A Flexible and Adaptive Q/V-band Feeder Link for Broadband

This paper presents the preliminary results of studies performed by European Space Agency (ESA), Politecnico di Milano, Italian National Research Council (CNR) and Italian Space Agency (ASI) on an adaptive feeder-link at Q/V-band, to be possibly adopted in future High Throughput Satellite (HTS) and Very High Throughput Satellite (VHTS) missions. Q/V-band is being considered for the feeder link of broadband telecommunication satellites in order to satisfy the increased need for available bandwidth. One major drawback of satellite communications at Q/V band (40 GHz and above) is constituted by the high gain margins for rain attenuation required. In order to guarantee the specified downlink availability in worst case conditions, on-board Power Amplifiers (TWTA's or SSPA's) risk to be oversized by a factor equal to rain attenuation margin. The proposed transponder configuration envisages the use of a multiport amplifier, in order to allow a flexible sharing of the available RF power among the beams and the implementation of a dynamic control of the EIRP towards each individual spot beam. Such flexibility can be used not only to adapt to propagation impairments, but also to cope with varying data throughput demand at spot beam level. This method, already considered for 20/30 GHz missions, is proved to substantially reduce the demand for RF power on-board the satellite and thus to guarantee high availability services, taking advantage of the statistics of rain attenuation at non-correlated earth stations sites.