Intermodulation Distortion

Intermodulation distortion is a form of nonlinear distortion that occurs in a radio-frequency amplifier when two or more signals are amplified simultaneously and interact to produce spurious signals at frequencies equal to sums and differences of integer multiples of the original signal frequencies. These unwanted products fall within or adjacent to the intended signal bandwidth and can interfere with other channels.

In satellite communications, intermodulation distortion is of particular concern in high-power amplifiers such as TWTAs and SSPAs operating near saturation, especially in multicarrier transponders. Intermodulation products reduce carrier-to-interference ratios, increase adjacent-channel interference, and degrade overall system performance. To control intermodulation distortion, amplifiers are operated with input and output backoff, trading reduced distortion against lower power efficiency.