There is a very common user-error that causes this problem. SpectreRF's PNoise analysis provides a parameter maxsideband. This parameter specifies the number of noise sidebands (or how much noise folding) to include in the output noise. For reasons that we still don't understand, both official Cadence documentation and training material mistakenly instructed users to set this parameter to zero. Using maxsideband=0 would prevent any frequency conversion effects from being taken into account; only the noise from sources at the analysis frequency would be included in the output. Thus, you would not be able to see the flicker noise up-conversion, and the result would be a significant under-estimation of the total phase noise of the oscillator.

To see the flicker noise that mixes up from low frequencies in the output, you would need to set maxsideband to at least one. However, in order to account for all significant noise folding, we recommend that you not use a value less than the default value of 7. To be sure you are using a high enough value, try increasing it until the noise results stop changing.

I apologize for this confusion and the trouble it has caused you.

-Ken