Microwave Metamaterial Circuits

Abstract

Electromagnetic metamaterials are usually defined as artificial effectively homogeneous structures with specific properties, that cannot be observed in natural materials. Different approaches are used for a description of the fundamental electromagnetic properties of metamaterials and the practical realization of these materials as well. Among them, the transmission line (TL) approach gives an efficient design tool for microwave applications. A conventional TL with the positive phase velocity behaves as a right‐handed transmission line (RH TL). An artificial RH TL is formed as a ladder network of capacitors connected in shunt and series inductors. The dual transmission line is designed as a ladder network of inductors connected in shunt and series capacitors. This line has the negative phase velocity and is referred to as the left‐handed transmission line (LH TL). A backward wave propagates along the LH TL, which can be considered as the one‐dimensional metamaterial. A more general model of an LH TL is the composite right/left handed (CRLH) structure. Many interesting features can be observed when a combination of RH TL and LH TL is used. The most important feature of the LH and RH TLs is that their dispersion characteristics are described by different equations. That can be used for many beneficial applications. Different combinations of LH and RH TLs are used for a design of miniature microwave devices with improved performance and enlarged functionality. Among them are microwave resonators and filters, microwave power divider/combiners, and microwave phase shifters. Multiband devices and tunable and reconfigurable microwave circuits are also under consideration.