Compact High-Gain Metasurface Antenna Arrays Based on Higher-Mode SIW Cavities

This communication presents novel compact linearly/circularly polarized metasurface antenna arrays based on higher mode substrate integrated waveguide cavities. The linearly polarized antenna is realized by an array of patch cells with similar TM resonant modes as traditional patch antennas, while the circularly polarized one is newly designed based on the proposed polarization-rotation metasurface structure. Moreover, the periodic metasurface antennas are modified with complemental boundaries to further enlarge effective radiation apertures for about 1.5 dB gain enhancement. In addition, a simple TE220 higher mode cavity is employed as a compact and symmetrical feeding network to provide perfectly uniform four-way excitations, resulting in relatively uniform radiation aperture for high gain. The simulation and measured results both indicate that the proposed linearly/circularly polarized metasurface arrays can, respectively, achieve very high directional gains of about 10.75/10.66 dBi with aperture efficiencies of about 90% and low cross-polarization suppressions. In addition, 3 dB axial ratio beamwidths of the circularly polarized array can be up to 68° and 57° at two pitch planes of $\varphi = 0^{\circ }$ and 90°.