A CURVATURE-CORRECTED KIRCHOFF FORMULATION FOR RADAR SEA-RETURN FROM THE NEAR VERTICAL

摘要

A new theoretical treatment of the problem of electromagnetic-wave scattering from a randomly-rough surface is given. A high frequency correction to the Kirchoff approximation is derived from a field integral equation for a perfectly conducting surface. The correction, which accounts for the effect of local surface curvature, is seen to be identical with an asymptotic form found by Fock (1945) for diffraction by a paraboloid. The corrected boundary values are substituted into the far-field Stratton-Chu integral, and average backscattered powers are computed assuming the scattering surface is a homogeneous Gaussian process. Preliminary calculations for a K ocean wave spectrum indicate a reasonable modelling of polarization effects near the vertical, θ < 1+5°. Correspondence with the results of small perturbation theory is shown.