Simultaneous AoA estimations for two passive UHF RFID tags

Using an RFID reader to estimate angle-of-arrival (AoA) of a passive UHF RFID tag backscatter signal has been extensively studied; however using an RFID reader to estimate AoA information of multiple passive UHF RFID tag backscatter signals simultaneously is scant in literatures. This work presents experimental results of simultaneous AoA estimation of two commercial passive UHF RFID tags using a receiver with four-element uniform linear array. The results show that AoA information of two tag backscatter signals can be accurately estimated using subspace-based methods without spatial smoothing processing. The work is useful for passive UHF RFID tag localization applications and the design of an RFID reader with spatial division multiple access ability.