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Phase coupler for rotating fields

  • US 8,933,790 B2
  • Filed: 04/30/2009
  • Issued: 01/13/2015
  • Est. Priority Date: 06/08/2007
  • Status: Active Grant
First Claim
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1. An electronic article surveillance system comprising:

  • a plurality of antenna structures, each antenna structure including three or more loops and wherein each antenna structure is connected to a single transmission driver, for generating respective electromagnetic fields from each antenna structure, and wherein said single transmission driver is arranged to drive said loops of said antenna structure in such a way that the vector sum of said electromagnetic fields of said antenna structures is null in a far field and wherein no vector is separated by another vector by 180°

    of phase;

    a plurality of electronics boards and wherein each electronics board has two independent transmission drivers thereon, and wherein one of said transmission drivers drives a first antenna structure and wherein the other one of said transmission drivers drives a second antenna structure; and

    wherein each of said antenna structures is coupled to said single transmission driver via a phase coupler, said phase coupler converting a transmission driver signal into two distinct phase driver signals for driving a first set of loops and a second set of loops for an antenna structure.

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