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Measurements >> Phase Noise and Jitter Measurements >> Phase Noise obtained from different methods
https://designers-guide.org/forum/YaBB.pl?num=1481530543

Message started by subtr on Dec 12^th, 2016, 12:15am

Title: Phase Noise obtained from different methods
Post by subtr on Dec 12^th, 2016, 12:15am

Hi,

I'm relatively new to design of PLL's/DLL's . I have constructed a delay line who's accumulated jitter is to be measured. I measured using :
1. Noise type = "time average" and plotted the PM and integrated it to get the jitter.

2. Noise type = "jitter" option and punched out Jc value.

3. Tran Noise : took each crossing of threshold and calculated the mean, std deviation of Period.

I don't see the results matching. I see there is always a factor of ~2 between 1) and 2). Are these methods consistent with each other? If not what do you suggest to be the right way of measurement of accumulated jitter in the output of a delay line? :-[

Please Help.
Thank you.

Title: Re: Phase Noise obtained from different methods
Post by deba on Dec 14^th, 2016, 10:26am

Hi

The jitter you calculated from the "time average", by integrating the phase noise is the absolute jitter. The Jc value is the cycle jitter. Jc jitter is first difference of the absolute jitter. Thus, Jc is ~2x the absolute jitter.

Title: Re: Phase Noise obtained from different methods
Post by subtr on Dec 19^th, 2016, 1:17am

Deba,

Thank you for the response. But I would also like to know why Tran Noise way of calculating accumulated jitter using matlab is not matching with the jitter Jc number. The matlab code has been tested and verified with many chip results is what I understand.

Regards
subtr