<title>Lincoln Laboratory millimeter-wave synthetic aperture radar imaging system</title>

Abstract

The Lincoln Laboratory millimeter-wave Synthetic Aperture Radar (SAR) imaging system is part of a DARPA-funded program that was established at Lincoln Laboratory to investigate the detection and classification of stationary targets using ultra-high resolution, fully polarimetric SAR and Real Aperture Radar (RAR) data. The system consists of an airborne radar that operates at 33.56 GHz. The raw radar data are recorded on high density digital tapes that are sent to the Radar Data Analysis Center, which is located at Lincoln Laboratory in Lexington, MA. This center processes the data to create calibrated SAR and RAR images. The Radar Data Analysis Center consists of a number of major data processing elements: an image formation processor, an archival storage and retrieval system, and a cluster of computer systems used for data analysis. In order to accomplish the goals of the DARPA program, it is essential that the radar data be very carefully calibrated. The calibration process consists of three major steps: (1) An internally-generated calibration pulse is inserted into the radar receiver at the front end. (2) Calibration targets (dihedrals and trihedrals) deployed on the ground are measured by the radar from the air. (3) Special calibration processing software uses the measurements from (1) and (2) to achieve polairmetric calibration. This paper will describe the airborne radar, the ground processing facility, and the calibration process. Recent SAR images, generated from airborne measurements, of ground clutter and selected urban areas will be presented. The images were generated using the polarimetric whitening filter (PWF), a novel processing technique developed at Lincoln Laboratory. The PWF process exploits the polarimetric measurement capability of the radar to create imagery the is nearly optical in quality.