Baseband Equivalent Volterra Series for Modelling Cross-channel Nonlinear Distortion

Mutual interference is a significant challenge for modern radars that is becoming increasingly problematic as the sensor is adopted onto new platforms. If nonlinearities are present in the radar receiver, interference signals may cause intermodulation and cross-modulation effects. This paper shows that cross-channel nonlinear distortion effects can be modelled accurately using a baseband equivalent Volterra series. The specific cross-channel baseband Volterra Series we derived from the full passband Volterra series is presented in the System Model section of this paper. Complex computer simulations were used to verify that all of the relevant nonlinear distortion effects are captured by this new behavioural model. The architecture of these simulations is outlined in this paper with particular emphasis on the techniques designed to identify the cross-channel bandwidth expansion effects caused by the nonlinearity. As a result, the derived model can capture all nonlinear distortion effect on the carrier due to the presence of an interference signal at half the carrier frequency. This is a significant result as it proves that the cross-channel nonlinear distortion effects of passband amplifiers can be accurately characterised using behavioural models based on baseband Volterra series. This result is of particular interest to radar systems as it will allow the nonlinear effects of receiver amplifiers to be characterised in greater detail.