Wideband high-gain Fabry-Perot resonator antenna based on a water-based metasurface

This paper proposes a Fabry-Perot resonator antenna (FPRA) based on a water-based metasurface. First, the metasurface was designed to serve as a partially reflecting surface. Then, a patch antenna was developed as the feed antenna, which was integrated with the metasurface to form the proposed FPRA. The overall dimensions of the proposed FPRA are 2.6 × 2.6 × 0.61 λ03. Simulation results indicate that the FPRA achieves an operating bandwidth of 8.3-12.2 GHz. Within this band range, the gain is substantially enhanced compared to the feed antenna, reaching a peak value of 14.6 dBi, which is attributed to the high reflection amplitude of the water-based metasurface. Theoretical analysis reveals that, owing to the high permittivity of water, the water-based metasurface excites electric and magnetic dipole Mie resonances, and the metal backplane generates an additional electric resonance. These combined resonances modulate the scattering and coupling processes of waves in the resonant cavity, thereby expanding the FPRA bandwidth. Measured reflection coefficient (S₁₁) and gain align closely with simulations, and radiation pattern measurements confirm its directional characteristics. Furthermore, temperature measurements verify the thermal stability of the FPRA, supporting the simulation results. This design effectively balances gain and bandwidth in the FPRA through integration of a water-based metasurface that excites Mie resonances and electric resonance, offering a feasible solution for designing broadband high-gain FPRAs. Attributed to its directional radiation characteristics and thermal stability, this antenna holds promising potential for practical applications, including ground-penetrating radar and wireless communication.