R&S®FSWP
I/Q Analyzer and Spectrum Monitor
User Manual
(;ÛÈÆ2)
1177585602
User Manual
Version 08
This manual describes the following R&S®FSWP models with firmware version 1.90 or higher:
●
R&S®FSWP8 (1322.8003K08)
●
R&S®FSWP26 (1322.8003K26)
●
R&S®FSWP50 (1322.8003K50)
The Spectrum Monitor is integral part of the R&S FSWP and is always available with firmware versions
1.60 and higher.
The full I/Q Analyzer is integral part of the following options:
●
R&S FSWP-B1 (1322.9997.08)
●
R&S FSWP-B1 (1322.9997.26)
●
R&S FSWP-B1 (1322.9997.50)
© 2019 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.
1177.5856.02 | Version 08 | R&S®FSWP
Throughout this manual, products from Rohde & Schwarz are indicated without the ® symbol , e.g. R&S®FSWP is indicated as
R&S FSWP.
R&S®FSWP
Contents
Contents
1 Preface.................................................................................................... 5
1.1 About this Manual......................................................................................................... 5
1.2 Documentation Overview............................................................................................. 6
1.3 Conventions Used in the Documentation...................................................................7
2 Welcome to the I/Q Analyzer Application............................................ 9
2.1 Starting the I/Q Analyzer Application........................................................................10
2.2 Understanding the Display Information.................................................................... 11
3 Measurement and Result Displays.....................................................14
4 Basics on I/Q Data Acquisition and Processing............................... 19
4.1 Processing Analog I/Q Data from RF Input.............................................................. 19
4.2 Basics on Input from I/Q Data Files...........................................................................25
4.3 Receiving and Providing Trigger Signals................................................................. 26
4.4 I/Q Data Import and Export.........................................................................................27
4.5 Basics on FFT..............................................................................................................28
4.6 I/Q Analyzer in MSRA Operating Mode..................................................................... 34
4.7 Measurements in the Time and Frequency Domain................................................ 35
5 Configuration........................................................................................36
5.1 Configuration Overview..............................................................................................36
5.2 Import/Export Functions............................................................................................ 38
5.3 Configuring Data Inputs and Outputs....................................................................... 41
5.4 Configuring the Amplitude.........................................................................................48
5.5 Configuring Frequency Characteristics....................................................................53
5.6 Configuring Triggered Measurements...................................................................... 54
5.7 Data Acquisition and Bandwidth Settings................................................................59
5.8 Display Configuration.................................................................................................66
5.9 Adjusting Settings Automatically..............................................................................67
6 Analysis................................................................................................ 70
6.1 Trace Configuration.................................................................................................... 70
6.2 Marker Settings........................................................................................................... 71
6.3 Display Lines and Limit Lines....................................................................................71
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Contents
7 How to Work with I/Q Data.................................................................. 73
7.1 How to Perform Measurements in the I/Q Analyzer Application............................ 73
7.2 How to Export and Import I/Q Data............................................................................74
8 Remote Commands for the I/Q Analyzer........................................... 77
8.1 Introduction................................................................................................................. 77
8.2 Common Suffixes........................................................................................................82
8.3 Activating I/Q Analyzer Measurements.....................................................................82
8.4 Performing Measurements.........................................................................................88
8.5 Retrieving Results.......................................................................................................95
8.6 Configuring I/Q Analyzer Measurements................................................................107
8.7 Analyzing Results..................................................................................................... 148
8.8 Importing and Exporting I/Q Data............................................................................149
8.9 Querying the Status Registers.................................................................................150
8.10 Programming Examples........................................................................................... 151
Annex.................................................................................................. 154
A Annex: Reference...............................................................................154
A.1 Formats for Returned Values: ASCII Format and Binary Format......................... 154
A.2 Reference: Format Description for I/Q Data Files.................................................. 154
A.3 I/Q Data File Format (iq-tar)......................................................................................156
List of Remote Commands (I/Q Analyzer)....................................... 162
Index....................................................................................................165
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1.1 About this Manual
About this Manual
1 Preface
This R&S FSWP I/Q Analyzer User Manual provides all the information specific to the
application and processing I/Q data. All general instrument functions and settings
common to all applications are described in the main R&S FSWP 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 I/Q Analyzer application
Introduction to and getting familiar with the application
●
Typical Applications for the I/Q Analyzer and optional input interfaces
Example measurement scenarios for I/Q data import and analysis
●
Measurements and Result Displays
Details on supported measurements and their result types
●
Basics on I/Q Data Acquisition
Background information on basic terms and principles in the context of the I/Q Analyzer application as well as processing I/Q data in general
●
Configuration and Analysis
A concise description of all functions and settings available to import, capture and
analyze I/Q data in the I/Q Analyzer, with or without optional interfaces, with their
corresponding remote control command
●
How to Work with I/Q Data
The basic procedure to perform an I/Q Analyzer measurement or capture data via
the R&S Digital Baseband Interface with step-by-step instructions
●
Optimizing and Troubleshooting the Measurement
Hints and tips on how to handle errors and optimize the test setup
●
Remote Commands to perform Measurements with I/Q Data
Remote commands required to configure and perform I/Q Analyzer measurements
or process digital I/Q data in a remote environment, sorted by tasks;
(Commands required to set up the environment or to perform common tasks on the
instrument are provided in the main R&S FSWP User Manual.)
