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difference between the two phase noise functions in Direct Plot Form?

Soner

Hi,

I am trying to simulate the phase noise of a 25GHz LC oscillator using pss (flexible balance) and pnoise analysis. In the Direct Plot Form, there are two different Phase Noise options:

1) Analysis: pnoise  Function:Phase Noise

2) Analysis: pnoise jitter Function: Phase Noise

The two above give different results (#1 is approximately ~2.3dBc lower than #2 @ 10MHz offset). What is the difference between these two functions?

I would like to note that #1 provides much more numerically stable results than #2.

 

Parents

  • Soner,

    The numerical noise floor is not a fixed number for either engine. It will typically be lower with harmonic balance than shooting, but even saying that shooting has a numerical noise floor of some fixed number (e.g. -120dB) is a bit cavalier! However, I can pretty safely say that it will be something above about -300dB since that's the (approximate) limit of double precision floating point numbers ;-)

    The numerical noise floor will depend upon the reltol and abstol (primarily) used, but there's a complex (and circuit dependent) relationship.

    Regards,

    Andrew.

Reply

  • Soner,

    The numerical noise floor is not a fixed number for either engine. It will typically be lower with harmonic balance than shooting, but even saying that shooting has a numerical noise floor of some fixed number (e.g. -120dB) is a bit cavalier! However, I can pretty safely say that it will be something above about -300dB since that's the (approximate) limit of double precision floating point numbers ;-)

    The numerical noise floor will depend upon the reltol and abstol (primarily) used, but there's a complex (and circuit dependent) relationship.

    Regards,

    Andrew.

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