HYBRID MODE HORN ANTENNAS

ABSTRACT Hybrid mode horns are of considerable practical importance, especially as feeds for lens and reflector antennas. In this tutorial review the boundary conditions necessary to support hybrid modes in round waveguide are derived. Expressions for the field components in HE1n and EH1n modes are given and from these the transverse field over the open mouth of the guide is found. The Fourier transform of this field is then used to calculate far field radiation patterns. Solutions to the characteristic equation for hybrid modes are indicated and the dispersion characteristics for balanced modes are presented graphically. Finally, a brief discussion of dielectric-lined waveguide is given and asymptotic solutions are developed to show that nearly balanced HE11 and EH11 modes can exist over a limited frequency range when the dielectric is lossless, but over an unlimited range when the dielectric is highly lossy.

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