model to the reference signal. When the model matches the characteristics of the DUT, the characteristics of the model signal are the same as those of the measured signal (minus noise). The modeled signal is represented by a line trace. When system modeling has been turned off, this trace is not displayed.

In addition, one or more horizontal lines can appear in the result display.

●

One line to indicate each compression point (1 dB, 2 dB and 3 dB).

●

One line to indicate the reference point (0 dB compression) that the compression points refer to.

Remote command: Selection: LAY:ADD? '1',LEFT,GC Result query: TRACe<n>[:DATA]? on page 143

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Measurements and result displays

Gain Deviation vs Time

The "Gain Deviation vs Time" result display shows the deviation of each measured signal sample from the average gain of the measured signal.

The x-axis shows the time in seconds. The y-axis shows the gain deviation in dB. The displayed results are based on the synchronized measurement data (represented

by the green bar in the capture buffer). Note that the result query and trace export only work for unencrypted reference signal

waveform files.

Remote command: Selection: LAY:ADD? '1',LEFT,GDVT Result query: TRACe<n>[:DATA]? on page 143

Magnitude Capture

The "Magnitude Capture" result display contains the raw data that has been recorded and thus represents the characteristics of the DUT.

The raw data is source for all further evaluations. You can also use the data in the capture buffer to identify the causes for possible unexpected results.

When you synchronize the reference signal and the measured signal, the synchronized area is indicated by a horizontal green bar on the bottom of the diagram.

The current reference level is indicated by a red horizontal line. The green bar at the bottom shows the current frame. In I/Q averaging mode, the aver-

age value is shown. In trace statistics mode, multiple values are possible. The currently selected value is symbolized by a blue bar.

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Measurements and result displays

Remote command: Selection (RF): LAY:ADD? '1',LEFT,RFM Result query: TRACe<n>[:DATA]? on page 143

Memory DPD Coefficients

The "Memory DPD Coefficients" result table shows basically complex filter coefficients for each polynomial degree. The two lines "1(Real)" and "1(Imag)" describe the complex impulse response for polynomial degree 1 (linear) of a filter from left to right. It is only available with application R&S VSE-K18M installed.

Remote command: Selection: LAY:ADD? '1',LEFT,MDPD Result query: FETCh:MDPD:COEFficients? on page 326

Parameter Sweep

The "Parameter Sweep" result display is a result display that shows a result of the DUT (for example the EVM) against two (custom) measurement parameters. The results of this measurement are displayed in graphical and numerical form.

The parameter sweep is a good way, for example, to find the location of the ideal delay time of the RF signal and the envelope signal if you are measuring an amplifier that supports envelope tracking. You can also use the parameter sweep to determine the characteristics and behavior of an amplifier over different frequencies and levels.

For more information about supported parameters and how to set them up see "Select-

ing the data to be evaluated during the parameter sweep" on page 115.

Parameter Sweep: Diagram ← Parameter Sweep

The parameter sweep diagram is a graphical representation of the parameter sweep results. The results are either represented as a two-dimensional trace or as a threedimensional trace, depending on whether you are performing a parameter sweep with one or two parameters.

In a two-dimensional diagram, the y-axis always shows the result. The displayed result depends on the result type you have selected. The information displayed on the x-axis depends on the parameter you have selected for evaluation (for example the EVM over a given frequency range). Values between measurement point are interpolated. Basically, you can interpret the two-dimensional diagram as follows (example): "at a frequency of x Hz, the EVM has a value of y."

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Measurements and result displays

In a three-dimensional diagram, the z-axis always shows the result. The information on the other two axes is arbitrary and depends on the parameters you have selected for evaluation. For a better readability, the result values in the three-dimensional diagram are represented by a colored trace: low values have a blue color, while high values have a red color. Values between measurement point are interpolated. Basically, you can interpret the three-dimensional diagram as follows (example): "at a frequency of x Hz and a level of y, the EVM has a value of z."

Parameter Sweep: Table ← Parameter Sweep

The parameter sweep table shows the minimum and maximum results for all available result types in numerical form. For each result type, the location where the minimum and maximum result has occurred is displayed.

Example:

A minimum EVM of 0.244 % and a maximum EVM of 0.246 % has been measured (first and second row). The minimum EVM has been measured at a frequency of 30 MHz and an output power of 0 dBm. The maximum EVM has been measured at a frequency of 10 MHz and an output power of 0 dBm.

The following result types are evaluated in the parameter sweep.

Result Description

EVM Error vector magnitude between synchronized reference and mea-

surement signal.

ACLR Power of the transmission channel.

ACLR Adj Upper / Lower Power of the adjacent channels (upper and lower).

ACLR Balanced (Adj, Alt1 and Alt2)

RMS Power RMS signal power at the DUT output.

Gain Gain of the DUT.

Crest Factor Out Crest factor of the signal at the DUT output. The crest factor is the

Curve Width ("AM/AM", "AM/PM") Spread of the samples in the "AM/AM" (or "AM/PM") result display

Power Out Signal power at the DUT output.

Difference between the lower and upper adjacent channel power

ratio of the RMS and peak power.

compared to the ideal "AM/AM" (or "AM/PM") curve.

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Result Description

Compression Point (1 dB / 2 dB / 3 dB)

Bal ACLR Magnitude Shows the difference between the lower and upper adjacent channel

Input power where the gain deviates by 1 dB, 2 dB or 3 dB from a reference gain (see "Configuring compression point calculation" on page 110).

power.

Remote command:

Chapter 5.4.3.3, "Retrieving results of the parameter sweep table", on page 160

Phase Deviation vs Time

The "Phase Deviation vs Time" result display shows the phase deviation of the measured signal compared to the reference signal over time.

The x-axis shows the time in seconds. The y-axis shows the phase deviation in degree.

The displayed results are based on the synchronized measurement data (represented by the green bar in the capture buffer).

Note that the result query and trace export only work for unencrypted reference signal waveform files.

Remote command: Selection: LAY:ADD? '1',LEFT,PDVT Result query: TRACe<n>[:DATA]? on page 143

Raw EVM

The "Raw EVM" result display shows the error vector magnitude of the signal over time.

The EVM is a measure of the modulation accuracy. It compares two signals and shows the distance of the measured constellation points and the ideal constellation points.

You can compare the measured signal against the reference signal and against the modeled signal.

●

Measured signal against reference signal Trace 1 compares the measured signal and the reference signal. To get useful results, the calculated linear gain is compensated to match both signals.

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Depending on the DUT, noise and nonlinear effects may have been added to the measurement signal. These effects are visualized by this trace.

●

Measured signal against modeled signal Trace 2 compares the measured signal and the modeled signal. The EVM between the measured and modeled signal indicates the quality of the DUT modeling. If the model matches the DUT behavior, the modeling error is zero (or is merely influenced by noise). This result display shows changes in the model and its parameters and thus allows you to optimize the modeling. When system modeling has been turned off, this trace is not displayed.

Note that the raw EVM is calculated for each sample that has been recorded. Thus, the raw EVM can differ from EVM values that are calculated according to a specific mobile communication standard that apply special rules to calculate the EVM, for example LTE.

Remote command: Selection: LAY:ADD? '1',LEFT,REVM Result query: TRACe<n>[:DATA]? on page 143

Numeric Result Summary

The "Result Summary" shows various measurement results in numerical form, combined in one table.

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For each result type, several values are displayed.

●

Current

Value measured during the last sweep. For measurements that evaluate each captured sample, this value represents the average value over all samples captured in the last sweep.

●

Min

For measurements that evaluate each captured sample, this value represents the sample with lowest value captured in the last sweep.

●

Max

For measurements that evaluate each captured sample, this value represents the sample with the highest value captured in the last sweep.

●

Unit

Unit of the result.

Results that evaluate each captured sample

●

"Raw EVM" and Raw Model EVM

●

Power In and Power Out

Note: When synchronization has failed or has been turned off, some results may be unavailable.

Remote command: Selecting the result display: LAY:ADD? '1',LEFT,RTAB Querying results: see Chapter 5.4.3, "Retrieving numeric results", on page 145

Results to check modulation accuracy ← Numeric Result Summary

Raw EVM Error vector magnitude between synchronized reference and measured sig-

nal.

FETCh:MACCuracy:REVM:CURRent[:RESult]? on page 149

Raw Model EVM Error vector magnitude between synchronized measured and model signal.

FETCh:MACCuracy:RMEV:CURRent[:RESult]? on page 150

Frequency Error Difference of the RF frequency of the reference signal compared to the mea-

sured signal. Note that a frequency error is not available if the frequency error estimation is

switched off. See also Chapter 3.9, "Estimating and compensating signal

errors", on page 90.

FETCh:MACCuracy:FERRor:CURRent[:RESult]? on page 147

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Sample Rate Error Sample rate difference between reference and measured signal.

Note that a sample rate error is not available if the sample rate error estimation is switched off. See also Chapter 3.9, "Estimating and compensating sig-

nal errors", on page 90.

FETCh:MACCuracy:SRERror:CURRent[:RESult]? on page 150

Magnitude Error Difference in magnitude between the reference signal and the measured sig-

nal.

FETCh:MACCuracy:MERRor:CURRent[:RESult]? on page 148

Phase Error Phase difference between reference and measured signal.

FETCh:MACCuracy:PERRor:CURRent[:RESult]? on page 149

Quadrature Error Phase deviation of the 90° phase difference between the real (I) and imagi-

nary (Q) part of the signal.

Within an ideal transmitter, the I and Q signal parts are mixed with an angle of 90° by the I/Q output mixer. Due to hardware imperfections, the signal delay of I and Q can be different and thus lead to an angle non-equal to 90°.

Note that quadrature rate error is not available if the I/Q Imbalance estimation is switched off. See also Chapter 3.9, "Estimating and compensating signal

errors", on page 90.

FETCh:MACCuracy:QERRor:CURRent[:RESult]? on page 149

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Gain Imbalance Gain difference between the real (I) and imaginary (Q) part of the signal.

This effect is typically generated by two separate amplifiers with a different gain in the I and Q path of the analog baseband signal generation.

Note that gain imbalance is not available if the I/Q Imbalance estimation is switched off. See also Chapter 3.9, "Estimating and compensating signal

errors", on page 90.

FETCh:MACCuracy:GIMBalance:CURRent[:RESult]? on page 147

I/Q Imbalance Combination of Quadrature error and Gain imbalance.

The I/Q imbalance parameter is a representation of the combination of Quadrature error and gain imbalance.

Note that I/Q imbalance is not available if the I/Q imbalance estimation is switched off. See also Chapter 3.9, "Estimating and compensating signal

errors", on page 90.

FETCh:MACCuracy:IQIMbalance:CURRent[:RESult]? on page 148

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I/Q Offset Shift of the measured signal compared to the ideal I/Q constellation in the I/Q

plane.

Note that I/Q offset is not available if the I/Q Offset estimation is switched off. See also Chapter 3.9, "Estimating and compensating signal errors", on page 90.

FETCh:MACCuracy:IQOFfset:CURRent[:RESult]? on page 148

Amplitude Droop Amplitude droop is a measure of the change in magnitude of the signal over

the frame (reference signal) being measured in dB. Note that amplitude droop is not available if the amplitude droop estimation is

switched off. See also Chapter 3.9, "Estimating and compensating signal

errors", on page 90.

Results to check power characteristics ← Numeric Result Summary

Power In Signal power at the DUT input when reference signal is active. The signal

generator level may change during direct DPD, but this result summary value will always refer to the reference signal – not the DPD signal.

FETCh:POWer:INPut:CURRent[:RESult]? on page 153

Power In (Sensor) Signal power at the input power sensor.

FETCh:POWer:SENSor:IN:CURRent[:RESult]? on page 156

Power Out Signal power at the DUT output.

Power Out (Sensor) Signal power at the output power sensor.

It is the RMS power of:

●

The currently selected frame, if R&S VSE-K18 has successfully synchronized.

●

The current capture buffer, if R&S VSE-K18 has not synchronized.

FETCh:POWer:OUTPut:CURRent[:RESult]? on page 153

FETCh:POWer:SENSor:OUT:CURRent[:RESult]? on page 157

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Gain Average gain calculated over all samples of the "Gain Compression" trace.

noise in

output signal

gain

Note that gain is not necessarily equal to the ratio "Power Out" / "Power In". Gain only describes the ratio of the correlated signal in "Power Out" to "Power In".

Gain is always referenced to the reference signal power, i.e. when DPD changes the generator level, the gain is still referenced to the input power of the reference signal - not the DPD signal.

Example: If the output signal contains the same amount of noise as the correlated signal (e.g. signal is 0 dBm and noise power is also 0 dBm), "Power Out" will show the sum (3 dBm). However, assuming an input signal power of

-10 dBm, gain will only show 10 dB, not 13 dB.

FETCh:POWer:GAIN:CURRent[:RESult]? on page 152

total output

signal

correlated

output signal

input signal

Crest Factor In Crest factor of the signal at the DUT input. The crest factor is the ratio of the

RMS and peak power.

FETCh:POWer:CFACtor:IN:CURRent[:RESult]? on page 152

Crest Factor Out Crest factor of the signal at the DUT output. The crest factor is the ratio of the

RMS and peak power.

FETCh:POWer:CFACtor:OUT:CURRent[:RESult]? on page 152

AM/AM Curve Width Vertical spread of the samples in the "AM/AM" result display.

The "AM/AM" curve width shows the standard deviation of the output voltage or the output phase deviation within a +/- 1% range around the mean amplitude in volt.

Output

amplitude

+/- 1%

σ of output

amplitude

in this range

10,5

Input amplitude

linear normalized

FETCh:AMAM:CWIDth:CURRent[:RESult]? on page 151

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AM/PM Curve Width Vertical spread of the samples in the "AM/PM" result display.

The "AM/PM" curve width shows the standard deviation of the output voltage or the output phase deviation within a +/- 1% range around the mean amplitude in volt.

Output

amplitude

+/- 1%

σ of output

amplitude

in this range

FETCh:AMPM:CWIDth:CURRent[:RESult]? on page 151

10,5

Input amplitude

linear normalized

Compression Point (1 dB / 2 dB / 3 dB)

Input power where the gain deviates by 1 dB, 2 dB or 3 dB from a reference gain (see "Configuring compression point calculation" on page 110).

In the graphical result, the compression points are indicated by horizontal red lines.

FETCh:POWer:P1DB:CURRent[:RESult]? on page 153

FETCh:POWer:P2DB:CURRent[:RESult]? on page 154

FETCh:POWer:P3DB:CURRent[:RESult]? on page 154

Output Compression Point (1 dB / 2 dB / 3 dB)

Output power where the gain deviates by 1 dB, 2 dB or 3 dB from a reference gain.

Uses identical operating points as "Compression Point (1 dB / 2 dB / 3 dB)", but is identified by output power at compression point rather than input power.

FETCh:POWer:P1DB:OUT:CURRent[:RESult]? on page 155

FETCh:POWer:P2DB:OUT:CURRent[:RESult]? on page 155

FETCh:POWer:P3DB:OUT:CURRent[:RESult]? on page 156

Occupied Bandwidth Occupied bandwidth calculated for the defined evaluation range.

Spectrum FFT

The "Spectrum FFT" result display shows the frequency spectrum of the signal. The spectrum FFT result shows the signal level in the spectrum around the center fre-

quency. The unit is dBm. You can display the spectrum of the measured signal and the reference signal. In the

best case, the measured signal has the same shape as the reference signal.

