What is Resonator

Metamaterials are artificially-engineered materials which possess unique properties not found in natural materials. The properties are derived from the structural designs of metamaterials and they allow the structure to manipulate electromagnetic waves and achieve desired responses in a certain frequency range. This chapter reviews past achievements, recent developments, and future trends on electromagnetic metamaterials in microwave regime. The chapter first briefly introduces electromagnetic metamaterials from a general prospect including the definition, historical overview, and classification of metamaterials. Furthermore, three selected applications of metamaterials which are microwave absorbers, sensors, and energy harvesters are discussed based on their operation principles, designs, and characteristics.