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pnoise spurs at multiples of clock frequency.

vamshiky over 11 years ago

Hi,

I have a simple inverter driven by a square wave, and ran pnoise on the circuit.

There is flicker and thermal noise and after that has huge spurs ( about +20dBc ) at 2*Ffref , 5*Fref.

And this goes away if I carefully choose the sweep type and step size (delberately avoiding those freq points during sim).

Also I have noticed from earlier posts that while running pnoise sim, simulator automatically skips the freq point which is exact multiple of beat frequency and gives a message "Infinite flicker noise is ignored"

however I dont see this happening in my sims.

Are there any additonal settings/options which I missed out.

Thanks,

Vamshi

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Andrew Beckett over 11 years ago

Vamshi,
Could you alter your input frequency to not be exact "decade" frequency? Then you could use a number of points per decade, and know that your harmonics don't coincide with 10M, 100M, 1G etc.
Andrew.
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Andrew Beckett over 11 years ago

Vamshi,
Could you alter your input frequency to not be exact "decade" frequency? Then you could use a number of points per decade, and know that your harmonics don't coincide with 10M, 100M, 1G etc.
Andrew.
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