Antenna technologies for multimedia mobile satellite communications

Today´s space industry is living in a fast growing phase of its history, due to the enormous success of wireless cellular telephony and the worldwide diffusion of the Internet. In the field of satellite personal communication networks (S-PCNs), the three main non-geostationary systems (Iridium, Globalstar, ICO), together with some regional GEO systems (e.g. AceS, Thuraya), triggered a substantial breakthrough in satellite active phased array techniques. Major advancements were achieved in printed array technologies; receive and transmit RF modules miniaturization and performances; passive Butler matrices and beam-forming networks in multi-layer, printed-circuit technology; digital beam-forming and signal processing techniques; thermo-mechanical design and integration techniques. Moreover, the above mentioned regional GEO satellites have qualified in orbit unfurlable reflectors of up to 15 meter diameter. Further antenna developments are likely to be required for the future provision of Third Generation (3G) mobile communications via satellite (S-UMTS), as a result of more stringent requirements in terms of link performance (G/T, EIRP) and frequency reuse. The forthcoming “broadband wave”, i.e. commercial broadband multimedia communications satellites (a mix of LEO, medium Earth orbit and geostationary orbit spacecraft), operating at Ku-band and Ka-band, will rely on the development of both multibeam reflector antennas and of active multiple beam antennas in a direct-radiating array configuration