IM2 calculation with ADS

[passerby]

Hi

I was trying to use ADS to check if I understand IM2 (2nd order Intermodulation) calculation correctly or not but the result confused me with ADS simulation.

In theory with 2-tone test (same amplitude for f1 and f2),
IM2@(f2-f1) & IM2@(f2+f1) = 2*pin(f1) - IIP2 = 2*pin(f2) - IIP2
IM2@DC = IM2@(f2-f1) +3dB = IM2@(f2+f1)+ 3dB
Am I correct for the above formula?
(Reference: rfdesign.com/mag/404rfdf3.pdf)

From the ADS simulation it gives me quite different results.
m1 and m2 are different level, and m3 is not 3dB above m1.

Could you please advise where goes wrong?
Did I configure ADS simulation parameters correctly?

Thanks a lot for your help.

 

[samchieh]

mmm....is it because your amplifier is Ideal and is not modeled to be non-linear? that's my guess....

 

[toonafishy]

Did you also calculate the third order products? And then add them to the second order products where they land on the same frequency?