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Measurements >> Phase Noise and Jitter Measurements >> Reference effect on PLL PN
https://designers-guide.org/forum/YaBB.pl?num=1541170315

Message started by Farzaneh on Nov 2^nd, 2018, 7:51am

Title: Reference effect on PLL PN
Post by Farzaneh on Nov 2^nd, 2018, 7:51am

Hi,
I followed Ken's paper "Predicting the Phase Noise and Jitter of PLL-Based Frequency Synthesizer" to simulate the PN of PLL. I also imported my data to Matlab. The problem is that the PN that I got from Matlab is like my open loop VCO and when I remove or add reference jitter the PN is same. I also tried it for the example at the end of paper, in this case the PN is like PLL PN but when I remove reference jitter, again there is no difference. what the problem is?

Farzaneh

Title: Re: Reference effect on PLL PN
Post by Ken Kundert on Nov 2^nd, 2018, 9:57pm

Is it possible that the other sources of noise are dominating over the noise from the reference.

-Ken

Title: Re: Reference effect on PLL PN
Post by Farzaneh on Nov 2^nd, 2018, 10:05pm

No, because only VCO and reference have noise and my PFD/CP isn't noisy. My blocks are exactly same as example at the end of paper and I only change the values with my values.

Farzaneh

Title: Re: Reference effect on PLL PN
Post by Ken Kundert on Nov 3^rd, 2018, 11:38pm

Why didn't you also turn off the noise in the VCO as well?

-Ken