Left-handed metamaterials and theirs applications at microwave frequency

Left-handed metamaterials are artificial and periodical materials which both the permittivity and permeability are simultaneously negative.Because their group velocity and phase velocity are in the opposite directions,they have many strange properties.The article firstly introduces the concept and realization of the left-handed metamaterials,then advances in research on theories and experiments,hot topic,defect effect and other ways to realize negative refraction are discussed.Finally theirs potential applications are also prospected.