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Window-passage detection system of an airplane

  • US 5,955,971 A
  • Filed: 07/15/1998
  • Issued: 09/21/1999
  • Est. Priority Date: 07/15/1997
  • Status: Expired due to Fees
First Claim
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1. A window-passage detecting system of an airplane having at least one ground system each comprising:

  • a first course generator for generating a horizontal DDM (Differential Depth of Modulation) pattern for defining a horizontal width of a virtual window frame through which a precision approach landing course of an airplane is set, by emitting a first carrier signal and a first side-band signal at the same time upwards toward the virtual window frame from a pair of first transmission antennae provided under the virtual window frame and arranged horizontally and line-symmetrically to a center line of a runway to generate a polarization plane parallel to a horizontal direction of the virtual window frame,said first carrier signal being obtained by amplitude-modulating a first base signal of a first frequency with a first and second modulation signal synchronized with each other,said first side-band signal being obtained by balanced-modulating the first base signal with the first modulation signal whereof phase is inverted and the second modulation signal,one of said first transmission antennae being supplied with the first side-band signal and the first carrier signal, andthe other of said first transmission antennae being supplied with the first side-band signal whereof phase is inverted and the first carrier signal;

    a second course generator for generating a vertical DDM pattern for defining a vertical width of the virtual window frame, by emitting a second carrier signal and a second side-band signal at the same time in the horizontal direction toward the virtual window frame from a pair of second transmission antennae provided sideways of the virtual window frame and arranged vertically and line-symmetrically to a horizontal line orthogonal to the center line and crossing with the precision approach landing course to generate a polarization plane parallel to a vertical direction of the virtual window frame,said second carrier signal being obtained by amplitude-modulating a second base signal of a second frequency which is a little shifted from the first frequency with the first and the second modulation signal,said second side-band signal being obtained by balanced-modulating the second base signal with the first modulation signal whereof a phase is inverted and the second modulation signal,one of said second transmission antennae being supplied with the second side-band signal and the second carrier signal, andthe other of said second transmission antennae being supplied with the second side-band signal whereof a phase is inverted and the second carrier signal; and

    a third course generator for generating a longitudinal DDM pattern for defining a longitudinal position of the virtual window frame, by emitting a third carrier signal and a third side-band signal at the same time in the horizontal direction toward the virtual window frame from a pair of third transmission antennae provided sideways of the virtual window frame and arranged horizontally and line-symmetrically to the horizontal line orthogonal to the center line and crossing with the precision approach landing course to generate a polarization plane parallel to a normal direction of the virtual window frame,said third carrier signal being obtained by amplitude-modulating a third base signal of a third frequency which is a little shifted from both of the first and the second frequency with the first and the second modulation signal,said third side-band signal being obtained by balanced-modulating the third base signal with the first modulation signal whereof a phase is inverted and the second modulation signal,one of said third transmission antennae being supplied with the third side-band signal and the third carrier signal, andthe other of said third transmission antennae being supplied with the third side-band signal whereof a phase is inverted and the third carrier signal.

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