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Measurements >> Phase Noise and Jitter Measurements >> What does Spectre pnoise output: Sv or Sphi?
https://designers-guide.org/forum/YaBB.pl?num=1132581197

Message started by Kiran B R on Nov 21^st, 2005, 5:53am

Title: What does Spectre pnoise output: Sv or Sphi?
Post by Kiran B R on Nov 21^st, 2005, 5:53am

Ken,

In "An introduction to cyclostationary noise", you say "PNoise computes Sv but does not predict the corner frequency".

If that's true, why do I sometimes see PNoise in dBc go above 0dB? What does it mean when PNoise is > 0dB 100Hz from the carrier?

Cheers
Kiran

Title: Re: What does Spectre pnoise output: Sv or Sphi?
Post by Ken Kundert on Nov 21^st, 2005, 3:35pm

See section 4.3 of http://www.designers-guide.org/Theory/cyclo-paper.pdf.

-Ken

Title: Re: What does Spectre pnoise output: Sv or Sphi?
Post by Kiran B R on Nov 21^st, 2005, 4:30pm

Ken,

That section didn't answer my question. Can you please explain?

Cheers
Kiran

Title: Re: What does Spectre pnoise output: Sv or Sphi?
Post by Ken Kundert on Nov 21^st, 2005, 9:27pm

Okay, try Section 3.2 in http://www.designers-guide.org/Analysis/rf-sim.pdf, especially pay attention to pages 12 & 13, especially the text found between (18) and (19).

-Ken

Title: Re: What does Spectre pnoise output: Sv or Sphi?
Post by Kiran B R on Nov 22^nd, 2005, 12:04am

Thanks. That was an eye opener.

Sorry to prolong this thread, but should I *always* estimate the corner frequency after running PNoise?

Title: Re: What does Spectre pnoise output: Sv or Sphi?
Post by Ken Kundert on Nov 22^nd, 2005, 12:07pm

Normally, the corner frequency is so low that it is not a concern. This is because the noise is generally very small. However, if you have a very high noise oscillator or an application where you are concerned about very close in phase noise, then you should estimate the corner frequency. In addition, if you are using PXF analysis to estimate the phase modulation that results from noisy supplies or substrates, then the noise source could be large and you should always use the power in the response to determine whether you are above or below the corner.

-Ken