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What is the use of No of harmonics option in PSS form

RFQuery

 Hi,

In PSS form, there is one option called Number of harmonics. I am NOT able to understand what is its use as PSS is any way a Steady state DC operating point analysis ?

Of course, No of harmonics actually controls the time step for better accuracy (like to avoid Aliasing effect etc). But the time step can easily controlled by maxacfreq OPTION.

 So my doubt is:- Whether the Harmonic Option in PSS form is needed for Some other reasons ?

IS there any documents which actually explains the need/use (OTHER than controlling Time Step) of No. of Harmonics option in PSS form

Thanks

 

Parents

  • Dear Andrew,

    Recently, I observed one thing ( though surprisingly to the above description) regarding Shooting PSS.

    I was doing PSS and PXF analysis for  a simple ring oscillator.

    From oscillator transient, I have set my PSS beat frequency to 2.5GHz.

    No. of Harmonics=1

    Maxacfreq:- 200GHz

    1st I did PXF with maxsideband 70. I got some result.

    The 1st Harmonic frequency PSS shows:-   2.503412490202536GHz

    Then I increasd the No. of Harmonics = 20. The PXF results were same.

    And the 1st Harmonic frequency PSS shows:-  2.503412490202536GHz

     

    But when I increased the  No. of Harmonics=40 ( This I did to accurately reproduce the PSS waveform with accurate phase from PSS harmonics. If there is some better way of reproducing PSS waveform with accurate phase please mention), the PXF result I got was differnt from previous results.

    Also  the 1st Harmonic frequency PSS shows:-  2.503562180960924GHz ( There is a clear difference)

    I wonder why it is happening so.

    Could you please tell why it is happening ? ( I am using Cadence (R) Virtuoso (R) Spectre (R) Circuit Simulator
     Version 12.1.0.402.isr5 64bit -- 7 Mar 2013 )

    Kind Regards,

     

Reply

  • Dear Andrew,

    Recently, I observed one thing ( though surprisingly to the above description) regarding Shooting PSS.

    I was doing PSS and PXF analysis for  a simple ring oscillator.

    From oscillator transient, I have set my PSS beat frequency to 2.5GHz.

    No. of Harmonics=1

    Maxacfreq:- 200GHz

    1st I did PXF with maxsideband 70. I got some result.

    The 1st Harmonic frequency PSS shows:-   2.503412490202536GHz

    Then I increasd the No. of Harmonics = 20. The PXF results were same.

    And the 1st Harmonic frequency PSS shows:-  2.503412490202536GHz

     

    But when I increased the  No. of Harmonics=40 ( This I did to accurately reproduce the PSS waveform with accurate phase from PSS harmonics. If there is some better way of reproducing PSS waveform with accurate phase please mention), the PXF result I got was differnt from previous results.

    Also  the 1st Harmonic frequency PSS shows:-  2.503562180960924GHz ( There is a clear difference)

    I wonder why it is happening so.

    Could you please tell why it is happening ? ( I am using Cadence (R) Virtuoso (R) Spectre (R) Circuit Simulator
     Version 12.1.0.402.isr5 64bit -- 7 Mar 2013 )

    Kind Regards,

     

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