In
telecommunications, a
third-order intercept point (
IP3 or
TOI) is a measure for weakly
nonlinear systems and devices, for example
receivers, linear
amplifiers and
mixers. It is based on the idea that the device nonlinearity can be modeled using a low-order polynomial, derived by means of
Taylor series expansion. The third-order intercept point relates nonlinear products caused by the third-order nonlinear term to the linearly amplified signal, in contrast to the
second-order intercept point that uses second order terms.