Programming examples demonstrate the use of many commands and can usually
be executed directly for test purposes.
●
Annex
Reference material, e.g. I/Q file formats and a detailed description of the LVDS
connector
●
List of remote commands
Alphabetical list of all remote commands described in the manual
●
Index
Preface
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1.2 Documentation Overview
1.2.1 Getting Started Manual
Preface
Documentation Overview
This section provides an overview of the R&S FSWP user documentation. Unless
specified otherwise, you find most of the documents on the R&S FSWP product page
at:
www.rohde-schwarz.com/manual/fswp
Introduces the R&S FSWP and describes how to set up and start working with the
product. Includes basic operations, typical measurement examples, and general information, e.g. safety instructions, etc.
A printed version is delivered with the instrument. A PDF version is available for download on the Internet.
1.2.2 User Manuals and Help
Separate user manuals are provided for the base unit and the firmware applications:
●
Base unit manual
Contains the description of all instrument modes and functions. It also provides an
introduction to remote control, a complete description of the remote control commands with programming examples, and information on maintenance, instrument
interfaces and error messages. Includes the contents of the getting started manual.
●
Manuals for (optional) firmware applications
Contains the description of the specific functions of a firmware application, including remote control commands. Basic information on operating the R&S FSWP is
not included.
The contents of the user manuals are available as help in the R&S FSWP. The help
offers quick, context-sensitive access to the complete information for the base unit and
the firmware applications.
All user manuals are also available for download or for immediate display on the Internet.
1.2.3 Service Manual
Describes the performance test for checking the rated specifications, module replacement and repair, firmware update, troubleshooting and fault elimination, and contains
mechanical drawings and spare part lists.
The service manual is available for download for registered users on the global
Rohde & Schwarz information system (GLORIS):
https://gloris.rohde-schwarz.com
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1.2.4 Instrument Security Procedures
1.2.5 Basic Safety Instructions
1.2.6 Data Sheets and Brochures
Preface
Conventions Used in the Documentation
Deals with security issues when working with the R&S FSWP in secure areas. It is
available for download on the Internet.
Contains safety instructions, operating conditions and further important information.
The printed document is delivered with the instrument.
The data sheet contains the technical specifications of the R&S FSWP. It also lists the
options and their order numbers, and optional accessories.
The brochure provides an overview of the instrument and deals with the specific characteristics.
See www.rohde-schwarz.com/brochure-datasheet/fswp
1.2.7 Release Notes and Open Source Acknowledgment (OSA)
The release notes list new features, improvements and known issues of the current
firmware version, and describe the firmware installation.
The open source acknowledgment document provides verbatim license texts of the
used open source software.
See www.rohde-schwarz.com/firmware/fswp
1.2.8 Application Notes, Application Cards, White Papers, etc.
These documents deal with special applications or background information on particular topics.
See www.rohde-schwarz.com/application/fswp
1.3 Conventions Used in the Documentation
1.3.1 Typographical Conventions
The following text markers are used throughout this documentation:
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Preface
Conventions Used in the Documentation
Convention Description
"Graphical user interface elements"
[Keys] Key and knob names are enclosed by square brackets.
Filenames, 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.
Filenames, commands, coding samples and screen output are distinguished by their font.
tion marks.
1.3.2 Conventions for Procedure Descriptions
When operating the instrument, several alternative methods may be available to perform the same task. In this case, the procedure using the touchscreen is described.
Any elements that can be activated by touching can also be clicked using an additionally connected mouse. The alternative procedure using the keys on the instrument or
the on-screen keyboard is only described if it deviates from the standard operating procedures.
The term "select" may refer to any of the described methods, i.e. using a finger on the
touchscreen, a mouse pointer in the display, or a key on the instrument or on a keyboard.
