Rohde & Schwarz CMW-KM645 User manual

R&S®CMW-KM645
FM Stereo Radio
Firmware Applications
User Manual
User Manual
(;×ïX2)
1173.9740.02 ─ 03
Test & Measurement
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This user manual describes the following R&S®CMW options:
●R&S®CMW-KM645 (FM Stereo Radio, TX measurement)
© 2013 Rohde & Schwarz GmbH & Co. KG
Mühldorfstr. 15, 81671 München, Germany
Phone: [phone] - 0
Fax: [phone]
E-mail: [email protected]
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.
The following abbreviations are used throughout this manual: R&S®CMW is abbreviated as R&S CMW.
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Contents
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Contents
1Preface....................................................................................................5
1.1 How to Read Firmware Application Chapters............................................................5
1.1.1 General Description........................................................................................................5
1.1.2 Application Sheets..........................................................................................................5
1.1.3 GUI Reference................................................................................................................6
1.1.4 Programming Examples..................................................................................................6
1.1.5 Command Reference......................................................................................................6
2What's New in this Revision..................................................................7
3 General Description...............................................................................8
3.1 Test Setup......................................................................................................................8
3.2 Measuring an FM Signal...............................................................................................9
3.3 AF Filter Settings..........................................................................................................9
3.4 Limit Settings and Conformance Requirements......................................................10
3.4.1 RF Carrier Requirements..............................................................................................11
3.4.2 RF Modulation Requirements.......................................................................................11
3.5 Measurement Results.................................................................................................11
3.5.1 RF Carrier Results........................................................................................................11
3.5.2 RF Modulation Results..................................................................................................13
3.5.3 AF Measurement Results..............................................................................................15
3.5.4 Selecting and Modifying Views.....................................................................................17
3.5.5 Common View Elements...............................................................................................17
4GUI Reference......................................................................................19
4.1 Measurement Control.................................................................................................19
4.2 Parameters and Settings............................................................................................19
4.2.1 Signal Routing and Analyzer Settings...........................................................................20
4.2.2 Measurement Control Settings......................................................................................22
4.2.3 Limit Settings.................................................................................................................24
4.2.4 Display Settings............................................................................................................25
4.3 Measurement Results.................................................................................................26
5Programming........................................................................................28
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Contents
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5.1 Key Features................................................................................................................28
5.2 Specifying General Measurement Settings..............................................................28
5.3 Specifying Measurement Control Settings...............................................................29
5.4 Specifying Limits........................................................................................................29
5.5 Performing Single Shot RF Measurements..............................................................29
5.6 Continuous and AF Measurements...........................................................................30
6Command Reference...........................................................................32
6.1 Conventions and General Information......................................................................32
6.1.1 MEAS<i>.......................................................................................................................32
6.1.2 FETCh, READ and CALCulate Commands..................................................................32
6.1.3 Current and Statistical Results......................................................................................33
6.1.4 Reliability Indicator........................................................................................................33
6.2 Signal Routing and Analyzer Settings......................................................................35
6.3 Measurement Control and States..............................................................................39
6.4 Measurement Control Commands.............................................................................41
6.5 Limits............................................................................................................................46
6.6 Measurement Results.................................................................................................50
6.6.1 RF Carrier Results........................................................................................................50
6.6.2 RF Modulation Results..................................................................................................53
6.6.3 AF Modulation Results..................................................................................................55
List of Commands................................................................................62
Index......................................................................................................64
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Preface
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1 Preface
The operation of the R&S CMW is described in several user manuals:
●The R&S CMW user manual describes the base software, common features of the
firmware applications and basic principles for manual operation and remote control.
●Additional user manuals, like this document, describe the firmware applications.
Rohde & Schwarz provides registered users a "CMW Customer Web" section on
GLORIS, the Global Rohde & Schwarz Information System: https://extranet.rohde-
schwarz.com. From this resource you can download software updates, waveform library
updates and documentation updates, e.g. updates of this document.
