The authors present a corrugated horn antenna with different beam properties in the two principal planes of radiation. It is designed to give a frequency independent wide beamwidth in the horizontal plane, by making it flare-angle controlled in that plane, and a beamwidth that is decreasing with increasing frequency in the vertical plane, by making it aperture controlled in that plane. The throat of the horn is designed to ensure excitation of the desired mode in the flared part of the horn and achieve the desired aperture distribution. The flare in the horizontal plane is gradually increased to the chosen value and the corrugations on the horizontal walls are curved to follow the curved phase front of the desired mode. Improved mode excitation by introducing several thin dielectric lenses in the throat is studied. The radiation patterns are calculated from an approximate aperture field, representing the lowest-order mode in a radial sector waveguide. A horn was built and measured. Results show that it is possible to make corrugated sector horns with different beam properties in the two principal planes over a relative bandwidth of 1.5. However, it is also clear that it would have been desirable to have available numerical design tools for such complicated geometries in order to get better results.
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