Defective ground structure for circularly polarized microstrip antenna with an irregular slot for 2.45 GHz RFID reader

A compact circularly polarized antenna for RFID reader is proposed in this paper. It consists of double stair shaped edge on one side and L-shaped feed line on the other side, which is a top plane. L-shaped feed can improve the circular polarization of antenna. The circular polarization mode of this structure is achieved at 2.45 GHz. The antenna provides an improved bandwidth for RFID readers which have more than −10dB reflection coefficient (return loss). The antenna also features 3 dB axial ratio and the VSWR is below 2 in the operating frequency band.