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tdnoise or pnoise?

PeppeW90

Hi,

I'm simulating a test bench consisting of a crystal oscillator, followed by several inverter stages that act as buffers.

I want to simulate the phase noise at the output of the last buffer, and eventually see how the added buffers contribute to the total phase noise.

What is the most accurate analysis to do in this case? PSS+PNOISE(sources option) or PSS+PNOISE(timedomain option)?

I don't want to see the integrated jitter or the noise in V^^2/Hz, but the phase noise at the output of the last buffer.

Thanks

Parents
  • Andrew Beckett

    It's 3dB higher because the PM output noise (in dBc) or the pnoise jitter Phase Noise outputs are double-sideband. You're getting the contributions from both the upper and lower sidebands. When  you run with pnoise sources, then you're just getting the single sideband results (you can see that by plotting the USB and LSB output noise in dBc). 

    With the new noisetype=timeaverage you get the choice on the direct plot form whether you want SSB or DSB results.

    So, it depends what you're expecting.

    I can't answer your question about the tdnoise approach because I don't know what was actually simulated or how the results were computed. I suggest you contact customer support so that an application engineer can take a look at your setup and results. It's hard to answer "how accurate" it is because that is a function of how the simulation was setup and how the results have been interpreted, not a fundamental limitation of the simulator.

    Regards,

    Andrew.

Reply
  • Andrew Beckett

    It's 3dB higher because the PM output noise (in dBc) or the pnoise jitter Phase Noise outputs are double-sideband. You're getting the contributions from both the upper and lower sidebands. When  you run with pnoise sources, then you're just getting the single sideband results (you can see that by plotting the USB and LSB output noise in dBc). 

    With the new noisetype=timeaverage you get the choice on the direct plot form whether you want SSB or DSB results.

    So, it depends what you're expecting.

    I can't answer your question about the tdnoise approach because I don't know what was actually simulated or how the results were computed. I suggest you contact customer support so that an application engineer can take a look at your setup and results. It's hard to answer "how accurate" it is because that is a function of how the simulation was setup and how the results have been interpreted, not a fundamental limitation of the simulator.

    Regards,

    Andrew.

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