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Simulators >> Circuit Simulators >> pnoise stop frequency sweep range
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Message started by conr on Jan 31^st, 2013, 12:37am

Title: pnoise stop frequency sweep range
Post by conr on Jan 31^st, 2013, 12:37am

Hi everybody,

I'm simulating the jitter of a low frequency crystal oscillator (32KHz) with pnoise analysis. I have read in many post that the stop frequency sweep range has to be set to half of the fundamental frequency (relative to the fundamental) to compute the jitter(in this case 16KHz).
Why? Is there any mathematical reason for that?
That means that the circuit noise contribute at frequency greather than f0/2 are not relevant for the jitter?

Thanks for your help.

Title: Re: pnoise stop frequency sweep range
Post by Frank Wiedmann on Feb 1^st, 2013, 1:52am

In the pnoise PM jitter analysis of SpectreRF, noise from higher frequencies is folded down into the range between zero and half the pss fundamental through the sampling operation of this analysis type. If you use a larger frequency range, you will count the corresponding noise more than once and get a wrong result.