FRINGE WAVES IN AN IMPEDANCE HALF-PLANE

Abstract

The uniform expressions of scalar fringe waves which are based on the physical theory of difiraction (PTD) were obtained for the impedance half plane in terms of the Fresnel integrals. Asymptotic and uniform forms of the fringe flelds were compared. The radiated flelds of the fringe expressions were analyzed numerically. Physical optics (PO) is based on the integration of surface currents which are induced by the incident flelds. This concept is valid and accurate for metallic scatterer surfaces and gives exact geometric optics (GO) waves in the high frequencies. There are lots of studies in the literature about the application of the PO method (1{3). The edge difiracted flelds which are found from the contribution of the PO surface integral are not correct. In addition PO currents just consider the illuminated part of the scatterer and ignore the shadow regions. The physical theory of difiraction (PTD) method was proposed by Uflmtsev to overcome the flrst defeat (4). The PTD consists of two main parts. The flrst part is the uniform part which is obtained from the PO and the second part is the contribution of the non-uniform or fringe part. The fringe part is the result of the fringe currents. It is pointed out that the fringe currents are obtained by dividing the induced surface currents into two parts. The flelds, radiated by the fringe currents, can be found by subtracting of uniform part from the exact solution. The method is widely used in the literature for investigation of the scattering problems (5{8). Using the uniform fringe flelds instead of the non-uniform version is more reliable. Non- uniform fringe flelds can be obtained by the subtraction of asymptotic