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Jitter transfer of a CDR system (Read 2952 times)
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Jitter transfer of a CDR system
Sep 19th, 2011, 3:15pm
 
Hi, Everyone, I am considering the jitter transfer of a CDR system which I am working on recently. And I have two questions and hope to get some help here

(1) I am struggling on finding out the jitter transfer curve of the CDR as it is based on BBPD, a non-linear block. I know there are a lot of publications about linearizing the BBPD. But this procedure need a knowledge of the input jitter(not only the bang bang tracking jitter) which is actually hard for me to find out.

Furthermore the theory about BBPD linearization is also confusing to me. C. Walker's paper(Designing Bang-Bang PLLs for Clock and Data Recovery in serial Data Transmission Systems) treats the BBPD as a unity gain element with quantization noise. This confused me the most.Because this conflicts with the papers which linearize the BBPD by convolving the static phase transfer curve of BBPD and the probability density function of the input jitter(Nicola da Dalt, IEEE TCAS I DEC.2008 and a tutorial written by Ken Kundert). In these papers, the PD gain is usually much larger than 1. So their results should be quite different from walker's. But they all have measurement data to support their theories. Is there anyone that can give some comments here?

(2) The jitter transfer is the ratio of the output jitter and input jitter. But at the output of a CDR, we cannot distinguish the transferred jitter and the jitter generated by the CDR itself( including the bang bang tracking jitter). So is the CDR self-generated jitter negligible when we measure the jitter transfer?

Thanks

Dep
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