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Design >> Mixed-Signal Design >> the noise simulation of switch capacitor filter.
https://designers-guide.org/forum/YaBB.pl?num=1164610870

Message started by holmes on Nov 26^th, 2006, 11:01pm

Title: the noise simulation of switch capacitor filter.
Post by holmes on Nov 26^th, 2006, 11:01pm

I read the <<simulating switched-capacitor filters with spectreRF>> by ken. I try to follow it. And I have simulated a switch capacitor filter. In the simulation, I found that the noise is double when the maxsideband and the number of harmonics changed from 100 to 200. I don't think the harmonics larger than 100 will contribute so much noise. So the question is , what's wrong with it? One part of netlist is listed below.

pss pss fund=1M harms=200 errpreset=moderate tstab=4.6u
+ method=gear2only tstabmethod=gear2only annotate=status maxiters=50
pnoise ( outp outn ) pnoise start=1 stop=1e6 dec=101
+ maxsideband=200 iprobe=V6 refsideband=0 annotate=status

I also include the noise file in the vdd. The frequency range is 10-20kHz. The total output noise is also measured in this range. The another question is , if I only provide 10-20kHz range noise, how will the simulator deal the noise out range of it? Is the noise file used in this method right or not?

thanks.

Title: Re: the noise simulation of switch capacitor filte
Post by Andrew Beckett on Jan 15^th, 2007, 7:38am

In recent versions of spectre, there's an option to save all the noise contributions - separating noise at source from noise gain for each device. This is the separatenoise=yes parameter to pnoise. Alternatively, you can use the saveallsidebands=yes parameter (this is implied by separatenoise=yes) to save the noise contribution from each individual sideband. That way you can see what the contribution of sideband 100 versus sideband 200 is, etc, etc. 200MHz is not _that_ high in frequency...

Regards,

Andrew.