Network Analyzer

[suktan]

Not sure my following question was asked and answered. I would like to know is there a tracking bandpass filter employed in network analyzer to improve SNR?

[attila]

I don't think is used because I don't know what this is

Could you provide some reference to "tracking bandpass filter" ?

[suktan]

A bandpass filter (BPF) is used to filter channel 2 (& 1 as well). Its center frequency is equal to the Wavegen's frequency (hence tracking). In a traditional network analyzer, bandwidth of the BPF is can be adjusted for various resolution bandwidths. Narrower bandwidth provides higher noise suppression at the expense of slower sweep.

[attila]

This is a digital solution, not a typical network analyzer bench device with analog bandpass filter.

The Network Analyzer in WaveForms uses the device (Analog Discovery, EExplorer) Wavegen (AWG) to generate excitation signal and the Scope input to acquire data.
The analysis is performed from start to stop frequency in the specified number of steps. For each step, the WaveGen channel is set to a constant frequency and the Oscilloscope performs an acquisition. Using the frequency transformation result from the index corresponding to the current frequency step, the magnitude and phase value is calculated. The magnitude of Channel 1 (filter input) is calculated relative to WaveGen Amplitude, and the magnitude and phase values of the other channels are relative to Channel 1.

In this solution the bandpass filter is the FFT resolution, which is determined (tracked) by the current frequency step and captured periods.
Under the Network Analyzer's WaveGen options you can find the Minimum Periods options. Increasing this will slow down the low frequency analysis but it will narrow the FFT bandwidth and improve the SNR. 

Considering the earlier, I think we can call it auto-tracking bandpass filter.

[suktan]

Thanks for your response.