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Ground-based beamforming for satellite communications systems

  • US 8,270,899 B2
  • Filed: 08/13/2010
  • Issued: 09/18/2012
  • Est. Priority Date: 08/25/2006
  • Status: Active Grant
First Claim
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1. 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;

    whereinthe 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.

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