Small-size tag antenna for UHF active RFID system

This work describes a novel compact design of planar ultra-high-frequency (UHF) tag antenna for radio-frequency identification (RFID) system by introducing an L-shaped metal plate connecting with the spiral monopole antenna. The obtained impedance bandwidth of 12 MHz can meet with Taiwan UHF operating band (922 ~ 928 MHz). The overall antenna size is only 13 × 9 × 1.6 mm3. The measured peak gain and antenna efficiency are approximately ™1.1 dBi and 27 % for Taiwan UHF band, respectively. Meanwhile, the measured reading distance can approach 250 m. Good tag sensitivity is obtained across the desired frequency band.