Antenna feed element for low circular cross-polarization

Antenna feed element performance is critical in obtaining low circular cross-polarization in multi-element feed arrays. The antenna feed element described in detail in this paper has been named the septum-polarizer, equalized, choked (SPEC) feed element. It consists of a low axial-ratio circular-waveguide septum polarizer and a conical horn with a single choke/corrugation at the aperture. This produces circularly symmetric, equalized E- and H-plane element patterns with low on-axis and off-axis axial ratios. Breadboard models of the SPEC feed element have been developed and measured results are provided. A flight hardware version of this feed element is being developed for satellite applications. These applications are for large antenna feed arrays that illuminate offset parabolic reflectors. In order to meet the low weight requirements, the flight SPEC feed elements will be constructed of carbon-cyanate-ester with electroless copper plating applied to the internal surfaces.