Quote:1. You said PSS simulation can find tc.I used transient to do this and found these two
simulations show different result. I mean, the zero-crossing point of my output clock are
different from these two simulations. I don't know why. And as you said, tc is"the time where the signal crosses the theshold level of the following stage", so do you think I shouldn't use zero-crossing point as tc? Do you think I should connect the following stage to my clock otherwise I can't find tc? I think the sizing of the following stage will affect tc value.
You have to use the PSS simulation to find tc, because the PSS simulation is used as the basis for the following PNOISE analysis. The timepoint tc is where you want to examine the jitter of your circuit. If you have a differential circuit, the zero-crossing point will probably be ok.
Quote: 2. In the direct plot form, when I chose tdnoise/integ output noise/total noise/spectrum/magnitude, I didn't
see any fields allowing me to input starting and ending frequencies. When I clicked "plot" then, I got an error
message "fprint/sprintf: format spec incompatible with data nil". I don't know why. The cadnece i am using is 5.0.0_MSR
I'm afraid I can't help you with problems you have with your specific Cadence installation. You should probably ask your local experts to examine these problems.
Quote: 3. If I chose 'output noise", not "integ output noise", I got the spectrum after clicking plot. The unit of Y-axis
is V/sqrt(Hz). Do you mean I should integrate this curve from 0 to Fs/2? I think the result will be different than
if I integrate power then take square root. I mean, integ(V) is not equal to sqrt (integ(Power)), am I wrong? I am a little confused here on the equation (53) and (54) in document "predicing the phase noise dn jitter of PLL....".
With noise, you always have to integrate the power. So, if you have the result in V/sqrt(Hz), you first have to square it in order to get the power, then integrate the power, and finally take the square root to get the "noise amplitude" in volts.
Quote:4. Since the jitter is in the order of ps, Do you think the tc I used should be accurate enough, for example, 21.12345n, not just 21.1n? And do you think tc should be within 0 and T. I found PSS only generata a transient waveform from 0 to T
This depends on your circuit. You can just try and see if it makes any difference. With PSS, the time will always be between 0 and T.