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Simulators >> Circuit Simulators >> Plot an oscillator output spectrum
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Message started by polyam on Apr 22^nd, 2021, 5:36pm

Title: Plot an oscillator output spectrum
Post by polyam on Apr 22^nd, 2021, 5:36pm

Hi,

I have an oscillator running at fosc. My question is how to plot the spectrum of the time domain output of the oscillator. What I am specifically looking for is the relation between the simulation time (time domain data record), the number of FFT points, and fosc to correctly plot the spectrum. Does the Coherent Sampling of a periodic waveform apply here? if so, how?

Thanks

Title: Re: Plot an oscillator output spectrum
Post by Ken Kundert on Apr 22^nd, 2021, 7:54pm

You have two choices, you can perform an FFT after the simulation, in which case the FFT will not be synchronous with the oscillation. In this case the period of the FFT will not match that of the oscillator. You can reduce the artifacts of the period mismatch by simulating many cycles while applying windowing.

Or, you can use SpectreRF. It computes the periodic steady state analysis, and so it directly computes the period. It can compute the spectrum without the artifacts.

-Ken