“A multiple beam shaped reflector antenna”

Shaped reflector antennas have become the standard for communication satellite antenna applications for more than five years. Another trend which is becoming evident is the requirement to provide higher power on the satellites. This requires that more beams be provided by the antenna system to make effective use of this increased power. In order to do this, more apertures, or more beams per aperture, are needed. This paper details the design of an antenna system which makes use of the high efficiency characteristics of shaped reflector antennas and provides additional beams within a common aperture, isolated from the other coverage beams, by use of multiple feed horns. The design methodology is to shape the reflector for the most important coverage beam to provide maximum efficiency. For one or more peripheral beams, multiple element feeds are used to cover the desired secondary region(s), and the coefficients of the feeds are optimized to provide sidelobe isolation in the direction of the other beams. This paper will discuss the design considerations and performance achieved for a multiple beam antenna which uses the best features of shaped reflector antennas and those of multiple feed reflector antennas. The virtues of this design fit well with the new requirements for high power satellites with many isolated coverage regions, employing multiple frequency reuses by polarization diversity and spatial diversity.