The Triply-Folded Horn Reflector: A Compact Ground Station Antenna Design for Satellite Communiations

Among the antennas suitable for ground stations of a satellite communications system, the horn reflector is highly desirable since it unites in one design such electrical characteristics as high-aperture efficiency, low-noise temperature, immunity from interfering signals and extreme broadband capabilities. High-aperture efficiency results from guiding the fundamental mode electromagnetic energy from the focal point by means of the horn directly to the parabolic reflector. In this way the aperture field distribution is not strongly tapered and energy loss due to spillover is minimized. The low noise temperature and immunity from interference results mainly from the inherent shielding afforded by the horn-reflector structure. Both the pyramidal and conical horn-reflector antenna designs have 1229 1230 THE BELL SYSTEM TECHNICAL JOURNAL, SEPTEMBER 196/S been investigated and applied in the past few years. 1,2,3 Notable among the applications is the large conical horn-reflector antenna at the ground station for satellite communications near Andover, Maine. The conical horn structure was chosen for this application because of its structural and electrical advantages. While this antenna has performed well, a number of areas exist where improvements would be desirable. For instance, the need for carrying large amounts of equipment on the rotating structure of the antenna contributes to its high weight and cost. Furthermore, the radome which is necessary for operation of a large horn-reflector antenna under high wind conditions, degrades antenna performance.