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Measurements >> Phase Noise and Jitter Measurements >> Question on PLL phase noise and jitter doc
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Message started by neoflash on Oct 29^th, 2005, 10:18pm

Title: Question on PLL phase noise and jitter doc
Post by neoflash on Oct 29^th, 2005, 10:18pm

Folks:

In Ken's document: Predicting the phase noise and jitter of PLL-based frequency synthesizers.

Page15, equation 27, he stated that L(df)=0.5*Sphi(df).

If L(df) is the measurement of PLL output in spectrum analyzer, isn't that the same thing as Sphi(df) called by other papers?

Where is the 0.5 coefficient coming from?
Question is simple, but really need someone help me out.

thanks,
Han

Title: Re: Question on PLL phase noise and jitter doc
Post by neoflash on Oct 30^th, 2005, 1:33am

Hajimiri's paper said that Sphi(f) could be approximated by L(f) for large offsets.

Why there is difference?

Title: Re: Question on PLL phase noise and jitter doc
Post by Ken Kundert on Oct 30^th, 2005, 8:15am

See footnote #4 at the bottom of page 13 in http://www.designers-guide.org/Analysis/PLLnoise+jitter.pdf.

-Ken