I'm simulating a free running oscillator for jitter and I have the following question:
I have to run a "PNOISE - sources" simulation in order to recieve phase noise, since I have to filter the phase noise before integrating in to extract jitter (in order to mimic a PLL / CDR transfer function).
A few papers were written on the subject, some of them state that the integration upper limit is Fc/2 while others state that it is a few Fc. I assume that it should be a few Fc if the tested wave is a sine wave (i.e. no harmonics appear in the phase noise) and Fc/2 if it is a square wave.
As far as I understand, for square waves the jitter behavior of the first harmonic is similar to the jitter behavior of the square wave, thus it is assumed that integration up to Fc/2 takes into account only the first harmonic, otherwise the jitter will be summed more than once.
Please correct me if so far I'm wrong. Otherwise, here is a correction that I would like to do in my PNOISE simulation settings: instead of mixing the noise with many harmonics (i.e. Maximum sideband >> 1) and then integrating up to Fc/2, I might set maximum sideband to 1, thus the noise will be mixed only with the first harmonic, such that I will see a phase noise as if I had a pure sine wave at the input and not a square wave. Then, I would integrate up to a few Fc and see a more accurate jitter result.
In my simulations I see substantial difference between the two options, that's why the question is very important.
Any respose will we appreciated. I would especially like to hear Andrew Beckett's opinion on this.
I'm still not convinced that what you're claiming is correct (I'm going to consult with R&D to try to come up with a more convincing explanation). For a start, in your circuit the noise around the first sideband of the oscillator may be dominant, and so neglecting the higher sidebands may not make a significant difference - so it's hard to confirm anything for sure in the general case from the numbers you've given.
BTW, the plots you are showing from the SpectreRF manual are actually explaining the effect of maxsidebands in how inclusion of noise contributions works in the simulator.