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Remote command: Selection (RF): LAY:ADD? '1',LEFT,RFS Result query: TRACe<n>[:DATA]? on page 143

Time Domain

The "Time Domain" result display shows the signal characteristics over time. It is similar to the "Power vs Time" and "Magnitude Capture" result displays in that it

shows the signal characteristics over time. However, it deliberately shows only a very short period of the signal. You can thus use it to compare various aspects of the signal, especially the timing of the displayed signals, in a single result display.

●

Measured signal Trace 1 shows the characteristics of the measured signal over time. The data should be the same as the results shown in the "Magnitude Capture" RF result display. In the best case, the measured signal is the same as the reference signal.

●

Modeled signal Trace 2 shows the characteristics of the modeled signal. When system modeling has been turned off, this trace is not displayed. If the model matches the behavior of the DUT, the characteristics of the signal are the same as those of the measured signal (minus the noise).

●

Reference signal Trace 3 shows the characteristics of the reference signal. The reference signal present at the DUT input represents the ideal signal.

Remote command: Selection: LAY:ADD? '1',LEFT,TDOM Result query: TRACe<n>[:DATA]? on page 143

Scale of the x-axis (display settings for the time domain) ← Time Domain

The scale of the x-axis depends on your configuration in the "Display Settings" dialog box.

The logic is as follows:

●

When you select automatic scaling (➙ "Position: Auto") and synchronization has failed, the application searches for the peak level in the capture buffer and shows the signal around the peak for the "Duration" that has been defined.

●

When you select automatic scaling (➙ "Position: Auto") and synchronization is OK, the application searches for the peak level in the synchronized area of the capture

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buffer and shows the signal around the peak for the "Duration" that has been defined.

●

When you select manual scaling (➙ "Position: Manual") and synchronization has failed, the x-axis starts at an "Offset" relative to the first sample in the capture buffer. The end of the x-axis depends on the "Duration" you have defined.

●

When you select manual scaling (➙ "Position: Manual") and synchronization is OK, the x-axis starts at an "Offset" relative to the first sample in the synchronized area of the capture buffer. The end of the x-axis depends on the "Duration" you have defined.

Note: The "Display Settings" for the time domain are only available after you have selected the "Specifics for: Time Domain" item from the corresponding dropdown menu at the bottom of the dialog box.

Scale of the y-axis (display settings for the time domain) ← Time Domain

The scale of the y-axis also depends on your configuration. The signal characteristics displayed in the time domain result display all have a differ-

ent unit. Therefore, the application provides a feature that normalizes all results to 1 (see "Configuring the time domain result display" on page 130). Normalization makes it easier to compare the timing between the traces. By default, normalization is on. Note that you can normalize each "Time Domain" window individually.

Unnormalized results are displayed in their respective unit.

Statistics Table

The results for the statistics table are available only after the statistics mode has been activated using [SENSe:]SWEep:STATistics[:STATe] on page 297. If statistics mode is switched off, the statistics table stays empty.

Each value in the statistics table has different rows describing a single frame: Average, Std. Dev, Maximum and Minimum. This is similar to the Numeric Result Summary.

The different color codes represent different result values:

●

Blue

Result of the current result range. The selected values are updated when the user sweeps through the result range selection.

●

Green

In I/Q averaging mode, the values in the green area are identical to the ones in the black background area. In trace statistics mode, the green area refers to all frames of the current capture buffer, whereas the black area refers to all measured frames (including previous

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capture buffers). Statistics is always done over sweep “Count” frames and then is being reset, unless the "Continuous Statistics" switch is activated. In this case, infinite statistics is executed.

●

Black / No selection

Statistical results that can also be based on result ranges that were captured in previous measurement sweeps.

Remote command: Adding statistics table: LAY:ADD? '1',LEFT,STAB Querying results: Chapter 5.4.3.4, "Retrieving results of the statistics table", on page 174 Configuring statistics table: Chapter 5.6.4, "Configuring the statistics table", on page 363 Navigating through results ranges found in a capture: CONFigure:RESult:RANGe[:

SELected] on page 298

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3 Configuration

Configuration

Configuration overview

● Configuration overview............................................................................................33

● Designing a reference signal...................................................................................35

● Configuring inputs and outputs............................................................................... 45

● Triggering measurements....................................................................................... 80

● Configuring the data capture...................................................................................81

● Sweep configuration................................................................................................84

● Synchronizing measurement data...........................................................................86

● Evaluating measurement data................................................................................ 88

● Estimating and compensating signal errors............................................................ 90

● Equalizer................................................................................................................. 91

● Applying system models......................................................................................... 92

● Applying digital predistortion................................................................................... 95

● Detailed MSE........................................................................................................ 108

● Configuring power measurements........................................................................ 109

● Configuring adjacent channel leakage error (ACLR) measurements....................110

● Configuring the parameter sweep......................................................................... 113

● Configuring power servoing...................................................................................117

3.1 Configuration overview

Throughout the measurement channel configuration, an overview of the most important currently defined settings is provided in the "Overview". The "Overview" is displayed when you select the "Overview" icon, which is available at the bottom of all softkey menus.

In addition to the main measurement settings, the "Overview" provides quick access to the main settings dialog boxes. The individual configuration steps are displayed in the order of the data flow. Thus, you can easily configure an entire measurement channel from input over processing to output and analysis by stepping through the dialog boxes as indicated in the "Overview".

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Configuration overview

In particular, the "Overview" provides quick access to the following configuration dialog boxes (listed in the recommended order of processing):

1. Reference Signal

See Chapter 3.2, "Designing a reference signal", on page 35.

2. Input and output

See Chapter 3.3, "Configuring inputs and outputs", on page 45.

3. Trigger

See Chapter 3.4, "Triggering measurements", on page 80.

4. Data Acquisition

See Chapter 3.5, "Configuring the data capture", on page 81.

5. Synchronization, error estimation and compensation

See Chapter 3.7, "Synchronizing measurement data", on page 86. See Chapter 3.9, "Estimating and compensating signal errors", on page 90.

6. Measurement

Modeling: see Chapter 3.11, "Applying system models", on page 92. DPD: see Chapter 3.12, "Applying digital predistortion", on page 95.

7. Result configuration

See Chapter 4, "Analysis", on page 119.

8. Display configuration

See Chapter 2, "Measurements and result displays", on page 12.

To configure settings

► Select any button in the "Overview" to open the corresponding dialog box.

Select a setting in the channel bar (at the top of the measurement channel tab) to change a specific setting.

Preset Channel

Select the "Preset Channel" button in the lower left-hand corner of the "Overview" to restore all measurement settings in the current channel to their default values.

Remote command:

SYSTem:PRESet:CHANnel[:EXEC] on page 141

Specifics for

The channel can contain several windows for different results. Thus, the settings indicated in the "Overview" and configured in the dialog boxes vary depending on the selected window.

Select an active window from the "Specifics for" selection list that is displayed in the "Overview" and in all window-specific configuration dialog boxes.

The "Overview" and dialog boxes are updated to indicate the settings for the selected window.

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3.2 Designing a reference signal

Configuration

Designing a reference signal

Access (source: generator): "Overview" > "Reference Signal" > "Current Generator Waveform"

Access (source: waveform file): "Overview" > "Reference Signal" > "Custom Waveform File"

Access (source: Amplifier application): "Overview" > "Reference Signal" > "Generate Own Signal"

Many of the results available in the application require a reference signal that describes the characteristics of the signal you feed into the amplifier.

The reference signal describes the characteristics of the signal that you feed into the amplifier and whose amplified version is measured by the application. You can define any signal you want as a reference signal.

The application provides several methods to design a reference signal:

●

Designing the signal on a generator (Having a Rohde & Schwarz generator is mandatory for this method.)

●

Designing the signal in a waveform file

●

Designing the signal in the amplifier application (Having a Rohde & Schwarz generator is mandatory for this method.)

For a list of supported signal generators, refer to the datasheet of the amplifier application.

The remote commands required to configure the reference signal are described in

Chapter 5.5.1, "Designing a reference signal", on page 228.

Reference signal information........................................................................................ 36

Using multi-segment waveform files............................................................................. 36

Transferring the reference signal.................................................................................. 37

Designing a reference signal on a signal generator......................................................38

Designing a reference signal in a waveform file............................................................39

Designing a reference signal within the R&S VSE-K18................................................ 40

└ Signal Bandwidth............................................................................................ 41

└ Pulse Duty Cycle.............................................................................................41

└ Signal Length..................................................................................................42

└ Ramp Length.................................................................................................. 42

└ Target Crest Factor......................................................................................... 42

└ Waveform File Name...................................................................................... 42

└ Notch Width.................................................................................................... 42

└ Notch Position.................................................................................................43

Crest Factor Reduction (Generator Option K548).........................................................43

└ Crest Factor Reduction State..........................................................................43

└ EVM Ref. Signal..............................................................................................43

└ Crest Factor Delta...........................................................................................44

└ Current Crest Factor....................................................................................... 44

└ Max Iterations................................................................................................. 44

└ Filter Mode......................................................................................................44

└ Signal Bandwidth............................................................................................ 44

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Designing a reference signal

└ Channel Spacing.............................................................................................44

└ Read CFR from Generator, Load....................................................................45

└ Passband Frequency......................................................................................45

└ Stopband Frequency.......................................................................................45

└ Maximum Filter Order..................................................................................... 45

Reference signal information

Each tab of the "Reference Signal" dialog box contains some basic information about the reference signal currently in use.

The information is only displayed when a reference signal has been successfully loaded. When you load a different waveform, the reference signal information is updated accordingly.

●

Waveform file Name and path of the waveform file currently in use.

●

Sample rate The sample rate in the header of the currently used reference signal waveform file in Hz.

●

Number of samples Length of the currently used reference signal waveform file in samples.

●

Crest Factor (File) Crest factor of the whole file currently in use. The crest factor of waveform files is read from their header. The crest factor of iq.tar files is calculated.

●

Bandwidth (OBW) The occupied bandwidth of the reference signal currently in use. A calculated bandwidth that contains 99% of signal power is displayed.

Remote command: File path: CONFigure:REFSignal:SINFo:FPATh? on page 235 Sample rate: CONFigure:REFSignal:SINFo:SRATe? on page 235 Sample length: CONFigure:REFSignal:SINFo:SLENgth? on page 235 Crest Factor: CONFigure:REFSignal:SINFo:CFACtor? on page 235 OBW: CONFigure:REFSignal:SINFo:OBW? on page 236

Using multi-segment waveform files

Modern chip technologies implement several communication standards within one chip and thus increase the requirements in spatial design and test systems. To fulfill the requirements in the test systems, and to enable a rapid change between different waveforms containing different test signals, the R&S SMW provides the functionality to generate multi-segment waveform files. Multi-segment waveform files are files that contain several different waveforms.

(For more information about creating and using multi-segment waveform files (including examples) refer to the documentation of the R&S SMW.)

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Configuration

Designing a reference signal

When you are testing amplifiers with the amplifier measurement application, you can use a multi-segment waveform file to create the reference signal. If you use one of these files, you have to select the segment that you want to use as a reference signal in the corresponding input field.

Note that the content of the segment you are using for the reference signal must match the content of the segment used by the ARB of the signal generator. You can select the segment for the used by the generator in the generator setup.

Remote command:

CONFigure:REFSignal:SEGMent on page 234

Transferring the reference signal

Both the signal generator and analyzer used in the test setup need to know the characteristics of the reference signal.

●

The signal generator needs that information to generate the signal.

●

The analyzer needs that information for the evaluation of the results.

This is why you have to transfer the signal information to both instruments. The transmission is done through a LAN connection that you have to establish when setting up the measurement. For more information on that see Chapter 3.3.6, "Controlling a sig-

nal generator", on page 61.

●

When you design the reference signal on the signal generator, transfer the signal information from the generator to the analyzer with the ➙"Read and Load Current Signal from R&S SMW" button. You can either design a reference signal with one of the available firmware options (for example an LTE signal with the R&S SMW-K55) or design a signal in a custom waveform file. Note that the R&S VSE-K18 does not support all firmware options of the signal generator.

●

When you load the reference signal from a waveform file or design the signal within the R&S VSE-K18, transfer the signal information from the analyzer to the generator. Depending on the signal source, you can do this either with the "Load and Export Selected Waveform File to Generator" or the "Generate and Load Signal and Export it to Generator" buttons.

When you send the signal information to the generator, the application automatically configures the generator accordingly.

Transmission state

The LED displayed with the transmission button shows the state of the reference signal transmission.

The LED is either gray, green or red:

●

Grey LED Transmission state unknown (for example when you have not yet started the transmission).

●

Green LED Transmission has been successful.

●

Red LED Transmission has not been successful. Check if the generator IP address / computer name are correct and if the connection has been established.

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Configuration

Designing a reference signal

Designing a reference signal on a signal generator

One way to design a reference signal is to design the signal on the signal generator itself.

You can design any signal you like, as long as it is storable as an arbitrary waveform (ARB) file. When you are done, you have to transfer the signal information from the signal generator to the signal analyzer with the "Read from Generator, Load" button.

The "Force ARB Mode" switch forces the signal generator to use its ARB mode (arbitrary waveform) rather than its real-time mode, whenever possible. As a result, switching between DPD on and off state is significantly faster. When the "Force ARB Mode" function is used, the peak power of the generator is read out and used within the process but as a result of this function the RMS power of the generator is modified. Also the waveform header of the file is recalculated to make sure that the peak input level stays constant or lower than the gain expansion during DPD calculation.

The parameters of the currently active reference signal are described in "Reference

signal information" on page 36.

The "Open Generator Control" button provides functionality to change the generator settings as described in Chapter 3.3.6, "Controlling a signal generator", on page 61.

Most of the options available for the connected generator are supported by the automatic signal import functionality of the R&S VSE-K18. If the signal import was not successful (indicated by a red LED), you have to transfer the reference signal in another way (for example with a memory stick).

For a comprehensive description of all features available on the signal generator and information on how to generate signals, refer to the documentation of the signal generator.

Remote command: See signal generator documentation.

CONFigure:REFSignal:CGW:AMODe[:STATe] on page 229 CONFigure:REFSignal:CGW:READ on page 229 CONFigure:REFSignal:CGW:LEDState? on page 229

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Configuration

Designing a reference signal

Designing a reference signal in a waveform file

One way to design a reference signal is to define its characteristics in a waveform file (*.wv or *.iq.tar).

You can create a waveform file, for example:

●

With the R&S®WinIQSIM2 software package

●

By exporting a signal designed on the signal generator

Basically, this file contains the characteristics of the reference signal. The generator then generates the reference signal based on the information in the file.

There are two ways to generate the reference signal through a custom waveform file.

●

The generator is connected to the R&S VSE in a LAN, and can be recognized by the R&S VSE-K18 (Rohde & Schwarz generators only, for example the R&S SMW) In that case, you can simply transfer the reference signal information to the generator with the features integrated into the R&S VSE-K18. The generator then generates the corresponding signal with the appropriate signal level, and the R&S VSEK18 is able to compare the measured signal to the ideal reference signal.

●

The generator is not connected to the R&S VSE In that case, you have to load the reference signal information onto the generator manually and turn off the "Export to Generator" function. Because no exchange of information is possible between generator and analyzer, it is required to specify the input level of the signal in the "DUT Peak Input Power" input field.

The parameters of the currently active reference signal are described in "Reference

signal information" on page 36.

The "Open Generator Control" button provides functionality to change the generator settings as described in Chapter 3.3.6, "Controlling a signal generator", on page 61.

For a comprehensive description of all features available on the signal generator and information on how to generate and export signals to a file, refer to the documentation of the signal generator.

