Monopole antenna with circular polarization for handheld RFID

A novel CP antenna for UHF RFID readers is proposed in this paper. An antenna prototype that operates in the UHF RFID band is successfully developed using an orthogonally truncated radiation patch, an obliquely slotted ground plane, and a 50- microstrip line that proximally fed the antenna. All elements are printed on a microwave substrate in a vertical structure. The antenna dimension of 65×90×0.8 mm³ is suitable to use for handheld devices. The impedance bandwidth for 2.5 VSWR and the 3-dB axial-ratio bandwidth are 15.2% (880 MHz~1025 MHz) and 6.5% (890 MHz~950 MHz), respectively.