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Method for identifying the position of a portable transponder, and an antitheft system

  • US 7,034,656 B2
  • Filed: 11/13/2002
  • Issued: 04/25/2006
  • Est. Priority Date: 05/26/2000
  • Status: Expired due to Fees
First Claim
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1. A method for identifying whether a portable transponder is located in the near area of a transmitting antenna of a base station, said method comprising:

  • the base station sends a first test signal with a defined power level, the transponder determines the field strength with which it receives the first test signal and sends a response signal to the base station, said response signal contains the field strength of the first test signal, the base station stores the field strength with which the transponder received the first test signal, the transponder sends a second test signal with a defined power level, the base station determines the field strength with which it receives the second test signal, and the two field strengths are compared in order to determine whether the transponder is located in the near area of the transmitting antenna of the base station.

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