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Cannot get the Lorentzian plot in Pnoise simulation

ycyang

Hi,

I am trying to run the PSS+Pnoise to get the linewidth of the VCO.
I have set the Pnoise option "augmented=yes" for PSS+Pnoise oscillator simulations.
Nevertheless, I cannot get the Lorentzian plot, the phase noise still goes up and becomes larger than 0 dBc at low frequencies.
The logfile says:"Compute Floquet mode for autonomous ciruits... ...".
It seems the simulator does not use frequency-aware PPV method.

Is there anything wrong in my setting?
By the way, the MMSIM version I use is 7.2ISR7

Thanks

Parents
  • Andrew Beckett

    The augmented parameter really has nothing to do with producing a Lorentzian plot. It is to enable an improvement in the PPV method to handle long time constants (often in the bias circuitry) which result in a hump in the phase noise transfer function. In fact from MMSIM72 ISR3 onwards augmented=yes by default in both shooting and HB pnoise.

    In earlier versions, when augmented=yes was turned on, it also enabled (for HB only) the calculation of the "line width" and computation of the Lorentzian (i.e. nonlinear) noise shape near the carrier. This was misleading because it was independent of the augmented algorithm, and also was doing it only for HB and not for shooting.

    What we did from MMSIM72 ISR4 onwards was to introduce a new parameter "lorentzian" on pnoise and hbnoise:

     43      lorentzian=cornerfreqonly
                              This option determines if the Lorentzian plot is used
                              in the oscillator noise analysis. Possible values are
                              no, cornerfreqonly or yes.

    The default is just to compute the corner frequency (i.e. the line width), and to get the Lorentzian shape curve you need to set it to "yes". 

    Regards,

    Andrew.

Reply
  • Andrew Beckett

    The augmented parameter really has nothing to do with producing a Lorentzian plot. It is to enable an improvement in the PPV method to handle long time constants (often in the bias circuitry) which result in a hump in the phase noise transfer function. In fact from MMSIM72 ISR3 onwards augmented=yes by default in both shooting and HB pnoise.

    In earlier versions, when augmented=yes was turned on, it also enabled (for HB only) the calculation of the "line width" and computation of the Lorentzian (i.e. nonlinear) noise shape near the carrier. This was misleading because it was independent of the augmented algorithm, and also was doing it only for HB and not for shooting.

    What we did from MMSIM72 ISR4 onwards was to introduce a new parameter "lorentzian" on pnoise and hbnoise:

     43      lorentzian=cornerfreqonly
                              This option determines if the Lorentzian plot is used
                              in the oscillator noise analysis. Possible values are
                              no, cornerfreqonly or yes.

    The default is just to compute the corner frequency (i.e. the line width), and to get the Lorentzian shape curve you need to set it to "yes". 

    Regards,

    Andrew.

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