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Method of quadrature-phase amplitude modulation

  • US 5,081,649 A
  • Filed: 06/01/1989
  • Issued: 01/14/1992
  • Est. Priority Date: 06/01/1989
  • Status: Expired due to Term
First Claim
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1. A method of quadrature-phase amplitude modulation comprising the step of amplitude modulating two carrier signal components I and Q in phase quadrature in accordance with signal points in a signal point constellation, the signal point constellation comprising 22n+1 signal points, where n is an integer equal to or greater than 4, arranged in a modified rectangular array with substantially 22n-1 points in each of four quadrants defined by I and Q axes intersecting at an origin of a phase-plane diagram, the signal points in each quadrant of the array having I and Q component amplitudes of 1,3,5, . . . units, the rectangular array being modified by relocating a plurality of points in each quadrant from positions adjacent to a corner of the rectangle to positions extrapolated from the rectangular array and having reduced distances from the origin, wherein in each quadrant each of a majority of the points so relocated is located in a position, relative to the position which it would have in the rectangular array, rotated through an angle of 180°

  • about a point having I and Q amplitude co-ordinates of substantially (2n,2n).

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