Problem in getting jitter from phase noise of pll

kooller

Hi all,

$ D  @; i( l$ E4 gI'm recently doing the jitter simulation of PLL, and I first got phase noise of PLL by adding every part of noise of PLL.
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3 h; Y! o+ T/ ~$ h) w( U( pThen calculate jitter by the following formula:
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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));
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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.
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! q2 u8 G+ _$ W) l  l: EThe calculated jitter results is :
6 ?0 B  ~; n3 Zphase jitter: 18.9ps.
6 u3 j! w6 q# k7 g3 |period jitter: 0.04ps.
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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?

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~