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Calculating Phase Noise from PSS-shooting simulation

KzzzJ

  • Dear KzzzJ,

    If I understand your comments, I believe teh reason your proposed computed result is not consistent with the simulated result is you are neglecting the aliasing of the presumably infinite noise bandwidth of your input noise source by the non-linear (large signal) behavior of the inverter. The small-signal noise will not be the same at the same offset frequency as that predicated by a shooting pss simulation since the latter will induce frequency aliasing and the former will not. Further, the gain of the inverter in a small-signal simulation where it is biased in its high gain region is radically different as the inverter spans its full dynamic range - the gain becomes far less as the input voltage approaches the positive and negative rails. I do not believe your use of the narrowband PM model captures any of this.

    These are my thoughts on your comment and question and others may have more insightful comments.

    Shawn

  • in reply to ShawnLogan

    Thank you for your comment.  There certainly would be noise from other tones mixed down, but I wouldn't expect the addition of the noise to be as substantive as the discrepancy shows since the next tone would be at 20GHz. So I would expect some but not a lot.  I could be wrong about that.  It wouldn't really be an infinite bandwidth, because the noise is based off real devices where I would think the model wouldn't be infinite.  The infinite bandwidth would be there if it was an ideal resistor.  Also, here, the inverter really isn't moving at all, it is only generating a DC voltage with noise.  The clock that is driving from low to high is the ideal vpulse so the gain doesn't change over the full range.  I would think the that the Narrowband PM equation would work well in this situation, but I'm only saying that because whenever I have dived into phase noise, the explanation is given in relation to that equation.  

  • in reply to Frank Wiedmann

    Thank you for the article.  This will take me some time to wade through.  

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