High-Gain Wideband CP S-shaped Slot Antenna with Metasurface Reflector for UHF-RFID Readers

This research proposes a high-gain wideband circularly polarized (CP) S-shaped slot antenna with metasurface (MTS) reflector for UHF-RFID handheld readers. The proposed antenna consisted of the S-shaped slot antenna with coplanar waveguide feed on the upper substrate and 4 × 4 periodically-arranged plus-sign-shaped slot MTS unit cells on the lower substrate functioning as a reflector. The MTS reflector was utilized to realize the high-gain of the CP S-shaped slot antenna. To achieve wide impedance bandwidth (IBW) and axial ratio bandwidth (ARBW), the evolution of the antenna was developed in four stages. The simulated IBW and ARBW of the Antenna IV (proposed antenna) at 0.9 GHz (center frequency) were 37.7% (0.66-1 GHz) and 27.7% (0.72-0.97 GHz), respectively. In addition, the maximum gain was 7.56 dBic at 0.78 GHz with left-hand circular polarization (LHCP) radiation characteristics. The dimension of the proposed antenna was 0.35?0 × 0.35?0 × 0.195?0.