Compact Circularly Polarized Tag Antenna based on EBG Structure for Metallic Objects

Abstract

In this paper, a compact circularly polarized (CP) radio frequency identification (RFID) tag antenna based on the electromagnetic band gap (EBG) structure is proposed for metallic objects. The compact EBG structure is composed of two-layer patches with offset vias. By inserting square loops into the patches, a reflection phase of +100° for X-polarization and −89° for Y-polarization at 915 MHz is achieved. A novel cross-dipole antenna is designed with meander arms and modified T-matching. The simulated −15 dB impedance bandwidth of the tag antenna is 100 MHz (860–960 MHz), and its corresponding 3 dB axial-ratio (AR) bandwidth is 6 MHz (917–923 MHz). In theory, the proposed tag antenna can provide a reading distance of 5.08 m when it is mounted on the metallic surface.