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Agilent PNA Microwave Network Analyzers Application Note 1408-11 Accurate Pulsed Measurements High Performance Pulsed S-parameter Measurements Vector network analyzers are traditionally used to measure the continuous wave (CW) S-parameter performance of components. Often under these operating conditions the analyzer is functioning as a narrowband measurement instrument. It transmits a known CW frequency to the component and measures the CW frequency response. If we were to look at the response of a single CW frequency we would see a single spectral tone in the frequency domain. The analyzer has a built in source and receivers that are designed to operate together in a synchronous manner, utilizing narrowband detection, to measure the frequency response of the component. Most analyzers can be configured to generate a frequency sweep over many frequency tones. In some cases the signal applied to the component must be pulsed (turned on and off) at a specific rate and duration. If we were to look at the frequency domain response of a single pulsed tone, it would contain an infinite number of spectral tones making it challenging to utilize a standard narrowband VNA. This article describes how to configure and make accurate pulsed S-parameter measurements using the Agilent microwave PNA network analyzer. Pulsed Signals To see what the frequency domain spectrum of a pulsed signal looks like we first mathematically analyze the time domain response. Equation 1 illustrates the time domain relationship of a pulsed signal. This is generated by first creating a rectangular windowed version (rect(t)) of the signal with pulse width PW. A shah function is then realized consisting of a periodic train of impulses spaced 1/PRF apart where PRF is the pulse repetition frequency. This can also be viewed as impulses at spacing equal to the pulse period. The windowed version of the signal is then convolved with the shah function to generate a periodic pulse train in time corresponding to the pulsed signal. 1 (t) y(t) = (rectpw(t)