Wideband Circularly Polarized Metasurface-Integrated Dipole Antenna for Bidirectional Applications

This study proposes a compact dipole antenna incorporating a wideband polarization-converting metasurface designed for bidirectional applications. The antenna comprises a stepped-width modified dipole structure with two strategically positioned parasitic patches located on the bottom side of the substrate and a metasurface polarization converter comprising four square metal plates arranged in a 2 × 2 layout on the top side. Each unit cell features a diagonally structured pattern created by etching lines into the metal plates, enabling phase manipulation and amplitude balancing for efficient linear-to-circular polarization conversion. The antenna achieves left-hand circular polarization on the broadside and right-hand circular polarization on the opposite side, making it suitable for bidirectional applications where polarization diversity is critical. The proposed antenna design achieves an axial ratio bandwidth of 45.7% (4.06–6.45 GHz), an |S11| < −10 dB impedance bandwidth of 46.1% (4.03–6.43 GHz), and a peak gain of 3.3 dBic at 5.2 GHz. This compact configuration, with dimensions of 32 × 32 × 0.508 mm (0.54 λo × 0.54 λo × 0.0086 λo at 5.1 GHz), enables bidirectional applications in wireless communication.