ISSN:0272-6343    

DOI:10.1080/02726349808908575

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

ISSN:0272-6343    

DOI:10.1080/02726349808908576

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Three-dimensional electromagnetic scattering of plane waves from a class of anisotropic impedance wedges is analyzed. All the configurations considered are characterized by anisotropic impedance faces with their principal anisotropy axes parallel and perpendicular to the edge, with one of the two elements characterizing the impedance tensors vanishing or diverging. Rigorous integral representations for the field are determined by resorting to the Maliuzhinets’ method; they are defined along the Sommerfeld's integration path, so that are suitable for their asymptotic evaluation. Although valid only for specific configurations, we note that the new rigorous solutions can be used for testing the accuracy of numerical or approximate analytical methods, applicable to more general cases. The particular category of impedance tensors considered for the wedge faces can be usefully applied for analyzing the specific case of the artificially hard and soft surfaces.

ISSN:0272-6343    

DOI:10.1080/02726349808908577

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The Green function of an angular sector with impedance boundary conditions is considered on the basis of Malyuzhinets’ solution for diffraction of a plane wave by an impedance wedge of external angle 2Φ. From alternative representations of the Malyuzhinets solution, by integrating them over the plane wave spectrum of a line source, two exact representations, integral and series, of the Green function are constructed so as to provide a complete set of analytic expressions for the Green function, covering all possible positions of the source and observation point with respect to the vertex. Specifically, the integral representation can be asymptotically evaluated in the high-frequency limit, while the series form is more preferential when the source or the observer or both, are located in an immediate vicinity of the edge of the wedge. Assuming that the wedge is acute (Φ>π/2), a complete description of the Green function in the far zone is given including geometrical optic, surface wave, and edge diffracted components. A uniform formula for the Green function is obtained and applied to the analysis of attenuation of an incident cylindrical wave by a wedge-like impedance barrier. Near-field approximations of the Green function are also presented and radiation from a current/ dipole linear source placed near the edge of an impedance wedge is analysed as a function of the wedge angle and face impedances.

ISSN:0272-6343    

DOI:10.1080/02726349808908578

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Adequate asymptotic treatment of the double diffraction by a pair of parallel edges in the overlapping transition regions requires a spectral integral representation of the singly-diffracted field. Such a representation is derived here for the diffraction by a convex cylinder. This enables one to extend the solutions for the double-edge diffraction to the case of two parallel convex cylinders, or of a cylinder parallel to an edge.

ISSN:0272-6343    

DOI:10.1080/02726349808908579

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

This work documents the existence of a coupling effect between transverse electric and transverse magnetic fields in slope diffraction by edges. For oblique incidence, a transverse magnetic incident field with a slope will produce a transverse electric slope-diffracted field and, in analogy, a transverse electric incident field with a slope will produce a transverse magnetic slope-diffracted field. This coupling effect is found by solving the scattering problem of a perfectly conducting wedge illuminated by a non-uniform plane wave possessing a linear amplitude variation, i.e., a slope, in the direction normal to the plane of incidence. This constitutes the most optimal canonical problem involving electromagnetic slope diffraction by edges for oblique incidence. Two solution procedures, based on two different representations of the non-uniform plane wave in terms of uniform plane waves, are employed to derive the exact solution for the half-plane and the high-frequency asymptotic solution for the wedge. In the high-frequency asymptotic solution for the slope-diffracted field the coupling manifests itself as non-zero terms outside the main diagonal of the slope diffraction matrix. These coupling terms are of the same order in the wave number k as are the well-known main diagonal terms. Although slope diffraction has been the subject of numerous works over many years, the vast majority of these works do not report this coupling effect which has remained practically unknown.

ISSN:0272-6343    

DOI:10.1080/02726349808908580

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The problem of scattering from an anisotropic impedance half-plane at skew incidence is considered. Application of Maliuzhinets’ technique in combination with an approximation leads to a solution for the scattered field expressed in terms of Maliuzhinets functions. Even though the approximation is not based on the assumption that the obliquity of the incident wave is small, the exact solution is identically recovered in the cases of perpendicular incidence and skew incidence on an isotropic half-plane.

ISSN:0272-6343    

DOI:10.1080/02726349808908581

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor