A passive ultra-high frequency (UHF) RF identification (RFID) system is proposed that employs multiple antennas at the reader and single antenna at each tag. The gain due to multiple antennas in terms of the maximum reader interrogation range is first quantified. Then, a blind adaptive beamforming (BABF) algorithm that does not require the channel state information (CSI) is presented to improve both the interrogation range and the data transmission performance of the system in both the full- and half-duplex configurations. Moreover, an estimator for the number of tags within the reader interrogation range is proposed to enhance the system throughput. Simulation results show that both the interrogation range and the packet error rate (PER) performance for data transmission can be improved significantly using multiple antennas at the reader. A Universal Software Radio Peripheral (USRP)-based prototype system is implemented to validate the interrogation range improvement by employing multiple-antenna readers with several beamforming schemes. The proposed multiantenna RFID reader with the BABF complies with the existing RFID standard and can be readily implemented in existing systems.
['Shaoyuan Chen', 'Shan Zhong', 'Siyi Yang', 'Xiaodong Wang']
A Multiantenna RFID Reader With Blind Adaptive Beamforming