High-Accuracy Positioning of Battery-Less Hybrid Gen2 UHF-UWB Tags

Passive RFID systems with energy autonomous tags are promising communication and localization technologies, because of their low complexity and for their low price, so they can be distributed massively in the environment. In this paper, we describe, from both a theoretical and experimental point-of-view, a hybrid Gen.2 ultra-high frequency (UHF) ultra-wideband (UWB) system for passive tag positioning. The considered battery-less tags are remotely addressed and collect energy within the UHF 865-868 MHz band, implementing the EPC Gen.2 standard protocol. At the same time, they are localized within the 3-5 GHz UWB band, that thanks to the available larger bandwidth allows a higher ranging accuracy. A dedicated signal processing algorithm for Time-Difference-of-Arrival (TDOA) localization is exploited for a quasi-real time tags positioning. Experimental results, achieved in indoor environment, show the feasibility of centimeter-level localization accuracy. The tags can be wirelessly switched on and localized up to 1.5 m (within the FCC mask limitations) and 2.5 m (considering 15 dB over the FCC mask) from the UWB source, with a position accuracy, respectively, less than 40 cm and 20 cm (for the 70 % of cases).