Beam-switching Circularly Polarized Antenna Array for Cold-chain Tracking RFID Applications

Abstract

The existence of blind spots in complex multipath environments such as the cold-chain of vaccine transportation is one of the main problems in applying the Radio Frequency Identification (RFID) system. To overcome this issue, a low-cost beam-switching antenna array for Ultra High Frequency (UHF) RFID was proposed in this letter, which can significantly lower the number of blind spots and improve the detection rate. Firstly, a low-cost circularly polarized (CP) antenna element is designed with compact size, wide impedance and axial ratio (AR) bandwidths. Then, an array makes use of orientation diversity and spatial diversity is designed with five switchable radiation beams. A simple, low-lost but effective feeding network is designed to avoid usage of phase shifters or power dividers, making the design economically efficient. Finally, numerical optimizations and experimental demonstrations are performed to investigate the performances of the proposed antenna array and good agreements are obtained. The measured results demonstrate that the presented beam-switching antenna array is very suitable for RFID applications.