PLL phase noise and jitter

hi, + d/ I/ U1 ~# {2 Y+ C
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. ( Z' M4 w- S6 h4 B& ~
The following matlab routine is used to convert phase noise to phase jitter and period jitter:
* _! e  d- m$ j9 a8 ?4 ]4 C2 I2 U1 h9 ophasejitter = sqrt(integral(fre,2*Lpll))*T/(2*pi);
5 H+ i: S& S# r3 ?periodjitter = sqrt(8*integral(fre,Lpll.*(sin(pi*fre*T)).^2)/((2*pi*f)^2)); : H4 G  M, W2 ~4 E; g

8 J- R2 F3 X  C$ Jwhere Lpll is the single-sideban phase nosie of the pll, the function integral is: - H, L1 Y$ |; C; R
function integ = integral(fre,L)
5 y0 E: B6 D; |6 `% calculate integral . M& D- b3 {# U
len=length(fre); 5 q8 M+ H! `3 q" J7 T3 N
for n = 1:len-1
8 E" A1 }# w; m* m8 j% v+ E1 Uareatrape(n) = (fre(n+1)-fre(n))*(L(n+1)+L(n))/2; , [; R7 G8 |4 }) N& v% L
end * M: k$ ^' l1 W2 S0 l3 R* {1 `$ F/ o
integ = sum(areatrape);
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1 ]7 z, @4 \8 SI expect the same results of phase jitter and period jitter because the pll locked. but the results are: # a  M% v1 W3 H( |( Z
phase jitter = 8.31e-11   and 4 m  v  h7 _; J( ^
period jitter = 3.27e-12
% U3 A9 ]1 E4 q5 b; s; U2 |) g) qrespectively.
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8 h$ b" G, S. n9 E6 o( J3 ^3 `Is there any error of my routine or my understanding of phase jitter and period jitter? 8 F; C1 L5 ]4 s
in the attached figure, the red curve is the phase noise of the PLL.