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 surfacewave resonances at different planes. To excite the surface waves, various configurations have been considered, namely, square-ring element above, below, and within theMS. The latter design, with a 0.07.o height profile, provides superior matching and gain performances compared to the others. It operates from3.8 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.