Performance Enhancement of Square-Ring Antennas Exploiting Surface-Wave Metasurfaces

This letter proposes a technique to enhance the performance of a square-ring antenna by exciting surface waves. An asymmetrical metasurface (MS) is utilized to control the surface-wave resonances at different planes. To excite the surface waves, various configurations have been considered, namely, square-ring element above, below, and within the MS. The latter design, with a 0.07 $\lambda _o$ height profile, provides superior matching and gain performances compared to the others. It operates from 3.8 to 5 GHz (27 $\%$ fractional bandwidth) with a stable realized gain up to 11.9 dBi in the broadside direction. A prototype of the structure, with a simple probe-feeding mechanism, was fabricated and measured. An excellent agreement was attained between the simulated and measured data.