I am running a transient PLL simulation. I check the phase noise and the jitter. I calculate the phase noise as follows: I check the delay between the input signal and the feedback signal, subtract its average and then get the rms of the whole thing. I calculate jitter at the output of the PLL using jitter function. Both these calculations give reasonable results and are correct in how I calculate. The weird thing comes now: I define the transient noise at 20G only for the divider, to check only the effect of the noise of the divider both at phase noise and at jitter. I find the phase noise(jitter between input and feedback signal) and the jitter at the output to have the same value in cadence. Matlab shows that these "2 jitters", one between input and feedback signal and the other one at the output, to have different values. I think Matlab calculation is reasonable because the noise of the divider sees a high pass function for phase noise (the jitter between input and feedback signal) and a low pass function when I check the output of the PLL. Has anyone faced this issue before?
I am looking forward to your reply.