ITD formulation for the currents on a plane angular sector

S Maci,M Albani,F Capolino

doi:10.1109/8.719975

Abstract

Approximate high-frequency expressions for the currents induced on a perfectly conducting plane angular sector are derived on the basis of the incremental theory of diffraction (ITD). These currents are represented in terms of those predicted by physical optics (PO) plus fringe contributions excited by singly and doubly diffracted (DD) rays at the two edges of the angular sector. For each of these two contributions, additional currents associated to vertex diffracted rays are introduced that provide continuity at the relevant shadow boundary lines. The transition region of DD rays is described by a transition function involving cylinder parabolic functions. The asymptotic solution presented is constructed in such a way to satisfy far from the vertex the expected edge singularities, which tend to be the same as those predicted by the exact solution of the half plane. Numerical results are compared with the exact solution of the same problem and with moments method results for scattering from polygonal plates.

Highlights

Conducting corner at the interconnection of two straight edges, joined by a plane angular sector is a basic canonical problem for the high-frequency description of electromagnetic scattering phenomena
Simple tools for providing an estimate of the currents associated to vertex discontinuity is useful for improving without substantial additional efforts, those numerical codes that use the direct integration of the physical optics (PO) currents to predict radar cross section (RCS) or antenna radiation
In the results presented the currents of the present formulation are used in a radiation integral for calculating the far-field pattern of flat polygonal plates

Summary

INTRODUCTION

Conducting corner at the interconnection of two straight edges, joined by a plane angular sector is a basic canonical problem for the high-frequency description of electromagnetic scattering phenomena. Asymptotic fringe currents have been derived by using approximate, but practical high-frequency solutions, which are based on modeling the vertex geometry as a superposition of two or more wedges In this framework, first-order vertex diffraction coefficients were formulated in [14] in order to compensate for the discontinuity of first-order UTD diffraction contributions without including second-order interactions between the edges. In deriving the present solution, terms of order up to (where is the distance from the tip) are retained in the asymptotic expansion, unlike our previous work [21], in which only order up to was considered These higher order contributions are consistent with those required to reconstruct the near-edge behavior, that are of order owing to their reactive nature. Examples of radar cross section of polygonal plates are presented and compared with MoM calculations

FIELD REPRESENTATION

NUMERICAL RESULTS

CONCLUSIONS