Compact broadband dual-band circularly polarised antenna for universal UHF RFID handheld reader and GPS applications

This study introduces a simple, compact broadband dual-band circularly polarised slot antenna suitable for the use in the compact universal ultra-high frequency (UHF) radio-frequency identification (RFID) reader devices and Global Positioning System (GPS) applications. The proposed antenna is fed using an open-end coplanar waveguide with an inverted 'L' structure. To realise a broadband circular polarisation and good impedance matching, an inverted L-shaped strip line is inserted adequately into a square slot at the right centre of the slot toward the slot centre. The experimental results demonstrate that the proposed antenna exhibits a 10 dB return loss bandwidth of 552 MHz (716-1268 MHz) and 3-dB axial ratio (AR) bandwidth of 564 MHz (824-1388 MHz). Additionally, the antenna gains are 3.8 and 4.29 dBi throughout UHF RFID band and GPS band, respectively. The proposed antenna has a wide AR bandwidth, a compact size, and a simple structure. Furthermore, the proposed antenna is printed on one substrate layer with an overall size of 112 x 112 x 1.6 mm(3), which makes it more practical for universal UHF RFID handheld readers and GPS applications.