Beam-Steerable Fabry–Perot Cavity Antenna With Mechanically Tunable Partially Reflective Surfaces for 6G Applications

A Fabry-Perot cavity antenna with beam steering capability enabled by the movement of a Partially Reflective Surface (PRS) is presented. Fabry-Perot cavities are commonly used due to their attractive properties, especially high gain and low profile. However, this configuration also presents design challenges when deployed for beam steering. Typically, beam steering is achieved by incorporating varactors into the metasurface unit-cells to locally modify the phase response with a controlled slope, which significantly complicates the implementation due to the feeding network introduction. To address this issue, the proposed solution involves designing the cavity in such a way that beam steering is achieved solely by moving the passive Partially Reflective Surface (PRS) along the cavity height direction. However, this approach leads to an increase in the Side Lobe Level (SLL) values, which worsens with progressively larger beam angles. To overcome the drawback, an aperiodic version of the PRS is opportunely introduced. By comparing the radiation patterns of the cavity equipped with the classical periodic metasurface against the aperiodic design, both gain preservation and SLL values reduction can be accomplished. Through accurate numerical simulations and experimental measurements acquired on fabricated prototypes, it emerges that the use of an aperiodic metasurface results in a SLL reduction ranging from 7.66 dB to 3 dB while maintaining the same gain level. The reduction in SLL up to 40° of beam tilting angle makes this antenna a suitable candidate for future 6G applications, in which beam scanning plays a critical role.