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tdnoise or pnoise?

PeppeW90

Hi,

I'm simulating a test bench consisting of a crystal oscillator, followed by several inverter stages that act as buffers.

I want to simulate the phase noise at the output of the last buffer, and eventually see how the added buffers contribute to the total phase noise.

What is the most accurate analysis to do in this case? PSS+PNOISE(sources option) or PSS+PNOISE(timedomain option)?

I don't want to see the integrated jitter or the noise in V^^2/Hz, but the phase noise at the output of the last buffer.

Thanks

Parents
  • Andrew Beckett

    The main issue is that you're not really getting phase noise. You're getting the output noise in dBc. Given that I doubt you have significant AM noise, it's probably fine - but we've cleaned things up so that you know you're definitely getting phase noise (i.e. just the PM part of the noise). It's been this way for years - and provided that you knew that the output was not really phase noise, it was fine. Oscillators (even with the buffers afterwards) tend to be dominated by PM noise because the amplitude is limited, so it's pretty safe, I'd say.

    Still, for the avoidance of doubt - if you can try the newer versions, I would - you can always compare the results!

    Andrew.

Reply
  • Andrew Beckett

    The main issue is that you're not really getting phase noise. You're getting the output noise in dBc. Given that I doubt you have significant AM noise, it's probably fine - but we've cleaned things up so that you know you're definitely getting phase noise (i.e. just the PM part of the noise). It's been this way for years - and provided that you knew that the output was not really phase noise, it was fine. Oscillators (even with the buffers afterwards) tend to be dominated by PM noise because the amplitude is limited, so it's pretty safe, I'd say.

    Still, for the avoidance of doubt - if you can try the newer versions, I would - you can always compare the results!

    Andrew.

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