標題: Problem in getting jitter from phase noise of pll [打印本頁] 作者: kooller 時間: 2010-11-18 09:18 AM 標題: Problem in getting jitter from phase noise of pll Hi all, ( M$ G. b) V( L: ]5 }1 S. z. A5 O; ]0 }
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. r( y9 O) g( y/ z+ m8 b8 W7 {0 F7 f8 D) _: P' m4 A) B$ P/ X% g
Then calculate jitter by the following formula:0 G3 t. n- S9 W! `# { d2 w
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phase jitter = sqrt(integral(fre,2*Lpll))/(2*pi*f); 3 O% l" o& i9 r5 |( ^9 hperiod jitter = sqrt(8*integral(fre,Lpll.*(sin(pi*fre*T)).^2)/((2*pi*f)^2)); / q, W& f, I7 M0 x9 k( ]) m1 \2 l
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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. 9 ~( E) P4 Q, u; K3 w, ? ; u' t' }5 `: {5 X5 l3 U% G& T& @5 {The calculated jitter results is :- z: J0 p4 b4 g9 @4 g/ d% \
phase jitter: 18.9ps.+ w) b7 A3 t) c; V9 a/ M- D) ~
period jitter: 0.04ps. 2 u" V7 K2 P6 [/ ?. P ' b g0 c4 v/ [( e. [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. & c) {' A( `* A0 x: e# P* m, h2 P% z! J* ]' x: L2 k; x
So can somebody tell me where is the problem of my calculation, and how much will phase jitter larger than period jitter?作者: anita66 時間: 2011-4-26 03:07 PM
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~