I was simulating the Mixer model in Verilog-a given in rfLib.
It is terminated with ports of 50 ohm at its input and output.
I did PSS and PAC simulation to find the IIP3 of the Mixer. I used Mixer Gain=20dB, LO power=10 dBm, Input Resistance = 50 Ohm, Output Resistance=50 Ohm Input referred IIP3=13dBm, All Isolation (from LO-RF...etc) = 50dB.
But the IIP3 curve is NOT giving the desired IIP3 = 13 dBm. The 1st Harmonic curve is almost Flat. I have attached the waveform file