hi,
I simulated my PLL's phase noise at behavior level and got a closed-loop pll phase noise curve. Than I tried to integrate the phase noise to get phase jitter and period jitter.
The follow matlab routine is used to convert phase noise to phase jitter and period jitter:
phasejitter = sqrt(integral(fre,2*Lpll))*T/(2*pi);
periodjitter = sqrt(8*integral(fre,Lpll.*(sin(pi*fre*T)).^2)/((2*pi*f)^2));

where Lpll is the single-sideban phase nosie of the pll, the function integral is:
function integ = integral(fre,L)
% calculate integral
len=length(fre);
for n = 1:len-1
   areatrape(n) = (fre(n+1)-fre(n))*(L(n+1)+L(n))/2;
end
integ = sum(areatrape);

I expect the same results of phase jitter and period jitter because the pll locked. but the results are:
phase jitter = 8.31e-11
period jitter = 3.27e-12

Is there any error of my routine or my understanding of phase jitter and period jitter?
in the attached figure, the red curve is the phase noise of the PLL.
Sun

sun wrote on Mar 11^th, 2009, 9:15am:


Hi Sun,

I understand your expression to convert from phase noise to jitter. That appears correct.  However, I do not understand your expression for period jitter.  I don't think you can obtain that from a phase noise plot as the phase noise plot is computed relative to a specific carrier frequency. Period jitter is a measure of the variation of the period from a fixed period T. A phase noise plot relates the variation from its carrier frequency - which may not be the frequency corresponding to the period T of your period jitter requirement.

A definition of period jitter can be found at URL:

http://www.jedec.org/download/search/jesd65b.pdf

Shawn

hello sun,
               Do you mean accumulated Jitter by the term period jitter that you are using ?  Because guessing from your simulation results, period jitter values might indicate accumulated jitter. single period jitter is given by delta(vcont) * del(f) / f^2 just multiply ur single period jitter here phase jitter by no. of vco cycles in 1 i/p period, if that matches with your period jitter, it is a measure of accumulated jitter wrt i/p time period