Frequency Tunable Antenna with Zeroth Order Resonator for UHF Near-field RFID Systems

摘要

This paper presents a frequency tunable antenna with epsilon negative (ENG) zeroth order resonator (ZOR) for ultra-high frequency (UHF) near-field radio frequency identification (RFID) systems. The ENG ZOR unit cell is composed of a toroidal inductor, a metal pin, a variable capacitor and an additional ground plane. The additional ground and the variable capacitor affect the shunt right-handed capacitance of the ENG ZOR unit cell. The measured resonant frequency of the antenna can be swept from 846 MHz to 1039 MHz by changing the capacitance of the variable capacitor. The measured maximum reading distance is 85 mm at 30 dBm input power. And the minimum input power for successful detecting of the near-field tag is -12 dBm, which is much lower than the conventional UHF near-field RFID reader antennas. The proposed antenna is suitable for UHF near-field RFID systems.