ABSTRACT
This chapter presents several concepts and structures related to and useful for composite right-/left-handed (CRLH) antennas and the fundamental theory of CRLH transmission line (TL) metamaterials. It provides a concise summary of the fundamental characteristics of CRLH TL metamaterials. Two types of TLs may be considered to approach TL metamaterials: ideal infinitesimal TLs and artificial effective TLs. The ideal infinitesimal TL description provides a simple and insightful model that represents a good approximation of the actual artificial structure in its metamaterial range. CRLH TL metamaterials exhibit various properties that are beneficial not only to the radiation mechanism but also to other aspects of antennas. The chapter considers several variations of CRLH TL structures allowing multiband component and antenna applications by dispersion and impedance engineering. While conventional TL structures are fundamentally monoband due to the linear frequency dependence of their propagation constant, CRLH TL structures are inherently dual-band.
