A High Gain and Circularly Polarization Antenna with AMC Reflector for 2.45 GHz RFID Reader

This paper introduces a high gain and circularly polarization (CP) patch antenna at the frequency of 2.45 GHz for RFID reader. The proposed antenna consists of a pin-loaded patch, a probe-fed perturbation ring resonator, an Artifactual Magnetic Conductor (AMC) reflector having 7 × 7 unit cells printed on the top side of substrate#1 - substrate#3, respectively. Both Sub#1 and Sub#2 are composed of Rogers RO4003C (εr = 3.55, tanδ = 0.0027) with the thickness of 0.508 mm and 1.524 mm, respectively. Sub#3 is made of FR4 epoxy (εr = 4.4, tanδ = 0.02) with the thickness of 0.8 mm. The four shorting pins of the patch radiator are used to enhance the gain of the antenna by increasing the radiating area of the antenna. The perturbation ring resonator produces two additional split degenerate modes which not only provide a quadrature phase shift for CP radiation but also widen the axial ratio bandwidth (ARBW). The AMC reflector is placed a small distance below the antenna to improve the gain. Simulated results show that good CP and high gain characteristics are obtained at desired frequency. ARBW < 3 dB achieved is 6.1% with the gain of 11.81 dBic at the frequency of 2.45 GHz.