Trust PSS or Transient simulation for VCO?

I encounter a difference in the simulated value of VCO output frequency when i run transient and PSS simulation...is this normal? has anybody experienced the same issue?

As an e.g. I get a frequency of 37 GHz from transient simulation (by using the frequency function from the calculator on the differential output voltage)

Whereas, the PSS finds an oscillation frequency of 38 GHz. I use Moderate as errpreset.

My question is which simulation result should i trust in designing for a specific tuning range?

Regards

check this link it is a appnote how to use spectreRF in oscillator design

ususally ppl use PSS periodic steady state , not the transient analysis
also the noise PSS to get the phase noise of the oscillator

http://www.cdnusers.org/community/vi...F_VCO533AN.pdf


khouly

PSS is more accurate than transient by using frequency function because of "settling of the frequency" at the beginning of transient state of the circuit. In generally, oscillator simulations are done by PSS NOT transient and also 37GHz is too much for MODEL continuity of the both passive and active components.

So 1GHz difference my be normal..

My apologies...i could not understand the above statement...can you please elaborate ?

Regards

My apologies...i could not understand the above statement...can you please elaborate ?

Regards