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Spread spectrum baseband modulation of magnetic fields for communications and proximity sensing

  • US 6,393,045 B1
  • Filed: 09/24/1998
  • Issued: 05/21/2002
  • Est. Priority Date: 09/26/1997
  • Status: Expired due to Term
First Claim
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1. A method of conducting a magnetic field communication comprising the steps of:

  • (a) controllably emitting from a transponder a magnetic field modulated with a spreading signal indicative of object data that had been read from a transponder memory in a read mode of operation and previously written to the transponder memory in a write mode of operation; and

    (b) detecting said magnetic field modulated with said spreading signal by a magnetic field detector of a reader, and processing an output of the magnetic field detector using a signal representative of one of a derivative or integral output of a replica of the spreading signal.

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