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Antenna for transponder

  • US 6,885,342 B2
  • Filed: 01/15/2001
  • Issued: 04/26/2005
  • Est. Priority Date: 02/08/2000
  • Status: Expired due to Term
First Claim
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1. An antenna for sending and receiving microwave radiation for use in a transponder system for wireless toll payment, comprising:

  • a dielectric antenna supporter (11) having a bearing surface (12), a frame shaped or loop shaped excited antenna element (13) extending in a first plane disposed on the dielectric antenna supporter bearing surface (12), a polarization transformer (22), wherein the excited antenna element is linearly polarized and disposed at a predetermined distance from the polarization transformer (22) to transform linearly polarized radiation to circular or elliptical polarized radiation, and wherein the polarization transformer (22) operates as a director, a reflector disposed at a predetermined distance from the excited antenna element, at least one parasite element or director placed in a predetermined distance from the excited antenna element, wherein the frame or loop antenna comprises two substantially equal shaped frames or loops placed at a predetermined distance, and a diode (25) connected to the frames or loops (14, 15) for demodulation, and a capacitor (23) connected to the frames or loops (14, 15).

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