Problem in getting jitter from phase noise of pll

kooller

Hi all,

- b  r& q, y. b; @& s" \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:

  ]& T1 v# U4 pphase jitter = sqrt(integral(fre,2*Lpll))/(2*pi*f);
% q) h: V% W. S7 N6 y" Aperiod jitter = sqrt(8*integral(fre,Lpll.*(sin(pi*fre*T)).^2)/((2*pi*f)^2));

' K0 I- D1 C. N0 Q% H+ m0 ~; ZFrequency 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.

8 o; z# x% E' _  h3 k5 {The calculated jitter results is :
phase jitter: 18.9ps.
period jitter: 0.04ps.
; U: N" I3 |4 g8 A
- |6 h5 i1 x, D# l5 @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.

% R( S' }% ~3 v5 q! ESo can somebody tell me where is the problem of my calculation, and how much will phase jitter larger than period jitter?

anita66

看您的PN那麼差,jitter應該不可能不到20ps,其實PN是ㄧ個積分所得到的數值,同樣,jitter換算回來時,也是要累加才對,所以,你的算法有問題,可以再找一下正確的計算公式,3Q~