Hi,

I am simulating the LNA + Mixer combination using PSS, PAC and PNOISE analysis ( I follow the method outlined in the cadence manual).
LNA has a tuned LC load at the output. Mixer is a standard gilbert cell.
I have individually characterized the LNA and mixer.
When I do the PSS + PAC analysis of the combination and see the response at the LNA output, I see a lot of difference from the expected response.I see a gain of 50 (magnitude) in the place where I expect a gain of 10.
Since PAC result is wrong, PNOISE result is also expected to be wrong.
PSS does not give any convergence errors.

When I do a QPSS analysiswith LO as large tone and LNA input as medium tone , the results are consistent with the expected values.
What could be wrong with the PAC analysis?
Are there any special precautions to be taken while simulating the LNA + Mixer combination?



I am stuck with this problem and any help will be greatly appreciated.

Prabhu