The Designer's Guide Community
Forum
Welcome, Guest. Please Login or Register. Please follow the Forum guidelines.
May 17th, 2022, 7:47am
Pages: 1
Send Topic Print
Plot an oscillator output spectrum (Read 207 times)
polyam
Community Member
***
Offline



Posts: 74

Plot an oscillator output spectrum
Apr 22nd, 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
Back to top
 
 
View Profile   IP Logged
Ken Kundert
Global Moderator
*****
Offline



Posts: 2335
Silicon Valley
Re: Plot an oscillator output spectrum
Reply #1 - Apr 22nd, 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
Back to top
 
 
View Profile WWW   IP Logged
Pages: 1
Send Topic Print
Copyright 2002-2022 Designer’s Guide Consulting, Inc. Designer’s Guide® is a registered trademark of Designer’s Guide Consulting, Inc. All rights reserved. Send comments or questions to editor@designers-guide.org. Consider submitting a paper or model.