Adaptive baseband interference suppression in multi-channel heterodyne radar receivers

In radar systems, heterodyne RF circuitry is commonly used to produce multi-channel in-phase and quadrature (I/Q) signals which are then beamformed and range-Doppler processed. Often such receivers are deployed in noisy environments, where interference signals at frequencies within the baseband bandwidth of the signal (e.g. less than 1 MHz) can corrupt the demodulated received RF signals prior to A-to-D conversion. Since this baseband interference is correlated across channels, it is often exacerbated by beamforming operations. Moreover, depending on the subsequent radar signal processing, such interference can appear very “target-like” after range-Doppler processing. In this paper, a relatively simple adaptive signal processing method is presented which exploits the Hilbert transform relationship between in-phase and quadrature channels of true demodulated RF signals in order to cancel baseband interference. The approach is demonstrated via simulation and also using real S-band microwave data from a testbed microwave radar system.