Read-Rate Improvement in 920MHz RFID System with Circular-Polarized 2D Beam Scan R/W Antenna

Radio frequency identification (RFID) is a promising Internet of things (IoT) solution that bring about innovation in supply chain management. However, RFID has a read reliability issue in multipath radio propagation environment. In order to improve the reliability, we proposed a reader/writer (R/W) beam modulating scheme with a moving conductor. By modulating the R/W antenna beam, the multipath propagation structure can be changed and null points caused by standing waves are shifted. Thus, read success rate can be improved by the combination of repeated transmission and selection combining. In this paper, we propose a new 2D beam scan antenna for circular-polarized operation that is necessary for actual RFID systems. It has been confirmed from the simulation that the electric field distribution in a typical storage shelf can be changed by the proposed scheme. A prototype beam modulator with a decentered rotating circular conductor is fabricated and tested. RFID read measurement result shows that the proposed scheme can reduce the dead zone rate to less than half of the normal system.