Rohde & Schwarz VSE-K7 User Manual
R&S®VSE-K7
Analog Demodulation Application
User Manual
(;ÚçW2)
1176893902
User Manual
Version 07
This manual applies to the following software, version 1.50 and later:
●
R&S®VSE Enterprise Edition base software (1320.7500.xx / 1320.7951.xx)
●
R&S®VSE Basic Edition base software (1345.1011.06)
The following software options are described:
●
R&S VSE-K7 (1320.7539.xx)
●
R&S®CMA-K310 (1320.7945.xx)
© 2018 Rohde & Schwarz GmbH & Co. KG
Mühldorfstr. 15, 81671 München, Germany
Phone: +49 89 41 29 - 0
Fax: +49 89 41 29 12 164
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.
1176.8939.02 | Version 07 | R&S®VSE-K7
The following abbreviations are used throughout this manual: R&S®VSE is abbreviated as R&S VSE.
R&S®VSE-K7
1.1 About this Manual......................................................................................................... 5
1.2 Typographical Conventions......................................................................................... 6
2.1 Starting the R&S VSE Analog Demodulation application......................................... 7
2.2 Understanding the Display Information......................................................................8
4.1 Demodulation Process............................................................................................... 20
4.2 Demodulation Bandwidth...........................................................................................22
Contents
Contents
1 Preface.................................................................................................... 5
2 Welcome to the R&S VSE Analog Demodulation application............7
3 Measurements and Result Displays...................................................11
4 Measurement Basics........................................................................... 20
4.3 Sample Rate and Demodulation Bandwidth.............................................................22
4.4 AF Filters......................................................................................................................23
4.5 Time Domain Zoom.....................................................................................................23
4.6 Working with Spectrograms.......................................................................................25
5 Configuration........................................................................................31
5.1 Configuration According to Digital Standards.........................................................31
5.2 Configuration Overview..............................................................................................33
5.3 Input and Frontend Settings...................................................................................... 35
5.4 Trigger Source Settings..............................................................................................50
5.5 Data Acquisition..........................................................................................................54
5.6 Demodulation.............................................................................................................. 58
5.7 Adjusting Settings Automatically..............................................................................75
6 Analysis................................................................................................ 78
6.1 Trace Settings..............................................................................................................78
6.2 Trace / Data Export Configuration.............................................................................81
6.3 Spectrogram Settings.................................................................................................84
6.4 Working with Markers in the R&S VSE Analog Demodulation application........... 87
6.5 Working with Limit Lines in the R&S VSE Analog Demodulation application.... 107
6.6 Zoom Functions........................................................................................................ 120
3User Manual 1176.8939.02 ─ 07
R&S®VSE-K7
9.1 Introduction............................................................................................................... 126
9.2 Common Suffixes......................................................................................................130
9.3 Activating Analog Demodulation Measurements.................................................. 131
9.4 Configuring the Measurement................................................................................. 131
9.5 Configuring the Result Display................................................................................201
9.6 Retrieving Results.....................................................................................................212
9.7 Analyzing Results..................................................................................................... 223
9.8 Programming Example............................................................................................. 276
Contents
7 How to Perform Measurements in the Analog Demodulation Appli-
cation...................................................................................................122
8 Optimizing and Troubleshooting the Measurement....................... 124
9 Remote Commands for Analog Demodulation Measurements..... 125
Annex.................................................................................................. 280
A Reference............................................................................................280
A.1 Menu Reference........................................................................................................ 280
A.2 Reference of Toolbar Functions.............................................................................. 285
A.3 Predefined Standards and Settings........................................................................ 288
A.4 Formats for Returned Values: ASCII Format and Binary Format......................... 290
A.5 Reference: ASCII File Export Format...................................................................... 291
List of Remote Commands (AnalogDemod)....................................294
Index....................................................................................................302
4User Manual 1176.8939.02 ─ 07
R&S®VSE-K7
1.1 About this Manual
About this Manual
1 Preface
This R&S VSE Analog Demodulation User Manual provides all the information specific
to the application. All general software functions and settings common to all applica-
tions and operating modes are described in the R&S VSE Base Software User Manual.
