Methods and Apparatuses For RFID Tag Range Determination
AssigneeThingMagic, Inc.
InventorsJohn C. Carrick, Yael G. Maguire
Life of this patent
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Abstract
Apparatus and methods are described which are useful for determining a location characteristic between an RFID tag and an RFID tag reader or a second RFID tag. 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.
Claims20
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;
- calculating, by the processor, a Fourier transform of the produced data set;
- evaluating, by the processor, the Fourier transform;
- and
- determining, by the processor, a distance between the RFID tag and the RFID tag reader based upon the evaluation of the Fourier transform.
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, a phase delay associated with each of the returned signals;
- monitoring, by the phase estimator, an uncertainty associated with each determined phase delay of each received signal;
- assigning, by a processor, a weighting coefficient to each determined phase delay, the weighting coefficient based upon the uncertainty associated with each determined phase delay;
- producing, by the processor, a data set comprising determined phase delays, frequencies associated with the phase delays, and weighting coefficients associated with the phase delays;
- determining, by the processor, a distance between the RFID tag and the RFID tag reader using at least a portion of the data from the produced data set.
A method of determining a relative velocity between an RFID tag and an RFID tag reader, the method comprising:
- broadcasting, by the tag reader, interrogation signals to the tag at a single frequency;
- receiving, by the tag reader, returned signals from the tag in response to the interrogation signals;
- determining, by a phase estimator, a phase delay associated with each of the returned signals;
- determining, by a processor, a rate of change of phase delays associated with the returned signals as a function of time;
- and
- calculating, by the processor, a relative velocity between the RFID tag and the RFID tag reader from the rate of change of the phase delay as a function of time.
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;
- comparing, by the processor, the data set with a second data set of a second RFID tag;
- and
- determining, by the processor, proximity of the RFID tag to the second RFID tag based on the comparison.
Dependencies are inferred from the claim text.