A small UHF RFID passive tag antenna using modified split ring resonator

This paper presents a UHF RFID tag antenna designed for using in Thailand (920-925 MHz). The modified split ring resonator (SRR) is used to reduce an antenna size. The antenna contains 3-ring resonator: 2-circular ring and 1-square ring. The outer ring is a square SRR which is connected to circular SRR on the radiating part. This structure can be matched the IC chip impedance by adjusting the space of the square SRR. The proposed tag antenna can operate to cover the frequency range of 920-925 MHz with the |S
₁₁
| of less than -10 dB. The antenna size is 38 mm × 38 mm. The proposed tag has maximum read range of 3.20 meters.