The main focus in this manual is on the measurement results and the tasks required to
obtain them. The following topics are included:
●
Welcome to the R&S VSE Analog Demodulation application Application
Introduction to and getting familiar with the application
●
Measurements and Result Displays
Details on supported measurements and their result types
●
Measurement Basics
Background information on basic terms and principles in the context of the measurement
●
Configuration + Analysis
A concise description of all functions and settings available to configure measurements and analyze results with their corresponding remote control command
●
How to Perform Measurements in the R&S VSE Analog Demodulation application Application
The basic procedure to perform each measurement and step-by-step instructions
for more complex tasks or alternative methods
●
Measurement Examples
Detailed measurement examples to guide you through typical measurement scenarios and allow you to try out the application immediately
●
Optimizing and Troubleshooting the Measurement
Hints and tips on how to handle errors and optimize the measurement configuration
●
Remote Commands for R&S VSE Analog Demodulation application Measurements
Remote commands required to configure and perform R&S VSE Analog Demodulation application measurements in a remote environment, sorted by tasks
(Commands required to set up the environment or to perform common tasks in the
software are provided in the R&S VSE Base Software User Manual)
Programming examples demonstrate the use of many commands and can usually
be executed directly for test purposes
●
List of remote commands
Alphabetical list of all remote commands described in the manual
●
Index
Preface
5User Manual 1176.8939.02 ─ 07
R&S®VSE-K7
1.2 Typographical Conventions
Preface
Typographical Conventions
The following text markers are used throughout this documentation:
Convention Description
"Graphical user interface elements"
[Keys] Key and knob names are enclosed by square brackets.
File names, commands,
program code
Input Input to be entered by the user is displayed in italics.
Links Links that you can click are displayed in blue font.
"References" References to other parts of the documentation are enclosed by quota-
All names of graphical user interface elements on the screen, such as
dialog boxes, menus, options, buttons, and softkeys are enclosed by
quotation marks.
File names, commands, coding samples and screen output are distinguished by their font.
tion marks.
6User Manual 1176.8939.02 ─ 07
R&S®VSE-K7
Welcome to the R&S VSE Analog Demodulation application
Starting the R&S VSE Analog Demodulation application
2 Welcome to the R&S VSE Analog Demodu-
lation application
The (optional) R&S VSE Analog Demodulation application converts the R&S VSE into
an analog demodulation analyzer for amplitude-, frequency- or phase-modulated signals. It measures not only characteristics of the useful modulation, but also factors
such as residual FM or synchronous modulation.
The digital signal processing in the R&S VSE is also ideally suited for demodulating
AM, FM, or PM signals. The R&S VSE Analog Demodulation application provides the
necessary measurement functions. This application is optional and requires an additional license.
The R&S VSE Analog Demodulation application features:
●
AM, FM, and PM demodulation, with various result displays:
– Modulation signal versus time
– Spectrum of the modulation signal (FFT)
– RF signal power versus time
– Spectrum of the RF signal
●
Determining maximum, minimum and average or current values in parallel over a
selected number of measurements
●
Error-free AM to FM conversion and vice versa, without deviation errors, frequency
response or frequency drift at DC coupling
●
Relative demodulation, in relation to a user-defined or measured reference value
This user manual contains a description of the functionality that the application provides, including remote control operation.
All functions not discussed in this manual are the same as in the base unit and are
described in the R&S VSE User Manual.
2.1 Starting the R&S VSE Analog Demodulation application
The R&S VSE Analog Demodulation application is a separate application on the
R&S VSE. It is activated by creating a new measurement channel in "Analog Demod"
mode.
To activate the R&S VSE Analog Demodulation application
1.
