Taming Fabry-Perot resonances in a dual-metasurface multiband antenna with beam steering in one of the bands

Metasurfaces are artificial materials that can provide properties not readily available in nature for the interaction with acoustic, elastodynamic, or electromagnetic waves. In Electromagnetics, metasurfaces allow particular functionalities to antennas, which in turn lately have been increasingly pushed to a multiband operation. To fully exploit metasurfaces' capabilities, the use of a metasurface reflector and a metasurface superstrate surrounding a radiating element in multiband antennas is interesting. However, such topology generally creates multiple reflections inside the formed cavity, known as Fabry-Perot resonances. Here we show that one should tame this phenomenon to use two parallel metasurfaces surrounding a planar radiating element. We present the conditions to obtain directive, multiband antennas under such circumstances. The concepts are validated with a compact device for 5G/4G/Wi-Fi 2.4/5/6E performing a beam steering in the 5G without disturbing the radiation patterns of the other bands. This device demonstrates that the functionalities of two metasurfaces may be exploited in a single design if the presented conditions are respected. We also anticipate our work to be a starting point for other studies in the wave domain. For example, compact, multiband, beam-steerable microphones or sonar transducers with two parallel metasurfaces could be investigated in the future.

Automated summary

Metasurfaces are artificial materials that provide unique properties for interacting with acoustic, elastodynamic, or electromagnetic waves. In the field of Electromagnetics, metasurfaces enable specific functions for antennas, particularly in the multiband operation. This study presents the conditions for obtaining directive, multiband antennas by using two parallel metasurfaces surrounding a planar radiating element, showing that the functionalities of metasurfaces can be effectively utilized in a single design. The findings are validated through a compact 5G/4G/Wi-Fi 2.4/5/6E device that demonstrates beam steering in the 5G band while maintaining the radiation patterns of other bands.