FM Distortion

(N5161A / N5162A / N5166B / N5171B / N5172B / N5181A / N5181B / N5182A / N5182B / N5182N Option UNT Only)

This test measures the total harmonic distortion (THD) of an FM signal produced by the DUT.

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 setup uses a spectrum analyzer with Analog Demodulation Measurement Application to both demodulate the signal and measure the distortion.

    Test Equipment

    Critical Specifications for This Test

    Recommended Model

    Alternate Model

    Spectrum Analyzer

    FM Demodulated Distortion < 0.1%

    N9030B Opt 5xx1, N9063EM0E Analog Demodulation Measurement Application

    N9030A Opt 5xx1, N9063EM0D Analog Demodulation Measurement Application2

    E444xA3 Option 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. The N9030A/B Option 550 frequency range is adequate for all DUT frequency configurations.
    2. To use the PXA N9030A with N9063EM0D 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. The E4448A frequency range is adequate for all DUT frequency configurations.

     

  2. Alternatively, an 8902A measuring receiver is used to demodulate the FM signal, and an 8903B audio analyzer will measure the demodulated distortion.

    Test Equipment

    Critical Specifications for This Test

    Recommended Models

    Measuring Receiver

    FM Demodulated Distortion < 0.1%

    8902A

    Audio Analyzer

    FM Demodulated Distortion < 0.1%

    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

Measuring Receiver Calibration

Test Setup

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. Refer to the troubleshooting section of the 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 search for your signal generator model number on the Keysight website.

  3. If necessary, obtain service from Keysight Technologies. Refer to Contacting Keysight Technologies.