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Passive ranging method and apparatus using interferometric scanning

  • US 4,642,649 A
  • Filed: 09/30/1983
  • Issued: 02/10/1987
  • Est. Priority Date: 09/30/1983
  • Status: Expired due to Fees
First Claim
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1. An apparatus for determining the range R of a distant source of electromagnetic emission Φ

  • from a monitoring platform, comprising;

    first and second radio frequency interferometer sensors mounted on said platform at spaced-apart positions separated by a baseline of length L, and each of said first and second interferometer sensors having a multilobe gain pattern of multiple, substantially equal strength, finger-like lobes extending outwardly from a center of the sensor in which individual lobes of the pattern associated with each sensor define receiving axes that are movable in a scanning motion across a field of interest containing the source of electromagnetic emission Φ

    ;

    a source of pilot signal mounted on said platform at a predetermined position relative to said first and second interferometer sensors;

    circuit means connected to said first and second interferometer sensors for causing said multilobe patterns to scan at a rate ws in said scanning motion across the field of interest, said circuit means including means responsive to said source of pilot signal for synchronizing the sweep angles of said multilobe patterns so that predetermined lobes of said patterns exhibit parallel axes and the sweeping motion thereof cause said first and second interferometer sensors to produce output signals that are time varying signals resulting from the spatial modulation of the source of emission Φ

    by the sweeping motion of said predetermined lobes;

    time difference processing means for responding to the output signals produced by said first and second interferometer sensors and developing a time difference signal t21 representing a range dependent time difference of the receptions of the source of emission Φ

    along parallel scanning axes; and

    range processor means for responding to said time difference signal t21 and producing a signal representing range R as a function of said signal t21 and as a function of the scan rate ws of the sweeping motion of said multilobe patterns, and of an angle of arrival θ

    of the source of electromagnetic emission measured at said platform relative to said baseline.

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