Axial Ring Feed Horn with Logarithmic Flare for Offset Gregorian Optics

We present an improved axial ring feed horn using a logarithmic spiral flare opening and tapered groove geometry that is suitable for wide-angle feeding, as required for offset Gregorian telescopes. To enable a design with maximum aperture efficiency, full 2-D field integration was calculated as part of the optimization loop. Since aperture efficiency includes the contributions of cross-polarization, phase, amplitude, and taper, directly optimizing against these terms will result in excellent wideband performance. An example design is shown and optimized for the 30–51 GHz band.