A dual-polarized metasurface with angle-selective character in elevation plane and stability in azimuth plane

In this paper, we propose a miniaturized angle-selective surface (ASS) with a unit cell size of about 0.3 λ. Compared with most previously published ASSs, the unit cell size is further reduced. The whole structure consists of two identical single-layer structures connected by an air gap. The single-layer structure contains identical bent cross-dipole structures and grid structures, printed on both sides of a dielectric substrate. The bent cross-dipole structures are connected by metallic vias. We reduce the TE-polarized transition bandwidth of bent cross-dipole structures printed on both sides of a dielectric substrate by adding grid structures around them in the single-layer structure, while maintaining structural miniaturization. Based on this single-layer structure, the double-layer structure with a suitable air gap can obtain a passband (|S₂₁| > −1 dB) for an incident elevation angle less than 15° and a stopband (|S₂₁| < −15 dB) for an incident elevation angle larger than 45° under TE-polarization at around 8.8 GHz. By introducing metallic vias to connect bent cross-dipole structures, we obtain the elevation angle selective character under TM-polarization while maintaining the elevation angle selective character under TE-polarization. For TM-polarization, its passband (|S₂₁| > −1 dB) is incident angles less than 10° and the stopband (|S₂₁| < −15 dB) is larger than 40°. Unlike most previously reported literature, this dual-polarized elevation angle selective character can be achieved not only within a given elevation plane but can also be extended to other elevation planes, thus demonstrating the advantages of a miniaturized unit cell. A prototype of our proposed ASS is fabricated and measured.