Agile Beamwidth Control and Directivity Enhancement for Aperture Radiation With Low-Profile Metasurfaces

Uniaxial anisotropic near-zero metamaterials have been utilized to design 2-D apertures with beamwidth control and directivity enhancement. Theoretical study shows that the two principal plane beamwidth of an aperture can be significantly reduced, both independently and simultaneously. With two proposed simplified loading models as a transitional structure, the 3-D bulk metamaterials are eventually reduced to 2-D metasurfaces with an array of metallic inclusions. In the design procedure, a critical equivalence between 2-D metasurfaces and 3-D metamaterial slabs with a specific thickness is discussed and validated. Measured results of the fabricated prototypes have demonstrated that a final aperture design loaded with low-profile electric LC and split-ring resonator metasurfaces has a substantial beamwidth reduction on both principal planes and a 4.32 dBi gain enhancement around the operating frequency.