ELECTROMAGNETIC AND SCALAR DIFFRACTION BY A RIGHT-ANGLED WEDGE WITH A UNIFORM SURFACE IMPEDANCE.

The diffraction of an electromagnetic wave by a perfectly-conducting right-angled wedge with one surface covered by a dielectric slab or absorber is considered. The effect of the coated surface is approximated by a uniform surface impedance. The solution of the normally incident electromagnetic problem is facilitated by introducing two scalar fields which satisfy a mixed boundary condition on one surface of the wedge and a Neumann or Dirchlet boundary condition on the other. A far zone approximation is made to obtain the scattered field from which the diffraction coefficient is found for scalar plane, cylindrical or spherical waves incident the edge. With the introduction of a ray-fixed coordinate system, the dyadic diffraction coefficient for plane or cylindrical EM waves normally incident on the edge is reduced to the sum of two dyads which can be written alternatively as a 2 multiplied by 2 diagonal matrix. This format is consistent with that being used in other Geometrical Theory of Diffraction studies being conducted at the Electro-Science Laboratory. The dyadic diffraction coefficient is valid in the transition region of the shadow and reflection boundaries. It is composed of trigonometric functions and Fresnal integrals which are easy to compute.