A study on flexible-metamaterial absorption properties of electromagnetic wave according to the substrate bending

Abstract

Metamaterials are materials artificially created by human to have characteristics that do not exist in nature. Metamaterials have received a great deal of interests in a variety of applications. By changing the geometric parameters of meta-atom, the electromagnetic properties of designated medium can be precisely adjusted. Metamaterials have a wide range of applications such as cloaking, stealth aircraft, solar harvesting, wireless power transmission and perfect absorbers. Much effort has been devoted to the use of flexible substrates to overcome the limited application of hard metamaterial. In this thesis, I study flexible metamaterial absorbers operating in the GHz range based on a simple laminated structure with a rod-resonator and single circular- resonator structure. This structure consists of a top-layer periodically-arranged metallic resonators and a bottom metallic ground plane separated by a dielectric layer. Usually, the dielectric layer is made of FR-4. The MM perfect absorber investigated in this study consists of three metallic layers separated by two flexible PET layers. The top and the middle metallic layers are composed of rectangular and circular meta-atoms, respectively, and the bottom layer is a continuous metal plane. This structure is theoretically and experimentally proven to have broadband absorption. A study on the absorption characteristics in a bent condition using a flexible material is also presented. It is theoretically proven that a broadband absorption band appears in the bent state. The study in this thesis can be applied to the development of a flexible perfect absorber to work even in the bent conditions.