Indoor Localization of Passive UHF RFID Tags Based on Phase-of-Arrival Evaluation

This paper introduces a two-dimensional localization system for passive UHF RFID transponders based on phase-of-arrival evaluation of the backscattered tag signal. A multiple-channel system, where alternately one path is configured as a transmitter and the remaining paths work as receivers, is used to permit the position estimation. To improve localization accuracy and reduce disturbances caused by multipath propagation, a frequency-stepped continuous-waveform approach is employed. To achieve proof of concept, a local position measurement system demonstrator comprising an RFID reader, passive EPC Gen 2 RFID tags, several transceivers, baseband hardware, and signal processing was used for measurements. The results show excellent localization accuracy, even in an indoor environment.