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Monitoring antenna system

  • US 6,351,215 B2
  • Filed: 01/20/1999
  • Issued: 02/26/2002
  • Est. Priority Date: 06/02/1998
  • Status: Expired due to Term
First Claim
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1. In a monitoring system for detecting the presence of a tag the improvement comprising:

  • a digital signal source for generating digital signals representing selected frequencies;

    an antenna tap connected to said signal source for receiving said digital signals and generating an analog signal having a signal frequency of one of said selected frequencies; and

    a planar antenna loop connected to said antenna tap for transmitting signals at the signal frequency of said analog signal;

    wherein said antenna is responsive to signals from said tap for generating a magnetic field surrounding said loop at said analog signal frequency.

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