RF front-end simulation

Dear collegues,

I am trying to simulate an RF front-end (LNA+VCO+MIXER) in order to get performances such as conversion gain, noise figure, etc.

If I simulate only the LNA+MIXER and use a Vsin to emulate the behavior of the VCO I can perform a PSS+PNOISE+PAC and get all the desired performances.

However, If i use the "real" VCO, which is an autonomous circuit, then the PSS does not work correctly:

- If I simulate the whole front-end and give the fundamental frequency, then it does not get the exact VCO frequency, and I cannot get the performances.

- If I simulate the whole front-end and the PSS is enable for autonomous circuits, then it simulates the entire front-end as an oscillator, and I cannot get the performances.

Can anyone help me with this issue?

Best Regards,
Fabio