Adaptive mainbeam jamming suppression for multi-function radars

One aspect of naval defence involves surveillance of the airspace in the vicinity of one's vessel. Both high-altitude and low-altitude missiles must be detected, tracked and targeted. A multi-function radar (MFR) that uses an electrically steerable pencil beam (phased array) to search the volume around the ship can provide the required capability. Monopulse sum and difference beams (azimuth and elevation) are provided to yield high resolution direction of arrival (DOA) estimates for detected targets, improving ship defence capabilities against modern threats. This paper is concerned with robust estimation of low-altitude targets such as sea skimming missiles for the challenging case where horizon-based jammers are present in the antenna's mainbeam. By exploiting the properties of the monopulse beams, spatially adaptive algorithms are developed that provide simultaneous mainbeam nulling and high-resolution target DOA estimation. Simulation results demonstrate the detection and estimation performance achievable. DOA estimates using suitably derived MUSIC (multiple signal classification), ML (maximum likelihood) and corrected adaptive monopulse (CAM) algorithms are compared.