Frequency Converter (User Correction)

Menu Path: Input > User Correction

Input > Playback User Correction

The Frequency Converter parameters are disabled (greyed-out) for Playback User Correction.

The Frequency Converter is used to specify the frequency parameters of an external downconverter connected to the analyzer hardware. The VSA uses this correction data to adjust the Center Frequency, marker readouts, and other frequency parameters and annotations so that they are correct relative to the input of the external converter. See Setting Up an 89640 with External Downconverter for an example setup using this feature.

After entering the user correction data, the VSA center frequency and bandwidth/span (MeasSetup > Frequency > Frequency tab) can be set to match the downconverter.

The Frequency Converter parameters apply to both I and Q channels of an I+jQ measurement channel.

The following parameters are available in this section:

The Frequency Converter parameters are disabled (greyed-out) during recording playback.

The settings in this section are remembered when the VSA is closed and restored when the VSA restarted.

When Frequency Converter is selected, the VSA is set by default to the specified IF Center Frequency. The trace data annotated measurement "Center" frequency is the specified RF Center Frequency. This reflects the fact that the external downconverter is tuned to the RF Center Frequency and produces an output at the IF Center Frequency. Select Inverted Spectrum if the downconverter outputs a spectrum that is mirrored relative to the input.

The measurement center frequency can be changed (see Changing Frequency Settings) within the limitations of the measurement hardware as well as the IF Bandwidth specified on the User Correction tab. When the measurement center frequency and span are changed, the measurement hardware is tuned within the IF range of the external downconverter. The displayed center frequency is changed appropriately, even though the RF Center Frequency is unchanged. This reflects the fact that a different portion of the bandwidth made available by the external converter is being looked at.

The measurement center frequency is limited to the RF Center Frequency ± ½ the IF Bandwidth, unless the measurement hardware limits are more restrictive. Spectrum displays are blanked outside the same limits.

If Fixed Equalization is selected while Frequency Converter is in use, the fixed equalizer will select relative or absolute frequency mapping based on the tuning of the VSA hardware (i.e. at the converter IF frequency), not the displayed center frequency. If Amplifier/Attenuator Delay is selected while Frequency Converter is in use, the delay is applied at the VSA input (i.e. at the converter IF frequency).