Patent ID: 8270899

Claim:
A satellite communications network having a ground-based beamforming (GBBF) system, said network comprising: a satellite, said satellite comprising a satellite communications payload, said satellite communications payload comprising a satellite return path and a satellite forward path; at least one gateway, communicatively coupled with the satellite via a feeder link; a plurality of user terminals, each communicatively coupled with the satellite by a user link; a plurality of pointing beacon stations adapted to transmit and receive signals to and from the satellite; wherein: the satellite communications payload comprises a satellite tracking master reference oscillator and a calibration network; and the GBBF system further comprises a master reference oscillator and a gateway tracking master reference oscillator; and the GBBF system: receives, via the feeder link, (i) a plurality of return path signals traveling from the user terminals via the satellite to the at least one gateway, and (ii) a plurality of forward path signals traveling from the at least one gateway via the satellite to the user terminals; measures a first set of amplitude and phase errors of the plurality of return path signals; corrects said first set of amplitude and phase errors by generating, on the ground, a first set of corrective beam forming coefficients and applying said first set of corrective beam forming coefficients to the return path signals; measures a second set of amplitude and phase errors of the plurality of forward path signals; and corrects said second set of amplitude and phase errors by generating, on the ground, a second set of corrective beam forming coefficients and applying said second set of corrective beam forming coefficients to the forward path signals; wherein the GBBF system corrects amplitude and phase errors of the plurality of return path signals by: generating an encoded return calibration signal having a known amplitude and phase that is received by the satellite communications payload and applied to each of a plurality of feed elements in a feed array; receiving from the calibration network over the satellite return path, and a return downlink between the satellite and the gateway, a plurality of tagged signals, each of the plurality of tagged signals comprising a combination of user communications traffic and the encoded return calibration signal; determining a difference between the known amplitude and phase of the encoded return calibration signal and an amplitude and a phase of each of the plurality of tagged signals, the difference being representative of amplitude and phase errors of the plurality of return path signals; and generating and applying corrective beamforming coefficients to minimize the amplitude and phase errors of the plurality of return path signals.