Wide Angle SAR Imaging.pdfVIP

Wide Angle SAR Imaging Randolph L. Mosesa, Lee C. Pottera and Mujdat C?etinb, aThe Ohio State University, Department of Electrical and Computer Engineering 2015 Neil Avenue, Columbus, OH 43210, USA (moses.2@, potter.36@) bMassachusetts Institute of Technology, Laboratory for Information and Decision Systems, 77 Massachusetts Ave, Cambridge, MA 02139 (mcetin@) ABSTRACT We consider imaging strategies for synthetic aperture radar data collections that span a wide angular aperture. Most traditional radar imaging techniques are predicated on the assumption of isotropic point scattering mech- anisms, which does not hold for wide apertures. We investigate point scattering center images for narrowband, wide angle data, and consider the effect of limited persistence on the resulting images. We investigate imaging strategies that apply to wide angle apertures. We show that coherent processing of the entire wide angle aperture may not be the best image formation strategy for objects of practical interest. Finally, we present initial results on resolution enhancement techniques for wide angle apertures. Keywords: synthetic aperture radar, wide angle, radar imaging 1. INTRODUCTION Wide-angle synthetic aperture radar (SAR) refers to any synthesized aperture whose angular extent, ?φ, exceeds the sector required for equal resolution in range and cross-range: ?φ 2 sin?1 (BW/(2fc)) (1) where BW and fc are the bandwidth and center frequency of the radar. For X-band systems, which operate near fc = 10GHz, Table 1 lists the aperture sizes to give equal downrange and crossrange resolution for several radar bandwidths. A number of recent technology advancements enable consideration of wide angle imaging. First, advancements in GPS and INS systems permit collection of coherent data across longer times and flight paths. Second, unmanned air vehicle (UAV) technology and collaboration among UAVs provide a number of wide angle imaging possibilities. UAVs can in many applications fly closer to