Design of a multiport amplifier beam forming network for a mobile communications antenna

Astrium¿s experience with Inmarsat has shown that a satellite designed for mobile telecommunications applications may consist of a large aperture parabolic reflector fed by an array at its principle focus. Both L and S-band are the frequencies of interest. Each radiator element on the array has a one to one correspondence with a spot position on the earth, so that radiation patterns are pointed at different locations on the earth by different combinations of the array element excitations. Before the signals arrive at the array with their specified complex weights they must undergo amplification, which is provided by a beam forming network composed of between 10 and 20 Multi-Port Amplifiers, (MPA).