PhD Final Oral Dissertation Defense: Molly Crane - Thursday, 1/19, 10am - 12pm, PHO339

Title: POLARIZATION TECHNIQUES FOR MITIGATION OF LOW GRAZING ANGLE SEA CLUTTER Presenter: Molly Crane Date: Thursday, January 19, 2017 Time: 10:00 a.m. - 12:00 p.m. Location: 8 Saint Mary’s Street, PHO339 Chair: TBD                          Advisor: S. Hamid Nawab (ECE) Committee: W. Clem Karl (ECE), Jeffrey Carruthers (ECE), Mabel D. Ramirez (MIT Lincoln Laboratory) Abstract:  Maritime surveillance radars are critical in commerce, transportation, navigation, and defense. However, the sea environment is perhaps the most challenging of natural radar backdrops because maritime radars must contend with electromagnetic backscatter from the sea surface, or sea clutter. Sea clutter poses unique challenges in low grazing angle geometries,where typical statistical assumptions regarding sea clutter backscatter do not hold. As a result, conventional constant false alarm rate (CFAR) detection schemes may yield a large number of false alarms while objects of interest may be challenging to detect. Solutions posed in the literature to date have been either computationally impractical or lacked robustness.    This dissertation explores whether fully polarimetric radar offers a means of enhancing detection performance in low grazing angle sea clutter. To this end, MIT Lincoln Laboratory’s Advanced Concepts Committee funded an experimental data collection using a fully polarimetric X-band radar assembled largely from commercial off-the-shelf components. The Point de Chene Dataset, collected on the Atlantic coast of Massachusetts' Cape Ann in October 2015, comprises multiple sea states, bandwidths, and various objects of opportunity. The dataset also features three polarimetric transmit schemes. In addition to discussing the radar, the dataset, and associated post-processing, this dissertation presents a derivation showing that an established multiple input, multiple output radar technique provides a novel means of simultaneous polarimetric scattering matrix measurement. A novel scheme for polarimetric radar calibration using a single active calibration target is also presented.   Subsequent research leveraged this dataset to develop Polarimetric Co-location Layering (PCL), a practical algorithm for mitigation of low grazing angle sea clutter, which is the most significant contribution of this dissertation. PCL routinely achieves a significant reduction in the standard CFAR false alarm rate while maintaining detections on objects of interest. Moreover, PCL is elegant: It exploits fundamental characteristics of both sea clutter and object returns to determine which CFAR detections are due to sea clutter and which are not. We demonstrate that PCL is robust across a range of bandwidths, pulse repetition frequencies, and object types. Finally, we show that PCL integrates in parallel into the standard radar signal processing chain without incurring a computational time penalty.