Hi, Ken and Frank
Thanks for your detailed description, I believe I have a further
understanding of phase noise and how SpectreRF calculate it now.
On the other hand, after going through the thread Frank provided,
I have some other questions:
1.How to determine the "threshold" in Pnoise jitter mode?
We usually set the threshold to Vdd/2 in logic circuits.
However this is an ideal value. In reality the threshold value
may vary according to many causes, like Vdd ripple, devices mismatches...and so on.
How can we precisely choose the threshold value?
Or the threshold value doesn't affect the result much?
(I myself have tried a chain of inverts with Vdd=1.2 V, and
set the threshold value from 0.4 to 0.8 V, the resulting jitter
doesn't have significant difference, the largest difference is less than 3 dB.)
2.It seems PM jitter in jitter mode is used to simulate oscillator followed by driven circuits, like buffer or divider.
Then what is FM jitter for? Is it like the PM noise in the modulated mode but just reported in the unit of second/sqrt(Hz)?
3.In the thread
http://www.designers-guide.org/Forum/YaBB.pl?num=1158788102;start=all, Ken said
"...If you are in the 1/Δf 2 region, then the noise from the phase mode in the oscillator is dominating.
In this case, using strobed noise to determine the phase noise should give the same result as using
the time-averaged noise..."
I don't understand what's the meaning of "if your are in the 1/Δf 2 region".
Does it mean that we concern about the spot phase noise at a certain frequency which is in the 1/Δf 2 region?
Regards,
YCY