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.
7User Manual 1176.8939.02 ─ 07
R&S®VSE-K7
Welcome to the R&S VSE Analog Demodulation application
Understanding the Display Information
2. Select the "Analog Demodulation" item.
The R&S VSE opens a new measurement channel for the R&S VSE Analog
Demodulation application.
2.2 Understanding the Display Information
The following figure shows a measurement diagram during an Analog Demodulation
measurement. All different information areas are labeled. They are explained in more
detail in the following sections.
8User Manual 1176.8939.02 ─ 07
R&S®VSE-K7
Welcome to the R&S VSE Analog Demodulation application
Understanding the Display Information
1 = Color coding for windows of same channel
2 = Channel bar with measurement settings
3 = Window title bar with diagram-specific (trace) information
4 = Diagram area
5 = Diagram footer with diagram-specific information, depending on result display
Channel bar information
In the R&S VSE Analog Demodulation application, the R&S VSE shows the following
settings:
Table 2-1: Information displayed in the channel bar in the Analog Demodulation application
Ref Level Reference level
m.+el.Att Mechanical and electronic RF attenuation
Offset Reference level offset
AQT Measurement time for data acquisition.
RBW Resolution bandwidth
DBW Demodulation bandwidth
Freq Center frequency for the RF signal
Window title bar information
For each diagram, the header provides the following information:
9User Manual 1176.8939.02 ─ 07
R&S®VSE-K7
Welcome to the R&S VSE Analog Demodulation application
Understanding the Display Information
Figure 2-1: Window title bar information in the Analog Demodulation application
0 = Color coding for windows of same channel
1 = Edit result display function
2 = Channel name
3 = Window number
4 = Window type
5 = Trace color, trace number, detector type, trade mode
6 = AF coupling (AC/DC), only in AF time domains, if applicable
7 = Reference value (at the defined reference position)
8 = Dock/undock window function
9 = Close window function
Diagram footer information
The diagram footer (beneath the diagram) contains the following information, depending on the evaluation:
RF Spectrum
CF: Center frequency
of input signal
RF Time domain
CF: Center frequency
of input signal
AF Spectrum
AF CF: center frequency of demodulated signal
AF Time domain
CF: Center frequency
of input signal
Sweep points Span: measured span
Sweep points Time per division
Sweep points AF Span: evaluated span
Sweep points Time per division
For most modes, the number of sweep points shown in the display are indicated in the
diagram footer. In zoom mode, the (rounded) number of currently displayed points are
indicated.
10User Manual 1176.8939.02 ─ 07
R&S®VSE-K7
Measurements and Result Displays
3 Measurements and Result Displays
Access: "Overview" > "Display Config"
Or: [MEAS] > "Display Config"
The data that was measured by the R&S VSE can be evaluated using various different
methods. In the Analog Demodulation application, up to six evaluation methods can be
displayed simultaneously in separate windows. The results can be displayed as absolute deviations or relative to a reference value or level.
The abbreviation "AF" (for Audio Frequency) refers to the demodulated AM, FM or PM
signal.
Result display windows
For each measurement, a separate channel is activated. Each channel can provide
multiple result displays, which are displayed in individual windows. The measurement
windows can be rearranged and configured in the R&S VSE to meet your requirements. All windows that belong to the same measurement (including the channel bar)
are indicated by a colored line at the top of the window title bar.
►
To add further result displays for the Analog Demodulation channel, select the
"Add Window" icon from the toolbar, or select the "Window" > "New Window" menu
item.
For details on working with channels and windows see the "Operating Basics"
chapter in the R&S VSE Base Software User Manual.
Basis for evaluation
All evaluations are based on the I/Q data set acquired during the measurement. The
spectrum of the modulated signal to be evaluated is determined by the demodulation
bandwidth. However, it can be restricted to a limited span ( "AF Span" ) if only part of
the signal is of interest. Furthermore, the time base for evaluations in the time domain
can be restricted to analyze a smaller extract in more detail, see Chapter 4.5, "Time
Domain Zoom", on page 23.