To transfer a waveform file from the analyzer to the generator and process it with the ARB generator of the R&S SMW, for example, proceed as follows:

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Configuration

Designing a reference signal

▶ In the "Custom Waveform" tab, select a file via the "Load, Play on Generator" button. ▶ Transfer the file to the generator with the "Select" button.

If a waveform is only used as a reference without transferring it to the signal generator, make sure that the generator control state "Off" is selected in the generator setup dialog.

Remote command: Select file: CONFigure:REFSignal:CWF:FPATh on page 230 Transfer file: CONFigure:REFSignal:CWF:WRITe on page 231 Transmission state: CONFigure:REFSignal:CWF:LEDState? on page 230 DUT input power: CONFigure:REFSignal:CWF:DPIPower on page 230

Designing a reference signal within the R&S VSE-K18

One way to design a reference signal is to design the signal within the R&S VSE-K18. The application provides functionality to design a basic reference signal and saves the

signal characteristics in a waveform file which you have to transfer to the signal generator with the "Generate and Load Signal and Export it to Generator" button.

When the data has been transferred, the signal generator (for example the R&S SMW) generates the corresponding signal.

The generated signal is a pseudo-noise signal, whose basic properties, like crest factor and bandwidth, you can specify as required.

The parameters of the currently active reference signal are described in "Reference

signal information" on page 36.

The "Open Generator Control" button provides functionality to change the generator settings as described in Chapter 3.3.6, "Controlling a signal generator", on page 61.

Table 3-1: Parameter dependencies

Parameter Min Value Max Value

Target Crest Factor 2 13

Signal Length ((N+2*RampLength)*100)/Pulse-

DutyCycle N=1000 for Target Crest Factor

< 12.5 dB N=25000 for Target Crest Factor

≥ 12.5 dB

Notch Width Signal Bandwidth/100 Signal Bandwidth

Ramp Length

0 if Pulse Duty Cycle is 100 % Otherwise (Signal Length*Pulse-

DutyCycle/100-N)/2

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Configuration

Designing a reference signal

To generate a reference signal within the application, proceed as follows: ▶ In the "Generate Own Signal" tab, design the reference signal as required. The application stores the current signal properties as an ARB signal in a waveform

file. ▶ Upload the data to the generator with the "Generate, Play on Generator" button. You can define the following signal characteristics.

●

"Signal Bandwidth" on page 41

●

"Pulse Duty Cycle" on page 41

●

"Signal Length" on page 42

●

"Ramp Length" on page 42

●

"Target Crest Factor" on page 42

●

"Waveform File Name" on page 42

●

"Notch Width" on page 42

●

"Notch Position" on page 43

Remote command:

CONFigure:REFSignal:GOS:WRITe on page 234 CONFigure:REFSignal:GOS:LEDState? on page 232

Signal Bandwidth ← Designing a reference signal within the R&S VSE-K18

Defines the bandwidth of the reference signal. The bandwidth should not be larger than maximum I/Q bandwidth supported by your

signal analyzer (which depends on the analyzer configuration). Remote command:

CONFigure:REFSignal:GOS:BWIDth on page 231

Pulse Duty Cycle ← Designing a reference signal within the R&S VSE-K18

Defines the duty cycle of a pulsed reference signal.

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Configuration

Designing a reference signal

The duty cycle of a pulse is the ratio of the pulse duration and the actual length of the pulse. A duty cycle of 100 % corresponds to a continuous signal.

Example:

The pulse duration is 2 μs. The actual length of the pulse is 1 μs. The duty cycle is 1 μs : 2 μs = 0.5 or 50 %.

Remote command:

CONFigure:REFSignal:GOS:DCYCle on page 232

Signal Length ← Designing a reference signal within the R&S VSE-K18

Defines the number of samples that the reference signal consists of. A number that is a power of 2 speeds up the internal signal processing. Thus, such a

number should be specified if no other requirements limit the choice of the sample count.

For more information, see "Pulse Duty Cycle" on page 41. Remote command:

CONFigure:REFSignal:GOS:SLENgth on page 233

Ramp Length ← Designing a reference signal within the R&S VSE-K18

Defines the number of samples used to ramp up the pulse to its full power and vice versa.

Remote command:

CONFigure:REFSignal:GOS:RLENgth on page 233

Target Crest Factor ← Designing a reference signal within the R&S VSE-K18

Defines the crest factor of the reference signal. The crest factor shows the RMS power in relation to the peak power. The crest factor is defined for a signal with 100 % pulse duty cycle and 0 Hz notch.

Changes to the pulse duty cycle and notch parameters will change the crest factor. Remote command:

CONFigure:REFSignal:GOS:CRESt on page 231

Waveform File Name ← Designing a reference signal within the R&S VSE-K18

Defines the name of the waveform file that the reference ARB signal configuration is stored in.

Remote command:

CONFigure:REFSignal:GOS:WNAMe on page 234

Notch Width ← Designing a reference signal within the R&S VSE-K18

Defines the width of a notch that you can add to the reference signal. Within the notch, all carriers of the reference signal have zero amplitude. You can use

the noise notch to, for example, determine the noise power ratio (NPR) before and after the DPD.

Remote command:

CONFigure:REFSignal:GOS:NWIDth on page 233

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Designing a reference signal

Notch Position ← Designing a reference signal within the R&S VSE-K18

Defines an offset for the noise notch relative to the center frequency. The offset moves the notch to a position outside the center of the signal. You can use

the offset to, for example, generate a one-sided noise signal or to examine asymmetric distortion effects.

Remote command:

CONFigure:REFSignal:GOS:NPOSition on page 232

Crest Factor Reduction (Generator Option K548)

The Crest Factor Reduction dialog provides functionality to control the main parameters of a Rohde & Schwarz signal generator equipped with option K548.

Crest Factor Reduction State ← Crest Factor Reduction (Generator Option K548)

Enables the crest factor reduction calculation. If "On" is selected and all input fields are editable, crest factor reduction is active on the

generator but the R&S VSE-K18 application has no CFR reference yet. If "On" is selected and "Read CFR from Generator, Load" is selected, all input fields

are grayed out. The CFR reference can now be used by the R&S VSE-K18 application. Remote command:

CONFigure:CFReduction[:STATe] on page 236 CONFigure:CFReduction[:STATe]:LEDState? on page 236

EVM Ref. Signal ← Crest Factor Reduction (Generator Option K548)

Loads a new ARB file as reference if "CFR" is selected. The original ARB file is stored. Remote command:

CONFigure:CFReduction:RSORignal on page 237

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Configuration

Designing a reference signal

Crest Factor Delta ← Crest Factor Reduction (Generator Option K548)

Sets the value difference by which you want to change your crest factor. Remote command:

CONFigure:CFReduction:CFDelta on page 239 CONFigure:CFReduction:CFDelta:LEDState? on page 239

Current Crest Factor ← Crest Factor Reduction (Generator Option K548)

Displays the current crest factor of the waveform after the calculation of the resulting crest factor is completed.

Remote command:

CONFigure:CFReduction:CCFactor? on page 239

Max Iterations ← Crest Factor Reduction (Generator Option K548)

Sets the number of iterations that are used for calculating the resulting crest factor. The iteration process is stopped when the desired crest factor delta is achieved by 0.1 dB.

Remote command:

CONFigure:CFReduction:ITERations on page 237 CONFigure:CFReduction:ITERations:LEDState? on page 237

Filter Mode ← Crest Factor Reduction (Generator Option K548)

Selects which filter mode is used for the filtering. In "Simple" mode, you can specify the RF bandwidth and channel spacing of the signal. The lowpass filter is designed to pass through frequency components inside the signal bandwidth and suppress components in the adjacent channel. In "Enhanced" mode, you can specify the passband and stopband frequencies of the lowpass filter.

Remote command:

CONFigure:CFReduction:FILTer on page 238 CONFigure:CFReduction:FILTer:LEDState? on page 238

Signal Bandwidth ← Crest Factor Reduction (Generator Option K548)

Sets the signal bandwidth. The value of the "Signal Bandwidth" should not be higher than the "Channel Spacing".

When in automatic mode, "Signal Bandwidth" shall be set to the OBW value of the reference file (shown in reference signal overview).

"Channel Spacing" shall be set to 1.15 times this value. Remote command:

CONFigure:CFReduction:SBANdwidth on page 236 CONFigure:CFReduction:SBANdwidth:AUTO on page 237 CONFigure:CFReduction:SBANdwidth:LEDState? on page 237

Channel Spacing ← Crest Factor Reduction (Generator Option K548)

Sets the channel spacing. Remote command:

CONFigure:CFReduction:CSPacing on page 238 CONFigure:CFReduction:CSPacing:AUTO on page 238 CONFigure:CFReduction:CSPacing:LEDState? on page 238

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Configuring inputs and outputs

Read CFR from Generator, Load ← Crest Factor Reduction (Generator Option K548)

Applies crest factor reduction on the connected signal generator. Remote command:

CONFigure:CFReduction:READ on page 240 CONFigure:CFReduction:READ:LEDState? on page 240

Passband Frequency ← Crest Factor Reduction (Generator Option K548)

Sets the passband frequency. Only available for "Enhanced" filter mode. Remote command:

CONFigure:CFReduction:PFRequency on page 241 CONFigure:CFReduction:PFRequency:LEDState? on page 241

Stopband Frequency ← Crest Factor Reduction (Generator Option K548)

Sets the stopband frequency. Only available for "Enhanced" filter mode. Remote command:

CONFigure:CFReduction:SFRequency on page 241 CONFigure:CFReduction:SFRequency:LEDState? on page 241

Maximum Filter Order ← Crest Factor Reduction (Generator Option K548)

Sets the maximum filter order. Only available for "Enhanced" filter mode. Remote command:

CONFigure:CFReduction:MFORder on page 240 CONFigure:CFReduction:MFORder:LEDState? on page 241

3.3 Configuring inputs and outputs

● Input source settings...............................................................................................45

● Configuring the frequency.......................................................................................52

● Defining level characteristics...................................................................................53

● Power sensors........................................................................................................ 56

● Configuring outputs.................................................................................................61

● Controlling a signal generator................................................................................. 61

● Reference: I/Q file input.......................................................................................... 66

3.3.1 Input source settings

Access: "Overview" > "Input/Frontend" > "Input Source"

Or: "Input & Output" > "Input Source"

The R&S VSE can control the input sources of the connected instruments.

● Radio frequency input............................................................................................. 46

● I/Q file input.............................................................................................................50

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3.3.1.1 Radio frequency input

Configuration

Configuring inputs and outputs

Or: "Input & Output" > "Input Source" > "Radio Frequency"

The default input source for the connected instrument is "Radio Frequency". Depending on the connected instrument, different input parameters are available.

Figure 3-1: RF input source settings for an R&S FSW with B2000 option

If the Frequency Response Correction option (R&S VSE-K544) is installed, the Amplifier measurement application also supports frequency response correction using Touchstone (.snp) files or .fres files.

Input Type (Instrument / File)........................................................................................46

Instrument..................................................................................................................... 47

Input 1 / Input 2............................................................................................................. 47

Input Coupling ..............................................................................................................47

Impedance ................................................................................................................... 47

Direct Path ................................................................................................................... 48

High Pass Filter 1 to 3 GHz ..........................................................................................48

YIG-Preselector ............................................................................................................48

B2000 State.................................................................................................................. 49

Oscilloscope Splitter Mode............................................................................................49

Oscilloscope IP Address............................................................................................... 49

Preselector State...........................................................................................................49

Preselector Mode..........................................................................................................50

10 dB Minimum Attenuation..........................................................................................50

Input Type (Instrument / File)

Selects an instrument or a file as the type of input provided to the channel.

Note: External mixers are only available for input from a connected instrument.

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Configuring inputs and outputs

Note: If the R&S VSE software is installed directly on an instrument, or integrated in Cadence®AWR®VSS, some restrictions apply on the available input type.

Remote command:

INSTrument:BLOCk:CHANnel[:SETTings]:SOURce<si> on page 261 INPut<ip>:SELect on page 260

Instrument

Specifies a configured instrument to be used for input.

Input 1 / Input 2

For instruments with two input connectors, you must define which input source is used for each measurement channel.

Note that you cannot use both RF inputs simultaneously. "Input 1"

R&S FSW85: 1.00 mm RF input connector for frequencies up to 85 GHz (90 GHz with option R&S FSW-B90G)

"Input2"

Remote command:

INPut<ip>:TYPE on page 261

Input Coupling

The RF input of the R&S VSE can be coupled by alternating current (AC) or direct current (DC).

The RF input of the connected instrument can be coupled by alternating current (AC) or direct current (DC).

For an active external frontend, input coupling is always DC. AC coupling blocks any DC voltage from the input signal. AC coupling is activated by

default to prevent damage to the instrument. Very low frequencies in the input signal can be distorted.

However, some specifications require DC coupling. In this case, you must protect the instrument from damaging DC input voltages manually. For details, refer to the data sheet.

Remote command:

INPut<ip>:COUPling<ant> on page 256

Impedance

For some measurements, the reference impedance for the measured levels of the connected instrument can be set to 50 Ω or 75 Ω.

R&S FSW85: 1.85 mm RF input connector for frequencies up to 67 GHz

Select 75 Ω if the 50 Ω input impedance is transformed to a higher impedance using a 75 Ω adapter of the RAZ type. (That corresponds to 25Ω in series to the input impedance of the instrument.) The correction value in this case is 1.76 dB = 10 log (75Ω/ 50Ω).

Remote command:

INPut<ip>:IMPedance<ant> on page 258

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Configuration

Configuring inputs and outputs

Direct Path

Enables or disables the use of the direct path for small frequencies. In spectrum analyzers, passive analog mixers are used for the first conversion of the

input signal. In such mixers, the LO signal is coupled into the IF path due to its limited isolation. The coupled LO signal becomes visible at the RF frequency 0 Hz. This effect is referred to as LO feedthrough.

To avoid the LO feedthrough the spectrum analyzer provides an alternative signal path to the A/D converter, referred to as the direct path. By default, the direct path is selected automatically for RF frequencies close to zero. However, this behavior can be disabled. If "Direct Path" is set to "Off" , the spectrum analyzer always uses the analog mixer path.

For an active external frontend, the direct path is always used automatically for frequencies close to zero.

"Auto"

"Off" Remote command:

INPut<ip>:DPATh on page 256

(Default) The direct path is used automatically for frequencies close to zero.

The analog mixer path is always used.

High Pass Filter 1 to 3 GHz

Activates an additional internal highpass filter for RF input signals from 1 GHz to 3 GHz. This filter is used to remove the harmonics of the analyzer to measure the harmonics for a DUT, for example.

For some connected instruments, this function requires an additional hardware option on the instrument.

Note: For RF input signals outside the specified range, the high-pass filter has no effect. For signals with a frequency of approximately 4 GHz upwards, the harmonics are suppressed sufficiently by the YIG-preselector, if available.)

Remote command:

INPut<ip>:FILTer:HPASs[:STATe] on page 257

YIG-Preselector

Enables or disables the YIG-preselector. This setting requires an additional option on the connected instrument. An internal YIG-preselector at the input of the connected instrument ensures that

image frequencies are rejected. However, image rejection is only possible for a restricted bandwidth. To use the maximum bandwidth for signal analysis you can disable the YIG-preselector at the input of the connected instrument, which can lead to image-frequency display.

Note: Note that the YIG-preselector is active only higher frequencies, depending on the connected instrument. Therefore, switching the YIG-preselector on or off has no effect if the frequency is below that value.

