Question regarding IIP3 plot?

Hi all,
I'm new to RF and works on direct conversion receiver. I want to measure out-of-band IIP3. Two-tone input signals are used. The IF of these signals is varied from 100kHz to 10MHz. The space between these signals is set so IM3 for every IF falls in-band at 30kHz.

The question is that which IF I should use as my fundamental when plotting IIP3. Should I stick with the lowest IF for my fundamental tone which is 100kHz and plotting all IM3 for all IFs? Or, should I use the IF tone associated with the two-tone signal?

Thank you so much in advance.

One.
2f2-f1 should be in band and let assume that it is constant. Therefore as you change f2 by delta_f , f1 should change by 2 delta_f.
Two.
Because of filtering effect of the baseband, the fundamental tone at f2 has more attenuation than f1, and then you might wonder for measuring the iip3, which one should we choose.
In this case, none of this will be used as a fundamental signal . For fundamental line, you just do another simulation with f at im3 and use it as a fundamental line.

when you do direct conversion then we loose the concept of 2f1-f2 etc.
you will see single fundamental and single IMD with zero offset.
Still i guess we can use the formula Pout+(Pout-Pimd)/2,
Just try may be we need to minus 3dB due to both fund powers get combine.

good query