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Electronic article surveillance system

  • US 5,103,234 A
  • Filed: 02/20/1991
  • Issued: 04/07/1992
  • Est. Priority Date: 08/28/1987
  • Status: Expired due to Term
First Claim
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1. An antenna for use in an article surveillance system comprising:

  • first and second loops arranged in a given plane, said second loop being situated entirely within said first loop so as to be in nested relationship with said first loop, said first loop having a first section and second and third sections extending from opposing ends of said first section of said first loop, said second loop having a first section and second and third sections extending from opposing ends of said first section of said second loop, said first, second and third sections of said second loop facing the first second and third sections, respectively, of said first loop, and the spacing of the first section of said second loop from the first section of said first loop being greater than the spacing of said second and third sections of said second loop from the second and third sections, respectively, of said first loop;

    third and fourth lops arranged in said given plane, said fourth loop being situated entirely within said third loop so as to be in nested relationship with said third loop, said third loop having a first section and second and third sections extending from opposing ends of the first section of said third loop, said fourth loop having a first section and second and third sections extending from opposing ends of said first section of said fourth loop, said first, second and third sections of said fourth loop facing said first, second and third sections, respectively, of said third loop, and the spacing of the first section of said fourth loop from the first section of said third loop being greater than the spacing of said second and third sections of said fourth loop from the second and third sections respectively, of said third loop;

    said first and second loops being arranged adjacent to said third and fourth loops such that the first section of said first loop and the first section of said third loop are at opposing ends of said adjacent arrangement of loops, said first through fourth loops being connected electrically such that said first and second loops have the same first phase and the third and fourth loops have the same second phase opposite said first phase, and said first and second loops and said third and fourth loops having relative sizes and arrangement such that, in combination with said nested relationship and phasing, cause said array to exhibit substantially a single null zone along a given direction in said plane.

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