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 Pnoise analysis 

Last post Tue, Mar 5 2013 9:09 PM by Jithin. 5 replies.
Started by Jithin 03 Mar 2013 10:43 PM. Topic has 5 replies and 1624 views
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  • Sun, Mar 3 2013 10:43 PM

    • Jithin
    • Top 500 Contributor
    • Joined on Wed, Mar 7 2012
    • Posts 28
    • Points 395
    Pnoise analysis Reply

    Hi,

    I have been designing a PLL which gives an output frequency in the range (400-500)MHz to the reference input frequency of (20-25)MHz.So for doing the pnoise analysis I have added the PSS as well as  Pnoise analysis

    I have  made the following as setup for the analysis for a frequency of 500MHz. I have chosen 1) shooting method instead of harmonic balance 2)beat frequency to be the output of the divider (divider ratio is 20) that is 25MHz and also output of the PLL is selected as divider out in Pnoise tab. But it seems that the PSS is not converging and thus pnoise is failing.

    So please direct me with the procedure for PSS as well as Pnoise for a PLL not for VCO alone.   

    • Post Points: 20
  • Mon, Mar 4 2013 3:35 PM

    • smlogan
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    Re: Pnoise analysis Reply

     Hi Jithin,

    Cadence has a methodology for simulating the pnoise of a PLL in lieu of a VCO. Have you examined either of these?

    http://support.cadence.com/wps/mypoc/cos?uri=deeplinkmin:DocumentViewer;src=dt;q=cic_design_entry_sim/PLL.pdf

    http://support.cadence.com/wps/PA_DocumentViewer/pubs//spectreRF/spectreRF11.1/spectreRF.pdf

    (Chapter 9 "Noise-Aware PLL Flow")

    Shawn

    • Post Points: 20
  • Mon, Mar 4 2013 8:32 PM

    • Jithin
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    • Joined on Wed, Mar 7 2012
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    Re: Pnoise analysis Reply
    Thank you smlogan,

    I have already gone through the above mentioned pdf and the situation is such that I'm not using a macro model and what I have been doing is that I have designed a PLL and trying to analyse its noise performance and  so my set up looks  as below .
    I used a port as my input reference  through which I generate a pulse of frequency 25MHz and the output is assumed to be 500 MHz .
    In PSS tab I have chosen Engine as Shooting and the beat frequency to be the output of the divider and also in the Pnoise tab I have chosen output to be a voltage and chosen the divider output and also I consider noise type as Jitter.
    So please again go through this and kindly give some ideas why my PSS is not converging and so failing the noise analysis.

    Thank you.
    • Post Points: 20
  • Mon, Mar 4 2013 8:58 PM

    • smlogan
    • Top 75 Contributor
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    Re: Pnoise analysis Reply
    Hi Jothin,

    There was no file attached to view your analysis. However, I would suggest you consider breaking the analysis into several analyses - one for the VCO, phase detector, and divider if you do not want to resort to a macro model. Please consider the complexity of the simulation you are trying to perform. You are asking to find the steady-state transient solution of a system with local and global feedback whose components react in a high non-linear fashion. It is not surprising (to me anyway) that you are experiencing convergence issues with PSS.

    By examining the noise contributions of each component, not only will you greatly simply the analyses, but you will also gain insight into the relative noise contributions of each component and how they impact your final requirement. This will allow you to optimize those components that most impact your end requirement.

    Shawn
    • Post Points: 20
  • Tue, Mar 5 2013 9:38 AM

    • Tawna
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    Re: Pnoise analysis Reply

    Hi Shawn, Jithin,

    The PLL Noise Aware flow is no longer recommended. It is being (or has been) removed from the documentation in MMSIM12.1.

     You may also want to look at transient/transient noise analysis.

     

    Best regards,

    Tawna

    Best regards, Tawna Wilsey Staff Support AE, Global Customer Support Cadence Design Systems, Inc.
    • Post Points: 20
  • Tue, Mar 5 2013 9:09 PM

    • Jithin
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    Re: Pnoise analysis Reply
    Thank you Tawna and Shawn for your kind reply.
    • Post Points: 5
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Started by Jithin at 03 Mar 2013 10:43 PM. Topic has 5 replies.