Issues of applications of metamaterials to miniaturization of antennas

With the significant reduction of wireless devices, miniaturized antennas are strong desired and one of key market drivers. In general, we can reduce the size of antennas in several ways, for instance, optimizing the shapes/patterns/structures of radiators, introducing natural or artificial materials as loading/substrates, as well as applying RF components/circuits to the antennas. Metamaterials, namely artificial materials (in general, periodic structures with special features such as negative-refractive-index) have been proposed to create new EM phenomena and enhance performance of RF components and antennas for years [1–3].