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Three dimensional RF signatures

  • US 8,330,601 B2
  • Filed: 09/22/2006
  • Issued: 12/11/2012
  • Est. Priority Date: 09/22/2006
  • Status: Active Grant
First Claim
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1. A method of detecting tampering of a physical article, the method comprising the steps of:

  • receiving a first collective response from a first set of tag response signals at a first point in time, the first collective response including a tag response signal from each RF tag of a first set of RF tags associated with the physical article;

    recording the first collective response as a first response signature for the physical article;

    receiving a second collective response from a second set of tag response signals at a second point in time, the second collective response including a tag response signal from each RF tag of the first set of RF tags associated with the physical article;

    comparing the second collective response with the first response signature;

    determining from the step of comparing whether any of the RF tags have been moved spatially relative to the other RF tags on the physical article; and

    interpreting a result of the step of determining as an indication that the physical article has been tampered, when the step of determining indicates;

    that a relative spacing between the RF tags associated with the physical article has changed from the first point in time to the second point in time;

    orthat a relative orientation of the RF tags associated with the physical article has changed from the first point in time to the second point in time.

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