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Simulators >> Circuit Simulators >> Help about .pnoise in SpcetreRF
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Message started by xiaodu2001 on Nov 13^th, 2008, 6:08pm

Title: Help about .pnoise in SpcetreRF
Post by xiaodu2001 on Nov 13^th, 2008, 6:08pm

In "Simulating Switched-Capacitor Filters with SpectreRF"(http://www.designers-guide.org/Analysis/sc-filters.pdf) Listing 1:

unsmpldNoise (out 0) pnoise start=0_Hz stop=10/TCLK maxsideband=100
smpldNoise (out 0) pnoise start=0_Hz stop=0.5/TCLK maxsideband=100 \
noisetype=timedomain noisetimepoints=[0] \
numberofpoints=1

Differente parameters bettween "unsmpldNoise" and "smpldNoise" is "stop", and so the power spectral density of the 2 pnoise analyse is greatly different.
my question is :
what does parameter "stop" mean in .pnoise analysis and how can i explain the phenomena occured above?

Title: Re: Help about .pnoise in SpcetreRF
Post by Frank Wiedmann on Nov 13^th, 2008, 11:46pm

In sampled (or strobed, or timedomain) pnoise analysis, all the noise is aliased into the frequency range between 0 and half the "Beat Frequency" of the associated pss analysis (see figure 3 of the paper). The parameters start and stop specify the frequency range for the analysis.

Title: Re: Help about .pnoise in SpcetreRF
Post by xiaodu2001 on Nov 14^th, 2008, 2:57am

Hello Frank:
Thanks for your advise.
best wishes!