A magnetic current loop array in a parabolic reflector

To eliminate the blockage caused by mechanical support, a self-supported magnetic current loop array operating at 9 GHz has been designed as a feed for a reflector antenna. In the present arrangement, the feed is a circular waveguide that protrudes into the paraboloidal reflector through the center. To generate magnetic current loops, circumferential slots can be cut on a coaxial or circular waveguide. For narrow slots, energy radiated per slot is small and negligible; the electromagnetic field inside the waveguide is therefore not affected. A number of prototype antenna feeds have been fabricated and compared. In the Fresnel zone, the E-plane and H-plane radiation patterns of the feed at center frequency, 9 GHz, are illustrated. The estimated efficiency of the antenna is greater than 80%.<>