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Usage of PN() after transient noise simulation

Lawrence Guan

In this document: Virtuoso Spectre Transient Noise Analysis

The PN() function is used to calculate the phase noise after transient simulation with this equation: (p.55)

What's the reason for the last term: dB20(twoPi*f0_pss), i.e. dividing the power by 2*pi*Fc ?

I'm confused how the PN() function implements the calculation of phase noise as defined in the same document: (p.53)

 

Does it automatically normalized the jitter power to signal power as the equation in this another document: Jee Measurement using PSS/Pnoise and Transient Noise Analysis? (p.33)

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  • Dear Lawrence,

    Lawrence Guan said:

    The PN() function is used to calculate the phase noise after transient simulation with this equation: (p.55)

    If you read on page 56 of the first document you quoted, the expression you are showing is not the phase noise. As stated on page 56:

    "Transient noise output waveform is stored as vt_tran variable. Absolute jitter time-domain waveform Ja_time and its power spectrum Ja_tran is calculated using the abs_jitter() and PN() functions, respectively. "

    The expression for ja_tran is the power spectrum - which differs from the phase noise. Does this help at all?

    Shawn

  • in reply to ShawnLogan

    Hi Shawn,

    Thank you for the prompt reply.

    In fig.33 of the same document, it shows that ja_tran is the same of ja. So I infer from that both of ja_tran and ja are phase noise.

Reply Children
  • in reply to Lawrence Guan

    Lawrence,

    I think the labelling of that figure is slightly misleading, but essentially this boils down to the units used. ja_tran is the power spectral density of the absolute jitter (in seconds) rather than phase noise (in radians). The 2pi*F is just the conversion factor to convert the phase noise (the PN results) into jitter - see Jitter conversions (as a very simple explanation - might well be in the app notes/RAK too but I didn't have time to hunt through the whole document to find it). In fig 33 everything has been adjusted to have the same units so that they can be compared. Given that phase noise and jitter are both expressions of the same phenomenon, it's just a matter of whether you want the measurement as a phase error or time error.

    Andrew.

  • in reply to Andrew Beckett

    Hi Andrew,

    Thank you for the clear explanation. Now I understand.

    Lawrence

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