Patent ID: 8446254

Claim:
A method of determining a position of a radio-frequency identification (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; and 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.