This book presentsoriginal findings on tunable microwave metamaterial structures, and describesthe theoretical and practical issues involved in the design of metamaterialdevices. Special emphasis is given to tunable elements and their advantages interms of feeding network simplification. Different biasing schemes and feedingnetwork topologies are presented, together with extensive prototypemeasurements and simulations. The book describes a novel, unique solution forbeam steering and beam forming applications, and thus paves the way for thediffusion of new agile communication system components. At the same time, itprovides readers with an outstanding and timely review of wave propagation inperiodic structures, tunability of metamaterials and the technologicalconstraints that need to be considered in the design of reconfigurablemicrowave components.