Item-level passive UHF RFID tag locating using reader antenna spatial diversity

A new concept of passive RFID tag position finding is presented for real world item-level applications and provides automatic guidance for order fulfillment centers and retail stores. The new technique does not require a radio map, reference tags, or any additional hardware. This is accomplished by using precise signal models, a minimum mean-square error estimator and four spatially diverse CP reader antennas. Experimental results show that the proposed method can make unprecedented robust real time estimation practical regardless of the type and orientation of the tag and the operating environment.