1.3.3 Notes on Screenshots
When describing the functions of the product, we use sample screenshots. These
screenshots are meant to illustrate as many as possible of the provided functions and
possible interdependencies between parameters. The shown values may not represent
realistic usage scenarios.
The screenshots usually show a fully equipped product, that is: with all options installed. Thus, some functions shown in the screenshots may not be available in your particular product configuration.
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Welcome to the I/Q Analyzer Application
2 Welcome to the I/Q Analyzer Application
The R&S FSWP I/Q Analyzer is a firmware application that adds functionality to perform I/Q data acquisition and analysis to the R&S FSWP.
The R&S FSWP I/Q Analyzer features:
●
Acquisition of analog I/Q data
●
Import of stored I/Q data from other applications
●
Spectrum, magnitude, I/Q vector and separate I and Q component analysis of any
I/Q data on the instrument
●
Export of I/Q data to other applications
Availability of the I/Q Analyzer and Spectrum Monitor
The full I/Q Analyzer becomes available when you equip the R&S FSWP with the
optional Spectrum Analyzer hardware (R&S FSWP-B1).
You can still analyze I/Q data without this hardware option in the Spectrum Monitor
application.
It runs on the phase noise analyzer hardware and is available for free with firmware
version 1.60.
Compared to the full I/Q analyzer, which runs on the optional spectrum analyzer hardware, it has the following characteristics and limitations.
●
When you open a spectrum monitor, the frequency, level and input parameters are
initially adopted from the phase noise application (you can change them in the
spectrum monitor, of course).
Those settings are the same as in the full I/Q analyzer.
●
Maximum analysis bandwidth of 20 MHz and sample rate of 25 MHz (and no support of bandwidth extensions).
●
Advanced data acquisition settings are unavailable.
●
I/Q data import and export are the same as in the full I/Q analyzer.
●
Spectrograms, general marker functionality, marker functions and limit lines are the
same as in the full I/Q analyzer.
●
Only external triggers are supported.
●
Only evaluation of the frequency spectrum is supported.
●
Trace mathematics are not available.
All other functionality is the same as that of the I/Q analyzer.
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 FSWP User Manual. The latest version is available for download
at the product homepage http://www.rohde-schwarz.com/product/fswp.
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2.1 Starting the I/Q Analyzer Application
Welcome to the I/Q Analyzer Application
Starting the I/Q Analyzer Application
Additional information
Several application notes discussing I/Q analysis are available from the Rohde &
Schwarz website:
1EF85: Converting R&S I/Q data files
1EF92: Wideband Signal Analysis
1MA257: Wideband mm-Wave Signal Generation and Analysis
1EF84: Differential measurements with Spectrum Analyzers and Probes
Installation
The R&S FSWP I/Q Analyzer application is part of the optional Spectrum application
and requires no further installation.
The I/Q Analyzer is an application on the R&S FSWP.
To activate the I/Q Analyzer application
1. Select the [MODE] key.
A dialog box opens that contains all applications currently available on your
R&S FSWP.
2. Select the "I/Q Analyzer" item.
The R&S FSWP opens a new channel for the I/Q Analyzer application.
The measurement is started immediately with the default settings.
It can be configured in the I/Q Analyzer "Overview" dialog box, which is displayed
when you select the "Overview" softkey from any menu (see Chapter 5, "Configura-
tion", on page 36).
Multiple Channels and Sequencer Function
When you activate an application, a new channel is created which determines the
measurement settings for that application (channel). The same application can be activated with different measurement settings by creating several channels for the same
application.
The number of channels that can be configured at the same time depends on the available memory on the instrument.
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2.2 Understanding the Display Information
Welcome to the I/Q Analyzer Application
Understanding the Display Information
Only one measurement can be performed at any time, namely the one in the currently
active channel. However, in order to perform the configured measurements consecutively, a Sequencer function is provided.
If activated, the measurements configured in the currently defined channels are performed one after the other in the order of the tabs. The currently active measurement is
indicated by a
symbol in the tab label.
The result displays of the individual channels are updated in the tabs (as well as the
"MultiView") as the measurements are performed. Sequential operation itself is independent of the currently displayed tab.
For details on the Sequencer function see the R&S FSWP User Manual.
The following figure shows a measurement diagram during I/Q Analyzer operation. All
different information areas are labeled. They are explained in more detail in the following sections.
