Flexible power and bandwidth allocation in mobile satellites

Abstract

ABsrRAcrThe introduction of LBand mobile communication seMccs by spot beam satellites creates a payload design challenge due to uncertainty in the location and size of the new market to be served. This paper describes a combination of payload technologies which allow a flexible allocation of power and bandwidth to any portion of the covcrage area.Power flexibility is achieved by a novcl combination of low level beam forming network and a matrix powtr module which ensures equal sharing of power among individual amplifiers. This eliminates the loss of efficiency and increased mass when an amplifier associated with a beam must be ovcrdesigned to meet uncertainties in power distribution between beams. The matrix power amplifier also benefits from the spreading of intermodulation products among output ports such that only a portion falls in the beam of interest yielding lower system level intermodulation.Flexibility in allocation of bandwidth to beams is achiewd by intermediate frequency subdivisions of the LBand seMce categories defined by ITU (AMSS, LMSS, MMSS). These spectral subdivisions are assigned to beams by an IF interconnect matrix having beam ports and filter ports as inputs and outputs respectively. Two such filter switch matrices are required, one for the inbound LBand to feeder link transponder, and one for the outbound feeder link to L-Band transponder.