Multiple-beam satellite communications system, e.g. for digital TV, uses same beam for each uplink and downlink with transmitter combining signals in single PA stage, individual downlink power control being available to ground stations

摘要

Each satellite transmitter uses a combiner (5) to feed signals which have been received in a particular uplink beam, frequency translated, and linearized (6), to a power amplifier (2) which preferably uses a single TWT or several such tubes in parallel. Each of the individual channel amplifiers (4) which feed the combiner preferably has a gain control input, responding to a control signal received from the relevant ground station, to set the power level in that downlink. An Independent claim is included for a communications satellite forming a number of beams covering regions on the earth and operating in a system according to the invention.