Figure 2-1: Screen elements in the I/Q Analyzer application
1 = Channel bar for firmware and measurement settings
2+3 = Window title bar with diagram-specific (trace) information
4 = Diagram area with marker information
5 = Diagram footer with diagram-specific information, depending on result display
6 = Instrument status bar with error messages and date/time display
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Welcome to the I/Q Analyzer Application
Understanding the Display Information
MSRA operating mode
In MSRA operating mode, additional tabs and elements are available. A colored background of the screen behind the channel tabs indicates that you are in MSRA operating
mode.
For details on the MSRA operating mode see the R&S FSWP MSRA User Manual.
Channel bar information
In the I/Q Analyzer application, the R&S FSWP shows the following settings:
Table 2-1: Information displayed in the channel bar for the I/Q Analyzer application
Ref Level Reference level
Att RF attenuation
Ref Offset Reference level offset
Freq Center frequency
Meas Time Measurement time
Rec Length Defined record length (number of samples to capture)
SRate Defined sample rate for data acquisition
RBW (Spectrum evaluation only) Resolution bandwidth calculated from the
sample rate and record length
In addition, the channel bar also displays information on instrument settings that affect
the measurement results even though this is not immediately apparent from the display
of the measured values (e.g. transducer or trigger settings). This information is displayed only when applicable for the current measurement. For details see the
R&S FSWP Getting Started manual.
Window title bar information
For each diagram, the header provides the following information:
Figure 2-2: Window title bar information in the I/Q Analyzer application
1 = Window number
2 = Window type
3 = Trace color
4 = Trace number
5 = Detector
6 = Trace mode
Diagram footer information
The information in the diagram footer (beneath the diagram) depends on the evaluation:
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Welcome to the I/Q Analyzer Application
Understanding the Display Information
●
Center frequency
●
Number of sweep points
●
Range per division (x-axis)
●
Span (Spectrum)
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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Measurement and Result Displays
3 Measurement and Result Displays
Access: "Overview" > "Display Config"
Or: [MEAS] > "Display Config"
The I/Q Analyzer can capture I/Q data. The I/Q data that was captured by or imported
to the R&S FSWP can then be evaluated in various different result displays. Select the
result displays using the SmartGrid functions.
Up to 6 evaluations can be displayed in the I/Q Analyzer at any time, including several
graphical diagrams, marker tables or peak lists.
For details on working with the SmartGrid see the R&S FSWP Getting Started manual.
Note that the Spectrum Monitor only supports the "Spectrum" result display.
Measurements in the time and frequency domain
The I/Q Analyzer application (not Master in MSRA mode) can also perform measurements on the captured I/Q data in the time and frequency domain (see also Chap-
ter 4.6, "I/Q Analyzer in MSRA Operating Mode", on page 34). They are configured
using the same settings and provide similar results. In addition, the analysis interval
used for the measurement is indicated as in all multistandard applications.
The time and frequency domain measurements and the available results are described
in detail in the R&S FSWP User Manual.
Result displays for I/Q data:
Magnitude..................................................................................................................... 14
Spectrum.......................................................................................................................15
I/Q-Vector......................................................................................................................16
Real/Imag (I/Q)..............................................................................................................16
Marker Table................................................................................................................. 17
Marker Peak List........................................................................................................... 18
Magnitude
Shows the level values in time domain.
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Measurement and Result Displays
Remote command:
LAY:ADD:WIND? '1',RIGH,MAGN, see LAYout:ADD[:WINDow]? on page 142
Results:
TRACe<n>[:DATA]? on page 101
Spectrum
Displays the frequency spectrum of the captured I/Q samples.
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Measurement and Result Displays
Remote command:
LAY:ADD:WIND? '1',RIGH,FREQ, see LAYout:ADD[:WINDow]? on page 142
Results:
TRACe<n>[:DATA]? on page 101
I/Q-Vector
Displays the captured samples in an I/Q-plot. The samples are connected by a line.
Note: For the I/Q vector result display, the number of I/Q samples to record ("Record
Length") must be identical to the number of trace points to be displayed ("Sweep
Points"; for I/Q Analyzer: 10001). For record lengths outside the valid range of sweep
points the diagram does not show valid results.
Remote command:
LAY:ADD:WIND? '1',RIGH,VECT, see LAYout:ADD[:WINDow]? on page 142
Results:
TRACe<n>[:DATA]? on page 101
Real/Imag (I/Q)
Displays the I and Q values in separate diagrams.
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Measurement and Result Displays
Remote command:
LAY:ADD:WIND? '1',RIGH,RIM, see LAYout:ADD[:WINDow]? on page 142
Results:
TRACe<n>[:DATA]? on page 101
Marker Table
Displays a table with the current marker values for the active markers.
This table is displayed automatically if configured accordingly.
