Intermodulation Squared Response [Microwave Bytes]

I think I have, on a few occasions, used the term "old chestnut" as a very old English way of describing a concept that has had a lengthy history of being kicked around and argued about, to the extent that one hesitates to give it yet another airing. The microwave field is certainly well supplied with such old chestnuts; maybe even the word ?microwave? itself is one. But more technically, I think of the well-worn arguments about conjugate match in power amplifiers (PAs), the justifications for the use of a standardized 50-X interface, and the frequently observed asymmetry of thirdorder intermodulation (IM3) spectra, to name just three. But for today, I will revisit, with a little trepidation, the subject of IM3 distortion (IMD3).