Spectrograms
Spectrograms are not configured as separate result displays, but as a subwindow of
any existing graphical result display window. They are activated and deactivated in the
"Spectrogram" tab of the "Traces" settings (see Chapter 6.3, "Spectrogram Settings",
on page 84).
AM Time Domain ..........................................................................................................12
FM Time Domain ..........................................................................................................12
PM Time Domain ..........................................................................................................13
AM Spectrum ............................................................................................................... 13
FM Spectrum ................................................................................................................14
11User Manual 1176.8939.02 ─ 07
R&S®VSE-K7
Measurements and Result Displays
PM Spectrum ............................................................................................................... 15
RF Time Domain ..........................................................................................................15
RF Spectrum ................................................................................................................16
Result Summary ...........................................................................................................17
Marker Table ................................................................................................................ 18
Marker Peak List .......................................................................................................... 19
AM Time Domain
Displays the modulation depth of the demodulated AM signal (in %) versus time.
Remote command:
LAY:ADD? '1',RIGH,'XTIM:AM:REL'
(See LAYout:ADD[:WINDow]? on page 206)
FM Time Domain
Displays the frequency spectrum of the demodulated FM signal versus time.
12User Manual 1176.8939.02 ─ 07
R&S®VSE-K7
Measurements and Result Displays
Remote command:
LAY:ADD? '1',RIGH,'XTIM:FM'
(See LAYout:ADD[:WINDow]? on page 206)
PM Time Domain
Displays the phase deviations of the demodulated PM signal (in rad or °) versus time.
Remote command:
LAY:ADD? '1',RIGH,'XTIM:PM'
(See LAYout:ADD[:WINDow]? on page 206)
AM Spectrum
Displays the modulation depth of the demodulated AM signal (in % or dB) versus AF
span. The spectrum is calculated from the demodulated AM signal in the time domain
via FFT.
13User Manual 1176.8939.02 ─ 07
R&S®VSE-K7
Measurements and Result Displays
Remote command:
LAY:ADD? '1',RIGH,'XTIMe:AM:REL:AFSPectrum1'
(see LAYout:ADD[:WINDow]? on page 206)
FM Spectrum
Displays the frequency deviations of the demodulated FM signal (in Hz or dB) versus
AF span. The spectrum is calculated from the demodulated AM signal in the time
domain via FFT.
14User Manual 1176.8939.02 ─ 07
R&S®VSE-K7
Measurements and Result Displays
Remote command:
LAY:ADD? '1',RIGH,'XTIMe:FM:AFSPectrum1'
(see LAYout:ADD[:WINDow]? on page 206)
PM Spectrum
Displays the phase deviations of the demodulated PM signal (in rad, ° or dB) versus
AF span. The spectrum is calculated from the demodulated AM signal in the time
domain via FFT.
Remote command:
LAY:ADD? '1',RIGH,'XTIMe:PM:AFSPectrum1'
(see LAYout:ADD[:WINDow]? on page 206)
RF Time Domain
Displays the RF power of the input signal versus time. The level values represent the
magnitude of the I/Q data set.
15User Manual 1176.8939.02 ─ 07
R&S®VSE-K7
Measurements and Result Displays
Remote command:
LAY:ADD? '1',RIGH,'XTIM:AM'
(see LAYout:ADD[:WINDow]? on page 206)
RF Spectrum
Displays the spectrum of the input signal. In contrast to the Spectrum application, the
frequency values are determined using FFT from the recorded I/Q data set.
16User Manual 1176.8939.02 ─ 07
R&S®VSE-K7
Measurements and Result Displays
Remote command:
LAY:ADD? '1',RIGH,'XTIM:SPECTRUM'
(see LAYout:ADD[:WINDow]? on page 206)
Result Summary
The result summary displays the results of the demodulation functions for all windows
in a table.
