Design and characterization of diagonal horn antennas using UCLA bi-polar near-field measurement and imaging facilities

A current study at UCLA deals with the design of various horn antennas and feeds for reflector antennas. In order to enhance the radiation performance of typical pyramidal horns, the application of a diagonal horn has been considered. The radiation pattern of this horn antenna shows almost perfect circular symmetry so that the 3 dB, 10 dB and 20 dB beam widths are very closely equal. This is true not only for the 0/spl deg/- and 90/spl deg/-cut but also in the 45/spl deg/- and 135/spl deg/-plane. All cross-sections through the diagonal horn antenna are square, starting from the feeding square waveguide to the aperture. For small flare angles the mode of propagation within the horn is principally such that the electric vector is parallel to one of the diagonals. Since orthogonal polarized beams will have the same far-field characteristic, the diagonal horn is an interesting candidate for use by itself or for reflector antennas. The emphasis of this article is on the investigation for some of the unique features of the diagonal horn by evaluating the images of its aperture field using the measured bi-polar near-field data.