Antenna pattern reconfiguration in the future direct broadcasting satellite at 22 GHz

The paper deals with the design of advanced direct-broadcasting satellite systems utilizing K frequency bands, as foreseen in the first decade of the next century. In such systems the compliance with a given availability target needs a careful design of the antenna coverage since, considering the hard constraint in power amplifiers technology [1], the on board available power cannot be wasted or under utilized by improper distribution across the served territory. In this scenario, some very promising techniques to maximize coverage and link availability while reducing the power to a minimum will make use of reconfigurable multibeam antenna systems. By adopting these power management criteria on the new generation satellites, radiation toward the served region can be optimally configured both to contour the geographic coverage area and to counteract the extra attenuation mainly due to rain occurrence. This study is focused on the application of such sort of reconfigurable antenna pattern to a Direct Broadcasting Satellite (DBS) in the new frequency of 22 GHz, where rain attenuation and water vapour absorption are the leading factors causing link outage. The advantages of different reconfigurable antennas over a traditional single beam system have been evaluated, considering the italian peninsula as the served region. To this aim two different strategies of power management have been developed: a fixed or static criterion and a time varying or dynamic reconfiguration. Depending on complexity of the directivity function, for a given outage figure the power saving can vary up to several dB. The basis of antenna pattern reconfiguration can extend also to future two-way telecommunication satellites, where power optimization is carried out over a multispot system. In this case, the advantages described in the present paper can be considered a well promising starting point for an optimized design.