Composite Right/Left-Handed Transmission Line Metamaterial-Inspired Small Antenna Design: Topologies, reconfigurability, and applications

With the development of modern wireless communication systems, the demand for high-performance, multifunctional, low-cost, and compact antennas has been increasing substantially. The greatest challenge when designing this type of antennas is the tradeoff between complexity and performance. More design freedom is therefore highly desired. As an important subtype of metamaterials, composite right/left-handed transmission line (CRLH-TL) metamaterials have paved the way to achieve this compromise. In this review article, first, the possible CRLH-TL topologies that can be used in antenna design are discussed, involving structures based on not only Cartesian but also polar coordinates and 2D CRLH-TLs. The reconfigurability of the CRLH-TLs in terms of operating mechanisms, reconfigurability methods, and control techniques is then reviewed. By applying these structures to electrically small antenna design, considerable extra design freedom can be obtained. In the literature, a whole range of novel antennas with remarkable performances have been reported, holding great potential for various applications, such as wireless body area networks (WBANs), multiple-input, multiple-output (MIMO), radio-frequency identification devices (RFIDs), wireless power harvesting, and so on. All of these applications are briefly discussed.