Type Shows the marker type and number ("M" for a nor-
mal marker, "D" for a delta marker).
Ref Shows the reference marker that a delta marker
refers to.
Trace Shows the trace that the marker is positioned on.
X- / Y-Value Shows the marker coordinates (usually frequency
and level).
Tip: To navigate within long marker tables, simply scroll through the entries with your
finger on the touchscreen.
Remote command:
LAY:ADD? '1',RIGH, MTAB, see LAYout:ADD[:WINDow]? on page 142
Results:
CALCulate<n>:MARKer<m>:X on page 106
CALCulate<n>:MARKer<m>:Y on page 106
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Measurement and Result Displays
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.
Tip: To navigate within long marker peak lists, simply scroll through the entries with
your finger on the touchscreen.
Remote command:
LAY:ADD? '1',RIGH, PEAK, see LAYout:ADD[:WINDow]? on page 142
Results:
CALCulate<n>:MARKer<m>:X on page 106
CALCulate<n>:MARKer<m>:Y on page 106
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Basics on I/Q Data Acquisition and Processing
Processing Analog I/Q Data from RF Input
4 Basics on I/Q Data Acquisition and Pro-
cessing
Some background knowledge on basic terms and principles used when describing I/Q
data acquisition on the R&S FSWP in general, and in the I/Q Analyzer application in
particular, is provided here for a better understanding of the required configuration settings.
The I/Q Analyzer provides various possibilities to acquire the I/Q data to be analyzed:
●
Capturing analog I/Q data from the "RF Input" connector
●
Importing I/Q data from a file
Background information for all these scenarios and more is provided in the following
sections.
● Processing Analog I/Q Data from RF Input.............................................................19
● Basics on Input from I/Q Data Files........................................................................ 25
● Receiving and Providing Trigger Signals................................................................ 26
● I/Q Data Import and Export..................................................................................... 27
● Basics on FFT.........................................................................................................28
● I/Q Analyzer in MSRA Operating Mode.................................................................. 34
● Measurements in the Time and Frequency Domain............................................... 35
4.1 Processing Analog I/Q Data from RF Input
Complex baseband data
In the telephone systems of the past, baseband data was transmitted unchanged as an
analog signal. In modern phone systems and in radio communication, however, the
baseband data is modulated on a carrier frequency, which is then transmitted. The
receiver must demodulate the data based on the carrier frequency. When using modern modulation methods (e.g. QPSK, QAM etc.), the baseband signal becomes complex. Complex data (or: I/Q data) consists of an imaginary (I) and a real (Q) component.
Sweep vs sampling
The standard Spectrum application on the R&S FSWP performs frequency sweeps on
the input signal and measurements in the frequency and time domain. Other applications on the R&S FSWP, such as the I/Q Analyzer, sample and process the individual I
and Q components of the complex signal.
I/Q Analyzer - processing complex data from RF input
The I/Q Analyzer is a standard application used to capture and analyze I/Q data on the
R&S FSWP. By default, it assumes the I/Q data is modulated on a carrier frequency
and input via the "RF Input" connector on the R&S FSWP.
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Basics on I/Q Data Acquisition and Processing
Processing Analog I/Q Data from RF Input
The A/D converter samples the IF signal at a rate of 200 MHz. The digital signal is
down-converted to the complex baseband, lowpass-filtered, and the sample rate is
reduced. The analog filter stages in the analyzer cause a frequency response which
adds to the modulation errors. An equalizer filter before the resampler compensates
for this frequency response. The continuously adjustable sample rates are realized
using an optimal decimation filter and subsequent resampling on the set sample rate.
A dedicated memory (capture buffer) is available in the R&S FSWP for a maximum of
400 Msamples (400*1000*1000) of complex samples (pairs of I and Q data). The number of complex samples to be captured can be defined (for restrictions refer to Chap-
ter 4.1.1, "Sample Rate and Maximum Usable I/Q Bandwidth for RF Input",
on page 21).
The block diagram in Figure 4-1 shows the analyzer hardware from the IF section to
the processor.
