Abstract
A novel compact design of planar circularly polarized (CP) tag antenna for UHF RFID system is proposed. By introducing the Y-shaped slit as the feed structure, the measured half-power bandwidth of the proposed CP tag antenna can be more than 135 MHz (860–1000 MHz), which includes the entire operating bandwidth for worldwide UHF RFID system. The obtained 3 dB axial-ratio (AR) bandwidth can be about 10 MHz suitable for Taiwan UHF RFID applications. The proposed tag antenna reduces the antenna size by at least 30% since the antenna size is only 40 × 40 × π mm2. The simulated peak gain and antenna efficiency are approximately 0.4 dBic and 91% for Taiwan UHF RFID band. Meanwhile, with omnidirectional reading pattern, the measured reading distance is about 7.2 m. Good tag sensitivity was obtained across the desired frequency band.
Acknowledgment
This paper was supported by the Ministry of Education, Taiwan, R.O.C., under Industry-Academy Cooperation Project MOE-101E-07-024 and 102E-07-013.