Abstract
The electromagnetic scattering of a corner at the interconnection of two straight edges joined by a plane angular sector is important in the framework of the geometrical theory of diffraction (GTD) and of its uniform extension (UTD). The same canonical problem is also useful in order to obtain fringe currents, namely the currents that are induced on the face by the total diffraction mechanism; their radiation provides the improvement of the field in the framework of the physical theory of diffraction (PTD). In this paper, asymptotic, closed form expressions of the fringe currents of the plane angular sector are derived by using the incremental theory of diffraction (ITD). The application of this theory in deriving currents has been found particularly attractive for the case of circular ground plane illuminated by a vertical dipole. This is due to the fact that the ITD diffraction coefficients satisfy the boundary conditions of their relevant canonical problem, so that they warrant a reasonably accurate prediction of the currents.
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
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
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