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Method for determining orientation and attitude of a satellite- or aircraft-borne phased-array antenna

  • US 5,790,071 A
  • Filed: 07/03/1997
  • Issued: 08/04/1998
  • Est. Priority Date: 07/03/1997
  • Status: Expired due to Term
First Claim
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1. A method for determining, from measurements made at a remote receiver, at least the orientation of a remote receiver relative to the local coordinate system of a remote phased-array antenna, said phased-array antenna having first and second mutually orthogonal axes of symmetry, said antenna including a plurality of individual antenna elements, and also including a beamformer with phase shifters capable of controlling the phase of the signals applied to the various individual antenna elements, said method comprising the steps of:

  • estimating the orientation of said receiver relative to the local coordinate system of said phased-array antenna;

    setting said phase shifters of said beamformer to a sum-beam phase condition which provides a planar wavefront having a normal directed toward said receiver, based on said estimate of the orientation of said receiver;

    with said phase shifters set to said first condition, transmitting at least a first pulse signal toward said receiver;

    setting said phase shifters of said beamformer to a first delta-beam phase condition, said first delta-beam condition being one in which said phase shifters associated with those of said antenna elements on a first side of said first axis of symmetry have said reference condition, and those of said phase shifters associated with those of said antenna elements on a second side of said first axis of symmetry have said reference phase shift plus 180°

    ;

    with said phase shifters of said beamformer set to said first delta-beam condition, transmitting at least a second pulse signal toward said receiver;

    setting said phase shifters of said beamformer to a second delta-beam condition, said third condition being one in which said phase shifters associated with those of said antenna elements on a first side of said second axis of symmetry have said reference condition, and those of said phase shifters associated with those of said antenna elements on a second side of said second axis of symmetry have said reference phase shift plus 180°

    ;

    with said phase shifters of beamformer set to said second delta beam condition, transmitting at least a third pulse signal toward said receiver;

    receiving said first pulse signal at said receiver, and extracting amplitude and phase of said first pulse signal relative to a reference signal, which may be derived from one of said first, second and third pulse signals;

    receiving said second pulse signal at said receiver, and extracting amplitude and phase of said second pulse signal relative to said reference signal;

    receiving said third pulse signal at said receiver, and extracting amplitude and phase of said third pulse signal relative to said reference signal;

    forming a first ratio of the complex amplitude of said first delta beam to said sum beam;

    forming a second ratio of the complex amplitude of said second delta beam to said sum beam;

    from said first and second ratios, determining the error in said initial estimate of said orientation of said receiver relative to said local coordinate system of said phased-array antenna.

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