Wideband Circularly Polarized Antenna Based on Gradual Capacitor Feeding for RFID Reader Applications

This paper proposes a wideband circular polarization antenna for RFID reader applications. The feeding form of the antenna adopts capacitive coupling feeding, and the width of the corresponding coupling open-circuit branch is set to be gradual, which can realize good impedance matching of the antenna. In addition, two pairs of degenerate separation units are introduced at the edge of the patch antenna. By adjusting its size, the axial ratio performance of the antenna can be improved. The simulation results show that the impedance bandwidth for return loss of antenna > 10 dB is in the frequency range of 0.84- 1.07 GHz. The peak gain is above 8.6 dBic, and the simulated axial ratio bandwidth for
$\text{AR} < 3\ \text{dB}$
is covered from 0.90 to 0.94 GHz.