Figure 4-1: Block diagram illustrating the R&S FSWP signal processing for analog I/Q data (without
Figure 4-2: Block diagram illustrating the R&S FSWP signal processing for analog I/Q data (with
bandwidth extension options)
option B320)
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4.1.1 Sample Rate and Maximum Usable I/Q Bandwidth for RF Input
Basics on I/Q Data Acquisition and Processing
Processing Analog I/Q Data from RF Input
Definitions
●
Input sample rate (ISR): the sample rate of the useful data provided by the device
connected to the input of the R&S FSWP
●
(User, Output) Sample rate (SR): the user-defined sample rate (e.g. in the "Data
Acquisition" dialog box in the "I/Q Analyzer" application) which is used as the basis
for analysis or output
●
Usable I/Q (Analysis) bandwidth: the bandwidth range in which the signal
remains undistorted in regard to amplitude characteristic and group delay; this
range can be used for accurate analysis by the R&S FSWP
●
Record length: Number of I/Q samples to capture during the specified measurement time; calculated as the measurement time multiplied by the sample rate
For the I/Q data acquisition, digital decimation filters are used internally in the
R&S FSWP. The passband of these digital filters determines the maximum usable I/Q
bandwidth. In consequence, signals within the usable I/Q bandwidth (passband)
remain unchanged, while signals outside the usable I/Q bandwidth (passband) are
suppressed. Usually, the suppressed signals are noise, artifacts, and the second IF
side band. If frequencies of interest to you are also suppressed, try to increase the output sample rate, which increases the maximum usable I/Q bandwidth.
Bandwidth extension options
You can extend the maximum usable I/Q bandwidth provided by the R&S FSWP in the
basic installation by adding options. The maximum bandwidth provided by the individual option is indicated by its number, for example, B40 extends the bandwidth to
40 MHz.
As a rule, the usable I/Q bandwidth is proportional to the output sample rate. Yet, when
the I/Q bandwidth reaches the bandwidth of the analog IF filter (at very high output
sample rates), the curve breaks.
● Bandwidth Extension Options................................................................................. 21
● Relationship Between Sample Rate, Record Length and Usable I/Q Bandwidth... 22
● R&S FSWP Without Additional Bandwidth Extension Options............................... 23
● R&S FSWP with I/Q Bandwidth Extension Option B80...........................................23
● R&S FSWP with Activated I/Q Bandwidth Extension Option B320.........................24
4.1.1.1 Bandwidth Extension Options
Max. usable
I/Q BW
40 MHz B40 U40
Required B-option Required U-option(s)
80 MHz B80 U40+U80 or
B40+U80
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Basics on I/Q Data Acquisition and Processing
Processing Analog I/Q Data from RF Input
Max. usable
I/Q BW
160 MHz B160 U40+U80+U160 or
80 MHz B80
320 MHz B320
Required B-option Required U-option(s)
B40+U80+U160 or
B80+U160
4.1.1.2 Relationship Between Sample Rate, Record Length and Usable I/Q Bandwidth
Up to the maximum bandwidth, the following rule applies:
Usable I/Q bandwidth = 0.8 * Output sample rate
Regarding the record length, the following rule applies:
Record length = Measurement time * sample rate
Maximum record length for RF input
The maximum record length, that is, the maximum number of samples that can be captured, depends on the sample rate.
Table 4-1: Maximum record length (without I/Q bandwidth extension options)
Sample rate Maximum record length
100 Hz to 200 MHz 440 Msamples
200 MHz to 10 GHz
(upsampling)
MSRA master:
200 MHz to 600 MHz
220 Msamples
MSRA operating mode
In MSRA operating mode, the MSRA Master is restricted to a sample rate of 600 MHz.
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Usable I/Q
bandwidth [MHz]
320
300
...
Basics on I/Q Data Acquisition and Processing
Processing Analog I/Q Data from RF Input
B320
200
...
100
80
40
20
Figure 4-3: Relationship between maximum usable I/Q bandwidth and output sample rate with and
without bandwidth extensions
10 MHz (without BW option)
40 80 120 160 200 240
B80
RF input:
BW = 0.80*f
280 320 360 400
4.1.1.3 R&S FSWP Without Additional Bandwidth Extension Options
Sample rate: 100 Hz - 20 GHz
Maximum I/Q bandwidth: 10 MHz
out
Output sample
[MHz]
rate f
out
MSRA operating mode
In MSRA operating mode, the MSRA Master is restricted to a sample rate of 600 MHz.
Table 4-2: Maximum I/Q bandwidth
Sample rate Maximum I/Q bandwidth
100 Hz to 10 MHz Proportional up to maximum 10 MHz
10 MHz to 20 GHz
MSRA master:
10 MHz to 600 MHz
10 MHz
4.1.1.4 R&S FSWP with I/Q Bandwidth Extension Option B80
Sample rate: 100 Hz - 20 GHz
Maximum bandwidth: 80 MHz
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Processing Analog I/Q Data from RF Input
MSRA operating mode
In MSRA operating mode, the MSRA Master is restricted to a sample rate of 600 MHz.
