Shared Transponder Performance with Selective Sub-channel Gain

A simplified expression is presented for finding end-to-end CNR of a signal relayed by a satellite with a wideband transponder, if the transponder bandwidth is separated into individual sub-channels, each of which may be independently amplified or attenuated before sub-channels are reassembled into a wideband downlink signal, amplified, and transmitted. This expression takes into account power sharing among multiple signals and transponder noise, finding CNR as a function of nominal link performance plus excess uplink loss and compensating sub-channel gain. Selection of sub-channel gain values is also discussed. It is shown that in some cases excess uplink loss may be entirely compensated for, and in other cases loss may be reduced but not eliminated.