I am running PNoise analysis for my Injection-locked oscillator before and after injection. Before injection, it's just a VCO, and in SweepType field, I choose "relative". However, when I inject a signal, "relative" option gets me the same PNoise of the VCO, which is not reasonable. My question is, since ILO is a driven circuit, should Sweeptype be "Absolute" or "default", especially as their results are very reasonable? and what are the difference between the three options?
I have one more question just to make sure I do it right: I inject my circuit with a 5-GHz signal and the o/p is 1GHz. Does it mean Sweeptype is "relative" in this case or still "absolute" as the circuit is actually driven?
I can not understand what you want to mean at all.
However if your analysis is a PSS analysis with fundamental_frequency=1GHz, it is a driven PSS analysis.
Why do you relay on default setting in Pnoise ? Simply set sweeptype as relative or absolute clearly without using default.
That's all.
And you can confirm actual sweeptype used for Pnoise in Spectre logfile.
Surely see logfile of Spectre.