We want to find the out-of-band IIP3 of the Circuits like active filters. In these cases, we like to find the iip3 as a function of \delta f. Assume that always 2f2-f1 should be equal to fIM3 which lies in the pass band of the filter. As you change f2 by \delta f, the f1 should be changed by 2\delta f . In this manner we can find the out of band linearity of circuits such as active filters.
Sorry I made a mistake
I want to draw the IIP3 vs power of RFfreq ( it btain from crossing two curve)
I can get exact amount of IIP3 from HB simulation but I need the curve