Dielectric lined circular waveguide as a feed

In past years the attenuation characteristics of a dielectric-lined waveguide have been studied by many investigators. The present investigation describes the theoretical and experimental radiation patterns and aperture efficiency of the dielectric-lined waveguide feed. The waveguide structure is shown schematically. It is a perfectly conducting cylindrical metallic tube of given radius to which a dielectric of given relative permittivity and thickness is bonded. This type of structure does not support TE and TM modes of conventional waveguide, so that hybrid modes containing longitudinal components of both electric and magnetic fields are considered. Good agreement is found between theoretical and experimental radiation patterns. The pattern has a rotationally symmetric beam, low cross-polariztion level and high aperture efficiency in the whole frequency range.