Realization of Split Beam Antenna Using Transmission-Type Coding Metasurface and Planar Lens

Abstract

In this paper, a novel compact split beam configuration of the transmission-type coding metasurface (MS) in combination with the planar lens and the patch antenna is presented. In the first stage, the spherical electromagnetic waves originating from the patch antenna are converted to plane waves by placing the planar MS lens at a height of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.55\lambda _{0}$ </tex-math></inline-formula> above the antenna aperture. This lens enhances the radiation along the broadside direction resulting in high-gain operation. Furthermore, a concept of the digital metamaterial is adopted by realizing 1 bit transmission-type coding MSs, capable of splitting the aforementioned high-gain beam pattern. These digital MSs (DMSs) have two different types of metaatoms with phase responses of 0 and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\pi $ </tex-math></inline-formula> , corresponding to two basic digital elements 0 and 1, respectively. The assembly of these metamaterial bits (either 0 or 1) leads to a lattice of size <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$D \times D$ </tex-math></inline-formula> . The proper spatial mixture of these lattices with different sequences facilitates different elemental metamaterial-pattern resulting in multiple-lobe radiation patterns, which are angularly oriented and symmetrical to the antenna axis. The designed planar lens and the DMS with the individual thickness of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.057\lambda _{0}$ </tex-math></inline-formula> are placed in the near field of antenna leading to an overall compact configuration with a total height of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.08\lambda _{0}$ </tex-math></inline-formula> . The aforementioned beam splitting using the proposed configuration is also validated both quantitatively (mathematically) and qualitatively (through the simulation and the measurement) for different types of DMSs.