Compact triple-band circularly-polarized directional antenna for UHF/ISM RFID mobile readers with GNSS band

Multi-band, multi-function, and miniaturization are very desirable for late-mode wireless mobile devices. In this paper, a compact triple-band circularly-polarized directional antenna at 920MHz, 1600MHz, and 2450 MHz is proposed for UHF/ISM RFID mobile readers with GNSS band. The antenna consists of a two-feed network and stacked radiating patches. Measured result shows that the 10 dB impedance bandwidths are 24, 430, and 340 MHz with 3-dB axial ratio bandwidths of 13, 230, and 365 MHz for the three bands. In these bands, the antenna provides the symmetric radiation patterns and the peak gains of 3.7, 6.6, and 8.8 dBic, respectively. Comparison shows that the antenna not only features compact size, simple configuration, and low cost but also provides wide CP bandwidths. Moreover, the operating frequencies can be changed conveniently and the large frequency ratio of 2.8 is achieved. It is the first design to integrate the UHF/ISM RFID reader application and GNSS function into a single antenna.