Design of high efficiency circular horn feeds for multibeam reflector applications

Design aspects of high efficiency profiled circular horns with thin walls as feeds for multibeam reflector antennas for satellite applications are presented in this paper. The modal content at the circular aperture of the horn necessary to closely approximate a unipolarized uniform distribution is first established. Slope discontinuities along the length of the horn are then used to generate the necessary aperture modes with the appropriate amplitudes and phases. The performance of the horn is calculated using the mode matching technique. Significant improvement in the horn aperture efficiency and reduction in the cross-polar level over a straight conical horn can be achieved over a single band or two bands that are widely separated in frequency. This conclusion is supported by the good agreement between predictions and measurements of a high efficiency dual-band horn.