What process combines two signals in a non-linear circuit to produce unwanted spurious outputs?

Intermodulation (often called intermod) occurs when two or more signals mix in a non-linear circuit, such as an overdriven amplifier or a receiver front end. This unintentional mixing creates unwanted spurious signals at the sum and difference frequencies of the original signals and their harmonics. While heterodyning is the intentional mixing of signals to change frequencies for processing, intermodulation specifically refers to the generation of unwanted, interfering signals that degrade performance. Detection is the process of extracting the original information from a modulated carrier, and rolloff refers to filter attenuation, making them incorrect choices.