Sample rate Maximum I/Q bandwidth
100 Hz to 100 MHz Proportional up to maximum 80 MHz
100 MHz to 20 GHz
MSRA master:
100 MHz to 600 MHz
80 MHz
4.1.1.5 R&S FSWP with Activated I/Q Bandwidth Extension Option B320
Usable I/Q
bandwidth [MHz]
320
300
...
200
...
100
80
B80
RF input:
BW = 0.80*f
out
B320
40
20
Figure 4-4: Relationship between maximum usable I/Q bandwidth and output sample rate with and
Sample rate Maximum I/Q bandwidth
100 Hz to 400 MHz Proportional up to maximum 320 MHz
400 MHz to 20 GHz
MSRA master:
400 MHz to 600 MHz
10 MHz (without BW option)
40 80 120 160 200 240
without bandwidth extensions
320 MHz
280 320 360 400
Output sample
rate f
out
[MHz]
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Basics on I/Q Data Acquisition and Processing
Basics on Input from I/Q Data Files
Table 4-3: Maximum record length with activated I/Q bandwidth extension option B320
Sample rate Maximum record length
100 Hz to 200 MHz*) 440 Msamples
200 MHz to 468 MHz 470 Msamples * sample rate / 1GHz
468 MHz to 20 GHz
MSRA master:
468 MHz to 600 MHz
*) for sample rates up to 200 MHz the I/Q Bandwidth Extension B320 is not used
220 Msamples
4.2 Basics on Input from I/Q Data Files
The I/Q data to be evaluated in a particular R&S FSWP application can not 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.
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).
The I/Q data must be stored in a format with the file extension .iq.tar. For a detailed
description see Chapter A.3, "I/Q Data File Format (iq-tar)", on page 156.
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
As opposed to importing data from an I/Q data file using the import functions provided
by some R&S FSWP applications (e.g. the I/Q Analyzer or the R&S FSWP VSA application), the data is not only stored temporarily in the capture buffer, where it overwrites
the current measurement data and is in turn overwritten by a new measurement.
Instead, the stored I/Q data remains available as input 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, in order to perform measurements
on an extract of the available data (from the beginning of the file) only.
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.
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Basics on I/Q Data Acquisition and Processing
Receiving and Providing Trigger Signals
Sample iq.tar files
If you have the optional R&S FSWP VSA application (R&S FSWP-K70), some sample
iq.tar files are provided in the C:/R_S/Instr/user/vsa/DemoSignals directory
on the R&S FSWP.
Furthermore, you can create your own iq.tar files in the I/Q Analyzer, see Chap-
ter 7.2, "How to Export and Import I/Q Data", on page 74.
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.
4.3 Receiving and Providing Trigger Signals
Using one of the "trigger" connectors of the R&S FSWP, the R&S FSWP can use a signal from an external device as a trigger to capture data. Alternatively, the internal trigger signal used by the R&S FSWP can be output for use by other connected devices.
Using the same trigger on several devices is useful to synchronize the transmitted and
received signals within a measurement.
For details on the connectors see the R&S FSWP "Getting Started" manual.
External trigger as input
If the trigger signal for the R&S FSWP is provided by an external device, the trigger
signal source must be connected to the R&S FSWP and the trigger source must be
defined as "External" in the R&S FSWP.
Trigger output
The R&S FSWP can provide output to another device either to pass on the internal
trigger signal, or to indicate that the R&S FSWP itself is ready to trigger.
The trigger signal can be output by the R&S FSWP automatically, or manually by the
user. If it is provided automatically, a high signal is output when the R&S FSWP has
triggered due to a measurement start ("Device Triggered"), or when the R&S FSWP is
ready to receive a trigger signal after a measurement start ("Trigger Armed").
Manual triggering
If the trigger output signal is initiated manually, the length and level (high/low) of the
trigger pulse is also user-definable. Note, however, that the trigger pulse level is always
opposite to the constant signal level defined by the output "Level" setting, e.g. for
"Level" = "High", a constant high signal is output to the connector until the "Send Trigger" button is selected. Then, a low pulse is provided.
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4.4 I/Q Data Import and Export
Basics on I/Q Data Acquisition and Processing
I/Q Data Import and Export
Baseband signals mostly occur as so-called complex baseband signals, i.e. a signal
representation that consists of two channels; the in phase (I) and the quadrature (Q)
channel. Such signals are referred to as I/Q signals. The complete modulation information and even distortion that originates from the RF, IF or baseband domains can be
analyzed in the I/Q baseband.
