Bandwidth and gain improvement of a crossed slot antenna with metasurface

A wideband metasurfaced (MS) slot antenna is proposed for circularly polarized (CP) operation. The antenna consists of a crossed slot antenna (CSA) and a MS placed at a short distance above the CSA. The CSA has two slots placed in orthogonal positions and with distributed elements to generate two E-fields with 90°-phase difference for CP radiation. A microstrip line is used to single feed the CSA at the center. Simulations and measurements are used to study and design the MS slot antenna. The measured results show that, with the use of the MS, the impedance bandwidth can be increased from 4.24–6.78 GHz (2.54 GHz, 46.1%) to 3.36–6.91 GHz (3.55 GHz, 69.13%), and the axial-ratio bandwidth (ARBW) can be increased from 4.38–4.96 GHz (0.58 GHz, 12.4%) to 3.96–6.02 GHz (2.06 GHz, 41.28%). Within the ARBW, the realized co-polarized gain can be increased by about 3 dB on average.