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Electronic identification system with improved sensitivity

  • US 6,472,975 B1
  • Filed: 06/20/1994
  • Issued: 10/29/2002
  • Est. Priority Date: 06/20/1994
  • Status: Expired due to Term
First Claim
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1. A reader for use with a tag, the reader comprising:

  • a coil;

    at least one capacitor;

    a means for coupling the capacitor(s) to the coil and coupling the coil to at least one other means, the signal(s) provided to the other means as a result of the coupling being called coupling-means signal(s), the combination of the coil, the capacitors and the coupling means being called the resonating circuit, the resonating circuit having a resonant frequency;

    a means for driving the coil through the capacitor(s) with a driving signal;

    a means for generating the driving signal;

    a resonating means for automatically maintaining the resonating circuit in a tuned condition, a tuned condition being the condition where the difference between the resonant frequency and the driving frequency is a predetermined value in the range from a negative predetermined value to a positive predetermined value.

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