Phase Noise and S-Parameters

Hi all,

I am simulating a VCO using an S-parameters inductor. I have the lumped elements pi-model fitted with it.

When I run PSS, transient, DC and so on, I get results almost fully compatible between the two cases. When it comes to the phase noise plot, I can observe significant differences (several dB). S-parameters are extracted down to 10e4 Hz, while my phase noise plot starts at 1 MHz. 

I was wondering if there are particular options to set or to work on when doing phase noise simulations with S-parameters. I have tried to work on interpolation method but I had no results.

Thanks in advance