a broad-band constant beamwidth corrugated rectangular horn

Using aperture field theory to predict the far-field radiation from a rectangular horn, a horn with substantially constantE- andH-plane beamwidths of17\degand10\degrespectively, is designed to operate over a 2.4:1 bandwidth. Assuming a cosine aperture field distribution in both theE- andH-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 approximately9\degto27\deg. TheE-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.