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Radio frequency identification system

  • US 6,411,199 B1
  • Filed: 08/21/1998
  • Issued: 06/25/2002
  • Est. Priority Date: 08/21/1998
  • Status: Expired due to Term
First Claim
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1. A transponder reader for use in a radio frequency identification system, said system including a transponder which, in response to an interrogation signal, transmits an identification signal, said transponder reader comprising:

  • means for producing an interrogation signal having a first RF frequency;

    means for receiving a transponder carrier signal having modulated thereon the identification signal, said transponder signal produces by the transponder in response to receipt of the interrogation signal;

    said means for receiving including an antenna, a PSK receive path disposed between said antenna and a first circuit node, an FSK receive path disposed between said antenna and said first circuit node, and a first filter for attenuating said first RF frequency disposed between said first circuit node and a second circuit node;

    said PSK receive path including a second filter for attenuating said first RF frequency and passing frequencies approximately one-half of said first RF frequency;

    said FSK receive path including a discriminator and a third filter, said third filter for attenuating frequencies approximately one-half of said first RF frequency and above and passing RF frequencies less than one-fourth of said first RF frequency.

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