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https://designers-guide.org/forum/YaBB.pl Design >> RF Design >> Relating phase noise & jitter https://designers-guide.org/forum/YaBB.pl?num=1340910402 Message started by Sharath Raju on Jun 28th, 2012, 12:06pm |
Title: Relating phase noise & jitter Post by Sharath Raju on Jun 28th, 2012, 12:06pm Hi, I am trying to calculate the phase noise of a clock signal given its jitter. I have used the equation given in Hajmiri's book - The Design of Low Noise Oscillators. I have attached a snapshot of my hand calculations. As shown in the calculations, the calculated phase noise is -67 dBc/Hz whereas the lecture slides report it to be -55 dBc/Hz. Link to Lecture slide: https://ccnet.stanford.edu/cgi-bin/course.cgi?cc=ee315b&action=handout_download&handout_id=ID131637959122829 Chapter 13, slide 12 Could you please comment on the difference ? Thanks, Sharath |
Title: Re: Relating phase noise & jitter Post by biff44 on Jul 7th, 2012, 10:38am Sorry, that link does not open up a lecture page. But what you are calculating seems to be somewhat wrong. Phase noise is a broadband noise. Phase noise is typically measured from 100 hz to 10 Mhz from the carrier, and the level at each frequency offset point varies. So if you have a phase noise measourement, and want to turn it into rms jitter, you have to INTEGRATE it over the frequency limits of 100 Hz to 10 MHz, do a little more math, and then you have an answer. Possibly the example you were looking at was not phase noise at all, but relating a discrete freuqency spurious sidband to the jitter that one tone would cause? here is a spreadsheet "allan variance from phase noise" that might help your understanding: http://www.wenzel.com/documents/spread1.htm there are other spreadsheets out there for jitter to phase noise calculation Rich Maguffin Microwave |
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