Importing and exporting I/Q signals is useful for various applications:
●
Generating and saving I/Q signals in an RF or baseband signal generator or in
external software tools to analyze them with the R&S FSWP later
●
Capturing and saving I/Q signals with an RF or baseband signal analyzer to analyze them with the R&S FSWP or an external software tool later
For example, you can capture I/Q data using the I/Q Analyzer application and then perform analog demodulation on that data using the R&S FSWP AnalogDemodulation
application, if available.
As opposed to storing trace data, which may be averaged or restricted to peak values,
I/Q data is stored as it was captured, without further processing. The data is stored as
complex values in 32-bit floating-point format. Multi-channel data is not supported. The
I/Q data is stored in a format with the file extension .iq.tar.
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
The import and export functions are available in the "Save/Recall" menu which is displayed when you select the "Save" or "Open" icon in the toolbar (see Chapter 5.2,
"Import/Export Functions", on page 38).
Export only in MSRA mode
In MSRA mode, I/Q data can only be exported to other applications; I/Q data cannot be
imported to the MSRA Master or any MSRA applications.
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4.5 Basics on FFT
Basics on I/Q Data Acquisition and Processing
Basics on FFT
The I/Q Analyzer measures the power of the signal input over time. To convert the time
domain signal to a frequency spectrum, an FFT (Fast Fourier Transformation) is performed which converts a vector of input values into a discrete spectrum of frequencies.
t[s]
FFT
4.5.1 Window Functions
The Fourier transformation is not performed on the entire captured data in one step.
Only a limited number of samples is used to calculate an individual result. This process
is called windowing.
After sampling in the time domain, each window is multiplied with a specific window
function. Windowing helps minimize the discontinuities at the end of the measured signal interval and thus reduces the effect of spectral leakage, increasing the frequency
resolution.
Various different window functions are provided in the R&S FSWP to suit different input
signals. Each of the window functions has specific characteristics, including some
advantages and some trade-offs. Consider these characteristics to find the optimum
solution for the measurement task.
Ignoring the window function - rectangular window
The rectangular window function is in effect not a function at all, it maintains the original sampled data. This may be useful to minimize the required bandwidth. However, be
aware that if the window does not contain exactly one period of your signal, heavy
sidelobes may occur, which do not exist in the original signal.
f[Hz]
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Basics on I/Q Data Acquisition and Processing
Basics on FFT
Table 4-4: Characteristics of typical FFT window functions
Window type Frequency
Rectangular Best Worst Worst No function applied.
Blackman-Harris
(default)
Gauss (Alpha
= 0.4)
Flattop Worst Best Good Accurate single tone measurements
5-Term Good Good Best Measurements with very high
4.5.2 Overlapping
The I/Q Analyzer calculates multiple FFTs per measurement by dividing one captured
record into several windows. Furthermore, the I/Q Analyzer allows consecutive windows to overlap. Overlapping "reuses" samples that were already used to calculate the
preceding FFT result.
Magnitude
resolution
Good Good Good Harmonic detection and spurious
Good Good Good Weak signals and short duration
resolution
Sidelobe suppression
Measurement recommendation
Separation of two tones with almost
equal amplitudes and a small frequency distance
emission detection
dynamic range
In advanced FFT mode with averaging, the overlapping factor can be set freely. The
higher the overlap factor, the more windows are used. This leads to more individual
results and improves detection of transient signal effects. However, it also extends the
duration of the calculation. The size of the window can be defined manually according
to the record length, the overlap factor, and the FFT length.
An FFT overlap of 67%, for example, means the second FFT calculation uses the last
67% of the data of the first FFT. It uses only 33% new data. The third FFT still covers
33% of the first FFT and 67% of the second FFT, and so on.
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Basics on FFT
Figure 4-5: Overlapping FFTs
In "Manual" or "Auto" FFT mode, an FFT length of 4096 and a window length of 4096
(or the record length, if shorter) is used to calculate the spectrum.
Combining results - trace detector
If the record length permits, multiple overlapping windows are calculated and combined
to create the final spectrum using the selected trace detector. If necessary, the trace
detector is also used to reduce the number of calculated frequency points (defined by
the FFT length) to the defined number of measurement points. By default, the Autopeak trace detector is used.
Since the frequency points are reduced to the number of measurement points, using a
detector other than "Auto Peak" and fewer than 4096 measurement points can lead to
false level results.
4.5.3 Dependencies Between FFT Parameters
FFT analysis in the R&S FSWP is highly configurable. Several parameters, including
the resolution bandwidth, record length, and FFT length, are user-definable. Note,
however, that several parameters are correlated and not all can be configured independently of the others.
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