DUAL FREQUENCY BAND OPERATION OF TE/TM12 MULTIMODE HORNS

Abstract

Multimode rectangular horn radiators have been in widespread use as reflector antenna feed elements for many years. These horns provide equal E and H planes over moderate bandwidths. With a few simple additional design considerations, however, these same horns can operate over two separate frequency bands. Dual mode operation is achieved by designing to prohibit generation of higher order beamshaping modes for lower operating band. Thus the horn operates as a square pyramidal horn at the low band and as a traditional multimode horn in the upper band. Upper band performance is not affected; however, efficiency in the lower band is somewhat less due to unequal beamshapes characteristic of square pyramidal horns. A horn utilizing these design concepts was developed and tested. Resultant horn geometry, corresponding reflector antenna aperture efficiencies and beamshapes at both bands are presented.