DESIGN OF SCANNING SPHERICAL TRIREFLECTOR ANTENNAS WITH HIGH APERTUREEFFICIENCY

It is frequently desirable to scan the main beam of a large antenna sy stem without moving the main aperture structure. Spherical reflectors have excellent potential in this application. However, they are not co mmonly used because of poor aperture efficiency and high side lobes in traditional implementations. This paper introduces a new dual-subrefl ector feed system design which does not require oversizing the spheric al main reflector to accommodate scan and yet permits a controlled ape rture illumination. The design yields high aperture efficiency, low cr oss-polarization, and low side lobes.