Imaging in a Gregorian antenna with excellent performance from 12 to 30 GHz.

A Gregorian antenna with the main reflector illuminated by a magnified image of a small horn aperture has been built and tested from 12 to 30 GHz. The image is approximately frequency- independent, and the main reflector is illuminated efficiently, with negligible spill-over. Polarization distortion caused by aberrations is very small, in excellent agreement with a simple expression derived previously.