Methods and apparatuses for RFID tag range determination
First Claim
1. A method of determining a position of an RFID tag, the method comprising:
- broadcasting, by the tag reader, interrogation signals to the tag at a plurality of discrete frequencies;
receiving, by the tag reader, returned signals from the tag in response to the interrogation signals;
determining, by a phase-estimator, phase delays associated with the returned signals;
producing, by a processor, a data set from the determined phase delays;
selecting, by the processor, a function having a periodic characteristic which best fits the produced data set; and
determining, by the processor, a distance between the RFID tag and the RFID tag reader based upon the selected function.
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Abstract
Apparatus and methods are described which are useful for determining a distance between an RFID tag and an RFID tag reader. In various embodiments, signals backscattered from a singulated tag over a range of frequencies are evaluated for in-phase I and in-quadrature Q signal components. The I-Q data is processed to determine phase delay angles associated with each signal frequency. The phase delay data can be processed by a sum of squared errors method or Fourier transform method to determine a distance to the singulated tag. The methods can also be used to determine any of a location, a radial velocity, a directional velocity of the singulated tag, and proximity of the singulated tag to a second tag.
91 Citations
31 Claims
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1. A method of determining a position of an RFID tag, the method comprising:
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broadcasting, by the tag reader, interrogation signals to the tag at a plurality of discrete frequencies; receiving, by the tag reader, returned signals from the tag in response to the interrogation signals; determining, by a phase-estimator, phase delays associated with the returned signals; producing, by a processor, a data set from the determined phase delays; selecting, by the processor, a function having a periodic characteristic which best fits the produced data set; and determining, by the processor, a distance between the RFID tag and the RFID tag reader based upon the selected function. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30)
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31. A system of determining a position of an RFID tag, the system comprising:
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means for broadcasting interrogation signals to the tag at a plurality of discrete frequencies; means for receiving returned signals from the tag in response to the interrogation signals; means for determining phase delays associated with the returned signals; means for producing a data set from the determined phase delays; means for selecting a function having a periodic characteristic which best fits the produced data set; and means for determining a distance between the RFID tag and the RFID tag reader based upon the selected function.
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Specification