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Received signal strength distance determination of low frequency tags

  • US 8,111,141 B1
  • Filed: 03/30/2007
  • Issued: 02/07/2012
  • Est. Priority Date: 03/30/2007
  • Status: Active Grant
First Claim
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1. A method of determining a distance between a signpost and a tag, the method comprising:

  • receiving at the tag a near-field magnetic signal from the signpost;

    measuring at the tag a first signal strength of the near-field magnetic signal received from the signpost with respect to a first antenna on the tag;

    calculating a received signal strength indication using the first signal strength of the near-field magnetic signal received from the signpost at the first antenna;

    determining a distance between the signpost and the tag based on the calculated received signal strength indication;

    measuring at the tag a second signal strength of a signal received from the signpost with respect to a second antenna on the tag;

    measuring at the tag a third signal strength of a signal received from the signpost with respect to a third antenna on the tag; and

    determining location information for the tag using the measured signal strengths from the first antenna, the second antenna, and the third antenna, wherein determining the location information comprises calculating an eight position vector using the measured signal strength of the signals received from the signpost at the first antenna, the second antenna, and the third antenna to yield eight possible locations for the tag.

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