To use the optional 90 GHz frequency extension (R&S FSW-B90G), the YIG-preselector must be disabled.

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Configuration

Configuring inputs and outputs

To use the optional 54 GHz frequency extension (R&S FSV3-B54G), the YIG-preselector must be disabled.

Remote command:

INPut<ip>:FILTer:YIG[:STATe] on page 257

B2000 State

Activates the optional 2 GHz bandwidth extension (R&S FSW-B2000). Note: The R&S VSE software supports input from a connected R&S FSW with a

B2000 option installed. However, the R&S FSW interface to the oscilloscope must be set up and aligned directly on the instrument before the R&S VSE software can start analyzing the input. The analysis bandwidth is defined in the data acquisition settings of the application as usual. Note that the maximum bandwidth cannot be restricted manually as for other bandwidth extension options.

Manual operation on the connected oscilloscope, or remote operation other than by the R&S VSE, is not possible while the B2000 option is active.

Remote command:

SYSTem:COMMunicate:RDEVice:OSCilloscope[:STATe] on page 263

Oscilloscope Splitter Mode

Activates the use of the power splitter inserted between the [IF 2 GHZ OUT] connector of the R&S FSW and the [CH1] and [CH3] input connectors of the oscilloscope. Note that this mode requires an additional alignment with the power splitter.

For details see the R&S FSW I/Q Analyzer and I/Q Input User Manual. Remote command:

SYSTem:COMMunicate:RDEVice:OSCilloscope:PSMode[:STATe] on page 264

Oscilloscope IP Address

When using the optional 2 GHz bandwidth extension (R&S FSW-B2000) with an R&S FSW as the connected instrument, the entire measurement, as well as both instruments, are controlled by the R&S VSE software. Thus, the instruments must be connected via LAN, and the TCPIP address of the oscilloscope must be defined in the R&S VSE software.

For tips on how to determine the computer name or TCPIP address, see the oscilloscope's user documentation.

Remote command:

SYSTem:COMMunicate:RDEVice:OSCilloscope:TCPip on page 263

Preselector State

Turns the preselector on and off. When you turn on the preselector, you can configure the characteristics of the prese-

lector and add the preamplifier into the signal path. When you turn off the preselector, the signal bypasses the preselector and the pream-

plifier, and is fed into the input mixer directly. Remote command:

INPut<ip>:PRESelection[:STATe] on page 258

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Configuring inputs and outputs

Preselector Mode

Selects the preselection filters to be applied to the measurement. "Auto"

"Auto Wide"

"Auto Narrow"

"Manual" Remote command:

INPut<ip>:PRESelection:SET on page 258

Automatically applies all available bandpass filters in a measurement. Available with the optional preamplifier.

Automatically applies the wideband filters consecutively:

●

Lowpass 40 MHz

●

Bandpass 30 MHz to 2250 MHz

●

Bandpass 2 GHz to 8 GHz

●

Bandpass 8 GHz to 26.5 GHz Available with the optional preselector. Automatically applies the most suitable narrowband preselection fil-

ters in a measurement, depending on the bandwidth you have selected. For measurement frequencies up to 30 MHz, the connected instrument uses combinations of lowpass and highpass filters. For higher frequencies, the connected instrument uses bandpass filters. Available with the optional preselector.

Applies the filter settings you have defined manually.

Configuration

10 dB Minimum Attenuation

Turns the availability of attenuation levels of less than 10 dB on and off. When you turn on this feature, the attenuation is always at least 10 dB. This minimum

attenuation protects the input mixer and avoids accidental setting of 0 dB, especially if you measure EUTs with high RFI voltage.

When you turn it off, you can also select attenuation levels of less than 10 dB. The setting applies to a manual selection of the attenuation as well as the automatic

selection of the attenuation. Remote command:

INPut<ip>:ATTenuation:PROTection:RESet on page 255

3.3.1.2 I/Q file input

Or: "Input & Output" > "Input Source" > "I/Q File"

Loading a file via drag&drop

You can load a file simply by selecting it in a file explorer and dragging it to the R&S VSE software. Drop it into the "Measurement Group Setup" window or the channel bar for any channel. The channel is automatically configured for file input, if necessary. If the file contains all essential information, the file input is immediately displayed in the channel. Otherwise, the "Recall I/Q Recording" dialog box is opened for the selected file so you can enter the missing information.

If the file contains data from multiple channels (e.g. from LTE measurements), it can be loaded to individual input sources, if the application supports them.

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Configuration

Configuring inputs and outputs

The "Input Source" settings defined in the "Input" dialog box are identical to those configured for a specific channel in the "Measurement Group Setup" window.

Encrypted .wv files can also be imported. Note, however, that traces resulting from encrypted file input cannot be exported or stored in a saveset.

Input Type (Instrument / File)........................................................................................51

Input File....................................................................................................................... 51

Zero Padding.................................................................................................................52

Input Type (Instrument / File)

Selects an instrument or a file as the type of input provided to the channel.

Note: External mixers are only available for input from a connected instrument. Note: If the R&S VSE software is installed directly on an instrument, or integrated in

Cadence®AWR®VSS, some restrictions apply on the available input type. Remote command:

INSTrument:BLOCk:CHANnel[:SETTings]:SOURce<si> on page 261 INPut<ip>:SELect on page 260

Input File

Specifies the I/Q data file to be used for input. Select "Select File" to open the "Load I/Q File" dialog box.

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Configuration

Configuring inputs and outputs

Zero Padding

Enables or disables zero padding for input from an I/Q data file that requires resampling. For resampling, a number of samples are required due to filter settling. These samples can either be taken from the provided I/Q data, or the software can add the required number of samples (zeros) at the beginning and end of the file.

If enabled, the required number of samples are inserted as zeros at the beginning and end of the file. The entire input data is analyzed. However, the additional zeros can effect the determined spectrum of the I/Q data. If zero padding is enabled, a status message is displayed.

If disabled (default), no zeros are added. The required samples for filter settling are taken from the provided I/Q data in the file. The start time in the R&S VSE Player is adapted to the actual start (after filter settling).

Note: You can activate zero padding directly when you load the file, or afterwards in the "Input Source" settings.

Remote command:

INPut<ip>:FILE:ZPADing on page 256

3.3.2 Configuring the frequency

Access: "Overview" > "Input / Output" > "Frequency"

The "Frequency" tab of the "Input / Output" dialog box contains settings to configure frequency characteristics.

The frequency settings are similar to those available in the spectrum application. For a comprehensive description of these settings, refer to the R&S VSE user manual.

The remote commands required to configure the frequency are described in Chap-

ter 5.5.4, "Configuring the frequency", on page 275.

Center Frequency......................................................................................................... 52

Center Frequency Stepsize...........................................................................................53

Frequency Offset ..........................................................................................................53

Center Frequency

Defines the frequency of the measured signal.

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Configuring inputs and outputs

The possible value range depends on the R&S VSE model you have. See the data sheet for more information about the supported frequency range.

Remote command:

[SENSe:]FREQuency:CENTer on page 275

Center Frequency Stepsize

Defines the step size by which the center frequency is increased or decreased when the arrow keys are pressed.

When you use the rotary knob the center frequency changes in steps of only 1/10 of the "Center Frequency Stepsize".

"= Center"

"Manual"

Remote command:

[SENSe:]FREQuency:CENTer:STEP on page 275

Sets the step size to the value of the center frequency and removes the coupling of the step size to span or resolution bandwidth. The used value is indicated in the "Value" field.

Defines a fixed step size for the center frequency. Enter the step size in the "Value" field.

Frequency Offset

Shifts the displayed frequency range along the x-axis by the defined offset. This parameter has no effect on the instrument's hardware, on the captured data, or on

data processing. It is simply a manipulation of the final results in which absolute frequency values are displayed. Thus, the x-axis of a spectrum display is shifted by a constant offset if it shows absolute frequencies. However, if it shows frequencies relative to the signal's center frequency, it is not shifted.

A frequency offset can be used to correct the display of a signal that is slightly distorted by the measurement setup, for example.

The allowed values range from -1 THz to 1 THz. The default setting is 0 Hz. Remote command:

[SENSe:]FREQuency:OFFSet on page 276

3.3.3 Defining level characteristics

Access: "Overview" > "Input / Output" > "Amplitude"

The "Amplitude" tab of the "Input / Output" dialog box contains settings to configure the signal level characteristics.

The level settings are the same as those available in the spectrum application. For a comprehensive description of these settings, refer to the R&S VSE user manual.

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Configuration

Configuring inputs and outputs

The remote commands required to configure the amplitude are described in Chap-

ter 5.5.5, "Defining level characteristics", on page 276.

Functions available in the "Amplitude" dialog box described elsewhere:

●

" Input Coupling " on page 47

●

" Impedance " on page 47

Reference Level ...........................................................................................................54

└ Shifting the Display ( Offset ).......................................................................... 55

Input Coupling ..............................................................................................................55

Impedance ................................................................................................................... 55

Attenuation Mode / Value ............................................................................................. 56

Using Electronic Attenuation ........................................................................................56

Reference Level

Defines the expected maximum input signal level. Signal levels above this value are possibly not measured correctly, which is indicated by the "IF Overload" status display.

Defines the expected maximum reference level. Signal levels above this value are possibly not measured correctly. Signals above the reference level are indicated by an "IF Overload" status display.

The reference level can also be used to scale power diagrams; the reference level is then used for the calculation of the maximum on the y-axis.

Since the hardware of the connected instrument is adapted according to this value, it is recommended that you set the reference level close above the expected maximum signal level. Thus you ensure an optimum measurement (no compression, good signal-tonoise ratio).

Note: Note that for input from the External Mixer (R&S VSE-B21) the maximum refer- ence level also depends on the conversion loss; see the R&S VSE base software user manual for details.

For an active external frontend, the reference level refers to the RF input at the external frontend, not the levels at the RF input of the connected instrument.

Remote command:

DISPlay[:WINDow<n>][:SUBWindow<w>]:TRACe<t>:Y[:SCALe]: RLEVel<ant> on page 276

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Configuring inputs and outputs

Shifting the Display ( Offset ) ← Reference Level

Defines an arithmetic level offset. This offset is added to the measured level. In some result displays, the scaling of the y-axis is changed accordingly.

Define an offset if the signal is attenuated or amplified before it is fed into the R&S VSE so the application shows correct power results. All displayed power level results are shifted by this value.

The reference level offset takes level offsets into account that occur after the signal has passed through the DUT (usually an amplifier). For level offsets occurring before the DUT, you can define a level offset on the signal generator from within the R&S VSEK18 user interface.

The setting range is ±200 dB in 0.01 dB steps. Note, however, that the internal reference level (used to adjust the hardware settings to

the expected signal) ignores any "Reference Level Offset" . Thus, it is important to keep in mind the actual power level the R&S VSE must handle. Do not rely on the displayed reference level (internal reference level = displayed reference level - offset).

Remote command:

DISPlay[:WINDow<n>][:SUBWindow<w>]:TRACe<t>:Y[:SCALe]: RLEVel<ant>:OFFSet on page 277

Input Coupling

The RF input of the R&S VSE can be coupled by alternating current (AC) or direct current (DC).

The RF input of the connected instrument can be coupled by alternating current (AC) or direct current (DC).

For an active external frontend, input coupling is always DC. AC coupling blocks any DC voltage from the input signal. AC coupling is activated by

default to prevent damage to the instrument. Very low frequencies in the input signal can be distorted.

However, some specifications require DC coupling. In this case, you must protect the instrument from damaging DC input voltages manually. For details, refer to the data sheet.

Remote command:

INPut<ip>:COUPling<ant> on page 256

Impedance

For some measurements, the reference impedance for the measured levels of the connected instrument can be set to 50 Ω or 75 Ω.

Remote command:

INPut<ip>:IMPedance<ant> on page 258

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Attenuation Mode / Value

The RF attenuation can be set automatically as a function of the selected reference level (Auto mode). Automatic attenuation ensures that no overload occurs at the RF Input connector for the current reference level. It is the default setting.

In "Manual" mode, you can set the RF attenuation in 1 dB steps (down to 0 dB). Other entries are rounded to the next integer value. The range is specified in the data sheet. If the defined reference level cannot be set for the defined RF attenuation, the reference level is adjusted accordingly and the warning "limit reached" is displayed.

NOTICE! Risk of hardware damage due to high power levels. When decreasing the attenuation manually, ensure that the power level does not exceed the maximum level allowed at the RF input, as an overload can lead to hardware damage.

Remote command:

INPut<ip>:ATTenuation on page 277 INPut<ip>:ATTenuation:AUTO on page 278

Using Electronic Attenuation

If the (optional) Electronic Attenuation hardware is installed on the connected instrument, you can also activate an electronic attenuator.

In "Auto" mode, the settings are defined automatically; in "Manual" mode, you can define the mechanical and electronic attenuation separately.

For an active external frontend, electronic attenuation is not available. Note: Note that restrictions can apply concerning which frequencies electronic attenua-

tion is available for, depending on which instrument is connected to the R&S VSE software. Check your instrument documentation for details. In "Auto" mode, RF attenuation is provided by the electronic attenuator as much as possible to reduce the amount of mechanical switching required. Mechanical attenuation can provide a better signal-to-noise ratio, however.

When you switch off electronic attenuation, the RF attenuation is automatically set to the same mode (auto/manual) as the electronic attenuation was set to. Thus, the RF attenuation can be set to automatic mode, and the full attenuation is provided by the mechanical attenuator, if possible.

If the defined reference level cannot be set for the given attenuation, the reference level is adjusted accordingly and the warning "limit reached" is displayed in the status bar.

Remote command:

INPut<ip>:EATT:STATe on page 279 INPut<ip>:EATT:AUTO on page 279 INPut<ip>:EATT on page 279

3.3.4 Power sensors

Access: "Overview" > "Input" > "Power Sensor" tab

A typical measurement using power sensors in the R&S VSE-K18 application is set up as shown below:

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For details on working with power sensors, see the R&S VSE User Manual.

Input and output sensors are configured individually on a separate tab.

State

.............................................................................................................................58

Apply Auto Level Correction..........................................................................................58

Select............................................................................................................................ 58

Zeroing Power Sensor ................................................................................................. 58

Frequency Manual ....................................................................................................... 59

Frequency Coupling .....................................................................................................59

Unit/Scale .....................................................................................................................59

Meas Time/Average .....................................................................................................59

Setting the Reference Level from the Measurement Meas -> Ref ...............................59

Reference Value ...........................................................................................................59

Use Ref Level Offset ....................................................................................................60

Sensor Level Offset.......................................................................................................60

Average Count ( Number of Readings )........................................................................60

Duty Cycle ....................................................................................................................60

Using the power sensor as an external trigger .............................................................60

└ External Trigger Level ....................................................................................60

└ Hysteresis ...................................................................................................... 61

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└ Trigger Holdoff ............................................................................................... 61

└ Drop-Out Time ............................................................................................... 61

└ Slope ..............................................................................................................61

State

Switches the power measurement for all power sensors on or off. Note that in addition to this general setting, each power sensor can be activated or deactivated individually by the Select setting on each tab. However, the general setting overrides the individual settings.

Apply Auto Level Correction

This function can be activated after "Auto Set Level Correction" has been used. If the input sensor is selected, the input power used to calculate the measurement

results is corrected so that it corresponds to the value measured by the input power sensor.

If the output sensor is selected, the power measured on the analyzer is corrected so that it corresponds to the value measured by the output power sensor.

Remote command:

CALCulate:PMETer:LEVel:CORRection on page 250 [SENSe:]PMETer:LEVel:CORRection:APPLy on page 249

Select

Selects the individual power sensor for usage if power measurement is generally activated ( State function).