For each demodulation, the following information is provided:
17User Manual 1176.8939.02 ─ 07
R&S®VSE-K7
power distortion noise
power total
log20dBSINAD
1
2
2
2
log20
i
i
i
i
U
U
dBTHD
Measurements and Result Displays
Table 3-1: Result summary description
Label Description
+Peak Positive peak (maximum)
-Peak Negative peak (minimum)
+/-Peak/2 Average of positive and negative peaks
RMS Root Mean Square value
Mod Freq Modulation frequency
SINAD Signal-to-noise-and-distortion
(Calculated only if AF Spectrum is displayed)
Measures the ratio of the total power to the power of noise and harmonic distortions.
The noise and harmonic power is calculated inside the AF spectrum span. The DC
offset is removed before the calculation.
THD Total harmonic distortion
The ratio of the harmonics to the fundamental and harmonics. All harmonics inside
the AF spectrum span are considered up to the tenth harmonic.
(Calculated only if AF Spectrum is displayed)
Note: Relative demodulation results. Optionally, the demodulation results in relation to
user-defined or measured reference values are determined. See Chapter 5.6.6, "Result
Table Settings", on page 72.
In addition, the following general information for the input signal is provided:
●
Carrier Power: the power of the carrier without modulation
●
Carrier Offset: the deviation of the calculated carrier frequency to the ideal carrier
frequency
●
Modulation Depth (AM or RF Time Domain only): the difference in amplitude the
carrier signal is modulated with
Remote command:
LAY:ADD? '1',RIGH,RSUM, see LAYout:ADD[:WINDow]? on page 206
Results:
CALCulate<n>:MARKer<m>:FUNCtion:ADEMod:PM[:RESult<t>]? on page 219
CALCulate<n>:MARKer<m>:FUNCtion:ADEMod:PM[:RESult<t>]:RELative?
on page 220
Marker Table
Displays a table with the current marker values for the active markers.
This table is displayed automatically if configured accordingly (see " Marker Table Dis-
play " on page 92).
18User Manual 1176.8939.02 ─ 07
R&S®VSE-K7
Measurements and Result Displays
Remote command:
LAY:ADD? '1',RIGH, MTAB, see LAYout:ADD[:WINDow]? on page 206
Results:
CALCulate<n>:MARKer<m>:X on page 225
CALCulate<n>:MARKer<m>:Y? on page 225
Marker Peak List
The marker peak list determines the frequencies and levels of peaks in the spectrum or
time domain. How many peaks are displayed can be defined, as well as the sort order.
In addition, the detected peaks can be indicated in the diagram. The peak list can also
be exported to a file for analysis in an external application.
Remote command:
LAY:ADD? '1',RIGH, PEAK, see LAYout:ADD[:WINDow]? on page 206
Results:
CALCulate<n>:MARKer<m>:X on page 225
CALCulate<n>:MARKer<m>:Y? on page 225
19User Manual 1176.8939.02 ─ 07
R&S®VSE-K7
4.1 Demodulation Process
Measurement Basics
Demodulation Process
4 Measurement Basics
Some background knowledge on basic terms and principles used in Analog Demodulation measurements is provided here for a better understanding of the required configuration settings.
● Demodulation Process............................................................................................20
● Demodulation Bandwidth........................................................................................ 22
● Sample Rate and Demodulation Bandwidth........................................................... 22
● AF Filters.................................................................................................................23
● Time Domain Zoom.................................................................................................23
● Working with Spectrograms.................................................................................... 25
The demodulation process is shown in Figure 4-1. All calculations are performed simultaneously with the same I/Q data set. Magnitude (= amplitude) and phase of the complex I/Q pairs are determined. The frequency result is obtained from the differential
phase.
For details on general I/Q data processing in the R&S VSE, refer to the reference part
of the I/Q Analysis remote control description in the R&S VSE User Manual.
