Exploiting dual-antenna diversity for phase cancellation in augmented RFID system

In this paper, we propose a dual antenna technique to lessen the phase cancellation effect in an augmented ultra high frequency (UHF) radio frequency identification (RFID) system. In the augmented RFID system, a recently developed semi-passive RFID component (sensatag) has the functionality to sense the backscattering communication between a reader and a passive tag being within its proximity. This unique functionality of sensatag allows for the development of proximity-based indoor localization solutions with high localization accuracy. However, due to the phase difference between RFID reader´s continuous carrier wave (CW) and tag´s backscattering signal, the backscattered signal from the tag received by the sensatag could be significantly attenuated. We call this destructive effect as phase cancellation. This problem exists in passive RFID system because the RFID reader transmits CW during tag´s communication. Taking advantage of the spatial diversity of dual antenna technique, the probability of phase cancellation effect could be reduced. In addition, we present an UHF RFID system simulation framework, that includes the model of the sensatag. Then we demonstrate the performance of the dual antenna technique with data obtained from computer simulation.