I am using PSS+PNOISE to estimate output jitter of a limiting amplifier as follows:-
1) Drive the input with a single tone at Fin
2) Run PSS with shooting method, beat frequency Fin, select number of output harmonics N such that Fin*N > circuit's 0dB gain
3) Run PNOISE with noisetype=jitter, maximum sideband=N, reference sideband=0, frequency sweep from 1Hz to Fin/2
4) Plot Jee with integration limits 1Hz to Fin/2
So far I have been happy with this procedure - the results for Jee etc are reasonable and agree with a few TRAN+NOISE sims run as spot checks. It also agrees with recommendations elsewhere on the forum (e.g.
www.designers-guide.org/Forum/YaBB.pl?num=1092399689) and my somewhat incomplete understanding of exactly how the simulator works its magic.
Recently, other members of my design group have questioned this approach. What they propose is mostly similar, but change PNOISE as follows:-
3a) Run PNOISE with noisetype=jitter, Sideband array of indices, additional indices=0, reference sideband=0, frequency sweep from 1Hz to 'very high' (well beyond circuit 0dB gain)
4a) Plot Jee with integration limits 1Hz to 'very high' (same as above)
Jitter numbers for both methods are very close (less than 1% mismatch, although not identical). However, when I run a few stripped-down test cases the actual output noise (using noisetype=sources) shows bigger deltas, up to 10% or so for the particular examples I have run so far.
My questions are therefore:-
a) Which of these methods is 'correct'?
(Maybe they are equivalent? Maybe they are both wrong?)
b) Can someone explain (or recommend a good reference to explain) the difference, if any, so I can improve my understanding?
Many thanks!
Pete