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Design >> RF Design >> Question on phase noise Sphi and normalized noise power L
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Message started by seekconfessor on Feb 16^th, 2016, 5:47am

Title: Question on phase noise Sphi and normalized noise power L
Post by seekconfessor on Feb 16^th, 2016, 5:47am

Referring to the paper "Predicting the Phase Noise and Jitter of PLL-Based Frequency Synthesizers", the normalized single-sideband noise power L and the phase noise Sphi has the relationship: L=Sphi/2. But I have some confusion on these two parameters.
Question 1: when we are talking about a VCO's phase noise , i.e. -95dBc/Hz@100kHz off, this value means L or Sphi?
Question 2: The spectre's Pnoise simulation of a VCO circuit can get a phase noise result, this result means L or Sphi?
best regards.

Title: Re: Question on phase noise Sphi and normalized noise power L
Post by Ken Kundert on Feb 16^th, 2016, 1:40pm

The answer is in the units. L is a normalized noise. The units you give are dBc, which is the noise power normalized to the carrier power. If the units in dBc it's L.

The phase noise function in ADE is misnamed. It is really the normalized noise. It makes no effort to extract the phase noise. It it the total SSB noise power relative to the carrier power. However, if you apply it to the output of an oscillator at a frequency where the phase noise dominates, you get what you want.

-Ken

Title: Re: Question on phase noise Sphi and normalized noise power L
Post by seekconfessor on Feb 17^th, 2016, 7:27am

I've got the points, Thanks for your reply.