The detected serial numbers of the power sensors connected to the instrument are provided in a selection list. For each of the four available power sensor indexes ( "Power Sensor 1" ... "Power Sensor 4" ), which correspond to the tabs in the configuration dialog, one of the detected serial numbers can be assigned. The physical sensor is thus assigned to the configuration setting for the selected power sensor index.

By default, serial numbers not yet assigned are automatically assigned to the next free power sensor index for which "Auto Assignment" is selected.

Alternatively, you can assign the sensors manually by deactivating the "Auto" option and selecting a serial number from the list.

Remote command:

[SENSe:]PMETer[:STATe] on page 249 SYSTem:COMMunicate:RDEVice:PMETer:DEFine on page 243 SYSTem:COMMunicate:RDEVice:PMETer:CONFigure:AUTO[:STATe]

on page 242

SYSTem:COMMunicate:RDEVice:PMETer:COUNt? on page 243

Zeroing Power Sensor

Starts zeroing of the power sensor. For details on the zeroing process refer to the R&S VSE User Manual. Remote command:

CALibration:PMETer:ZERO:AUTO ONCE on page 244

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Frequency Manual

Defines the frequency of the signal to be measured. The power sensor has a memory with frequency-dependent correction factors. This allows extreme accuracy for signals of a known frequency.

Remote command:

[SENSe:]PMETer:FREQuency on page 246

Frequency Coupling

Selects the coupling option. The frequency can be coupled automatically to the center frequency of the instrument or to the frequency of marker 1.

Remote command:

[SENSe:]PMETer:FREQuency:LINK on page 247

Unit/Scale

Selects the unit with which the measured power is to be displayed. Available units are dBm, dB, W and %.

If dB or % is selected, the display is relative to the reference value that is defined with either the "Meas -> Ref" setting or the "Reference Value" setting.

Remote command:

UNIT<n>:PMETer:POWer on page 251 UNIT<n>:PMETer:POWer:RATio on page 251

Meas Time/Average

Selects the measurement time or switches to manual averaging mode. In general, results are more precise with longer measurement times. The following settings are recommended for different signal types to obtain stable and precise results:

"Short"

"Normal" "Long"

"Manual"

Remote command:

[SENSe:]PMETer:MTIMe on page 247 [SENSe:]PMETer:MTIMe:AVERage[:STATe] on page 248

Setting the Reference Level from the Measurement Meas -> Ref

Sets the currently measured power as a reference value for the relative display. The reference value can also be set manually via the Reference Value setting.

Remote command:

CALCulate<n>:PMETer:RELative[:MAGNitude]:AUTO ONCE on page 245

Stationary signals with high power (> -40dBm), because they require only a short measurement time and short measurement time provides the highest repetition rates.

Signals with lower power or modulated signals Signals at the lower end of the measurement range (<-50 dBm) or

Signals with lower power to minimize the influence of noise Manual averaging mode. The average count is set with the Average

Count ( Number of Readings ) setting.

Reference Value

Defines the reference value in dBm used for relative power meter measurements.

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Remote command:

CALCulate<n>:PMETer:RELative[:MAGNitude] on page 244

Use Ref Level Offset

If deactivated, takes the Sensor Level Offset into account. Remote command:

[SENSe:]PMETer:ROFFset[:STATe] on page 248

Sensor Level Offset

Takes the specified offset into account for the measured power. Only available if Use

Ref Level Offset is disabled.

Remote command:

[SENSe:]PMETer:SOFFset on page 249

Average Count ( Number of Readings )

Defines the number of readings (averages) to be performed after a single sweep has been started. This setting is only available if manual averaging is selected ( Meas

Time/Average setting).

The values for the average count range from 0 to 256 in binary steps (1, 2, 4, 8, …). For average count = 0 or 1, one reading is performed. The general averaging and sweep count for the trace are independent from this setting.

Results become more stable with extended average, particularly if signals with low power are measured. This setting can be used to minimize the influence of noise in the power sensor measurement.

Remote command:

[SENSe:]PMETer:MTIMe:AVERage:COUNt on page 248

Duty Cycle

Sets the duty cycle to a percent value for the correction of pulse-modulated signals and activates the duty cycle correction. With the correction activated, the sensor calculates the signal pulse power from this value and the mean power.

Remote command:

[SENSe:]PMETer:DCYCle[:STATe] on page 246 [SENSe:]PMETer:DCYCle:VALue on page 246

Using the power sensor as an external trigger

If activated, the power sensor creates a trigger signal when a power higher than the defined "External Trigger Level" is measured. This trigger signal can be used as an external power trigger by the connected instrument.

This setting is only available in conjunction with a compatible power sensor. Remote command:

[SENSe:]PMETer:TRIGger[:STATe] on page 253

TRIG:SOUR PSE, see TRIGger[:SEQuence]:SOURce on page 250

External Trigger Level ← Using the power sensor as an external trigger

Defines the trigger level for the power sensor trigger. For details on supported trigger levels, see the data sheet.

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Remote command:

[SENSe:]PMETer:TRIGger:LEVel on page 253

Hysteresis ← Using the power sensor as an external trigger

Defines the distance in dB to the trigger level that the trigger source must exceed before a trigger event occurs. Setting a hysteresis avoids unwanted trigger events caused by noise oscillation around the trigger level.

Remote command:

[SENSe:]PMETer:TRIGger:HYSTeresis on page 252

Trigger Holdoff ← Using the power sensor as an external trigger

Defines the minimum time (in seconds) that must pass between two trigger events. Trigger events that occur during the holdoff time are ignored.

Remote command:

[SENSe:]PMETer:TRIGger:HOLDoff on page 252

Drop-Out Time ← Using the power sensor as an external trigger

Defines the time the input signal must stay below the trigger level before triggering again.

Slope ← Using the power sensor as an external trigger

Defines whether triggering occurs when the signal rises to the trigger level or falls down to it.

Remote command:

[SENSe:]PMETer:TRIGger:SLOPe on page 253

3.3.5 Configuring outputs

Access: "Overview" > "Input / Output" > "Output"

The "Output" tab of the "Input / Output" dialog box contains settings to configure the various signal outputs available on the R&S VSE.

The functionality is the same as in the spectrum application. For more information about the output functions, refer to the R&S VSE user manual.

3.3.6 Controlling a signal generator

Access: "Overview" > "Input / Output" > "Generator Setup"

The "Generator Setup" tab of the "Input / Output" dialog box contains settings to control the signal generator from within the R&S VSE-K18. A remote control connection between the R&S VSE and the signal generator has to be established to be able to do so.

Because a signal generator is (mostly) mandatory in the test setup, these features make measurement configuration as easy as possible. This way, you can control both analyzer and generator from within the application without having to operate the two instruments to configure the measurement.

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While generator control is active, you cannot change the connection information. When you switch on generator control while it is still active in another channel, the con-

trol is disabled in the other channel. Only one channel can control a generator at any time.

The remote commands required to configure the generator are described in Chap-

ter 5.5.6, "Controlling a signal generator", on page 282.

State of operation

Most settings have an LED that shows the state of the corresponding setting on the signal generator.

The LED is either gray, green or red:

●

Grey LED Configuration state unknown (for example when you have not yet started the transmission).

●

Green LED Configuration has been successful. Generator has been configured correctly.

●

Red LED Configuration has not been successful. Check if the connection between analyzer and generator has been established or if the IP address has been stated correctly.

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The "Generator Control" functions are activated, when a signal generator is selected in the RF generator selection box:

If no signal generator is selected ("NONE"), the "Generator Control" functions are turned off.

Generator details

The "Generator Details" contain information about the connected signal generator, like the software version or the serial number of the generator.

Updating generator settings

When you change the generator level or frequency in this dialog, the application automatically updates those settings on the generator.

When you use the "Upload All Settings To Generator" button, you can force an update of all generator settings available in this dialog box. Useful when you change the level or frequency on the generator itself. In that case, those settings remain the same in the R&S VSE-K18. To restore the original settings defined within the R&S VSE-K18, use that button to restore the generator settings.

Remote command:

CONFigure:GENerator:SETTings:UPDate on page 290

Querying generator settings

Similarly, you can transfer the current generator configuration into the amplifier application with the "Query All Settings From Generator" button.

Note that the center frequency is not updated when you attach the generator frequency to that of the R&S VSE.

Remote command:

CONFigure:SETTings on page 290

IP Address.....................................................................................................................64

RMS Level.....................................................................................................................64

Maximum DUT Input Level............................................................................................65

Attach to Analyzer Frequency.......................................................................................65

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Center Frequency......................................................................................................... 65

Reference Frequency....................................................................................................65

Path RF / BB................................................................................................................. 65

Segment........................................................................................................................65

Digital Attenuation.........................................................................................................66

RF Output......................................................................................................................66

Settling Delay................................................................................................................66

IP Address

Opens a dialog box to configure the network properties of the signal generator. You can connect to the generator either by entering its IP address ("123" button), or its

computer name ("ABC" button). If you are not sure about the IP address or computer name of your generator, check its

user interface or kindly ask your IT administrator to provide them. After you have entered IP address or computer name, use "Connect" to establish the

connection. The R&S VSE shows if the connection state, and, if the connection was successful, the connected generator type.

Remote command:

CONFigure:GENerator:CONNection:CSTate? on page 286

RMS Level

Defines the RMS level of the signal that is generated. When you define the RMS level here, the signal generator is automatically configured

to that level. In addition, you can define a level offset (for example to take external attenuation into

account). Note that the level offset is a purely mathematical value and does not change the actual level of the signal at the RF output.

The level offset takes level offsets into account that occur before the signal has passed through the DUT (usually an amplifier). For level offsets occurring after the DUT, define a level offset in the "Amplitude" menu of the signal analyzer.

You can also define a Digital Attenuation that you can use for fast output level changes.

NOTICE! Risk of damage to the DUT. RMS levels that are too high can damage or destroy the DUT.

Make sure to keep an eye on the RMS level, especially when defining a level offset. A level offset changes the displayed value of the RMS level, but not the real RMS level.

Displayed RMS level = real RMS level + level offset Thus, the actual RMS level can be higher than the displayed level.

Note: Always change the generator level from within the R&S VSE-K18 user interface and thus synchronize the levels of both instruments. If you change the generator level on the signal generator, the R&S VSE-K18 does not synchronize the levels and measurement results are going to be invalid.

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Remote command: RMS level: CONFigure:GENerator:POWer:LEVel on page 286

CONFigure:GENerator:POWer:LEVel:LEDState? on page 287

Level offset: CONFigure:GENerator:POWer:LEVel:OFFSet on page 287

CONFigure:GENerator:POWer:LEVel:OFFSet:LEDState? on page 288

Maximum DUT Input Level

Defines the maximum level that the generated signal can have. Selecting a higher level is not possible.

Defining a maximum output level is useful if you are measuring sensitive DUTs. Remote command:

CONFigure:GENerator:DUT:INPut:MAXimum:POWer on page 283 CONFigure:GENerator:DUT:INPut:MAXimum:POWer:LEDState? on page 284

Attach to Analyzer Frequency

Turns synchronization of the analyzer and generator frequency on and off. When you turn on this feature, changing the frequency on the analyzer automatically

adjusts the frequency on the generator. Remote command:

CONFigure:GENerator:FREQuency:CENTer:SYNC[:STATe] on page 285

Center Frequency

Defines the frequency of the signal that the generator transmits. When you turn on Attach to Analyzer Frequency, any changes you make to the gener-

ator frequency are also adjusted on the analyzer. Remote command:

CONFigure:GENerator:FREQuency:CENTer on page 285 CONFigure:GENerator:FREQuency:CENTer:LEDState? on page 285

Reference Frequency

Selects the source of the generator reference frequency. The internal reference is that of the signal generator itself. When you select an external

reference, you can use another frequency reference, for example that of the R&S VSE. Remote command:

CONFigure:GENerator:EXTernal:ROSCillator on page 284 CONFigure:GENerator:EXTernal:ROSCillator:LEDState? on page 284

Path RF / BB

Selects the RF signal path of the generator that is used for signal generation. Remote command:

RF path: CONFigure:GENerator:TARGet:PATH:RF on page 290 BB path: CONFigure:GENerator:TARGet:PATH:BB? on page 290

Segment

If you are using a waveform file that contains several different waveforms, you have to select the segment to transfer to the signal generator.

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Note that the segment that you have selected in the "Generator Setup" has to match the segment selected for the reference signal, regarding the signal characteristics.

Remote command:

CONFigure:GENerator:SEGMent on page 289 CONFigure:GENerator:SEGMent:LEDState? on page 289

Digital Attenuation

Attenuates or amplifies the internal, digitally modulated I/Q signal on the signal generator. The level of the RF signal is thus adjusted accordingly.

Digital attenuation allows very fast level changes of the internal I/Q signals. Note that digital attenuation only has an effect on the RF output level if the internal I/Q

modulator of the generator is active. Remote command:

CONFigure:GENerator:POWer:LEVel:ATTenuation on page 286

RF Output

Turns the RF output on the connected signal generator on and off. When you turn off the RF output, the generator does not feed a signal into the connec-

ted DUT. Remote command:

CONFigure:GENerator:RFOutput[:STATe] on page 288 CONFigure:GENerator:RFOutput:LEDState? on page 288

Settling Delay

The "Settling Delay" defines a time period between the time a parameter changes on the generator and the start of the next measurement. The R&S VSE automatically waits for the defined time period whenever one of the relevant generator settings has been changed.

Defining a delay time is especially useful for measurements that automatically change generator settings (for example the parameter sweep). The delay time considers the settling time of the generator's hardware components between individual measurements.

Remote command:

CONFigure:DUT:STIMe on page 283

3.3.7 Reference: I/Q file input

● Basics on input from I/Q data files.......................................................................... 66

● I/Q data file format (iq-tar).......................................................................................67

3.3.7.1 Basics on input from I/Q data files

The I/Q data to be evaluated in a particular R&S VSE application cannot only be captured by the application itself, it can also be loaded from a file, provided it has the correct format. The file is then used as the input source for the application.

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For example, you can capture I/Q data using the I/Q Analyzer application, store it to a file, and then analyze the signal parameters for that data later using the Pulse application (if available).

An application note on converting Rohde & Schwarz I/Q data files is available from the Rohde & Schwarz website:

1EF85: Converting R&S I/Q data files

When importing data from an I/Q data file using the import functions provided by some R&S VSE applications, the data is only stored temporarily in the capture buffer. It overwrites the current measurement data and is in turn overwritten by a new measurement. If you use an I/Q data file as input, the stored I/Q data remains available for any number of subsequent measurements. Furthermore, the (temporary) data import requires the current measurement settings in the current application to match the settings that were applied when the measurement results were stored (possibly in a different application). When the data is used as an input source, however, the data acquisition settings in the current application (attenuation, center frequency, measurement bandwidth, sample rate) can be ignored. As a result, these settings cannot be changed in the current application. Only the measurement time can be decreased, to perform measurements on an extract of the available data (from the beginning of the file) only.

For input files that contain multiple data streams from different channels, you can define which data stream to be used for the currently selected channel in the input settings.

You can define whether the data stream is used only once, or repeatedly, to create a larger amount of input data.

When using input from an I/Q data file, the [RUN SINGLE] function starts a single measurement (i.e. analysis) of the stored I/Q data, while the [RUN CONT] function repeatedly analyzes the same data from the file.

