FM Distortion

This test measures the total harmonic distortion (THD) of an FM signal produced by the UUT. This test is currently performed in only one frequency band. Due to the signal generator’s design, this band is also representative of the signal generator’s full frequency range.

Required Test Equipment

This test supports two equipment setups using either a spectrum analyzer or a measuring receiver. The spectrum analyzer is the preferred solution.

  1. The preferred solution uses a spectrum analyzer with Analog Demodulation Measurement Application to demodulate the signal and measure the deviation.

    Test Equipment

    Critical Specifications for This Test

    Recommended Models

    Alternate Models

    Spectrum Analyzer

    FM Demodulated Distortion < 0.1%

    N9030B Opt 5xx1, N9063EM0E Analog Demodulation Measurement Application

    N9030A Opt 5xx1 and N9063EM0E Analog Demodulation Measurement Application2

    E444xA3 Opt 233

    1. Select any option of PXA spectrum analyzer (503, 508, 513, 526, 543, 544, 550) that has a maximum frequency greater than or equal to the maximum frequency of the unit under test.

    2. To use the PXA N9030A with N9063EM0E analog demodulation measurement application functionality above 3.5 GHz, the N9030A must be upgraded with either Option MTU or TES. For more information, see the main Required Equipment table.

    3. Select any model of PSA spectrum analyzer (E4440A, E4443A, E4445A, E4446A, E4447A, E4448A) that has a maximum frequency greater than or equal to the maximum frequency of the unit under test.

  2. The alternate solution uses an 8902A measuring receiver to demodulate the signal and measure the deviation.

    Test Equipment

    Critical Specifications for This Test

    Recommended Models

    Measuring Receiver

    FM Deviation Accuracy

    8902A

    Audio Analyzer

    Distortion Accuracy

    8903B

Connections and Setup Procedures
  • All test equipment requires a 30 minute warmup period to ensure accurate performance.
  • In the following test setup, cables are designated as solid lines and direct connections are designated as dashed lines.
  1. Connect all test equipment as shown.
  2. Connect GPIB cables to all GPIB-controlled test equipment.
  3. While performing this test, follow all instructions on the controller display.

 

Spectrum Analyzer Test Setup

 

 

 

Measuring Receiver Test Setup

 

Calibration Setup

 

FM Distortion Test Setup with Measuring Receiver

 

In Case of Difficulty

If this performance test fails, perform the following steps in order:

  1. Check the equipment setup (see above). If the setup is incorrect, make the necessary corrections and rerun the performance test.

  2. If this test fails with the equipment set up properly, refer to the troubleshooting section of the signal generator's service guide. If you do not have a printed copy of the service guide (Option OBW), one is available either on the CD-ROM that came with your signal generator shipment or on the Keysight Website.

  3. If you cannot correct the problem using the troubleshooting procedures in the Service Guide, obtain service from Keysight Technologies. Refer to Contacting Keysight Technologies.