The Designer's Guide Community
Forum
Welcome, Guest. Please Login or Register. Please follow the Forum guidelines.
Jun 24th, 2019, 6:39pm
Pages: 1
Send Topic Print
question on pnoise sim theory (Read 149 times)
dog1
Community Member
***
Offline



Posts: 52

question on pnoise sim theory
Apr 09th, 2019, 12:35pm
 
Hello all,

I have a question about the pnoise simulation.

I understand that in frequency domain, the switching system should translate noise in the following way:

cross correlate the noise source spectra with the model of the system large signal behavior (eg. square or sin signal in a mixer)

However, I read in the manuel that the pnoise is actually "a time-average of the noise at the output is computed as a spectral density versus frequency". This I could not understand, because it looks to me that "the model of the system large signal behavior" as mentioned previously is different from "a time-average of the system transfer function at each bias point in a period".

For example, for a simple mixer, "the model of the system large signal behavior" could be a square wave, while at each time point, this simple model results in a transfer with infinite BW, thus the "time-averaged" version also having infinite BW.

I don't know where goes wrong. Could anybody help me? Thanks.
Back to top
 
 
View Profile   IP Logged
Ken Kundert
Global Moderator
*****
Offline



Posts: 2173
Silicon Valley
Re: question on pnoise sim theory
Reply #1 - Apr 11th, 2019, 12:41pm
 
SpectreRF performs a detailed noise analysis including all correlations, and then presents the time-average of the noise. So the time-averaging only occurs after the noise leaves the circuit and is being processed for display.

This is very analogous to the case where you are observing the noise of a circuit with a spectrum analyzer. The circuit processes the noise including the effect of all correlations, and the result is observed by the spectrum analyzer when then computes the time-average of the noise before displaying it.

-Ken
Back to top
 
 
View Profile WWW   IP Logged
dog1
Community Member
***
Offline



Posts: 52

Re: question on pnoise sim theory
Reply #2 - Apr 12th, 2019, 2:19am
 
Hello Ken,

Thanks very much for your reply. Now it is clear for me:)

Best regards,

Chen
Back to top
 
 
View Profile   IP Logged
Pages: 1
Send Topic Print
Copyright 2002-2019 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.