Analysis of the diffracted current basis functions used in the hybrid MoM-PO method

Abstract

field distribution in a given medium. As a low-frequency technique, the method has been applied to such problems for which the structure, owing to the memory storage, is small in terms of wavelength. At the same time, the physical optics (PO) and the geometrical theory of diffraction (GTD) [11] are applicable to bodies that are arbitrarily large in the electrical sense and may subsequently be referred to as high frequency techniques. The applications of diffraction theories, however, are limited to geometries for which the diffraction coefficient is known. Therefore, a combination of MoM and PO or GTD may lead to a power tool of handling a whole host of new problems.Brunside utilized the hybrid MoM-GTD technique to solve scattering problems of incident plane waves by perfectly conducting right-angled wedge [12]. Bilow developed a hybrid MoM-PO solution for the currents induced by incident plane waves on infinite two-dimensional wedges with faces characterized by arbitrary tensor impedances [13]. The difference of their methods is essentially a variation in DCBF. One is based on GTD and another is based on uniform geometrical theory of diffraction (UTD). The results obtained by using Bilow's diffracted current basis function (DCBF) are in good agreement with the exact solutions in general cases. However, Bilow's basis function results in grave errors in some cases. In terms of the theory of diffraction and the fundamental theory of electromagnetism, we modify their basis functions both within and outside the transition regions. Comparison between Burnside's DCBF and Bilow'sThe geometry for the scattering problem is illustrated in Fig. 1. The wedge has its edge along the z-axis of a cylindrical reference frame and a monochromatic plane wave with an arbitrary polarization impinges on the edge from a direction determined by the two angles wp and bp. bp refers to the edge of the wedge, and the case bp = p/2 corresponds to normal incidence. The exterior wedge angle is np. The face w = 0 of the wedge relies on the x-z plane. An e −jvt time dependence is assumed and suppressed.Abstract The combined moment method (MoM)-physical optics (PO) approach proposed by Bilow fails in some cases. Based on the theory of diffraction and the fundamental theory of electromagnetism, Bilow's diffracted current basis function was modified both within and outside the transition regions. The improved MoM-PO technique is validated by comparison with exact solutions for a right-angled perfectly conducting wedge at normal incidence.