Rohde & Schwarz CMW-KM645 User manual

R&S®CMW-KM645
FM Stereo Radio
Firmware Applications
User Manual
User Manual
1173.9740.02 ─ 04
(;×ïX2)
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)
© 2015 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
1 Preface.................................................................................................... 5
1.1 How to Read Firmware Application Chapters............................................................ 5
1.1.1 General Description........................................................................................................ 5
1.1.2 Application Sheets.......................................................................................................... 6
1.1.3 GUI Reference................................................................................................................ 6
1.1.4 Programming Examples..................................................................................................6
1.1.5 Command Reference...................................................................................................... 6
2 What'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
4 GUI 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
5 Programming........................................................................................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
6 Command 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 Values for RF Path Selection........................................................................................ 33
6.1.5 Keywords...................................................................................................................... 34
6.1.6 Reliability Indicator........................................................................................................ 34
6.2 Signal Routing and Analyzer Settings...................................................................... 37
6.3 Measurement Control and States.............................................................................. 40
6.4 Measurement Control Commands.............................................................................42
6.5 Limits............................................................................................................................48
6.6 Measurement Results................................................................................................. 51
6.6.1 RF Carrier Results........................................................................................................ 51
6.6.2 RF Modulation Results..................................................................................................54
6.6.3 AF Modulation Results.................................................................................................. 56
List of Commands................................................................................63
Index......................................................................................................65
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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.
There is a separate manual version for each R&S CMW model.
●Additional user manuals, like this document, describe the firmware applications.
There is only one version of these manuals for all R&S CMW models.
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, for example 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 descrip-
tions.
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 measurement applications a detailed description of measurement results and a
description of configurable limits is given, including the relation to conformance require-
ments defined in network standard specifications.
How to Read Firmware Application Chapters
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Preface
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1.1.2 Application Sheets
This optional section provides short application examples for select issues and related
background information.
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 hid-
den 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 "Com-
mand Reference" is provided. Ranges for numeric parameters and reset values are
given there.
For measurement results links to the corresponding command descriptions are provi-
ded (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 applica-
tion via a remote-control program and how to retrieve measurement results. The exam-
ples consist of comprehensive command sequences. You can check just a single com-
mand 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 com-
mand script, under consideration of dependencies and required orders of the com-
mands.
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 firm-
ware 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 3.5.10 and later of the "FM Stereo Radio Measure-
ment" firmware application. Compared to version 3.2.10, there are only editorial
changes.
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 follow-
ing).
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
Connect the external RF signal source (mobile station, signal generator etc.) to one of
the bidirectional RF connectors on the front panel of the R&S CMW.
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 ana-
lyzed signal:
●The analyzer "Frequency" (RF carrier frequency)
●The "Expected Nominal Power" and (optional) a "User Margin" and "External
Attenuation". 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 Distor-
tion 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
measurements" 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 stand-
ards; the following sections give an overview.
●RF Carrier Requirements........................................................................................11
●RF Modulation Requirements................................................................................. 11
Limit Settings and Conformance Requirements
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