Programming a Distortion Measurement

Last updated: January 16, 2009

This section provides an example of how to make distortion measurements via GPIB. Distortion measurements are not typically made when testing W-CDMA mobiles, but are more common when testing AMPS or other analog mobiles. The programming example below is typical for an AMPS mobile.

SINAD and Distortion measurements are affected by the same STATe and INITiate commands, so both measurements are enabled and triggered at the same time. However, measurement results are queried separately. See Audio Analyzer Measurement Description .

The following procedure assumes that the mobile's audio output is connected to the AUDIO IN connectors and the mobile is on an analog voice channel (AVC). The AVC is being modulated with a 1004 Hz tone at ± 8 kHz peak deviation, and a 6000 Hz SAT at ± 2 kHz peak deviation. It is also assumed that the Cell Power from the test set is set to -50 dBm (IS-137 standard).

Configure audio analyzer measurement parameters using the SETup subsystem.
Start the audio analyzer measurement using the INITiate subsystem.
Use the FETCh? subsystem to obtain audio analyzer measurement results.

Programming Example

 
10  OUTPUT 714;"SETup:AFANalyzer:CONTinuous OFF" !Set the audio analyzer
20                                           !measurements to single trigger mode.
30  OUTPUT 714;"SETup:AFANalyzer:PEAK:VOLTage 3V" !Set the Expected Amplitude level for
40                                                !audio input voltage in Vpeak.
50  OUTPUT 714;"SETup:AFANalyzer:SDIStortion:STATe ON" !Turn on the SINAD and
60                                                  !distortion measurements.
70  OUTPUT 714;"SETup:AFANalyzer:SDIStortion:FREQuency 1004 HZ" !Specify the audio
80                                      !frequency to use for the measurements.
90  OUTPUT 714;"SETup:AFANalyzer:FILTer CMessage" !Select the c-message filter.
100 OUTPUT 714;"SETup:AFANalyzer:DEMPhasis:STATe OFF" !Turn off de-emphasis.
110 OUTPUT 714;"SETup:AFANalyzer:EXPandor:STATe OFF" !Turn off the expandor.
120 OUTPUT 714;"SETup:AFANalyzer:TIMeout 3S" !Set a timeout value of 3 seconds
130                                      !in case the measurement cannot be made.
140 OUTPUT 714;"INITiate:AFANalyzer" !Start the AF Analyzer measurement.                               
150 OUTPUT 714;"FETCh:AFANalyzer:INTegrity?" !Query the integrity indicator to
160                           !verify that a reliable measurement was made.
170 ENTER 714;Integrity  !Enter the returned value into a variable for comparison
180                      !with possible integrity indicator values (not shown here).
190 IF Integrity=0 THEN  !Only fetch measurement result if integrity indicator is 0.
200 OUTPUT 714;"FETCh:AFANalyzer:DISTortion?" ! Fetch the Distortion result.
210 ENTER 714;Distortion !Enter the returned value into a variable.
220 END IF
230 END

Returned Values

The results returned by this program are:

Integrity returns the measurement integrity indicator; 0 means a successful measurement with no errors. See Integrity Indicator .
Distortion returns the Distortion measurement value in percent (%).

Programming a Distortion Measurement

Programming Example

Returned Values

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