Polarization Control Schemes For Satellite Communications with Multiple Uplinks

Orthogonal polarizations will be more and more widely used in satellite communications in the near future because of their efficiency in utilizing the spectrum, but the currently designed compensation control systems can compensate for signals coming from only one uplink station. This paper therefore discusses generally the control schemes feasible to solve the multiple Uplink problem, in which there are many stations transmitting uplink signals simultaneously. The general approach proposed is that for each uplink station two Compensators can be used to compensate for the uplink and, downlink separately. This will require the station to transmit its own pilot signals and receive them back from the satellite as the control reference. Two basic techniques can be used to realize this approach. The first, correlation technique, is based on the assumption that an obtainable correlation between uplink and downlink cross-polarizations exists, and tries to compensate for uplink and downlink separately using this correlation. The second, separate link technique, uses an additional pair of pilotsignals to obtain seiJarate control references and decouples the compensations of uplink and downlink. The discussions indicate that the separate downlink technique, whose design considerations and system performance are examined carefully is most attractive.