1.1 How to Read Firmware Application Chapters
Each firmware application is described in a separate chapter. These chapters can be
read independently of each other. However, they are all organized as follows:
1. General Description
2. Application Sheets (optional)
3. GUI Reference
4. Programming Examples
5. Command Reference
The chapters "System Overview" and "Remote Control" in the R&S CMW user manual
provide additional important information independent of the individual firmware applica-
tions. The most important parts are referenced by the firmware application descriptions.
1.1.1 General Description
This section provides a general description of the firmware application, independent of a
specific operation mode (manual or remote control). It gives a high-level introduction to
the capabilities of the firmware application. Background information related to the network
standard is given as far as it is directly related to administrable parameters. For mea-
surement applications a detailed description of measurement results and a description
of configurable limits is given, including the relation to conformance requirements defined
in network standard specifications.
1.1.2 Application Sheets
This optional section provides short application examples for select issues and related
background information.
How to Read Firmware Application Chapters
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Preface
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1.1.3 GUI Reference
The GUI reference describes the manual operation of the firmware application via the
Graphical User Interface (GUI).
The description of a configuration dialog usually starts with a screenshot presenting the
preset values of the parameters (sometimes preset values are modified to enable hidden
parts of a dialog). Below the screenshot all shown parameters are described. For each
single parameter a link to the corresponding command description in the "Command
Reference" is provided. Ranges for numeric parameters and reset values are given there.
For measurement results links to the corresponding command descriptions are provided
(commands to retrieve the results). The measurement results are described in detail in
the "General Description".
1.1.4 Programming Examples
The programming examples show how to control and configure the firmware application
via a remote-control program and how to retrieve measurement results. The examples
consist of comprehensive command sequences. You can check just a single command
of a sequence to get an example for the syntax of this single command. But you can also
consider an entire sequence showing the commands in the context of a command script,
under consideration of dependencies and required orders of the commands.
The command sequences are written with the intention to list most commands of the
firmware application. They do not show the fastest way for a given configuration task.
The fastest way would use many reset values and omit the corresponding commands.
The examples are referenced by the command descriptions of the "Command Refer-
ence".
1.1.5 Command Reference
The command reference provides information on the remote commands of the firmware
application. The commands are grouped according to their function.
Each command description indicates the syntax of the command header and of the
parameters. For input parameters the allowed ranges, reset values and default units are
listed, for returned values the expected ranges and default units. Most commands have
a command form and a query form. Exceptions are marked by "Setting only", "Query only"
or "Event". Furthermore a link to the "Programming Examples" is provided and the first
software version supporting the command is indicated.
How to Read Firmware Application Chapters
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What's New in this Revision
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2 What's New in this Revision
This revision describes version 3.2.10 and later of the "FM Stereo Radio Measurement"
firmware application. Compared to version 3.0.10 it provides the following new features
and changes:
●Configurable frequency offset, see Frequency Offset
●Configurable mixer level offset, see Mixer Level Offset
Software Version
To check your R&S CMW software version, open the "Setup" dialog and click "HW/SW
Equipment". The initial software version for each remote control command is quoted in
the reference description.
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General Description
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3 General Description
The "FM Stereo Radio Measurement" application (option R&S CMW-KM645) provides
transmitter (TX) tests on FM-modulated RF signals (called "FM signals" in the following).
The tests cover the following FM signal properties:
●RF carrier characteristics including the carrier power, frequency error, and the fre-
quency deviation due to a composite modulating signal ("multiplex deviation")
●RF modulation characteristics including the frequency deviation due to the 19-kHz
pilot, the left and the right audio channels, and the pilot frequency error
●Characteristics of the demodulated AF baseband signal including a Total Harmonic
Distortion (THD), Signal to Noise and Distortion ratio (SINAD), and Signal to Noise
Ratio (SNR) measurement
For background information on FM signals and conformance requirements refer to the
relevant standards, e.g.:
●IEC 60315-4 (1997), Methods of measurement on radio receivers for various classes
of emission
●ITU-R Recommendation BS.450-3, Transmission standards for FM sound broad-
casting at VHF
All "FM Stereo Radio" measurements are combined in a single, multi evaluation mea-
surement group.
