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understanding of frequency folding in Cadence pnoise set-up

eeask

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!

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  • Hi, Andrew

    What I’m looking for is to get to understand how noise from 0.5GHz to 1 GHz will contribute to 1.0000002G to 1.5G Hz, If VCO output freq=1GHz and sweep start=200 and stop = 0.5GHz (standard setup for pss/pnoise).

    I think it just can’t. Instead Cadence somehow assume VCO's noise profile is symmetric along 1GHz. It means that noise profile between 0.5G and 1G is just mirror of noise from 1G to 1.5GHz. So in simulation we only look into noise from 1G + 200Hz to 1G + 0.5GHz.

    Correct me if my understanding is not right.

    Thanks!
Reply
  • Hi, Andrew

    What I’m looking for is to get to understand how noise from 0.5GHz to 1 GHz will contribute to 1.0000002G to 1.5G Hz, If VCO output freq=1GHz and sweep start=200 and stop = 0.5GHz (standard setup for pss/pnoise).

    I think it just can’t. Instead Cadence somehow assume VCO's noise profile is symmetric along 1GHz. It means that noise profile between 0.5G and 1G is just mirror of noise from 1G to 1.5GHz. So in simulation we only look into noise from 1G + 200Hz to 1G + 0.5GHz.

    Correct me if my understanding is not right.

    Thanks!
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