An ellipse-shaped with slanted slot circularly polarized monopole antenna for UHF RFID readers

An ellipse-shaped circularly polarized (CP) monopole antenna is proposed in this paper. A slanted slot is added into the antenna to enhance 3-dB axial ratio bandwidth. The antenna operates at ultrahigh frequency (UHF) band for radio-frequency identification (RFID) reader applications. The measured bandwidth of standing wave ratio (SWR) <; 2 is 535 MHz (553 MHz-1088 MHz) and the measured 3-dB axial ratio (AR) bandwidth 45MHz (900MHz-945MHz). The size of the radiating element is 137 mm × 122 mm.