Evaluation of reflected fields at caustic regions using a set of GO equivalent line currents

A set of equivalent electric and magnetic line currents is derived which supplements the geometrical optics (GO) solution in the far zone whenever one of the surface principal radii becomes very large. These hypothetical currents lie along the specular line of the surface and are shown to produce the same result as the stationary phase contribution of the physical optics integral. An example of a systematic application of such equivalent currents for the computation of the scattered field from a complex structure is also demonstrated.