Correction term of MER for PO surface-to-line integral reduction for curved surfaces

Abstract

Summary form only given. In diffraction theory, the currents generated on the scatterer are integrated over the surface to give the scattered field; the surface-to-line integral reduction is important not only for reducing the computational load but also for extracting the mechanism of the field and relieving the difficulties in ray theories such as GTD and UTD. In view of asymptotic approximation such as Stationary Phase method (SP), it is understood that the radiation integral could be decomposed into two components in general, the reflection from Stationary Phase Point (SPP) and the diffraction given by a line integral of the equivalent edge currents (EECs) along the edge of the scatterer. The Modified Edge Representation (MER) is a concept to define the EECs on whole the contour of line integration for diffraction. Physical Optics (PO) is one of the high frequency asymptotic techniques which consists of the surface radiation integrals of PO currents. It has been reported that MER as applied to PO surface integration (PO-MER) has remarkable accuracy for the diffraction in line integration (P. Lu and M. Ando, 2013 IEEE AP-S/URSI, 539.4) provided the surface is flat or concave. For convex surfaces with aberration, the errors become notable around the geometrical reflection shadow boundaries (RSB). In this talk, we will focus on the correction of PO-MER for the edge diffraction from convex surfaces with big curvature, in order to enhance the accuracy near RSB. The higher order term initially appeared in the derivation of MER's by Stokes theorem and being overlooked for the flat surfaces in (K. Sakina and M. Ando, IEICE Trans. Electron., E84-C(1), 74-83) gives the basic correction for the curved surfaces. Accuracy enhancement due to inclusion of higher order term is the main topic and will be discussed numerically in the symposium. Another unique characteristic of MER from other EECs method is that the MER method can not only be used at the edge but also everywhere on the scatterer. It has been verified that the infinitesimally small indentation integration around the inner SPP gives approximate GO component. Consequently, both the reflection and diffraction are extracted from the surface integral of PO currents in terms of MER-EEC line integration. Comparison of errors of MER for GO and diffraction near RSB will be discussed as well.