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Ground-based beamforming for satellite communications systems

  • US 7,787,819 B2
  • Filed: 08/25/2006
  • Issued: 08/31/2010
  • 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, a satellite tracking master reference oscillator, a calibration network, a plurality of couplers, a satellite generated payload beacon signal, a satellite generated payload pilot signal, and a plurality of multipart amplifiers coupled to a plurality of hybrid matrixes;

    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; and

    a plurality of pointing beacon stations adapted to transmit and receive signals to and from the satellite;

    wherein the GBBF system;

    comprises a plurality of hybrid matrix outputs corresponding to a plurality of feed elements, a gateway generated pilot signal, a master reference oscillator, and a gateway tracking master reference oscillator;

    measures a first set of amplitude and phase errors of a plurality of return path signals traveling from the user terminals via the satellite to the at least one gateway 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; and

    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 said first set of amplitude and phase errors;

    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 said return path signals to minimize the amplitude and phase errors of the plurality of return path signals;

    measures a second set of amplitude and phase errors of a plurality of forward path signals traveling from the at least one gateway via the satellite to the user terminals; 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 said forward path signals.

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