Radio Frequency Identification Reader Antenna Design With High Gain And Circular Polarization

In this paper, the design of a high gain circular polarization (CP) radio frequency identification (RFID) reader antenna for the ultra-high frequency (UHF) band is described. The antenna is designed with a 2 ${\times\ 2}$ array configuration by applying the sequential rotation technique, which guarantees excellent axial ratio (AR) performance and high gain. Furthermore, in order to maximize the antenna gain, both the height of the CP antenna elements and the antenna element arrangement have been optimized. In addition, the two-level series power divider based feed network central element has been opportunely rotated to minimize the feed network insertion loss. A CP gain larger than 12 dBic and 14.6 dBic with a ${600\times 600\ \text{mm}^{2}}$ antenna array has been measured within the UHF bandwidth 860–960 MHz and the FCC bandwidth 902–928 MHz, respectively, with outstanding impedance matching and AR performance.