The following sections describe how to configure and perform the "FM Stereo Radio
Measurement".
●Test Setup.................................................................................................................8
●Measuring an FM Signal...........................................................................................9
●AF Filter Settings.......................................................................................................9
●Limit Settings and Conformance Requirements......................................................10
●Measurement Results.............................................................................................11
3.1 Test Setup
The external RF signal source (mobile station, signal generator etc.) is connected to one
of the RF input connectors (RF COM) at the front panel of the R&S CMW. No additional
cabling and no external trigger is needed.
The input level ranges of all RF COM connectors are identical.
See also: "RF Connectors" in the R&S CMW user manual, chapter "Getting Started"
Test Setup
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General Description
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Fig. 3-1: Connecting an RF transmitter to the instrument
The measurement is performed in free run mode; no trigger signal is needed.
3.2 Measuring an FM Signal
After connecting your FM signal source to the R&S CMW as shown in section Test
Setup, you have to adjust the following analyzer settings to the properties of the analyzed
signal:
●The analyzer "Frequency" (RF carrier frequency)
●The "Expected Nominal Power" and (optional) a "User Margin" and "External Attenu-
ation". Recommended values: "Expected Nominal Power" = nominal power of the RF
carrier. FM signals are transmitted at constant power (constant-envelope signals), so
the default "User Margin" of 0 dB should be sufficient.
With the settings described above, the R&S CMW is able to receive and demodulate the
FM stereo signal and obtain the essential measurement results.
The following measurements require additional settings:
●The demodulated left and right AF channel signals can be measured with different
filter settings in the AF analyzer path ("Deemphasis Filter", "Lowpass Filter", "High-
pass Filter", "Weighting Filter", "Bandpass Variable"). See section AF Filter Set-
tings.
●To determine the Total Harmonic Distortion (THD), the Signal to Noise and Distortion
Ratio (THD + N / SINAD), and the Signal to Noise Ratio (SNR), two fixed, sine wave
audio tones are transmitted over the left and right audio channels ("THD (N) Freq.
Left" and "THD (N) Freq. Right"). See description of "THD / SINAD / SNR measure-
ments" in chapter 3.5.3, "AF Measurement Results", on page 15.
3.3 AF Filter Settings
The audio receive path of the R&S CMW provides optional filter stages which affect the
AF results:
●A deemphasis filter with a time constant of either 50 μs or 75 μs. A deemphasis is
designed to decrease the magnitude of the higher frequencies with respect to the
magnitude of the lower frequencies in order to improve the overall signal-to-noise
ratio.
Measuring an FM Signal
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General Description
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A 50 μs time constant is used for FM broadcasting in Europe, North American FM
stations use a 75 μs time constant.
●An A-weighting filter defined in IEC 60651. The A-weighting filter deemphasizes the
very low and very high frequency components of the sound in a manner similar to the
frequency response of the human ear and correlates well with subjective reactions
to noise. Thus, noise levels stated in terms of dBA reflect the response of the human
ear by filtering out some of the noise in the low- and high-frequency ranges that the
ear does not detect well. The A-weighted scale commonly is used in local ordinances
and standards.
●A lowpass filter and a highpass filter with selectable cutoff frequencies. You can use
the highpass filter to eliminate a possible DC component in the audio signal that may
cause measurement inaccuracies.
●A variable bandpass filter with configurable center frequency and bandwidth.
Each of the left and right channels from the FM stereo decoder (see figure 3-7) is mea-
sured as shown below.
Fig. 3-2: Filters in the audio receive path
3.4 Limit Settings and Conformance Requirements
Conformance requirements for tests on FM signals are specified in the various standards;
the following sections give an overview.
●RF Carrier Requirements........................................................................................11
●RF Modulation Requirements.................................................................................11
Limit Settings and Conformance Requirements
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