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Simulators >> Circuit Simulators >> Noise simulation in Cadence
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Message started by manodipan on Oct 1^st, 2008, 2:16am

Title: Noise simulation in Cadence
Post by manodipan on Oct 1^st, 2008, 2:16am

Hi all,
I am trying to do some noise simulation in Cadence.In that i put an input port,and select the output for noise .The simulator gives output referred noise but not input referred noise.How to get the input referred noise?????
By the awy i have heard some term like transient noise simulation,what is that??

Title: Re: Noise simulation in Cadence
Post by ywguo on Oct 10^th, 2008, 10:50pm

Hi manodipan,

Please set the input source as a voltage source in order to observe the input referred noise.

Yawei

Title: Re: Noise simulation in Cadence
Post by Geoffrey_Coram on Oct 14^th, 2008, 6:21am

manodipan wrote on Oct 1^st, 2008, 2:16am:

By the awy i have heard some term like transient noise simulation,what is that??

Spice's "noise" is a small-signal analysis, like ac: the circuit is linearized about an operating point to compute the transfer function from the noise generators to the output.

PNoise goes a step further and computes a "time-varying operating point" but again linearizes the circuit. Similar for HBnoise.

Transient noise does a regular transient analysis, but then uses the noise equations to inject random amounts of charge (or voltage) and attempts to compute the full nonlinear response in the presence of noise. I think there's a whitepaper on SourceLink. It's really the only way to get the noise performance of sigma-delta converters (and other circuits that aren't periodic nor linear). But it's tricky to not lose the noise in the numerical roundoff of finite-precision computer arithmetic, and to have good convergence in the presence of the random noise.

Title: Re: Noise simulation in Cadence
Post by manodipan on Nov 17^th, 2008, 1:03am

Hi Geoffrey,
So what is the procedure to do some transient noise simulation...Is it like first transient and then noise simulation....or do noise analysis with type time domain...what is the significance of that analysis??

Title: Re: Noise simulation in Cadence
Post by Geoffrey_Coram on Nov 17^th, 2008, 4:37am

Cadence has a whitepaper on transient noise available on SourceLink; you should read it to understand the assumptions and limitations.

It's a transient analysis, as I said before; the noise is injected at each timepoint during the analysis.

Title: Re: Noise simulation in Cadence
Post by Frank Wiedmann on Nov 17^th, 2008, 5:55am

The whitepaper can be found at http://sourcelink.cadence.com/docs/files/Application_Notes/2006/TrnoiseAN.pdf.

Title: Re: Noise simulation in Cadence
Post by manodipan on Nov 21^st, 2008, 3:12am

Hi Frank,
can you attach the pdf,because i have to register to source link and i dont know the hostid of our license server..thanks a lot..

Title: Re: Noise simulation in Cadence
Post by Frank Wiedmann on Nov 21^st, 2008, 6:11am

I'm afraid I can't because the whitepaper is proprietary to Cadence and they chose not to make it available to everyone. Try to find out the hostid of your license server and register on SourceLink.