CORRUGATED SOFT SECTOR HORN WITH DIFFERENT BEAM PROPERTIES IN THE 2 PRINCIPAL PLANES

The authors present a corrugated horn antenna with different beam prop erties in the two principal planes of radiation. It is designed to giv e a frequency independent wide beamwidth in the horizontal plane, by m alting it flare-angle controlled in that plane, and a beamwidth that i s decreasing with increasing frequency in the vertical plane, by makin g it aperture controlled in that plane. The throat of the horn is desi gned to ensure excitation of the desired mode in the flared part of th e horn and achieve the desired aperture distribution. The flare in the horizontal plane is gradually increased to the chosen value and the c orrugations on the horizontal walls are curved to follow the curved ph ase front of the desired mode. Improved mode excitation by introducing several thin dielectric lenses in the throat is studied. The radiatio n patterns are calculated from an approximate aperture field, represen ting the lowest-order mode in a radial sector waveguide. A horn was bu ilt and measured. Results show that it is possible to make corrugated sector horns with different beam properties in the two principal plane s 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.