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Hi all,
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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.
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' }2 I% e6 n0 R( z; D3 pThen calculate jitter by the following formula:7 u- b9 n. U, t4 ^
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phase jitter = sqrt(integral(fre,2*Lpll))/(2*pi*f); 3 U& j! _# p! I- u3 h
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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The calculated jitter results is :
+ e0 P: r+ k' u! T. Z# ]phase jitter: 18.9ps./ E' W1 g3 Y9 P% a
period jitter: 0.04ps.' g1 T$ q# R- E8 H
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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.) M e* P) L- U* K
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So can somebody tell me where is the problem of my calculation, and how much will phase jitter larger than period jitter? |
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