Reconfigurable Antennas and Their Applications

Reconfigurable antennas are capable of dynamically altering their frequency, polarization, and radiation properties in a controlled and reversible manner. They modify their geometry and behaviour to maximize the antenna performance in response to changes in their surrounding conditions. To implement a dynamical response, they employ different mechanisms such as PIN diodes, varactors, radio-frequency microelectromechanical systems (RF-MEMS), field effect transistors (FETs), parasitic pixel layers, photoconductive elements, mechanical actuators, metamaterials, ferrites, and liquid crystals. These mechanisms enable intentional distribution of current on the antenna surface producing reversible modification of their properties. This paper presents the design process and applications of reconfigurable antennas. The activation mechanisms of reconfigurable antennas, and their design and operation optimization are discussed. The latest advances on reconfigurable metamaterial engineering, and the current trends and future directions relating to reconfigurable antennas are reviewed. Finally, the applications of reconfigurable antennas in cognitive radio, multi-input multi-output (MIMO) systems, satellite communications, and biomedical devices are highlighted.