20User Manual 1176.8939.02 ─ 07
R&S®VSE-K7
Measurement Basics
Demodulation Process
Figure 4-1: Block diagram of software demodulator
21User Manual 1176.8939.02 ─ 07
R&S®VSE-K7
Measurement Basics
Sample Rate and Demodulation Bandwidth
The AM DC, FM DC and PM DC raw data of the demodulators is fed into the "Trace
Arithmetic" block that combines consecutive data sets. Possible trace modes are:
Clear Write, Max Hold, Min Hold and Average. The output data of the "Trace Arithmetic" block can be read via remote control ([SENS:]ADEM:<evaluation>:RES?,
see [SENSe:]ADEMod<n>:AM[:ABSolute][:TDOMain]:RESult? on page 213.
The collected measured values are evaluated by the selected detector. The result is
displayed on the screen and can be read out via remote control.
In addition, important parameters are calculated:
●
A counter determines the modulation frequency for AM, FM, and PM.
●
average power = carrier power (RF power)
●
average frequency = carrier frequency offset (FM)
●
The modulation depth or the frequency or phase deviation; the deviations are
determined from the trace data
AC coupling is possible with FM and PM display.
4.2 Demodulation Bandwidth
The demodulation bandwidth determines the span of the signal that is demodulated. It
is not the 3 dB bandwidth of the filter but the useful bandwidth which is distortion-free
with regard to phase and amplitude.
Therefore the following formulas apply:
●
AM: demodulation bandwidth ≥ 2 x modulation frequency
●
FM: demodulation bandwidth ≥ 2 x (frequency deviation + modulation frequency)
●
PM: demodulation bandwidth ≥ 2 x modulation frequency x (1 + phase deviation)
If the center frequency of the analyzer is not set exactly to the signal frequency, the
demodulation bandwidth must be increased by the carrier offset, in addition to the
requirement described above. This also applies if FM or PM AC coupling has been
selected.
In general, the demodulation bandwidth should be as narrow as possible to improve
the S/N ratio. The residual FM caused by noise floor and phase noise increases dramatically with the bandwidth, especially with FM.
For help on determining the adequate demodulation bandwidth see "Determining the
demodulation bandwidth" on page 124.
4.3 Sample Rate and Demodulation Bandwidth
The maximum demodulation bandwidths that can be obtained during the measurement, depending on the sample rate, are listed in the tables below for different demod-
22User Manual 1176.8939.02 ─ 07
R&S®VSE-K7
Measurement Basics
Time Domain Zoom
ulation filter types. The allowed value range of the measurement time and trigger offset
depends on the selected demodulation bandwidth and demodulation filter. If the AF filter or the AF trigger are not active, the measurement time increases by 20 %.
A maximum of 24 million samples can be captured, assuming sufficient memory is
available; thus the maximum measurement time can be determined according to the
following formula:
Meas.time
The minimum trigger offset is (-Meas.time
Large numbers of samples
Principally, the R&S VSE can handle up to 24 million samples. However, when 480001
samples are exceeded, all traces that are not currently being displayed in a window are
deactivated to improve performance. The traces can only be activated again when the
samples are reduced.
= Sample count
max
/ sample rate
max
max
)
Effects of measurement time on the stability of measurement results
Despite amplitude and frequency modulation, the display of carrier power and carrier
frequency offset is stable.
This is achieved by a digital filter which sufficiently suppresses the modulation, provided, however, that the measurement time is ≥ 3 x 1 / modulation frequency, i.e. that at
least three periods of the AF signal are recorded.
The mean carrier power for calculating the AM is also calculated with a digital filter that
returns stable results after a measurement time of ≥ 3 x 1 / modulation frequency, i.e.
at least three cycles of the AF signal must be recorded before a stable AM can be
shown.
