Frequency Counter (Markers)

When Frequency Counter is enabled, the VSA uses a narrower resolution bandwidth around the marker to more precisely calculate the frequency of the largest signal component at the marker.

The Frequency Counter is enabled for a marker when the Frequency Counter check box is selected in the Markers Calculation tab.

Only one marker per trace may have Frequency Counter enabled.

Frequency Counter is available only for Vector and Analog Demod measurement types.

To use the frequency counter, follow these steps:

Set Input > Data From to Hardware.
Set Trigger Style to Free Run.
Disable Time Gating.
Start the measurement.
Choose a frequency domain Trace Data (Spectrum, PSD Power Spectral Density: See power spectral density., or Inst Spec).
Add a marker and position the marker at a peak (or right-click the trace and choose Peak).
Click Markers > Calculation.
Select the Frequency Counter check box.

The Markers Window will show a line labeled Freq X (where X is the marker number) that shows the calculated frequency each time a measurement update is completed.

The VSA center frequency can be set to the value calculated by the frequency counter by clicking Markers > Copy Marker to > Copy Counter to Center Frequency.

Now you can vary the frequency span to more closely examine the peak signal.

Frequency Counter does not work with recalled traces, recorded data, or data from Simulation Software. Frequency Counter works with simulated hardware, but the results are not quite as accurate as with live data from measurement hardware.

Frequency Counter validity

The Frequency Counter readout is valid only for the configurations in the following table:

Parameter:	Setting:
Measurement Type	Vector or Analog Demod
Marker	On
Trigger Type	Free run
Time gating	Off
Measurement Data	Spectrum, PSD, or instantaneous spectrum

When the Frequency Counter is enabled and the conditions listed in the previous table are not met, the marker readout indicates that the frequency is not valid. Here are some examples of an invalid Frequency Counter:

Low SNR: When Frequency Counter is on, the VSA estimates the length of the data block required to calculate the frequency. If the signal-to-noise ratio is very low, or the frequency span is very narrow, the VSA will be unable to accurately estimate the frequency. In this case, the Frequency Counter readout shows "Low SNR Signal-to-Noise Ratio" next to the frequency estimate.
Not a valid measurement: The Frequency Counter counts only data from the current input spectrum. If a trace data is selected that is not linked to the input spectrum¾for example, Auto Correlation¾the readout displays "Not a valid measurement."
Trace data not countable: If the Frequency Counter is enabled for a marker on recalled traces, recorded data, data register contents, or data from Simulation Software, the readout shows "Trace data not countable."