Novel schemes for sidelobe reduction in horn antennas

Abstract

A numerical technique based on the moment method is used to study different schemes for reducing the E-plane sidelobe and backlobe power levels of waveguides and horn antennas by attaching elliptic and spiral shaped flanges to the aperture edges of these antennas. It is shown that a flared spiral flange attached to the edges of a rectangular waveguide can produce a very wide half power beam-width of 160° and backlobes as low as − 30dB which is highly desirable for compact range applications. A second horn design is also investigated whereby the aperture edges of the horn are shielded by a specially designed metallic cap, hence isolating the edge diffracted fields and minimizing their interference. A reduction in some sidelobes of more than 20dB is achieved by the so called ‘capped-edge’ horn. The final design investigated deals with introducing an active source placed at an optimum position inside the horn and having a particular phase excitation relative to the edge fields. These active sources, which ar...