4.4 AF Filters
Additional filters applied after demodulation help filter out unwanted signals, or correct
pre-emphasized input signals. A CCITT filter allows you to evaluate the signal by simulating the characteristics of human hearing.
4.5 Time Domain Zoom
For evaluations in the time domain, the demodulated data for a particular time span
can be extracted and displayed in more detail using the "Time Domain Zoom" function.
This is useful if the measurement time is very large and thus each sweep point represents a large time span. The time domain zoom function distributes the available
sweep points only among the time span defined by the zoom area length. The time
span displayed per division of the diagram is decreased. Thus, the display of the
extracted time span becomes more precise.
23User Manual 1176.8939.02 ─ 07
R&S®VSE-K7
Measurement Basics
Time Domain Zoom
Figure 4-2: FM time domain measurement with a very long measurement time (200 ms)
Figure 4-3: FM time domain measurement with time domain zoom (2.0 ms per division)
The time domain zoom area affects not only the diagram display, but the entire evaluation for the current window.
In contrast to the time domain zoom, the graphical zoom is available for all diagram
evaluations. However, the graphical zoom is useful only if more measured values than
trace points are available. The (time) span represented by each measurement point
remains the same.
24User Manual 1176.8939.02 ─ 07
R&S®VSE-K7
Measurement Basics
Working with Spectrograms
Time domain zoom Graphical zoom
4.6 Working with Spectrograms
In addition to the standard "level versus frequency" or "level versus time" traces, the
R&S VSE Analog Demodulation application also provides a spectrogram display of the
measured data. A special feature of the R&S VSE software is that it provides spectrograms for applications based on I/Q data, such as the I/Q Analyzer and the Analog
Demodulation application.
A spectrogram shows how the spectral density of a signal varies over time. The x-axis
shows the frequency, the y-axis shows the time. A third dimension, the power level, is
indicated by different colors. Thus you can see how the strength of the signal varies
over time for different frequencies.
25User Manual 1176.8939.02 ─ 07
R&S®VSE-K7
Measurement Basics
Working with Spectrograms
Example:
In this example you see the spectrogram for the calibration signal of an R&S FSW,
compared to the standard spectrum display. Since the signal does not change over
time, the color of the frequency levels does not change over time, i.e. vertically. The
legend above the spectrogram display describes the power levels the colors represent.
Spectrogram based on specific trace
The R&S VSE software allows you to define which trace of a particular result display
the Spectrogram is calculated from, if multiple traces are available. For example, if a
Spectrum is displayed with a Maxhold, a Minhold and an Average trace, you can activate a Spectrogram that displays the maximum, minimum, or average power levels
over time and frequency.
Result display
The spectrogram result can consist of the following elements:
26User Manual 1176.8939.02 ─ 07
R&S®VSE-K7
Measurement Basics
Working with Spectrograms
2
1
7
3
6
5
Figure 4-4: Display elements for a result display with a spectrogram subwindow
1 = Main result display (in this case: Spectrum)
2 = Marker info with frame number
3 = Spectrogram subwindow title with trace information
4 = Color map
5 = Spectrogram subwindow
6 = Current frame indicators
7 = Deltamarker in Spectrogram and Spectrum displays
8 = Current frame number
4
6
7
8
For more information about spectrogram configuration see Chapter 6.3, "Spectrogram
Settings", on page 84.
Remote commands:
Activating and configuring spectrograms:
Chapter 9.4.11, "Configuring Spectrograms", on page 195
Storing results:
MMEMory:STORe<n>:SPECtrogram on page 216
● Time Frames...........................................................................................................27
● Color Maps..............................................................................................................28
4.6.1 Time Frames
The time information in the spectrogram is displayed vertically, along the y-axis. Each
line (or trace) of the y-axis represents one or more captured sweep and is called a
time frame or simply "frame". As with standard spectrum traces, several measured
values are combined in one sweep point using the selected detector.
