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Design >> Analog Design >> Sampled noise simulation w/ Spectre
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Message started by chiu on Oct 11^th, 2005, 7:55pm

Title: Sampled noise simulation w/ Spectre
Post by chiu on Oct 11^th, 2005, 7:55pm

The PNOISE analysis in Spectre gives strange results of sampled thermal noise from a simple resistor-capacitor network. After SINC compensation, the noise PSD is flat, but the integrated noise from 0 to fs/2 varies depending on the resistance R instead of 64uV/1pF fixed. Why is this?

Thanks,

- Yun Chiu
10/11/05

Title: Re: Sampled noise simulation w/ Spectre
Post by Frank Wiedmann on Oct 11^th, 2005, 11:33pm

Did you set the maxsideband parameter large enough? Please see section 2.2 of http://www.designers-guide.org/Analysis/sc-filters.pdf for details.

Title: Re: Sampled noise simulation w/ Spectre
Post by chiu on Oct 12^th, 2005, 3:51pm

Thanks for your suggestion.

I used a 1k resistor and a 1pF capacitor, sampled at 10MHz. The following is my PSS and PNOISE statement:

pss_x pss period=T tstab=0 maxacfreq=1000*fclk
swp_x sweep param=nres values=[100 1k 10k] {
pns_x (vo vss) pnoise start=0 stop=0.5*fclk lin=1e2 maxsideband=1000 \
noisetype=timedomain noisetimepoints=[0] numberofpoints=1
}

I got a total sampled noise 177, 56, and 18uV for the resistance 100, 1k, 10k ohm, respectively.
Any suggestions?