The 3rd-order nonlinearity will accommodate all the distortion products of interest in a radio receiver or amplifier circuit, and so the IP3 is an important measure of the circuit or system linearity. It is used to determine the amount of intermodulation (IM) distortion in the circuit at high signal levels. In a radio receiver, for example, the IM rejection, which is the difference between the receiver sensitivity S and an input signal level sufficient to produce interference, is calculated from the system input intercept point:
where CR is the cochannel rejection or capture ratio. See also intermodulation.