Microwave Metamaterials

Metamaterials (MTMs) are artificial materials composed of subwavelength particles, which are engineered to achieve various electromagnetic (EM) responses. Since the first practical realization and experimental verification of MTMs by Pendry et al. in the late 1990s, great efforts have been made in theoretical study as well as practical utilizations. Among them, the effective medium theory provides a basis for the description as well as an accurate method for the design of MTMs, and leads to the development of many novel devices with interesting functionalities. With the employment of transformation and geometric optics, more high-performance engineering applications have been realized using MTMs. Recently, the concept of metasurfaces has been proposed, which further promotes the practical applications of advanced MTMs. Herein, the effective medium theory is first introduced. After that, typical devices and applications based on conventional bulk MTMs and newly-conceived metasurfaces are summarized to demonstrate the flexible capability of microwave MTMs in the manipulation of EM waves.