A broad-band constant beamwidth corrugated rectangular horn

Abstract

Using aperture field theory to predict the far-field radiation from a rectangular horn, a horn with substantially E - and H -plane beamwidths of 17\deg and 10\deg respectively, is designed to operate over a 2.4:1 bandwidth. Assuming a cosine aperture field distribution in both the E - and H -planes of the horn, the general conclusion is first made that an aperture phase error of 0.37 wavelengths at the lowest operating frequency produces the least beamwidth variation (3 dB) over the band. A general design curve showing constant beamwidth as a function of horn throat length is produced, furthering the design of such horns with beamwidths in the range approximately 9\deg to 27\deg . The E -plane walls of the horn are corrugated, and to cover the bandwidth corrugations are comprised of T -section slots which are designed from a simple transmission line model. To realize the specified beamwidths, a compound horn configuration is adopted. Some experimental results obtained from a prototype horn are given.