Since the first communications satellites have been launched to space with the beginning of the 1960s, these systems have undergone a rapid development. Amongst others, this development is driven by an increasing number of subscribers exchanging larger and larger data volumes. This need of data capacity cannot be satisfied alone by raising the sheer number of communications satellites, but requires powerful individual systems, which operate reliably and are cost effective at the same time. In this context two requirements on the communications antenna are the provision of high directional gain and robustness in terms of beam stability.
Classically, large unfurlable mesh reflector antennas in conjunction with feed arrays are adopted to illuminate a certain region on ground with high gain. An inherent problem of such reflector-feed configurations is that these systems are prone to feed element failures. In the worst case, this could result in a `blind’ spot, where no communication is possible. This paper introduces a robust antenna concept, which combines the virtue of reflector antennas, namely the large aperture, with the advantage of direct radiating planar array antennas, which is the beam stability in the presence of element failures. In order to unfold its full potential this concept makes use ofdigital beamforming techniques, which allow to control the illumination in a flexible way.