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Phase Noise vs frequency graph problem

rohan kr

Hello

I am a newbie engineer starting my career in IC design and working on a  high frequency oscillator (38 GHz). I am using Cadence IC6.1.5-64b.500 version and using spectre simulator for the schemtic design and simulations.

 I am having doubts about my 'pnoise' analysis. All the research papers I have referred show the graph of phase noise (dbc) vs. frequency which have values of phase noise(PN) in negative i.e. around -90 to -100 dbc (the graph should be like the flicker noise graph) but I am getting positive  values of PN(with similar type of curve). I have used the 'relative harmonic as 1 and all the settings seem to be as described in the cadence simulation guide. 

 I have referred most of the  community forum in EDAforum,designer-guide and even the Cadence community...there are problems related to this..but there is no definite answer as to how i can get the correct graph as shown in most of the research papers...In one of the community one guy gave an explanation of the equation spectre uses to simulate pn...My question is whether i need to make changes in the circuit or some settings in cadence...

Kindly help me as it is my first major project and need to do well...thanks in advance.. 

Parents

  • Thanks Frank for replying. Yes, I have seen that post-it explains the equation which spectre uses to find the pnoise...but it doesnt help me to get the right graph with negative values of pn.

    I am doing the pss-pnoise simulation using the following settings:

    PSS : Harmonic Balance

    beat freq - 37.93G

      no of harmonics -10 

    accuracy defaults - liberal 

    Pnoise : sweeptype - relative

    relative harmonic - 1 

    start stop from 10K to 10 M

    sweeptype - log & points per decade -10

    max sideband - 10

    positive o/p node -  q+

    negative o/p node  -  q-

    input source - none

    noise type - sources 

    And there is no augmented option in the convergence parameters in options....I think Andrew mentined it in his post that augmented is used in the new version by default... 

Reply

  • Thanks Frank for replying. Yes, I have seen that post-it explains the equation which spectre uses to find the pnoise...but it doesnt help me to get the right graph with negative values of pn.

    I am doing the pss-pnoise simulation using the following settings:

    PSS : Harmonic Balance

    beat freq - 37.93G

      no of harmonics -10 

    accuracy defaults - liberal 

    Pnoise : sweeptype - relative

    relative harmonic - 1 

    start stop from 10K to 10 M

    sweeptype - log & points per decade -10

    max sideband - 10

    positive o/p node -  q+

    negative o/p node  -  q-

    input source - none

    noise type - sources 

    And there is no augmented option in the convergence parameters in options....I think Andrew mentined it in his post that augmented is used in the new version by default... 

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