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Meaning of the "Event Time" in Direct Plot form of Pnoise Jitter

RFStuff

Dear All,

I am doing Pnoise-Jitter analysis (for both Rise and Fall edge).

In the direct plot form I see Event Time (Please see the attached Snapshot).

What it actually means ? 

Kind Regards,

Parents

  • When you set up the jitter analysis, it finds the crossing points of the signal (either rising or falling or both) during the PSS interval itself. If you were to plot the PSS time domain results (not the tstab, which is what you're showing above), then the event times correspond to the crossing points during that time domain period. If there's only a single pulse, and you've asked for both, there will be two crossing points (one for rising and  one for falling). The jitter is calculated using the noise at the output of an ideal sampler which samples at exactly the threshold crossing combined with the slew rate (at the threshold crossing) from the PSS analysis. That's what the "Threshold Xing" shows on the direct plot form.

    Regards,

    Andrew.

  • in reply to Andrew Beckett

    Dear Andrew,

    Thanks  a lot.

    It is indeed the case.

    One more thing, for plotting Jee, Jc it asks for Integration of Frequency Limit.

    I am little bit confused of what range should be given as Jee and Jc are time domain parameter.

    Kind Regards,

  • in reply to RFStuff

    It's worth reading <SPECTREinstDir>/tools/spectre/examples/SpectreRF_workshop/JitterAN.pdf. Normally the noise (and hence the jitter) is in a 1Hz bandwidth (so noise in V/sqrt(Hz) and so jitter  would be in s/sqrt(Hz)). Since the noise across the bandwidth of your circuit is all going to produce jitter, you want to integrate the noise/jitter across that bandwidth to find the total jitter.

    Given that in the jitter analysis you shouldn't be sweeping beyond half the PSS fundamental (otherwise the ideal sampler I mentioned earlier causes the noise to be folded by the sampler and hence double-counted (or more)), you probably just want to use the same frequency range as your frequency sweep in the pnoise analysis.

    Regards,

    Andrew.

Reply
  • in reply to RFStuff

    It's worth reading <SPECTREinstDir>/tools/spectre/examples/SpectreRF_workshop/JitterAN.pdf. Normally the noise (and hence the jitter) is in a 1Hz bandwidth (so noise in V/sqrt(Hz) and so jitter  would be in s/sqrt(Hz)). Since the noise across the bandwidth of your circuit is all going to produce jitter, you want to integrate the noise/jitter across that bandwidth to find the total jitter.

    Given that in the jitter analysis you shouldn't be sweeping beyond half the PSS fundamental (otherwise the ideal sampler I mentioned earlier causes the noise to be folded by the sampler and hence double-counted (or more)), you probably just want to use the same frequency range as your frequency sweep in the pnoise analysis.

    Regards,

    Andrew.

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