High-Isolation Tripolarized Metasurface Antenna for Access-Point Applications

In this communication, a high-isolation tripolarized metasurface antenna with a low profile is presented based on characteristic mode analysis (CMA) for indoor access-point applications. To realize triple polarization diversity, two differential-mode (DM) excitations and one multiport common-mode excitation are utilized to excite the shared metasurface. Based on the proposed feeding schemes, two pairs of degenerate characteristic modes (CMs) with broadside radiation and two CMs with radiation nulls at the broadside are selected for different polarizations. In addition, nonuniform unit patches and slot structures are elaborately introduced on the metasurface, which can tune the resonant frequencies of target CMs into the desired band. Finally, the proposed tripolarized metasurface antenna was fabricated and measured. Measured results show that the impedance bandwidth for $x$ - and $y$ -polarization ports can cover 3.4–3.8 GHz, and the $ {z}$ -polarization port can cover 3.4–4.0 GHz. The isolation in the operating band is better than 37 dB. Good diversity characteristics are also validated by the measured radiation patterns.