Liquid Based Reconfigurable Metasurface for Beam Steering Applications

Abstract

Beam steerable antennas find their applications in diverse areas such as satellite communication systems, AESA and PESA Radars and millimeter wave communication systems in order to maintain a continuous link between the nodes and avoiding obstacles in the path. Beam steering can be achieved using several different techniques such as classic mechanical steering methods, the use of lenses and reflectors, phased arrays, and modern metamaterial-based beam steering methods. The use of metamaterials and metasurfaces (MS) for beam steering is gaining importance as it offers a relatively simple and cost-effective alternate to the conventional techniques. It can lead to beam steering with relatively compact antenna size and use of fewer number of antenna elements. A Fabry-Pérot cavity is formed when a partially reflecting surface is positioned at an appropriate height over a planar antenna between antenna and the PRS which improves the gain of the antenna and if a phase gradient is created along the surface of the MS then the beam of the antenna can be steered away from broadside to an offset angle. In this thesis, a liquid-based reconfigurable metasurface (LB-RMS) based antenna for beam-steerable antenna application is presented. The proposed antenna system consists of a patch antenna resonating at 10 GHz and a tri-layer metasurface acting as a phase gradient partially reflective surface superstrate in the Fabry-Pérot cavity configuration. The metasurface consists of 2x2 3D printed liquid chambers inside polylactic acid (PLA) substrate that is sandwiched between two 16x16 cross-grid square patch conductive element array layers realized on a very thin dielectric substrate. Phase gradient is created by filling different chambers of the metasurface with distilled water. Eight different steering angles are realized by filling different chambers of the metasurface. A scan range of more than ±30º is achieved in both E-plane and H-plane, with a stable gain greater than 7.5 dBi. Whereas steering of ±17º is achieved in the EH-plane with a stable gain greater than 6.5 dBi. The proposed concept is validated by fabricating a prototype antenna and measuring its reflection coefficient and radiation patterns. The proposed approach is validated by the measured results, which accord well with the simulated results.