Mitigation of Cross-modulation Effects in Radar Receivers with Memory

Modern mass produced radar systems offer a wide variety of advantages over their bespoke predecessors however to achieve these benefits the linearity of their RF receivers is often sacrificed. This compromise leaves these modern sensors susceptible to unwanted cross-modulation effects and with the RF spectrum becoming increasingly crowded this problem is only going to become more pertinent. If mitigation techniques are to be developed they must correct for the nonlinear distortion applied to both the amplitude and phase of the returned radar signal. In order to accurately model nonlinear phase effects in the radar receiver we must consider memory. This paper studies how introducing nonlinear memory in the radar receiver affects the cross-modulation distortion generated. It also presents a simple cross-modulation mitigation technique developed in the communications literature and applies it to the radar cross-modulation problem. As a result the simple communications based mitigation technique successfully corrects for cross-modulation distortion generated from a memoryless nonlinear radar receiver. However, it is ineffective when nonlinear memory effects are introduced. This is a significant result as it suggests that if the nonlinearities generating cross-modulation effects in modern radar are found to have memory then sophisticated memory mitigation techniques will have to be developed.