A hybrid EM scheme for the composite scattering and the SAR imaging of a low-altitude target above the electrically large and multi-scale sea surface

Abstract

ABSTRACTThis article has developed a feasible hybrid electromagnetic scheme to evaluate the composite scattering and the Synthetic Aperture Radar(SAR) image characteristics of a low altitude perfect electric conductor (PEC) target above the sea surface at the high microwave frequency bands. In this method, the scattering upon the target surface is calculated by the Physical Optics (PO) method; the sea surface scattering is evaluated by a Bragg Modified Small Scale Approximation (BMSSA) method; the coupling components are considered by the Geometrical Optics (GO) method with efficient ray tracing techniques; finally, the diffractions from the edged structures are considered by the Equivalent Edge Current (EEC) method. The hybrid method can give a physical insight of the composite scattering mechanisms, and it can overcome the difficulties in accurately evaluating the composite scattering characteristics of a target above the electrically large and multi-scale sea surface in the real scene. The computation model and method is validated by the exact numerical solver. Numerical results compare the scattering characteristics of a missile-like target above the electrically large sea surface in the conditions of different incident frequencies, incident angles and sea states. Finally, SAR image characteristics at different sea states are presented, with the target scattering, sea scattering and coupling scattering characteristics further discussed in details.