Meteorology-Driven Optimum Control of a Multibeam Antenna in Satellite Telecommunications

The control of the radiation of a telecommunication multispot satellite antenna is discussed in which the power can be flexibly routed towards the various spots so as to contrast at best the time variant atmospheric attenuation while keeping at minimum the number of users which do not receive enough signal level. The antenna control is exerted by applying a particular strategy based on the knowledge of the distribution of the weather conditions all over the served region as derived by standard sources like the European Centre for Medium Range Weather Forecasting (ECMWF) or the Meteosat. The paper describes the principles of two types of optimizations: a fixed one based on climatological long term data, which acts as reference, and an adaptive one based on quasi instantaneous pictures that represent the weather situation across the served region. After an explanation of the basic principles of the optimizations, the paper gives an example of application that, despite the brevity of the trial period we are now able to present, indicates an excellent effectiveness of the system which, in the period observed, allows a reduction of the number of non-served users of the two orders of magnitude in the case of low-margin systems (approximately 2–3 dBs over free space) and a still conspicuous advantage (a reduction of a factor about 5) for greater available margins (approximately 6–7 dBs).

I. Foreword

The extensive use of frequencies in the Ka band and beyond in satellite Telecommunications forces the adoption of particular techniques, known as propagation impairment mitigation techniques (PIMT), to counteract the difficulties posed by the strong atmospheric attenuation. A PIMT of particular interest in satellite applications is the one based on the possibility to control, instant by instant, the flux radiated over the served area with the criterion of favouring the subregions more affected by adverse weather conditions; this allows an optimum exploitation of the limited power available on board. The problem involves a great number of aspects: technological, meteorological, of system control etc. This paper is specifically addressed to this last issue and describes a new theoretical method to optimally control the powers injected in the beam-ports of an on-board multibeam antenna used in Telecommunication applications, aiming at minimizing, any time, the number of users in outage owing to severe weather conditions [1]; basic principles, optimization criteria, necessary input data and their treatment are outlined along with a preliminary assessment of the obtained performance. The impact of a reconfigurable antenna as a possible PIMT is obtaining a certain interest in research, as testified by the rising number of projects [2]–[4] and papers [5], [6] related to the field.