Journal ArticleDOI
A uniform geometrical theory of diffraction for an edge in a perfectly conducting surface
R.G. Kouyoumjian,P.H. Pathak +1 more
- Vol. 62, Iss: 11, pp 1448-1461
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In this article, a compact dyadic diffraction coefficient for electromagnetic waves obliquely incident on a curved edse formed by perfectly conducting curved plane surfaces is obtained, which is based on Keller's method of the canonical problem, which in this case is the perfectly conducting wedge illuminated by cylindrical, conical, and spherical waves.Abstract:
A compact dyadic diffraction coefficient for electromagnetic waves obliquely incident on a curved edse formed by perfectly conducting curved ot plane surfaces is obtained. This diffraction coefficient remains valid in the transition regions adjacent to shadow and reflection boundaries, where the diffraction coefficients of Keller's original theory fail. Our method is based on Keller's method of the canonical problem, which in this case is the perfectly conducting wedge illuminated by plane, cylindrical, conical, and spherical waves. When the proper ray-fixed coordinate system is introduced, the dyadic diffraction coefficient for the wedge is found to be the sum of only two dyads, and it is shown that this is also true for the dyadic diffraction coefficients of higher order edges. One dyad contains the acoustic soft diffraction coefficient; the other dyad contains the acoustic hard diffraction coefficient. The expressions for the acoustic wedge diffraction coefficients contain Fresenel integrals, which ensure that the total field is continuous at shadow and reflection boundaries. The diffraction coefficients have the same form for the different types of edge illumination; only the arguments of the Fresnel integrals are different. Since diffraction is a local phenomenon, and locally the curved edge structure is wedge shaped, this result is readily extended to the curved wedge. It is interesting that even though the polarizations and the wavefront curvatures of the incident, reflected, and diffracted waves are markedly different, the total field calculated from this high-frequency solution for the curved wedge is continuous at shadow and reflection boundaries.read more
Citations
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Journal ArticleDOI
High-frequency Green's function for a semi-infinite array of electric dipoles on a grounded slab .I. formulation
TL;DR: In this paper, a uniform high-frequency solution for the electromagnetic field radiated at finite distance by a semi-infinite array of elementary electric dipoles placed on an infinite grounded dielectric slab is presented.
Journal ArticleDOI
The Modified Surface-Normal Vectors in the Physical Optics
TL;DR: In this paper, simple equivalent surface currents perturbed from the physical optics (PO) are proposed, which predict accurate scattering fields without using a special knowledge about the high frequency asymptotic theories such as the geometrical theory of diffraction (GTD).
Journal ArticleDOI
High-frequency diffraction of a line-source field by a half-plane: Solutions by ray techniques
J. Boersma,Shung-Wu Lee +1 more
TL;DR: In this paper, the diffraction of an arbitrary cylindrical wave due to a line source and incident on a half-plane is treated by the uniform asymptotic theory of edge diffraction.
Book ChapterDOI
Asymptotic High Frequency Methods
Hsi-Tseng Chou,Teh-Hong Lee +1 more
TL;DR: In this paper, the fundamental concepts of asymptotic high frequency (HF) techniques including geometrical optics, physical optics, and physical theory of diffraction (PTD) are reviewed.
Journal ArticleDOI
The effect of terrain on radio propagation in urban microcells
G. Lampard,T. Vu-Dinh +1 more
TL;DR: In this article, a model based on the geometrical theory of diffraction is proposed for predicting radio propagation in urban microcells in the presence of undulating terrain, but the effect of terrain fluctuations which do not obscure the line of sight is smaller than the model predicts.
References
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Journal ArticleDOI
Geometrical Theory of Diffraction
TL;DR: The mathematical justification of the theory on the basis of electromagnetic theory is described, and the applicability of this theory, or a modification of it, to other branches of physics is explained.
Journal ArticleDOI
Ray techniques in electromagnetics
TL;DR: In this paper, a systematic use of matrix representation for the wavefront curvature and for its transformations simplify the handling of arbitrary pencils of rays and, consequently, the field computations.
Journal ArticleDOI
Diffraction by an Aperture
TL;DR: In this paper, the geometrical theory of diffraction was introduced to account for diffraction by introducing new rays called diffracted rays, which are produced when incident rays hit the aperture edge.