Input Backoff (IBO)

Input backoff (IBO) is the reduction applied to the input power of a radio-frequency power amplifier relative to the input level that would drive the amplifier into saturation. It is used to operate the amplifier in a more linear region of its transfer characteristic, thereby reducing nonlinear distortion such as intermodulation products and spectral regrowth.

In satellite communications, input backoff is particularly important for traveling-wave tube amplifiers and solid-state power amplifiers carrying multicarrier or spectrally efficient modulated signals. Increasing input backoff improves signal linearity and adjacent-channel interference performance, but at the cost of reduced output power and lower power efficiency. The required input backoff depends on the modulation scheme, the number of carriers, and the linearity requirements of the link.