Problem in getting jitter from phase noise of pll

[kooller]

Hi all,

I'm recently doing the jitter simulation of PLL, and I first got phase noise of PLL by adding every part of noise of PLL.

Then calculate jitter by the following formula:

phase jitter = sqrt(integral(fre,2*Lpll))/(2*pi*f);
period jitter = sqrt(8*integral(fre,Lpll.*(sin(pi*fre*T)).^2)/((2*pi*f)^2));

Frequency of PLL is 5GHz, and the integral band of phase noise is 100Hz~100MHz, phase noise of PLL is as follows: -85dBc/Hz @100Hz; -64dBc/Hz @100kHz; -80dBc/Hz @1MHz; -102dBc/Hz@10MHz; -125dBc/Hz@100MHz.

The calculated jitter results is :
phase jitter: 18.9ps.
period jitter: 0.04ps.

This shows that the period jitter is so small, and only 1/450 times of phase jitter, while our test results shows that the period jitter is about 1.8ps.

So can somebody tell me where is the problem of my calculation, and how much will phase jitter larger than period jitter?

 

[kooller]

Anybody give some advise?

 

[yxh12321]

hi kooller,
I want to know how did u get the noise of every part of PLL? and hspicerf or cadence?