UHF RFID Indoor Positioning System With Phase Interference Model Based on Double Tag Array

A UHF radio-frequency identification (RFID) indoor positioning system based on phase difference is presented in this paper. An additional auxiliary tag and the target tag make up a double tag array to eliminate the phase ambiguity. To quantify the phase offset caused by the interference between tags, a mathematical model is built. Based on the double tag array and the interference model, a hyperbolic positioning algorithm, combining the genetic algorithm, is implemented to improve the positioning accuracy. Compared with other RFID positioning systems, the proposed system achieves a better positioning accuracy of 0.2217 m.