PSS+Pnoise. Result interpretation

Discussion in 'Cadence' started by dionisij, Oct 18, 2007.

  1. dionisij

    dionisij Guest

    Hi all,

    noticed, that resulting phase noise curve I'm geting through PSS
    +PNoise simulation starts from positive value if small frequency
    offsets are used (like 10..100 Hz). One would expect it to start from
    0, since it in dBc/Hz. Is it simulation accuracy (reltol) issue or
    something fundamental in how SpectreRF handles this type of
    simulations or something wrong can be with setup/circuitry?

    Thanks
    Dio
     
    dionisij, Oct 18, 2007
    #1
  2. Well, you can interpret it in several ways. The real explanation is that noise
    models aren't really accurate at very low frequency (say 10 Hz) and so the
    numbers aren't meaningful. Adjusting the simulator tolerance won't help...

    Another way of thinking about it is that the phase is more than one cycle out -
    but in essence that doesn't really help you.

    Recent versions of spectre have started outputing a quantity which we've
    termed the "line width" (which borrows similar terminology from laser
    oscillation I think?) which is the lowest frequency where the phase noise
    is meaningful.

    Regards,

    Andrew.
     
    Andrew Beckett, Nov 15, 2007
    #2
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