Space multibeam antenna with very high G/T, for ka-band multimedia via satellite missions

A typical multimedia via satellite mission needs to cover, from a geostationary orbit, a large terrestrial zone with 40 to 50 semi-contiguous beams, for very high gain & re-using 10 to 12 times the same frequency resource, by dividing the available bandwidth in 4 sub-bands, 1 spot-beam over 4. Such multibeam antenna much increases the System capacity, for providing broadband services directly to users at home or office, wherever in the world. We point out the Focal Array Fed Reflector as the most suited receive-antenna architecture, for various kinds of coverages, to provide high figure of merit (G/T) and inter-beams isolation. A demonstrator has being built under the IST/ MultiKaRa contract, co-funded by the European Union. We present the design and performances of the whole antenna, especially the highly integrated “active receiving feeds”, and explain how a cold thermal control of the active focal array improves the antenna G/T by 1 dB, allowing cheaper User terminals (20% less power to be transmitted).