Slope Diffraction Coupling Effect

Abstract

ABSTRACT This work documents the existence of a coupling effect between transverse electric and transverse magnetic fields in slope diffraction by edges. For oblique incidence, a transverse magnetic incident field with a slope will produce a transverse electric slope-diffracted field and, in analogy, a transverse electric incident field with a slope will produce a transverse magnetic slope-diffracted field. This coupling effect is found by solving the scattering problem of a perfectly conducting wedge illuminated by a non-uniform plane wave possessing a linear amplitude variation, i.e., a slope, in the direction normal to the plane of incidence. This constitutes the most optimal canonical problem involving electromagnetic slope diffraction by edges for oblique incidence. Two solution procedures, based on two different representations of the non-uniform plane wave in terms of uniform plane waves, are employed to derive the exact solution for the half-plane and the high-frequency asymptotic solution for the wedge. In the high-frequency asymptotic solution for the slope-diffracted field the coupling manifests itself as non-zero terms outside the main diagonal of the slope diffraction matrix. These coupling terms are of the same order in the wave number k as are the well-known main diagonal terms. Although slope diffraction has been the subject of numerous works over many years, the vast majority of these works do not report this coupling effect which has remained practically unknown.