Design and performance of sliced-aperture corrugated feed horn antennas

We report on the design of corrugated feed horn microwave antennas at 3.3, 5.6, 7.8, and 10.2 GHz for the absolute radiometer for cosmology, astrophysics, and diffuse emission experiment. These horns have low sidelobe symmetrical beams with 12 degrees full width at half power, and three noteworthy features: a 30 degrees slice at the aperture, a profiled rather than a linear taper, and a slowly varying groove depth along the length of the horn. The profiled taper and varying groove depth provided a narrow beam given the existing physical spatial constraints of the instrument in which the horns are used. The 30 degrees slice was necessary for instrumental considerations and has a minimal effect on the symmetry of the beam. The slice reduces the effective aperture radius and overall length to that corresponding to an unsliced horn with an aperture at roughly the middle of the slice and does not introduce any undesirable effects. (c) 2005 American Institute of Physics.