English: Thumbnail for File:Two carrier 3rd order intermod measurement.png

The non-linear amplifier produces undesirable intermodulation products (D3, D4) at 2*f1-f2 (D3) and 2*f2-f1 (D4). Note that the 3rd order intermods grow by 3 dB for every 1 dB increase in input power, while the carriers increase by 1 dB for every 1 dB increase in input power. The spectrum becomes highly distorted at higher power levels as the odd order intermod products (3rd, 5th, 7th, 9th, ...) increase in level with respect to the carriers. An nth order intermod grows by n dB for every 1 dB increase in input power.

I captured these screenshots from a Rohde & Schwarz FSW spectrum analyzer (non-free software) and created the animation myself. Usage of these screenshots constitutes fair use.