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.