Pre-trigger and post-trigger samples

In applications that use pre-triggers or post-triggers, if no pre-trigger or post-trigger samples are specified in the I/Q data file, or too few trigger samples are provided to satisfy the requirements of the application, the missing pre- or post-trigger values are filled up with zeros. Superfluous samples in the file are dropped, if necessary. For pretrigger samples, values are filled up or omitted at the beginning of the capture buffer. For post-trigger samples, values are filled up or omitted at the end of the capture buffer.

3.3.7.2 I/Q data file format (iq-tar)

I/Q data is packed in a file with the extension .iq.tar. An iq-tar file contains I/Q data in binary format together with meta information that describes the nature and the source of data, e.g. the sample rate. The objective of the iq-tar file format is to separate I/Q data from the meta information while still having both inside one file. In addition, the file format allows you to include user-specific data and to preview the I/Q data in a web browser (not supported by all web browsers).

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The iq-tar container packs several files into a single .tar archive file. Files in .tar format can be unpacked using standard archive tools (see http://en.wikipedia.org/wiki/

Comparison_of_file_archivers) available for most operating systems. The advantage

of .tar files is that the archived files inside the .tar file are not changed (not compressed) and thus it is possible to read the I/Q data directly within the archive without the need to unpack (untar) the .tar file first.

Sample iq-tar files

Some sample iq-tar files are provided in the C:\ProgramData\Rohde-Schwarz\VSE\<version_no>\user/Demo/ directory

on the R&S VSE. These files are also available in the demo mode of the R&S VSE software.

An application note on converting Rohde & Schwarz I/Q data files is available from the Rohde & Schwarz website:

1EF85: Converting R&S I/Q data files

Contained files

An iq-tar file must contain the following files:

●

I/Q parameter XML file, e.g. xyz.xml Contains meta information about the I/Q data (e.g. sample rate). The filename can be defined freely, but there must be only one single I/Q parameter XML file inside an iq-tar file.

●

I/Q data binary file, e.g. xyz.complex.float32 Contains the binary I/Q data of all channels. There must be only one single I/Q data binary file inside an iq-tar file.

Optionally, an iq-tar file can contain the following file:

●

I/Q preview XSLT file, e.g. open_IqTar_xml_file_in_web_browser.xslt Contains a stylesheet to display the I/Q parameter XML file and a preview of the I/Q data in a web browser (not supported by all web browsers). A sample stylesheet is available at http://www.rohde-schwarz.com/file/

open_IqTar_xml_file_in_web_browser.xslt.

● I/Q parameter XML file specification....................................................................... 69

● I/Q data binary file...................................................................................................78

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I/Q parameter XML file specification

The content of the I/Q parameter XML file must comply with the XML schema RsIqTar.xsd available at: http://www.rohde-schwarz.com/file/RsIqTar.xsd.

In particular, the order of the XML elements must be respected, i.e. iq-tar uses an "ordered XML schema". For your own implementation of the iq-tar file format make sure to validate your XML file against the given schema.

The following example shows an I/Q parameter XML file. The XML elements and attributes are explained in the following sections.

Sample I/Q parameter XML file: xyz.xml

<?xml version="1.0" encoding="UTF-8"?>

<?xml-stylesheet type="text/xsl"

href="open_IqTar_xml_file_in_web_browser.xslt"?>

<RS_IQ_TAR_FileFormat fileFormatVersion="1"

xsi:noNamespaceSchemaLocation="RsIqTar.xsd"

xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"> <Name>R&S VSE</Name>

<Comment>Here is a comment</Comment>

<Format>complex</Format>

<DataType>float32</DataType>

<DataFilename>xyz.complex.float32</DataFilename>

<UserDefinedElement>Example</UserDefinedElement>

</UserData>

</RS_IQ_TAR_FileFormat>

Minimum data elements

The following data elements are the minimum required for a valid iq-tar file. They are always provided by an iq-tar file export from a Rohde & Schwarz product. If not specified otherwise, it must be available in all iq-tar files used to import data to a Rohde & Schwarz product.

Element Possible Values Description

<RS_IQ_TAR_FileFormat>

<Name>

- The root element of the XML file. It must contain the attribute fileFormatVersion that contains the number of the file format definition.

string Optional: describes the device or application that created the file.

string Optional: contains text that further describes the contents of the

file.

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<Clock>

yyyy-mm-ddThh:mm:ss Contains the date and time of the creation of the file. Its type is

xs:dateTime (see RsIqTar.xsd).

integer Contains the number of samples of the I/Q data. For multi-chan-

nel signals all channels have the same number of samples. One sample can be:

●

A complex number represented as a pair of I and Q values

●

A complex number represented as a pair of magnitude and phase values

●

A real number represented as a single real value

User-defined data elements

You can insert additional user, application or device-specific XML data that is not part of the iq-tar specification in the <UserData> element. User data must be valid XML content.

Rohde & Schwarz products use this element to import and export application-specific data. While some elements are mandatory in order to import the iq-tar file to the product, others are optional.

The subelements within the <UserData> element provided by the Rohde & Schwarz products are <DataImportExport_MandatoryData> and <DataImportExport_OptionalData>. To import an iq-tar file to the R&S VSE software, either both of these elements or none of them must be provided.

Mandatory data elements

The following information is always provided by an iq-tar file export from Rohde & Schwarz products. It is contained in the <DataImportExport_MandatoryData> element. It must be available in all iq-tar files used to import data to the R&S VSE software if optional data is included (see

"Optional data elements" on page 72).

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Table 3-2: Subelements of <DataImportExport_MandatoryData>

Element Name Possible Values Description

String Channel name in R&S VSE software

Double Center frequency of captured I/Q data

Mapping of channels in iq-tar file to channel names in R&S VSE software.

CH_1 = first <ChannelName>

CH_2 = second <ChannelName>

... CH_n = last <ChannelName>

Optional data elements

Optionally, the following information can be provided in iq-tar files used to import data to Rohde & Schwarz products. This information can also be provided by an iq-tar file export from the R&S VSE software, if selected. Note that the available information during data export depends on the connected instrument.

Optional information is contained in the <DataImportExport_OptionalData> element. If this element is included in the <UserData> element, the <DataImportExport_MandatoryData> element must also be included (see "Man-

datory data elements" on page 71).

Optional data is included in <Key> subelements with a specific name attribute. Keys for an individual channel are provided together, i.e. first all keys for CH_1, then all keys for CH_2 etc. The channel index is provided as a prefix for the key name attribute and corresponds to the mapping defined in the <ChannelNames> in <DataImportExport_MandatoryData> (see "Mandatory data elements" on page 71).

Table 3-3: Possible information in <DataImportExport_OptionalData>

<Key> element name attribute Possible Values

Ch<n>_RefLevel[dBm] Double

Ch<n>_RefLevelOffset[dB] Double

Ch<n>_AttenuMech[dB] Integer

Ch<n>_AttenuElecState ON | OFF

Ch<n>_AttenuElecValue[dB] Integer

Ch<n>_PreampState ON | OFF

Ch<n>_PreampGain[dB] Integer

Ch<n>_PreSelectorState ON | OFF

(R&S FSWT only)

Ch<n>_PreSelectorType NARROW | WIDE

(R&S FSWT only)

Ch<n>_Impedance[Ohm] 50 | 75

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<Key> element name attribute Possible Values

Ch<n>_InputCoupling AC | DC

Ch<n>_DeviceId String

Ch<n>_DeviceOptions String

Ch<n>_DeviceHwInfo String

Ch<n>_DeviceVersions String

Ch<n>_CalibrationState ON | OFF

Ch<n>_RefOscillatorInput OFF | ON

Ch<n>_RefOscillatorFreq[Hz] Double

Ch<n>_InputPath RF

Ch<n>_InputSelection INPUT1 | INPUT2

(R&S FSWT only)

Ch<n>_HighPassFilterState ON | OFF

Ch<n>_YigPreSelectorState ON | OFF

Ch<n>_ExtMixerState ON | OFF

Ch<n>_MeasBandwidth[Hz] Double

Ch<n>_FilterSettings FLAT | GAUSS | OFF

Ch<n>_TrgSource Extern <1 ..4> | I/Q Power | IF Power | RF Power |

Power Sensor | Time

Ch<n>_TrgLevel[dB] Double

Ch<n>_TrgHysteresis[dB] Double

Ch<n>_TrgTpis[s] Double

Ch<n>_TrgOffset[s] Double

Ch<n>_TrgSlope Rising | Falling | Rising/Falling

Ch<n>_TrgHoldoff[s] Double

Ch<n>_TrgDropOut[s] Double

Ch<n>_NumberOfPostSamples Integer

Ch<n>_NumberOfPreSamples Integer

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Example: Example for <DataImportExport_OptionalData>

<DataImportExport_OptionalData>

<Key name="Ch1_DeviceId">Rohde-Schwarz,RTP,1320.5007k08/101011,4.15.1.0</Key>

<Key name="Ch2_DeviceId">Rohde-Schwarz,RTP,1320.5007k08/101011,4.15.1.0</Key>

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</DataImportExport_OptionalData>

Example: userdata for I/Q recordings by R&S VSE software

<DataImportExport_MandatoryData>

</DataImportExport_MandatoryData>

<DataImportExport_OptionalData>

<Key name="Ch1_DeviceId">string</Key>

<Key name="Ch1_DeviceOptions">string</Key>

<Key name="Ch1_DeviceHwInfo">string</Key>

<Key name="Ch1_DeviceVersions">string</Key>

<Key name="Ch1_DeviceHwInfo">string</Key>

<Key name="Ch1_FilterSettings">FLAT | GAUSS | OFF</Key>

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<Key name="Ch1_TrgSlope">Rising | Falling</Key>

</DataImportExport_OptionalData>

</RohdeSchwarz>

</UserData>

Example

The following example demonstrates the XML description inside the iq-tar file. Note that this preview is not supported by all web browsers.

Open the xml file in a web browser, e.g. Microsoft Internet Explorer. If the stylesheet open_IqTar_xml_file_in_web_browser.xslt is in the same directory, the web browser displays the xml file in a readable format.

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<?xml version="1.0" encoding="UTF-8"?>

<?xml-stylesheet type="text/xsl" href="open_IqTar_xml_file_in_web_browser.xslt"?>

<RS_IQ_TAR_FileFormat fileFormatVersion="1" xsi:noNamespaceSchemaLocation=

"http://www.rohde-schwarz.com/file/RsIqTar.xsd" xmlns:xsi=

"http://www.w3.org/2001/XMLSchema-instance">

<Format>complex</Format>

<DataType>float32</DataType>

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<DataFilename>File.complex.1ch.float32</DataFilename>

<DataImportExport_MandatoryData>

<ChannelName>IQ Analyzer</ChannelName>

</ChannelNames>

</DataImportExport_MandatoryData>

<DataImportExport_OptionalData>

</DataImportExport_OptionalData>

</RohdeSchwarz>

</UserData>

</RS_IQ_TAR_FileFormat>

Example: ScalingFactor

Data stored as int16 and a desired full scale voltage of 1 V ScalingFactor = 1 V / maximum int16 value = 1 V / 215 = 3.0517578125e-5 V

Scaling Factor Numerical value Numerical value x ScalingFac-

tor

Minimum (negative) int16 value

Maximum (positive) int16 value

- 215 = - 32768

215-1= 32767

-1 V

0.999969482421875 V

I/Q data binary file

The I/Q data is saved in binary format according to the format and data type specified in the XML file (see <Format> element and <DataType> element). To allow reading and writing of streamed I/Q data, all data is interleaved, i.e. complex values are interleaved pairs of I and Q values and multi-channel signals contain interleaved (complex) samples for channel 0, channel 1, channel 2 etc. If the <NumberOfChannels> element is not defined, one channel is presumed.

Example: Element order for real data (1 channel)

I[0], // Real sample 0

I[1], // Real sample 1

I[2], // Real sample 2

...

Example: Element order for complex cartesian data (1 channel)

I[0], Q[0], // Real and imaginary part of complex sample 0

I[1], Q[1], // Real and imaginary part of complex sample 1

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I[2], Q[2], // Real and imaginary part of complex sample 2

...

Example: Element order for complex polar data (1 channel)

Mag[0], Phi[0], // Magnitude and phase part of complex sample 0

Mag[1], Phi[1], // Magnitude and phase part of complex sample 1

Mag[2], Phi[2], // Magnitude and phase part of complex sample 2

...

Example: Element order for complex cartesian data (3 channels)

Complex data: I[channel no][time index], Q[channel no][time index]

I[0][0], Q[0][0], // Channel 0, Complex sample 0

I[1][0], Q[1][0], // Channel 1, Complex sample 0

I[2][0], Q[2][0], // Channel 2, Complex sample 0

I[0][1], Q[0][1], // Channel 0, Complex sample 1

I[1][1], Q[1][1], // Channel 1, Complex sample 1

I[2][1], Q[2][1], // Channel 2, Complex sample 1

I[0][2], Q[0][2], // Channel 0, Complex sample 2

I[1][2], Q[1][2], // Channel 1, Complex sample 2

I[2][2], Q[2][2], // Channel 2, Complex sample 2

...

Example: Element order for complex cartesian data (1 channel)

This example demonstrates how to store complex cartesian data in float32 format using MATLAB®.

% Save vector of complex cartesian I/Q data, i.e. iqiqiq...

N = 100

iq = randn(1,N)+1j*randn(1,N)

fid = fopen('xyz.complex.float32','w');

for k=1:length(iq)

fwrite(fid,single(real(iq(k))),'float32');

fwrite(fid,single(imag(iq(k))),'float32');

end

fclose(fid)

Example: PreviewData in XML

<Min>

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...

</ArrayOfFloat>

</Min>

<Max>

...

</ArrayOfFloat>

</Max>

</PowerVsTime>

<Min>

...

</ArrayOfFloat>

</Min>

<Max>

...

</ArrayOfFloat>

</Max>

</Spectrum>

<IQ>

</IQ>

</Channel>

</ArrayOfChannel>

</PreviewData>

3.4 Triggering measurements

Access: "Overview" > "Trigger"

The R&S VSE-K18 provides functionality to trigger measurements.

The "Trigger" dialog box contains settings to configure triggered measurements.

The following trigger sources are supported:

●

Free Run

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3.5 Configuring the data capture

Configuration

Configuring the data capture

●

External

●

I/Q Power

●

IF Power

●

RF Power

●

Time If the time trigger is used, the R&S VSE automatically sets the repetition interval to match the length of the reference file. "Auto Time Trigger" sets the trigger offset to the current trigger to sync (TTS) value.

The trigger settings are similar to those in the spectrum application. For a comprehensive description of the trigger functionality, refer to the R&S VSE user manual.

Access: "Overview" > "Data Acquisition"

The "Data Acquisition" dialog box contains settings to configure the process of how the application records the signal.

The remote commands required to configure the data capture are described in Chap-

ter 5.5.7, "Configuring the data capture", on page 291.

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Configuring the data capture

Configuring the measurement bandwidth..................................................................... 82

└ Automatic adjustment..................................................................................... 82

└ Manual definition.............................................................................................82

└ Maximum bandwidth.......................................................................................82

Configuring the measurement time...............................................................................83

└ Automatic adjustment..................................................................................... 83

└ Manual definition.............................................................................................83

Inverting the I/Q branches.............................................................................................84

Defining the resolution bandwidth for spectrum measurements................................... 84

Configuring the measurement bandwidth

The sample rate defined for data acquisition is the sample rate with which the analyzer samples the amplified signal.

The measurement bandwidth defines the flat, usable bandwidth of the final I/Q data. The application allows you to adjust both values automatically or manually.

