Dual mode feed system for contour beam antenna

Future European communication satellites may be required to provide two contoured beam coverages with a high degree of overlap. This can be achieved by use of a single antenna incorporating a so called `dual mode´ beamforming network. The authors report on the study carried out for the European Space Agency (ESA) the objective of which was to develop a feed array incorporating such a dual mode beamforming network feeding an array of high efficiency rectangular feeds. The overall antenna was required to provide two orthogonal beams (dual mode) each associated with one of the two different but largely overlapping Eutelsat II type coverage areas known as the West and the Continental coverages. These consist of a common `high gain´ central area with a minimum of 31 dBi gain requirement and a partially shared `lower gain´ area with a minimum gain requirement of 28 dBi. The West and Continental coverages are shown in two figures. The overall antenna was designed to operate over both the 10.95-11.7 GHz and 12.5-12.75 GHz bands simultaneously