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understanding of frequency folding in Cadence pnoise set-up (Read 240 times)
Go,TB
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understanding of frequency folding in Cadence pnoise set-up
Mar 04th, 2015, 2:15pm
 
Hello, there

I went through previous discussions and try to confirm my understanding regarding pnoise simulation set-up is correct.

Let’s take an example:



VCO output freq = 1G Hz

Sweep Start= 200; Stop=0.5G Hz (half of fundamental freq)

Relharmum=1: it means that frequency range from 1.0000002G Hz to 1.5G Hz is output noise frequeny of interest.



The noise from 1.0000002 to 1.5 GHz will be directly added to output noise spectrum without conversion effect.

The noise from 200 to 0.5G Hz will be upconverted to 1.0000002 to 1.5 GHz by 1st harmonic.



How about the noise from 0.5G Hz to 1 GHz?



If by 1st harmonic: It will be converted into from 1.5G to 2GHz and from -0.5G to 0 Hz. It means that noise from 0.5G to 1GHz won’t contribute to the output noise. It seems like it is not quite right. Please help me to clarify. Thanks!

Best
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Ken Kundert
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Re: understanding of frequency folding in Cadence pnoise set-up
Reply #1 - Mar 5th, 2015, 11:43am
 
Assume that you use the default maxsidebands value of 7. That means the computed noise will include 7 folds up and 7 folds down. For simplicity, consider only the output noise at 1.1GHz. It will include contributions from 1.1GHz + k fosc where k ranges from ±7.

-Ken
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Go,TB
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Re: understanding of frequency folding in Cadence pnoise set-up
Reply #2 - Mar 5th, 2015, 3:26pm
 
Hi, Ken

Thank you for quick reply. I agree with what you said. But I wonder, in your example, how the noise from 0.5G to 0.9G Hz will contribute to my interest output noise frequency range that is from 1G to 1.5G Hz?

Appreciated!

Ken Kundert wrote on Mar 5th, 2015, 11:43am:
Assume that you use the default maxsidebands value of 7. That means the computed noise will include 7 folds up and 7 folds down. For simplicity, consider only the output noise at 1.1GHz. It will include contributions from 1.1GHz + k fosc where k ranges from ±7.

-Ken

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Ken Kundert
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Re: understanding of frequency folding in Cadence pnoise set-up
Reply #3 - Mar 6th, 2015, 9:24am
 
It won't.
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