A review of the early developments of circular-aperture hybrid-mode corrugated horns

The simultaneous but independent development in the United States and Australia of circular-aperture corrugated horns in the early 1960's is reviewed. The features of this development include the wide flare-angle corrugated "scalar" horn and the characteristics of focal-region fields of reflector antennas and the single- and multimode cylindrical corrugated horns necessary to feed them.