A Circularly Polarized UHF RFID Tag Antenna Design

This paper proposes a circularly polarized (CP) radio frequency identification (RFID) tag antenna design that operates in the ultra-high frequency (UHF) band. The proposed tag antenna has a size of 100×100 mm
³
, and it is composed of two main structures, namely, an eccentric circular slot patch and a coupled arc-shaped feeding strip. The RFID tag chip is embedded near one end of the feeding strip and it is also shorted to the main ground through a via hole. The size of the circular slot can aid in achieving good impedance matching between the tag antenna and the chip. The CP characteristic of the tag antenna is excited due to the feeding and slot position, as well as the gap slot loaded on the radiation surface of the patch. The 10-dB impedance bandwidth of the proposed tag antenna is 1.62% (914-929 MHz), and its corresponding 3-dB axial ratio (AR) bandwidth is 0.97% (919-928 MHz).