Reconfigurable antennas for MIMO applications: An overview

The advancement in wireless communication in recent years requires a telecommunication system which is capable of maximizing connectivity. Reconfigurable multiple-input multiple output (MIMO) antennas with the ability to radiate more than one radiation pattern at different frequencies and polarizations, significantly improves their channel capacity and throughput. Improved system gain and security are achieved by their capability to adapt to the changes in surrounding conditions, and to avoid noisy environments. In this paper, state-of-the-art reconfigurable antennas in terms of radiation pattern, frequency and polarization are presented. Reconfiguration is performed by using techniques such as radio-frequency microelectromechanical system (RF-MEMS), PIN diodes, varactors, photoconductive elements, physical alteration of the radiating structure, or by using material such as ferrites and liquid crystals. The effect of mutual coupling in MIMO system by integrating more than one reconfigurable antenna is discussed. An important observation is that mutual coupling effect reduction will optimize the performance of reconfigurable antennas.