Hi Frank, I simulated pxf with two specialized analysis. one in none mode, the other in sampled mode. I post the results for comparision.
I found that there is big difference between them. To my opinion, the none mode make sense beacuse the low frequency gain of the tf is about 0.5 since the power is used to power supply the common inverter which is output buffer of the xosc. The sampled result seems much worse than none mode. which is correct for evaluating effect of the power supply noise for measuing the jitter performance of the xosc? why they have so big difference? please correct me. Thanks a lot.
Frank Wiedmann wrote on Apr 25th, 2012, 12:58am:The standard mode ("none") works in a way that is similar to a spectrum analyzer. The sampled mode is typically used to determine the jitter of a signal edge. The modulated mode gives you amplitude and phase modulation and assumes a filtered output signal (only one sideband at each side of the output signal is evaluated).
You can find additional information about sampled analysis in
http://www.designers-guide.org/Analysis/sc-filters.pdf. Chapter 4 "Time Domain Analysis: Shooting Newton" of the manual "Virtuoso Spectre Circuit Simulator and Accelerated Parallel Simulator RF Analysis User Guide" also has some information about and examples for the different pxf analysis modes. Further resources are the forum at
http://www.cadence.com/community/forums/33.aspx and the Cadence support site at
http://support.cadence.com/.