CORRU_PRIMER

Tom Milligan
Miligan & Associates
8204 West Polk Place
Uttleton, CO 80123
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Design of Corrugated Horns: A Primer
Christophe Granet and Graeme L. James
CSIRO ICT Centre, Electromagnetics & Antennas
PO Box 76, Epping 1710, NSW, Australia
E-mail: [e-mail]
Keywords: Corrugated horn antennas; antenna feeds; reflector antenna feeds

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1. Introduction

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ver the past 40 years, corrugated horns supporting so-called hybrid modes have become well established as feeds for reflector antennas, and even as direct radiators. It is not difficult to trace the popularity of the corrugated hom, given the ability of certain hybrid modes to produce radiation patterns having extremely good beam symmetry with low cross-polarization levels, a high beam efficiency with very low sidelobes, and the potential for wide-bandwidth performance [ l , 21. Why they are called “corrugated” is clear from the typical example of a horn shown in Figure 1, where the inside wall is manufactured in a succession of slots and “teeth.” The purpose of the corrugated surface is to provide the means to support the propagation of hybrid modes within the horn. Hybrid modes are basically a combination of TE and TM

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Mode Converter

Figure la. A cut-away view of a typical corrugated horn.
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Figure lb. The details of the corrugated inside wall of a typical corrugated horn.
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modes. For this combination to propagate as a single entity with a common propagating velocity, the horn or waveguide must have anisotropic surface-reactance properties: properties that are satisfied by the corrugated surfacc. It is worth pointing out that hybrid modes can also be supported by other means, such as waveguides or horns partially filled with dielectric

References: Microwave Horns and Feeds, London, IEE Electromagnetic Wave Series 39, 1994, ISBN 0 85296 809 4. tions on Microwave Theory and Techniques, MTT-29, 1981, pp. IO. C. Granet, “Profile Options for Feed Horn Design,” Proceedings of the Asia Pacific Microwave Conference, Vol. I, 2000, pp. 10, October 1984, pp. 1134-1138. Techniques for Reflector Antennas, 1983, pp. 211-216. ISAP’96, Chiba, Japan, pp. 1133-1136.