# GTD analysis of the radiation patterns of wide-flare corrugated conical and E-plane sectoral horns

Abstract: The E -plane radiation patterns of wide-flare corrugated conical and E -plane sectoral horns ( 2\alpha_{0} ) excited in the dominant mode are obtained employing the theory of Kouyoumjian and Pathak [12] and the slope diffraction technique [11]. Besides the other parameters of the horn, the finite thickness of the corrugated edge has been taken into account with a view to improve the accuracy of the pattern computation. The analysis presented enables one to predict accurately radiation patterns over the main beam, near and far sidelobes, and the back lobes of the horns. Validity of the analysis is established by satisfactory agreement between the calculated and measured E -plane patterns of a few typical experimental wide-flare corrugated conical and E -plane sectoral horns.

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Topics: Plane (geometry) (51%)

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Abstract: Approximate boundary conditions are a means for simulating material and surface effects in scattering and propagation. A number of conditions are discussed, and criteria are given for their validity.

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167 citations

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01 Nov 1974-

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.

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2,478 citations

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Abstract: The fields diffracted by a body made up of finite axially symmetric cone frustums are obtained using the concepts of the geometrical theory of diffraction. The backscattered field for plane-wave incidence on such a target is obtained with particular emphasis on those regions that are usually avoided, namely, the caustic region and its immediate vicinity. The method makes use of equivalent electric and magnetic current sources which are incorporated in the geometrical theory of diffraction. This solution is such that it is readily incorporated in a general computer program, rather than requiring that a new program be written for each shape. Several results, such as the cone, the cylinder and the conically capped cylinder, are given. In addition, the method is readily applied to antenna problems. An example which is reported consists of the radiation by a stub over a circular ground plane. This present theory yields quite good agreement with experimental results reported by Lopez, whereas the original theory given by Lopez is in error by as much as 10 dB.

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190 citations

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05 Jun 1970-

Abstract: : A ray-fixed coordinate system is introduced and used to derive a new, compact form of the dyadic diffraction coefficient for an electromagnetic wave incident on a perfectly-conducting wedge. This diffraction coefficient is merely the sum of two dyads; furthermore, with the use of simple correction factors which have the same form for plane, cylindrical, conical or spherical waves incident on the edge, the dyadic diffraction coefficient is valid in the transition regions of the shadow and reflection boundaries.

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83 citations

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Abstract: The first order geometrical theory of diffraction (GTD) predicts vanishing fields along the surface of a conducting wedge for the incident electric field polarized parallel to the diffracting edge The slope diffraction coefficient is a valid correction term for incidence angles removed from the shadow boundary A new slope diffraction function for the half plane is presented along with applications This new form of slope diffraction coefficient for the half plane is valid through the shadow region Reciprocity is invoked to find the far-fields for a source on the surface of the conducting wedge In addition to applying the two-dimensional slope diffraction analysis to practical problems, the equivalent current concepts have been extended to include equivalent slope currents for the analysis of either finite or curved edges This new form of the slope diffraction function has been successfully used to provide an H -plane horn pattern analysis that is considerably less tedious than previously possible with GTD Both pure GTD solutions and hybrid solutions using conventional aperture integration for the main beam region and GTD for the far-out side and back lobes are compared with experimental results

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48 citations

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Abstract: The corrugated horn has been established as an antenna with low sidelobes and backlobes, rotationally symmetric patterns (for square pyramidal and conical horn shapes), and broad-band performance [1]-[9]. These properties make this horn useful for many applications. Previous studies have used conventional aperture integration techniques to evaluate the patterns of the corrugated horn. In general, the near axis E -plane radiation pattern of a pyramidal corrugated horn may be adequately predicted from standard analysis established for the H -plane patterns of conventional horn geometries [3]. This method, however, fails to predict the far-out sidelobe and backlobe radiation levels. The work presented here uses a knowledge of the aperture fields to predict the pattern using aperture integration and diffraction theory. The assumptions made concerning the aperture fields were verified by probing the internal fields and aperture fields of an X band corrugated horn. The results of this field probing are contained in the Appendix. The method of solution used in this paper parallels that used in previous publications [10]-[12]. Specifically, the pattern in the main beam region is computed using conventional aperture integration procedures, the contribution of the H -plane edges is found using a slope diffraction analysis, and the contribution of the E -plane edges is found by use of duality.

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31 citations