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PN function in Visualizaion & Anaysis XL Calculator

JaeWook

Hi,

I have a question about the PN function, available in the Calculator.

 

Is an output phase noise spectrum is a signle sideband or a double sideband spectrum?

To avoid any confusions, I mean the 'double sideband' by a spectrum 3dB more than the 'single sideband' in magnitude.

 

Thanks for any comment or answers.

Jae Wook

  • I suspect it's single sideband, but I'm not sure (I've never used it). It's for analysing transient results, and is defined this way:

    PN
     
    Calculates the transient phase noise of the input waveforms in
    decibels (dBc/Hz). Phase noise is defined as the power spectral
    density of the absolute jitter of an input waveform.

    You tagged this post with lots of terms like pss, pnoise etc - so you would not use this function if you're using pnoise. You'd use the pn() or phaseNoise() functions, and these will give you the single sideband phase noise (strictly the output noise in dBc if using "sources"). You'd be better off using "modulated" pnoise and then you can get either from the direct plot form.

    Regards,

    Andrew.

  • Dear Andrew,

    Thank you for the reply.

    What I try to do is to make a transient phase noise model of a VCO in veriloga. In order to verify my veriloga model by comparison, I need to run both a pss/pnoise analysis in transistor level and a transient analysis in behavioral level. Then I compare two spectrums from the pnoise and the transient analyses. That is why I care about the PN function as much as other pnoise functions.

    I appreciate your help again, and if any futher comment or suggestion possible, please let me know.

     

    Jae Wook

  • Hi JaeWook,

    The December 2012 ViVa reference manual describes the pn() function as follows:

    "Returns a waveform for the transient phase noise of the input waveforms in decibels (dBc/
    Hz). Phase noise is defined as the power spectral density of the absolute jitter of an input
    waveform."

    Hence, as Andrew mentions, it is not the classical L(f) function which expresses the single sideband phase noise of a signal. The manual further defines it as:
     
     
    I hope this helps!
     
    Shawn 

  • Shawn,

    The question is about the PN function not the pn function. They are different. The definition you've given is from the PN function (just trying to avoid confusion)

    Regards, 

    Andrew 

  • Hi,
    I am not sure I fully understand this function. As test, I generate a narrow FM sine wave using standard Cadence sin voltage source. When processing the output with PN function there is no trace of the FM component. Pretty much a smooth line. When I try high modulation index (wide band) then the component appears, but does not make sense.

    How does it work?

    Thanks,

    Kristopher

  • Kristopher,

    Because you posted on the end of an old thread (which the forum guidelines tell you not to do), your question got overlooked (which is why the guidelines tell you not to do this). If you still need an answer to this, I suggest you give some details as to what the netlist statement for the sine source looked line, and what the arguments to the PN function you used were.

    Kind Regards,

    Andrew.

  • Hi Andrew,

    Thanks for the follow up. Yes, I can see that I posted it on a old thread “cold”, something to watch out for in the future. The issue has been resolved so for the time being it is OK.

    Kristopher

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