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Simulators >> Circuit Simulators >> Transient noise, how accurate?
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Message started by pekkle on Jan 26^th, 2008, 7:43pm

Title: Transient noise, how accurate?
Post by pekkle on Jan 26^th, 2008, 7:43pm

I just leant that there is "transient noise" option in transient sim.
It is said it can simulate noise without using SpectreRF.

One instantaneous question that arose was
how accurate this transient noise sim would be?
I expect it would be pretty accurate for time-invariant circuits,
but not sure for time-variant circuits like mixers.
Or is this the ultimate test of checking the accuracy of
fancy noise analysis provided by SpectreRF?

I would appreciate if any can share your experience with these.

Thanks

Title: Re: Transient noise, how accurate?
Post by Stefan on Jan 27^th, 2008, 2:39am

Transient noise is just as accurate as you specify it.
You need to specify a very high frequeny range, which leads to small simulation time steps.
If you want to measure high and low frequency noise effects you need to simulate a pretty long period of time.
Both of this together lead to the classical problems of time and memory :)

My own experience is that behavioral models with modeled noise effects are pretty accurate compared to their parameters, but transient noise analysis of transistor level circuits often differ in their results.
Or like Ken said in one of his papers - "transient noise analysis is very error prone."

Title: Re: Transient noise, how accurate?
Post by vivkr on Jan 28^th, 2008, 5:22am

I think you ought to get good results with standard PSS/PNOISE without having to resort to transient
noise which would only make things very slow. However, that's just my opinion.

I have not looked into it but maybe transient noise analysis could be useful when making nonlinear circuits where
there are large and non-periodic changes in the bias point of the circuit and other methods are not applicable
for noise analysis.

Does anyone know whether transient noise analysis calculates the noise parameters at each time step? Would be
logical.

Vivek