A Compact Low-Cost Circular Polarized Patch Antenna for RFID Reader Application

A compact low-cost circularly-polarized antenna for RFID reader is proposed. A metal square patch, an L-shaped ground plane, and a cavity with three slots on each side make up the antenna. The cavity etching slots can significantly reduce the working frequency of the antenna, which is of great significance to antenna miniaturization. The L-shaped ground plane in the middle of radiation patch and cavity could generate circularly-polarized radiation, which not increase the profile or reduce the effective radiation area of the antenna. According to the simulation results, the impedance bandwidth of antenna is 13.1% (850–970 MHz) and 3-dB AR bandwidth is 3.4% (895–926 MHz). The average gain of this antenna over a 3-dB AR bandwidth is 7.5 dBic. The proposed antenna is quite cost-effective among antennas completely made of metal. The size of the antenna is
$0.40 \lambda_{0} \times 0.40 \lambda_{0} \times 0.071 \lambda_{0}(\lambda_{0}$
is the wavelength at 910 MHz).