Three-dimensional position accuracy in circular synthetic aperture radar

This article evaluates the three-dimensional (3-D) location information provided by spotlight-mode circular synthetic aperture radar (SAR). The circular synthetic aperture refers to a single circular flight path of 360° azimuth at a constant altitude and broadside squint angle. The motivating operational concept is persistent wide-area surveillance from a single airborne radar platform. The circular SAR data collection geometry inherently presents a near-field inverse scattering problem; however, the far-field plane wave propagation assumption is accurate for a region about the scene center. Early SAR manuscripts noted that nonlinear flight paths provide k-space data not confined to a plane, thus providing some 3-D resolution [1]. Resolution in 3-D was likewise demonstrated for ultrahigh frequency (UHF) and X-band systems using circular apertures [2].