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Time Domain Gate Filtering of Vector Network Analyzer (Part I)

Use of time domain gate function can select or filter a specific response in time domain, while the Vector and Analyzer can transform the processed time domain data to frequency domain again for observation. That is to say, after time domain filtering is performed to time domain data, function of time domain transformation can be turned off, and then frequency domain response of the measured piece can be observed in the condition that function of time domain is effective. For example, during transmission Measure, eliminate effect of multi-pass transmission by use of time domain gate, or observe a single time domain response signal at a time and then Analysis the effect of each single response toward Measure result in frequency domain. This section will be divided into two parts (Part II).

1. How to Use Gate Function

In actual Measure, Measure steps with time domain gate function are as follows:

1) Measure the measured piece in frequency domain.

2) Witch on time domain transformation function and the Analyzer will calculate time domain response of the measured piece.

3) Select gate type:

Band-pass: set the gate at the center requiring response reservation, switch on gate function and response outside the gate is removed from the displayed Measure through mathematical manipulation.

Band-stop: set the gate at the center from which the response is to be eliminated, switch on gate function and response inside the gate is removed from the displayed Measure through mathematical manipulation.

4) Turn off time domain transformation function, observe frequency domain response of the measured piece and see the effect of specific response toward Measure result. Figure below illustrates the Measure application of a band-pass time domain gate:

Fig.1 Observing effect of single response toward measure result by use of time domain gate

2. Gate Settings

Border and function of the gate can be set and defined as below:

1) Start and stop: to define -6dB cut-off time of the gate.

2) Center: to define center time of the gate.

3)  Span: it equals to terminal time minus start time.

4) Gate Type:

Band-pass: to filter response outside the gate.

Band-stop: to filter response inside the gate.