27User Manual 1176.8939.02 ─ 07
R&S®VSE-K7
Measurement Basics
Working with Spectrograms
Frames are sorted in chronological order, beginning with the most recently recorded
frame at the top of the diagram (frame number 0). With the next sweep, the previous
frame is moved further down in the diagram, until the maximum number of captured
frames is reached. The display is updated continuously during the measurement, and
the measured trace data is stored. Spectrogram displays are continued even after single measurements unless they are cleared manually.
The maximum number of frames that you can capture depends on the number of
sweep points that are analyzed during the measurement.
The scaling of the time axis (y-axis) is not configurable. However, you can enlarge the
spectrogram display to the full window size using the State: "Full" .
Displaying individual frames
The spectrogram diagram contains all stored frames since it was last cleared. Arrows
on the left and right border of the spectrogram indicate the currently selected frame.
The spectrum diagram always displays the spectrum for the currently selected frame.
The current frame number is indicated in the diagram footer. The current frame, displayed at the top of the diagram, is frame number 0. Older frames further down in the
diagram are indicated by a negative index, e.g. "-10" . You can display the spectrum
diagram of a previous frame by changing the current frame number.
4.6.2 Color Maps
The color display is highly configurable to adapt the spectrograms to your needs. You
can define:
●
Which colors to use (Color scheme)
●
Which value range to apply the color scheme to
●
How the colors are distributed within the value range, i.e where the focus of the visualization lies (shape of the color curve)
The individual colors are assigned to the power levels automatically by the R&S VSE.
The Color Scheme
●
Hot
Uses a color range from blue to red. Blue colors indicate low levels, red colors indicate high ones.
●
Cold
Uses a color range from red to blue. Red colors indicate low levels, blue colors
indicate high ones.
The "Cold" color scheme is the inverse "Hot" color scheme.
28User Manual 1176.8939.02 ─ 07
R&S®VSE-K7
Measurement Basics
Working with Spectrograms
●
Radar
Uses a color range from black over green to light turquoise with shades of green in
between. Dark colors indicate low levels, light colors indicate high ones.
●
Grayscale
Shows the results in shades of gray. Dark gray indicates low levels, light gray indicates high ones.
The Value Range of the Color Map
If the measured values only cover a small area in the spectrogram, you can optimize
the displayed value range so it becomes easier to distinguish between values that are
close together. Display only parts of interest.
The Shape and Focus of the Color Curve
The color mapping function assigns a specified color to a specified power level in the
spectrogram display. By default, colors on the color map are distributed evenly. However, to visualize a certain area of the value range in greater detail than the rest, you
can set the focus of the color mapping to that area. Changing the focus is performed
by changing the shape of the color curve.
The color curve is a tool to shift the focus of the color distribution on the color map. By
default, the color curve is linear. If you shift the curve to the left or right, the distribution
becomes non-linear. The slope of the color curve increases or decreases. One end of
the color palette then covers a large range of results, while the other end distributes
several colors over a relatively small result range.
You can use this feature to put the focus on a particular region in the diagram and to be
able to detect small variations of the signal.
29User Manual 1176.8939.02 ─ 07
R&S®VSE-K7
Measurement Basics
Working with Spectrograms
Example:
In the color map based on the linear color curve, the range from -100 dBm to -60 dBm
is covered by blue and a few shades of green only. The range from -60 dBm to
-20 dBm is covered by red, yellow and a few shades of green.
Figure 4-5: Spectrogram with (default) linear color curve shape = 0
The sample spectrogram is dominated by blue and green colors. After shifting the color
curve to the left (negative value), more colors cover the range from -100 dBm to
-60 dBm (blue, green and yellow). This range occurs more often in the example. The
range from -60 dBm to -20 dBm, on the other hand, is dominated by various shades of
red only.
Figure 4-6: Spectrogram with non-linear color curve (shape = -0.5)
30User Manual 1176.8939.02 ─ 07
Loading...