Time Domain Measure; Principle For Time Domain Measure - Saluki S3601 Series User Manual

8. Time Domain Measure

This chapter describes the basic principle for time domain Measure performed by Analyzer, how to set up the instrument to improve
accuracy of time domain Measure and how to analyze result of time domain Measure, including contents below:

Principle for time domain Measure

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Resolution and range of time domain Measure
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Window filtering
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Time domain gate filtering
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Time domain Measure data
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Band pass and low pass time domain modes
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Setting time domain transformation Measure
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8.1.Principle for Time Domain Measure
In general Measures, the Analyzer displays the response of measured piece which varies with frequency, and this is called frequency
domain Measure. When performing time domain Measure, the Analyzer obtains time domain data through inverse Fourier Transform
of frequency domain, the Measure results are indicated by taking time as X axis, the response values appear at the time of separation
and characteristics or fault points of the measured piece can be Analysisd. Figure below is the reflection Measure result of frequency
domain and time domain of the same cable which has two bends, both bending points resulting in transmission line mismatch or
impedance change.
Frequency domain response of S11 measured at input port indicates the combined reflection response caused by interaction of
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mismatched cable waves; however, definite physical location of the cable mismatch is hard to be determined.
Time domain response indicates location and size of each mismatch and we can see from the response that apparent mismatch
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occurs at the second bend of the cable.
In time domain, the Analyzer can filter undesired responses by using gate function and then converts time domain data back to
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frequency domain data. This function can be used to measure response of specific signal in network and filter effects of external
instruments such as connector or adapter.
Time domain Measure function of the Analyzer simulates conventional time domain reflectometer (TDR). An impulse or step-function
signal is transmitted to the measured piece from time domain reflectometer, then observe energy of the reflected signal and
impedance change of the measured piece can be determined by analyzing amplitude, duration and waveform of the reflected signal.
When performing time domain Measure, Network Analyzer doesn't generate incident impulse or step-function signal actually, but
performs Sweep Measure and then calculates time domain information from frequency domain Measure result through Fourier
Algorithm.
Fig. 8-1 Frequency Domain and Time Domain Measures
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