Hexagonal hard metamaterial hybrid-mode horn with applications in multibeam reflector antennas

A hexagonal metamaterial hard horn design was shown with better aperture efficiency and relative cross polarization than existing circular horns used in multibeam reflector antennas. The horn antenna achieves an aperture efficiency greater than 83% and a relative cross polarization level less than 30 dB over a 27% bandwidth. If a profiled horn were used to eliminate the phase variation, the aperture efficiency could be increased to 87%. Additionally, arrays of hexagonal apertures can be packaged without gaps, corresponding to up to a 10% increase in aperture efficiency or 0.42 dB increase in gain over circular apertures. This design is dependent on the ability to construct a metamaterial with the desired dispersion characteristics and on the ability to cope with the mutual coupling of tightly packed horn antennas. An accompanying paper analyzes the hexagonal metamaterial horn´s performance in a multibeam reflector antenna, comparing it to one using multi-mode horns.