Sectorization of UHF RFID tags using a steerable phased antenna array

The paper presents the development of an RFID antenna array test bed for determining the sector location of a passive UHF RFID tag. The sectorization is achieved by using a 4-element uniform linear phased array of right-hand circularly polarized (RHCP) patch antennas at the receiver, which is also shown to improve the read range of the system. The uniform linear phased antenna array is able to electronically steer a beam with the use of a programmable phase shift network. The phase shifters are able to provide 0° to 180° shifts for each element, thus providing maximum steering angles of +/-20° off broadside. The phase shift network is controlled by a microcontroller with onboard digital-to-analog converters (DAC). A 13-dB low-noise-amplifier stage was also added to compensate for insertion losses in the network. Experiments were performed to characterize the sectorization performance of the system for fixed and moving tags.