Automatic adjustment ← Configuring the measurement bandwidth

When you select automatic adjustment of sample rate and measurement bandwidth, the application selects a bandwidth that is appropriate for the characteristics of the reference signal and adjusts the sample rate accordingly.

For more information about the reference signal, see Chapter 3.2, "Designing a refer-

ence signal", on page 35.

Remote command: Mode: TRACe:IQ:SRATe:AUTO on page 294

Manual definition ← Configuring the measurement bandwidth

When you define the sample rate and measurement bandwidth manually, you can select values that you are comfortable with. Because the bandwidth is a function of the sample rate (and vice versa), the application adjusts the values when you change either setting.

The following dependencies apply:

●

When you change the sample rate, the application updates the bandwidth accordingly (and vice versa). It also adjusts the capture length to the new values. The capture time remains the same.

●

When you change the capture time or capture length, the sample rate and bandwidth remain the same.

Remote command: Sample Rate: TRACe:IQ:SRATe on page 294 Bandwidth: TRACe:IQ:BWIDth on page 294

Maximum bandwidth ← Configuring the measurement bandwidth

The maximum bandwidth you can use depends on your hardware configuration. For an overview of available bandwidth extensions, refer to the datasheet.

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By default, the application automatically determines the maximum bandwidth. When you select a maximum bandwidth other than "Auto", the bandwidth is restricted to that value. When you select the maximum bandwidth manually, make sure that this bandwidth is suited for the signal you are testing. Otherwise, the signal can be distorted and results are no longer valid.

If you have no bandwidth extension this setting is not available. For more information about the maximum bandwidth, refer to the user manual of the

R&S VSE I/Q Analyzer. Remote command:

TRACe:IQ:WBANd[:STATe] on page 295 TRACe:IQ:WBANd:MBWidth on page 295

Configuring the measurement time

The measurement time (or capture time) defines the duration of a measurement in which the required number of samples is collected.

The capture length is the number of samples that are captured during the selected measurement time. The capture length is a function of the sample rate and the capture time.

Automatic adjustment ← Configuring the measurement time

When you select automatic adjustment of capture time, the application selects a capture time that is appropriate for the characteristics of the reference signal.

As orientation, the application shows the length of the reference signal in the corresponding field in the dialog box (➙ "Ref Signal Duration").

For more information about the reference signal, see Chapter 3.2, "Designing a refer-

ence signal", on page 35.

Remote command: Mode: [SENSe:]SWEep:TIME:AUTO on page 293 Reference signal: [SENSe:]REFSig:TIME? on page 292

Manual definition ← Configuring the measurement time

When you define the capture length and time manually, you can select values that you are comfortable with.

However, make sure to define a capture time that is greater than the length of the reference signal - otherwise the application is not able to analyze the signal correctly.

The following dependencies apply:

●

When you change the capture time, the application updates the capture length accordingly (and vice versa). Sample rate and bandwidth remain the same.

●

When you change the sample rate or bandwidth, the application updates the cap-

ture length accordingly. The capture time remains the same. Note that the maximum capture time depends on the current measurement bandwidth. Remote command:

Time: [SENSe:]SWEep:TIME on page 293 Capture length: [SENSe:]SWEep:LENGth on page 293

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Sweep configuration

Inverting the I/Q branches

The application allows you to swap the I and Q branches of the signal. Swapping the branches is useful, for example, when the DUT inverts the real (I) and

imaginary (Q) parts of the signal and transfers the signal that way. Note that the sideband is also inverted when you turn on this feature. Remote command:

[SENSe:]SWAPiq on page 292

Defining the resolution bandwidth for spectrum measurements

The resolution bandwidth (RBW) defines the bandwidth of the resolution filter applied to spectrum measurements (like the "Spectrum FFT" result).

The "RBW Mode" selects whether the application automatically selects a suitable resolution bandwidth based on the signal you are measuring, or if you define the resolution bandwidth manually. When you select manual definition of the RBW (for example when you want to do a measurement according to a certain telecommunications standard), you can enter the bandwidth in the "RBW" field.

The amplifier measurement application supports any bandwidth between 1 Hz and 10 MHz.

Remote command:

[SENSe:]BANDwidth[:RESolution]:AUTO on page 292 [SENSe:]BANDwidth[:RESolution] on page 292

3.6 Sweep configuration

Access: "Overview" > "Data Acquisition" > "Sweep"

The "Sweep" dialog box contains settings to configure the characteristics of a single data recording (a sweep).

The remote commands required to configure the sweep are described in Chap-

ter 5.5.8, "Sweep configuration", on page 296.

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Sweep configuration

Statistics State.............................................................................................................. 85

Statistics Mode..............................................................................................................85

Continuous Statistics.....................................................................................................85

Statistics Count............................................................................................................. 85

Select Result Rng......................................................................................................... 85

Statistics State

Turns the sweep statistics calculation on and off. Remote command:

[SENSe:]SWEep:STATistics[:STATe] on page 297

Statistics Mode

Sets the statistics mode. If I/Q averaging is selected, the IQ data is averaged over several data captures after

synchronization to the reference file. This leads to a significant noise reduction. Be aware that I/Q averaging is only possible for synchronized parts of the captured signal, because it only makes sense if the same samples in the I/Q data stream are averaged. Therefore, make sure that the measurement is synchronized. Otherwise, the results would be invalid.

If trace statistics is selected, multiple frames are measured to create a graphical or scalar statistics result.

Remote command:

[SENSe:]SWEep:STATistics:MODE on page 298

Continuous Statistics

If continuous statistics is enabled, it does not reset the results when the average count is through. Instead, it continues to average the data. The continuous statistics setting only has an effect in continuous sweep mode.

If continuous statistics is turned off, averaging starts again from "0" after the defined

statistics count is reached.

Remote command:

[SENSe:]SWEep:STATistics:CONTinuous[:STATe] on page 297

Statistics Count

Defines the number of single data captures the application uses to average the data. Remote command:

[SENSe:]SWEep:STATistics:COUNt on page 297

Select Result Rng

Sets the result range. Remote command:

CONFigure:RESult:RANGe[:SELected] on page 298

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3.7 Synchronizing measurement data

Configuration

Synchronizing measurement data

Access: "Overview" > "Sync / Error Est / Comp" > "Sync and Eval Range" > "Synchronization"

The application allows you to synchronize the measured signal with the reference signal and provides various features to control synchronization.

Synchronization consists of signal estimation and compensation. After the application has detected the position of the reference signal in the capture buffer, it estimates possible errors in the measured signal (for example the sample error rate or the amplitude droop) by comparing it to the reference signal. The estimated errors can optionally be compensated for.

The remote commands required to configure signal synchronization are described in

Chapter 5.5.9, "Synchronizing measurement data", on page 298.

Turning synchronization of reference and measured signal on and off.........................86

Selecting the synchronization method.......................................................................... 87

Defining a synchronization confidence level................................................................. 87

Defining the estimation range....................................................................................... 88

Turning synchronization of reference and measured signal on and off

During measurements, the application tries to synchronize the measured signal with the reference signal. When no significant correlation between the measured and reference signal can be found, synchronization fails.

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Synchronizing measurement data

However, you can turn off synchronization if you would like to run unsynchronized measurements. Note however, that the calculation of some results in the result summary requires synchronization. These results cannot be calculated when you turn off synchronization.

When you turn off synchronization, the results are always calculated over the complete capture buffer. When synchronization is on, the results are always calculated over the synchronized data range of the capture buffer. Therefore, the result values can be different for unsynchronized measurements, even if you measure the same signal (the result is still valid and correct, though).

Failed synchronization

When you turn on "Stop on Sync Failed", the application automatically aborts the measurement, in case synchronization fails.

Remote command:

CONFigure:SYNC:STAT on page 301 CONFigure:SYNC:SOFail on page 300

Selecting the synchronization method

The application allows you to select the method with which the application synchronizes the signals with the "Synchronization Mode" parameter. The following methods are available.

●

I/Q Direct

The I/Q data for the reference signal is directly correlated with the reference and

measured signal. The performance of this method degrades in the presence of a

frequency offset between the measured and reference signals.

●

I/Q Phase Difference

Correlation on the phase differentiated I/Q data. This method retains phase change

information and can handle a frequency offset , but is more sensitive to noise than

the "I/Q Direct" method.

●

I/Q Magnitude

Correlation on the magnitude of the I/Q data with no regard for phase information.

This method can handle a frequency offset and is less sensitive to noise that the

"I/Q Phase Difference" method, but is only useful with amplitude modulated sig-

nals.

●

Trigger

It is assumed that the capture is triggered at the start of the reference waveform.

Only minimal correlation is performed to account for trigger jitter. This method is the

fastest synchronization method. Remote command:

CONFigure:SYNC:DOMain on page 300

Defining a synchronization confidence level

The synchronization confidence level ("Sync Confidence") is a percentage that describes how similar (or correlated) reference and measured signal need to be in order for synchronization to be successful.

A value of 0 % means that synchronization is always successful even if the signals are not correlated at all. However, results that rely on a good synchronization (like the EVM) do contain reasonable values in that case. A value of 100 % means that the signals are identical (in that they are linearly dependent).

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Evaluating measurement data

The cross-correlation is calculated over all samples in the capture buffer (or the estimation range, if you have defined one).

When the cross-correlation coefficient falls below the confidence level you have defined, synchronization is no longer successful.

Remote command:

CONFigure:SYNC:CONFidence on page 300

Defining the estimation range

The estimation range has several effects on the synchronization process.

●

It defines which part of the reference signal is used for cross-correlation within the

capture buffer in order to align the reference and measured signals.

●

It defines which part of the reference signal is used for error estimation. By default, the application estimates over the complete reference signal. However, you

can also estimate over a given range in the capture buffer only. In that case, turn off the "Use Full Ref Signal" feature. When you are not using the full reference signal, the "Eval Start" and "Eval Stop" fields become available. The allowed values are offsets relative to the beginning of the capture buffer (0 s). The highest offset possible depends on the size of the capture buffer.

Defining an estimation range is useful in the following cases.

●

If you want to limit the estimation to a specific part of the signal, for example if the

signal contains a preamble or midamble.

●

If you want to limit the estimation to the ON part of a TDD signal.

●

If you want to increase the measurement speed for relatively long signals, for

example an LTE signal. On the downside, limiting the estimation range leads to a higher empirical variance of

the results. In the preview pane displayed in the dialog box, the currently defined estimation range

is represented by two red vertical lines. Tip: You can also use the touchscreen to move the lines to a new position in the pre-

view pane. However, this way is not as accurate as entering a number into the input field.

Remote command:

CONFigure:ESTimation:FULL on page 298 CONFigure:ESTimation:STARt on page 299 CONFigure:ESTimation:STOP on page 299

3.8 Evaluating measurement data

Access: "Overview" > "Sync / Error Est / Comp" > "Sync and Eval Range" > "Eval

Range"

The application allows you to define the time frame in the reference signal used to evaluate and calculate the measurement results.

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Evaluating measurement data

The remote commands required to configure signal evaluation are described in Chap-

ter 5.5.10, "Defining the evaluation range", on page 301.

Defining the evaluation range....................................................................................... 89

Defining the evaluation range

The evaluation range defines the data range in the capture buffer over which the application calculates the measurement results.

By default, the application calculates the results over the complete capture buffer. If synchronization has been successful, the application calculates the results over the capture buffer range in which the reference signal has been found. If you have turned off synchronization or if it has not been successful, the complete capture buffer is used to calculate the remaining results.

Example:

The capture buffer is 30 ms long, the reference signal starts at 9 ms and is 10 ms long. When synchronization is successful, the evaluation range starts at 9 ms and ends at 19 ms. If synchronization has been turned off, the evaluation range is the full capture buffer.

However, you can also select a particular data range within the reference signal. In that case, turn off the "Use Full Ref Signal" feature. When it is off, the "Eval Start" and "Eval Stop" fields become available. The allowed values are offsets relative to the beginning of the reference signal (0 s). The highest offset possible depends on the length of the reference signal.

Example:

The situation is as described above (30 ms capture buffer, 10 ms reference signal). Let's say you want to evaluate milliseconds 2 to 6 of the reference signal. In that case, you would have to define a start offset of 11 ms (the reference signal starts at 9 ms, plus the first 2 ms you are not interested in = 11 ms) and a stop offset of 15 ms (9 ms + 6 ms).

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3.9 Estimating and compensating signal errors

Configuration

Estimating and compensating signal errors

In the preview pane displayed in the dialog box, the currently defined evaluation range is represented by two blue vertical lines.

Tip: You can also use the touchscreen to move the lines to a new position in the preview pane. However, this way is not as accurate as entering a number into the input field.

Remote command:

CONFigure:EVALuation:FULL on page 301 CONFigure:EVALuation:STARt on page 302 CONFigure:EVALuation:STOP on page 303

Access: "Overview" > "Sync / Error Est / Comp" > "Error Est / Compensation"

The application allows you to estimate possible undesired effects in the signal, and, if there are any, also compensate these effects.

The remote commands required to configure error compensation and equalization are described in Chapter 5.5.11, "Estimating and compensating signal errors", on page 303.

Estimation and compensation

When you turn on error estimation only, the results are not compensated for the corresponding errors.

When you turn on error compensation, the displayed results are also corrected by the estimated errors. Note that in that case, the signal might look better than it actually is.

Compensation without estimation is not possible.

Generally, it is recommended to switch off the estimation of a certain parameter if it is not existent. E.g., if generator and analyzer are frequency locked, it is recommended to switch off the frequency error estimation. Furthermore sample rate error estimation can be switched off if the frequency locked generator is a vector signal generator, i.e. includes the DAC.

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3.10 Equalizer

Configuration

Equalizer

You can estimate and compensate the following effects:

●

I/Q Imbalance: combined effect of amplitude and phase error.

●

I/Q Offset: shift of the constellation points in a particular direction.

●

Frequency Error: difference between measured and reference center frequency.

●

Amplitude Droop: decrease of the signal power over time in the transmitter.

●

Sample Error Rate: difference between the sample rate of the reference signal

and the measured signal.

In addition, the amplifier application provides equalizer functionality. The equalizer corrects distortions in the frequency characteristics during the transmission of the signal. It can thus help to faithfully reproduce the input signal at the amplifier output.

Using the equalizer

Using the equalizer requires a description of the equalizer filter. You can either train (and save) such a filter automatically with the R&S VSE, or use one that you already have.

Training (or creating) the equalizer filter is a process in which the R&S VSE compares the frequency response of the input and output signal and equalizes potential distortion. The goal is to match the frequency response of the output signal and the input signal. The R&S VSE is able to train the filter based on all samples in the evaluation range.

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Configuration

Applying system models

The "Equalizer Filter Length For Training" property defines the number of FIR filter coefficients to be calculated. A larger number of samples generally yields better results, but takes longer to calculate. After you have defined the filter length (coefficients), you can start the training sequence with the "Train Equalizer Filter on Current I/Q Data" feature. To apply the filter, turn on the equalizer with the "Equalizer State" toggle.

Note that the reference and measured signal need to be synchronized for a successful filter training. Make sure to turn on signal synchronization before you train a filter.

When the filter training is done, you can save the filter in a csv or a fres file (➙ "Save Equalizer").

For more information about the fres file format, refer to the R&S VSE user manual. If you want to use an equalizer filter that you already have from a previous measure-

ment, you can restore that filter (➙ "Load Equalizer Filter") and apply it without a training sequence.

The dialog box also shows the information about the filter file that is currently in use. This information includes the file name, the date it was modified last and the length of the filter (in samples).

