3. Electromagnetic Metamaterials and Metadevices

Electromagnetic metamaterials are engineered materials that exhibit controllable and tunable electromagnetic properties within a desired frequency range. They are usually made of periodic metallic resonant inclusions with dimensions much smaller than the operational wavelength. Since their introduction, many applications have been found from the radio (RF) and microwave frequency range up to the terahertz and optical ranges. One key advantage of electromagnetic metamaterial lies in their subwavelength resonators making them suitable for miniaturization of RF circuits and components. This chapter mainly addresses the electromagnetic metamaterials applied in the RF and the microwave frequency ranges, covering background theory, single- and double-negative metamaterials, magneto-dielectrics and zero-index metamaterials, LC-loaded transmission line metamaterials, electromagnetic bandgap, bi-isotropic and bi-anisotropic metamaterials, as well as microwave metamaterial-inspired metadevices.