Noncoherent 2d and 3d Sar Reconstruction from Wide-angle Measurements

This paper considers processing and visualization of radar scattering measurements from one or more wide-angle synthetic apertures. We consider both two-dimensional imaging and three-dimensional interferometric reconstructions. A point-scattering assumption is poorly suited to wideangle scattering; scattering objects within a target typically have narrow beam patterns, resulting in limited angles of persistence. We revisit traditional imaging in 2D or 3D to propose image formation techniques that use nonlinear, non-coherent combinations of subaperture data. The proposed techniques can be interpreted as approximations to a generalized likelihood ratio test. For sufficiently high resolutions, individual reflectors are resolved, and hence the phase and amplitude of their responses are stable under small changes in viewing angle. This stability is in contrast to the scintillation observed in low-resolution data. Three processing techniques benefit as a result: interferometric measurement of 3D location is possible without wide-area averaging; polarimetric features may be used to describe local geometry; and, bandwidth enhancement is possible. We illustrate processing and visualization techniques using X-band scattering predictions of a backhoe computed using X-patch. The reconstructions permit an approximation to the literal interpretation afforded by optical imaging, but with millimeter wave sensing. In addition, angledependent and polarization-dependent behaviors are displayed for enhanced recognition.