Performance comparison of high-gain horn antennas

High gain horns are used in multi-feed (cluster feed) reflector antennas, producing less spillover loss than conventional horns like dual-mode or corrugated horns. They can also be employed as an antenna element in limited-scan phased arrays, generating high aperture efficiency and good scan performance, and as a feed for quasi-optical amplifier arrays. The most promising high gain horns, high-gain hybrid-mode or "hard" horns and multi-mode horns, are compared with respect to their bandwidth potential. High-gain horns have, in general, considerably lower bandwidth than low-gain horns or "soft" horns. They have decreasing bandwidth and increasing aperture efficiency with increasing aperture diameter and with increasing dielectric constant of the wall material (hard horns). For apertures of about 3λ, the hard corrugated horn yields the largest bandwidth, while for 4λ apertures, hard and multi-dielectric horns all exhibit similar bandwidth. The hard horns under study, although they are not optimized, exhibit approximately 50% higher bandwidth than the optimized multi-mode horns. The multi-dielectric horn yields considerably higher aperture efficiency than the other horns. The comparison study is not considered complete because of limited data being available.