Note: Any equalizer filter is only valid for the sample rate it has been trained for. If you change the sample rate when an equalizer filter is active, the R&S VSE automatically turns off the equalizer filter. If you still want to use an equalizer filter with the new sample rate, you have to train and apply the equalizer filter again.

Note: An I/Q data export always exports the unequalized (raw) data. If you want to export the equalized data, you can do so with the following SCPI command.

TRACe:IQ:EQUalized? on page 226

Remote command: Filter length: CONFigure:EQUalizer:FILTer:LENGth on page 306 Start training: CONFigure:EQUalizer:TRAin on page 307 Store filter: MMEMory:STORe<n>:EQUalizer:FILTer:COEFficient on page 308 File format: CONFigure:EQUalizer:FILTer:FILE:FORMat on page 306 Restore filter: MMEMory:LOAD:EQUalizer:FILTer:COEFficient on page 308 Equalizer state: CONFigure:EQUalizer[:STATe] on page 307 Manual filter definition: CONFigure:EQUalizer:FPARameters on page 307

3.11 Applying system models

Access: "Overview" > "Measurement" > "Modeling"

A polynomial model describes the characteristics of the DUT based on the input signal and the output signal of the amplifier.

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Applying system models

The remote commands required to configure system models are described in Chap-

ter 5.5.12, "Applying a system model", on page 308.

Turning system modeling on and off.............................................................................93

Selecting the degree of the polynomial.........................................................................94

Defining the modeling range......................................................................................... 94

Selecting the modeling scale........................................................................................ 95

Turning system modeling on and off

You can use the system modeling functionality to calculate a mathematical model that describes the properties of the DUT.

Using a model is useful to observe and estimate the behavior of the amplifier and, if necessary, adjust the DUT behavior. The application supports memory-free polynomial models to the 18th degree.

The following diagrams contain traces that show the model. These traces are calculated by using the model function on the reference signal.

●

"AM/AM"

●

"AM/PM" Note that the model traces are also the basis for the DPD functionality available in the

R&S VSE-K18. When the characteristics of the modeled signal match those of the measured signal,

the model describes the DUT behavior well. If not, you can try to get a better result by adjusting the model properties.

When you turn on modeling, the application shows an additional trace in the graphical result displays. This trace corresponds to the signal characteristics after the model has been applied to the reference signal.

Selecting the modeling sequence

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Configuration

Applying system models

The modeling sequence selects the sequence in which the models are calculated. The application then either calculates the "AM/AM" model before calculating the "AM/PM" model (default), or vice versa.

Remote command:

CONFigure:MODeling[:STATe] on page 310 CONFigure:MODeling:SEQuence on page 310

Selecting the degree of the polynomial

In addition to the type of curve, you can also select the order of the polynomial model. The order of the model defines the degree, complexity and number of terms in the pol-

ynomial model. In general, a polynomial of the Nth degree looks like this: y = a0 + a1x + a2x2 + … + aNx

The degree of the model is defined by N (as an index or exponent). The higher the order, the more complex the calculation and the longer it takes to calculate the model. Higher models do not necessarily lead to better fitting model curves.

Note that the nonlinear effects consume an additional bandwidth proportional to 2 times the number of odd factors in the polynomial, excluding the linear one.

Example:

If the signal bandwidth is 1 MHz and the highest degree is 5, the bandwidth of the resulting signal is increased by 2 times 2 (because there are the variables a3 and a5)

times 1 MHz which are 4 MHz. This leads to a total signal bandwidth of 5 MHz (1 MHz + 4 MHz). The configured recording bandwidth must be at least 5 MHz to record all nonlinear effects generated by the DUT.

Tip: To select a specific subset of polynomial degrees you want to apply, you can either:

●

Define a range of degrees (e.g. "0 - 5", in that case the application applies all

degrees in that range).

●

Define a set of individual degrees only (e.g. "1;3;5;7", in that case the application

applies those degrees only). Note that the "." key on the front panel draws the ";"

character.

●

Define a combination of the methods mentioned above (e.g. "1;3;5-7")

Remote command: "AM/AM": CONFigure:MODeling:AMAM:ORDer on page 308 "AM/PM": CONFigure:MODeling:AMPM:ORDer on page 309

Defining the modeling range

The modeling range defines the part of the signal that the model is applied to. When you limit the level range that the model is applied to, only samples with levels

between peak level and "peak level minus modeling level range value" are used during the model calculation. Note that the modeling range is also the range the DPD is applied to.

You can also define a smaller or larger modeling level range. Make sure, however, that the range is large enough not to distort the model.

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Applying digital predistortion

In addition, you can define the number of points on the curve that the application uses to calculate the model. The selected points are spaced equidistant on a logarithmic scale (an equidistant spacing on a linear scale is also possible if you prefer that). Using fewer modeling points further speeds up measurement times (but can reduce the quality of the model if set too low).

Remote command: Range: CONFigure:MODeling:LRANge on page 309 Points: CONFigure:MODeling:NPOints on page 309

Selecting the modeling scale

The input power range is split into several equally spaced subranges (= modeling points) for the calculation of the amplifier model.

With the "Modeling Scale", you can select whether the split is done on a logarithmic or linear basis.

Remote command:

CONFigure:MODeling:SCALe on page 310

3.12 Applying digital predistortion

Access: "Overview" > "Measurement" > "DPD"

Digital predistortion (DPD) is a method to improve the linearity of an RF power amplifier. Basically, DPD is a set of correction values that is added to the input signal to compensate the non-linearities that occur in the amplifier. The output signal measured by the R&S VSE then shows the corrected amplifier characteristics.

You can compensate non-linearities with the functionality of the amplifier application. The application provides two compensation methods: polynomial DPD and direct DPD.

Note that you can only use one of the two DPD types at any time. When you turn on the polynomial DPD, the R&S VSE automatically turns off the direct DPD and vice versa.

Using the DPD functionality requires a connection to a signal generator. For more information about configuring generators, see Chapter 3.3.6, "Controlling a signal genera-

tor", on page 61.

Remote command:

CONFigure:DDPD[:STATe] on page 315

● Polynomial DPD......................................................................................................96

● Direct DPD (R&S VSE-K18D).................................................................................98

● Memory polynomial DPD (R&S VSE-K18M).........................................................103

● Hammerstein model (R&S VSE-K18M)................................................................ 105

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3.12.1 Polynomial DPD

Configuration

Applying digital predistortion

For polynomial DPD, the application calculates the correction values based on a polynomial function, whose characteristics you can define with the settings available for the

system models. The polynomial DPD approach used by the R&S VSE compensates

for "AM/AM" (amplitude-to-amplitude) distortion and "AM/PM" (amplitude-to-phase) distortion.

When you apply the DPD, the correction values are applied to the input signal to improve the linearity of the amplifier.

The remote commands required to configure the polynomial DPD are described in

Chapter 5.5.13, "Applying digital predistortion", on page 311.

Selecting the DPD method............................................................................................96

Selecting the DPD shaping method.............................................................................. 97

Polynomial DPD Power / Linearity Tradeoff..................................................................97

Selecting the order of model calculation....................................................................... 98

Selecting the DPD method

The amplifier application provides a couple of DPD calculation methods.

●

"Use Generator DPD Option K541"

The signal generator corrects the input signal in real time.

This method requires a Rohde & Schwarz signal generator equipped with option

R&S SMx-K541.

The source of the predistortion values is either a table or a polynomial function.

After a successful measurement, you can apply the predistortion values that were

calculated by the R&S VSE with the "Update" button. (The button is only available

when data has been captured on the R&S VSE and synchronization was success-

ful).

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Note that you have to turn on the DPD model in order to make the DPD work.

As long as you use the same amplifier, the polynomial DPD calculated with this

method is valid for all signals that use a similar bandwidth and frequency as the

signal it was calculated for.

●

"Generate Pre-Distorted Waveform File"

The R&S VSE applies the correction values taken from the table or polynomial

function to each measured sample and generates a waveform file that contains the

corrected input signal. For TDD and FDD signals, we recommend that you use the

full reference signal to generate the DPD.

You can start the DPD calculation and transfer the resulting waveform file to the

connected generator with the "Generate and Load" button. Successful calculation

and transfer are indicated by a green LED. Note that you have to turn on the DPD

model in order to make the DPD work.

Note:

When you use this method, the predistortion information only applies to the cur-

rently selected reference signal and generator level. When you change the refer-

ence signal or generator level, you have to create a file that applies to the new ref-

erence signal.

You can also save the predistorted waveform into a waveform file with the "Store

Pre-Distorted Waveform File" feature for later reference. Remote command:

CONFigure:DPD:METHod on page 319

Selecting the DPD shaping method

The application provides several ways for DPD calculation (or shaping).

●

"From Table"

Shapes the DPD function based on a table that contains the correction values

required to predistort the signal.

The calculation of the table is based on the "AM/AM" and "AM/PM" polynomial

models.

For more information about the contents and usage of the shaping table, refer to

the documentation of the R&S SMW-K541.

You can define a file name for the DPD table in the corresponding field.

●

"From Polynomial"

Shapes the DPD function based on a correction polynomial that is calculated out of

the model polynomial.

Compared to DPD based on a shaping table, this method does not transfer a list

with correction values. Instead, the application transfers the polynomial coefficients

of the correction polynomial.

For more information, see Chapter 3.11, "Applying system models", on page 92. You can update the DPD shaping on the signal generator comfortably with the

"Update" button. Remote command:

Mode: CONFigure:DPD:SHAPing:MODE on page 321 Table name: CONFigure:DPD:FNAMe on page 319

Polynomial DPD Power / Linearity Tradeoff

The "DPD Power / Linearity Tradeoff" describes the effects of the DPD on the amplifier characteristics.

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Applying digital predistortion

When you define a tradeoff of 0 %, the DPD aims for the best linearity (green line in the illustration below). When you increase the tradeoff value, the DPD aims for an optimization of the output power at the expense of linearity. In the ideal case (red line), the DPD affects the amplifier characteristics in a way that the best output power is achieved.

Output Power [dBm]

100 %

Original AM/AM Curve

0 %

Input Power [dBm]

Remote command:

CONFigure:DPD:TRADeoff on page 321

Selecting the order of model calculation

The application allows you to compensate for "AM/AM" distortion, "AM/PM" distortion or both simultaneously. You can turn correction of the distortion models on and off in the corresponding fields.

If you want to predistort both the "AM/AM" distortion and the "AM/PM" distortion simultaneously, you can select the order in which the curves are calculated and applied to the I/Q signal on the R&S SMW.

●

"AM/AM" First

Calculates the "AM/AM" first, then calculates the "AM/PM" based on the signal that

has already been corrected by its "AM/AM" distortions.

●

"AM/PM" First

Calculates the "AM/PM" first, then calculates the "AM/AM" based on the signal that

has already been corrected by its "AM/PM" distortions. Note: the DPD sequence is displayed by the diagram that is part of the dialog box. Remote command:

"AM/AM" state: CONFigure:DPD:AMAM[:STATe] on page 317 "AM/PM" state: CONFigure:DPD:AMPM[:STATe] on page 318 Both: CONFigure:DPD:AMXM[:STATe] on page 318 Calculation order: CONFigure:DPD:SEQuence on page 320

3.12.2 Direct DPD (R&S VSE-K18D)

The direct DPD is an iterative process in which the correction values are determined for each sample of the input signal. Compared to the polynomial DPD, the direct DPD

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Applying digital predistortion

is not based on a model. It rather calculates the correction values for each sample directly.

Determining the DPD directly is based on a sequence of individual measurements (iterations). When one iteration is done, the R&S VSE applies the correction values, measures the improved input signal again, applies the correction values etc. This process goes on until the number of iterations that you have defined is done. Usually, the predistortion gets better with an increasing number of iterations. On the other hand, increasing the number of iterations also increases the measurement time.

Note that if synchronization is not possible during direct DPD, R&S VSE-K18 continues with a new measurement (including capture) until synchronization was successful. Reducing the synchronization confidence level can help in that case.

The result of the direct DPD is an I/Q file that contains a predistorted waveform. When you save the I/Q file, you can later play it back on a signal generator.

For TDD and FDD signals, we recommend that you use the full reference signal to generate the DPD.

Further improvement of predistortion

In addition to increasing the number of iterations, it is recommended to apply signal averaging during each iteration. Averaging helps to remove noise from the signal, which in turn improves the quality of the predistortion values.

Without averaging, each iteration consists of a single measurement. When you apply averaging, the number of measurements during each iteration increases, depending on the number of averages you have defined.

The advantage of the direct DPD compared to the polynomial DPD is, that it takes memory effects into account. This, and the fact that it is not based on a model, but corrects each sample individually, makes the direct DPD the superior method to predistort the input signal and determine the ideal DPD effect for your DUT. Note however, that the correction values that have been determined are only applicable to the signal and amplifier you have used. If the signal characteristics change in any way, you have to predistort the signal again.

The direct DPD is especially useful for the following test cases:

●

Determining the best performance of a DUT.

●

Removing external effects from the measurement results, for example a preampli-

fier that should not be considered in the final measurement results.

Continuous statistics during direct DPD calculation

Continuous statistics is automatically disabled during the direct DPD calculation.

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Generator control during direct DPD calculation

When direct DPD is activated, the generator is prevented from changing its attenuator setting automatically, i.e. it is being set into mode "Fixed" if it was in "Auto" mode so far. The attenuator mode is switched back to "Auto" when direct DPD is turned off. If the generator was in "Fixed" or "Manual" mode, the mode is not changed.

Also, the I/Q modulator of the signal generator is set to high quality table mode.

The remote commands required to configure the direct DPD are described in Chap-

ter 5.5.13, "Applying digital predistortion", on page 311.

Automated direct DPD sequence................................................................................100

Manual direct DPD sequence..................................................................................... 101

Direct DPD Power / Linearity Tradeoff........................................................................102

Automated direct DPD sequence

The direct DPD method requires one or more measurements (or iterations) to determine the correction values.

When you select the "Start Direct DPD Sequence" button, the R&S VSE initiates a sequence of measurements during which the DPD is calculated. The number of measurements performed during the sequence depends on the number of "Iterations" you have defined. It is also recommended to average each iteration for further improvement of the quality of the input signal. The "Gain Expansion" defines the increase of input power relative to the peak power value of the reference signal.

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Specifications and Main Features

Frequently Asked Questions

User Manual

Contents

Welcome to the amplifier measurement application

1.1 Starting the application

1.2 Understanding the display information

2 Measurements and result displays

3 Configuration

3.1 Configuration overview

3.2 Designing a reference signal

3.3 Configuring inputs and outputs

3.3.1 Input source settings

3.3.1.1 Radio frequency input

3.3.1.2 I/Q file input

3.3.2 Configuring the frequency

3.3.3 Defining level characteristics

3.3.4 Power sensors

3.3.5 Configuring outputs

3.3.6 Controlling a signal generator

3.3.7 Reference: I/Q file input

3.3.7.1 Basics on input from I/Q data files

3.3.7.2 I/Q data file format (iq-tar)

I/Q parameter XML file specification

Minimum data elements

User-defined data elements

Mandatory data elements

Optional data elements

Example: userdata for I/Q recordings by R&S VSE software

Example

I/Q data binary file

3.4 Triggering measurements

3.5 Configuring the data capture

3.6 Sweep configuration

3.7 Synchronizing measurement data

3.8 Evaluating measurement data

3.9 Estimating and compensating signal errors

3.10 Equalizer

3.11 Applying system models

3.12 Applying digital predistortion

3.12.1 Polynomial DPD

3.12.2 Direct DPD (R&S VSE-K18D)