PSA YTF Optimization

The PSA switches in a YIG Tuned Filter (YTF) for frequencies above 3 GHz. The YTF bandwidth is from 60 to 100 MHz. Unfortunately, within this bandpass the filter isn't flat and contains peaks and troughs that may vary in amplitude by 2 dB. The filter will also change its filter shape and center frequency due to heat being dissipated from the YIG tuning coils. At higher frequencies more current is supplied to the coils and, thus, more heat.

To compensate for the YTF behavior a calibration is done to find the flattest area of the filter. For each test frequency the flat part of the filter is found and stored for later use. This calibration only needs to be done once per PSA or if the YTF is replaced. When Power Level Accuracy (PLA) is performed this software will be called and the previously stored offset frequency will be passed in for the center frequency being tested. The software will then perform an optimization around the passed in frequency to ensure the signal is in the flat section of the YTF. The "Preselect Adjust" function of the PSA is used to detune the YTF center frequency. This shifts the YTF's flattest area over the DUT output signal during PLA.

Required Test Equipment

Instrument

Recommended Model1

Spectrum Analyzer

E444xA2 Opt 1DS, 1233
  1. Refer to the main equipment list for alternate models.
  2. Depending on your frequency range needs, choose either an E4440A, E4443A, E4445A, E4446A, or E4448A. (E4447A is for Power Level Accuracy adjustment only.)
  3. Option 123 is for ESGs > 3 GHz. All models require Option 1DS.

 

Connections and Setup Procedures

All test equipment requires a 30 minute warm-up period to ensure accurate performance.

In the following test setup, direct cable and adapter connections are designated as solid lines. Changeable cable and adapter 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 adjustment, follow all instructions on the controller display.

Setup for PSA YTF Optimization Utility