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Phased array antenna for radio frequency identification

  • US 5,686,928 A
  • Filed: 10/13/1995
  • Issued: 11/11/1997
  • Est. Priority Date: 10/13/1995
  • Status: Expired due to Term
First Claim
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1. A radio-frequency interrogation system for reading a transponder tag on a moving vehicle as the transponder tag moves along a path adjacent a fixed position adjacent said path, said system comprising in combination:

  • a phased array antenna comprised of a plurality of radiating dipole elements disposed at said fixed position;

    said phased array antenna including a pair of printed circuit boards disposed with their respective interior surfaces disposed so that they are spaced apart, facing one another;

    said plurality of radiating elements attached to respective ones of a plurality of printed circuit terminals on the interior surfaces of said pair of printed circuit boards with one radiating element of each of said dipole elements extending outwardly from an exterior surface on one of said pair of printed circuit boards and the other radiating element of each of said dipole elements extending outwardly from an exterior surface of the other of said pair of printed circuit boards;

    a plurality of matching traces on corresponding interior surfaces of each of said printed circuit boards forming broadside coupled transmission lines for coupling RF energy to said terminals; and

    an RF reflector disposed in a plane perpendicular to the said pair of printed circuit boards and separated from said plurality of dipole elements at a distance approximately equal to one-half wavelength of said RF energy.

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