A polarization technique for mitigating low-grazing-angle radar sea clutter

Abstract

Traditional detection schemes in conventional maritime surveillance radars may suffer serious performance degradation due to sea clutter, particularly in low-grazing-angle (LGA) geometries. In such geometries, typical statistical assumptions regarding sea clutter backscatter do not hold. Trackers can be overwhelmed by false alarms, while objects of interest can be challenging to detect. Despite several decades of attempts to devise a means of mitigating the effects of LGA sea clutter on traditional detection schemes, minimal progress has been made in developing an approach that is both robust and practical. To supplement work exploring whether polarization information might offer an effective means of enhancing target detection in sea clutter, MIT Lincoln Laboratory (MIT LL) collected a fully polarimetric X-band radar dataset on the Atlantic coast of Massachusetts Cape Ann in October 2015. Leveraging this dataset, MIT LL developed Polarimetric Co-location Layering (PCL), an algorithm that uses a fundamental polarimetric characteristic of sea clutter to retain detections on objects of interest while reducing the number of false alarms in a conventional single-polarization radar by as many as two orders of magnitude. PCL is robust across waveform bandwidths, pulse repetition frequencies, and sea states. Moreover, PCL is practical: It can plug directly into the standard radar signal processing chain.