ORBITER: Phase-Based Localization of RFID Tags via Circular Antenna Trajectory

In this article we present a method for ultrahigh-frequency (UHF)–radio frequency identification (RFID) tag localization via phase measurements gathered during a circular trajectory of the reader antenna, that is, ORBITER. The localization is pursued by exploiting both the minimum and the variability of the unwrapped phase curve via appropriate mathematical operators. We investigate the sensitivity of the method, by highlighting the conditions for its applicability and the proper choice of the measurement parameters. For the experimental validation, we use a 3-D Cartesian portal for antenna motion along circular trajectories, that allows us to assess the performance and reliability of the method in a controlled environment. Results show that the proposed method achieves good accuracy and robustness in localizing UHF-RFID passive tags. The method finds applications in both indoor and outdoor scenarios.