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Pnoise analysis

Jithin

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.   

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  • ShawnLogan
    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
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  • ShawnLogan
    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
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