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Simulators >> RF Simulators >> Pnoise issues with transient noise
https://designers-guide.org/forum/YaBB.pl?num=1216434198

Message started by Rwalker on Jul 18^th, 2008, 7:23pm

Title: Pnoise issues with transient noise
Post by Rwalker on Jul 18^th, 2008, 7:23pm

Been working on a SC BPF for a while, simulating with spectreRF. I use current mode integration sampling at the input to a SC biquad, and find that noise aliasing at the input is described by a transient noise derivation I came up with involving finite integration length. When simulating with pnoise I see the expected noise in baseband (including the folding predicted by the transient derivation), but I also see up-conversion of strong low frequency noise to my clock freq and 10x clock freq. I recognize that the spectrum of the noise currents should have up-conversion of the low-f noise (I essentially chop them with my sampling phase), yet I feel that the noise at the output of my filter due to these low-f components should all be at baseband, and I bang my head against the wall trying to find a physical explanation.

Could these be sim artifacts from trying to do a periodic noise simulation on a transient noise phenomenon? Or maybe I should bang my head more? Thanks!!

Title: Re: Pnoise issues with transient noise
Post by pancho_hideboo on Jul 18^th, 2008, 8:12pm

Rwalker wrote on Jul 18^th, 2008, 7:23pm:

and find that noise aliasing at the input is described by a transient noise derivation I came up with involving finite integration length.

What do you mean by "transient noise" also in "Pnoise issues with transient noise" ?

Rwalker wrote on Jul 18^th, 2008, 7:23pm:

Could these be sim artifacts from trying to do a periodic noise simulation on a transient noise phenomenon?

I can't know your situation.
Show me more detail simulation setup and result's graph.

Rwalker wrote on Jul 18^th, 2008, 7:23pm:

Or maybe I should bang my head more?

Maybe, yes.

Title: Re: Pnoise issues with transient noise
Post by Rwalker on Jul 21^st, 2008, 2:06pm

Thanks for the reply.

Found my issue, I had a poorly chosen Pnoise frequency sweep and had points right on fclk and 10*fclk. I seem to have minor up-conversion of low-f noise that was being greatly exaggerated.

Title: Re: Pnoise issues with transient noise
Post by pancho_hideboo on Jul 21^st, 2008, 5:00pm

Rwalker wrote on Jul 21^st, 2008, 2:06pm:

Found my issue, I had a poorly chosen Pnoise frequency sweep and had points right on fclk and 10*fclk. I seem to have minor up-conversion of low-f noise that was being greatly exaggerated.

Maybe no one can understand your situation at all with your explanation.
What do you mean by "transient noise" in "a transient noise derivation" and "Pnoise issues with transient noise" ?
Do you mean "time domain noise" in Pnoise analysis or "monte calro type noise" in transient analysis ?

Title: Re: Pnoise issues with transient noise
Post by Rwalker on Jul 21^st, 2008, 5:07pm

pancho_hideboo: I'm not trying to explain my situation anymore because it is solved. Please see my post above. Thank you.