I have some problem in prediction of 3-rd order inter-modulation product level
. Usually, IMP3 is defined analytically for the case that both tones are of the same level and frequency difference between them is less than 5% of their frequency (in-band conditions).
I have a different case: f1 tone is of 49 dBm at 430 MHz, and f2 tone is of 29 dBm at 549 MHz. So, they have different levels and are spread wide.
I am interested to predict the level of lower IMP3 (2*f1-f2) at 311 MHz.
I am looking for analytical equation and physical/mathematical explanation, which will take in account the wide distance between tones at frequency axes and also their difference in power levels.
Any theoretical explanation and/or links will be appretiated.
I look also for translation between measurement results taken by classical approach and my special case.
For example, I have to understand whether results of classical measurement of OIP3 may be applied somehow to my special case and reliably predict "my" IMP3 at 311 MHz.