| Since the last past decades, the telecommunication industry has been demanding for a higher degree of integration and miniaturization of microwave components and improved performance characteristics. The elements driving these requirements are, for example, the necessity to integrate multiple functionalities in mobile communication devices, also the necessity to improve the energy efficiency consumption of those, or simply the necessity to enhance the amount and quality of information being transmitted. On the other hand, new technologies in communications such as software-defined radio (SDR) and Radio-Frequency (RF) switches implemented using micro-electromechanical systems (MEMS), present new challenges and opportunities for antenna design.;With all these new technological elements and in order to satisfy such stringent industry requirements in an optimal manner, it has come the necessity to conduct a multidisciplinary research that combines electromagnetism, microsystems, and communication theory. Within this framework, this dissertation focused on the design of high-performance low-cost and low-power adaptive wireless communications systems by means of using reconfigurable antennas. In particular, we investigate the interrelationship of the disciplines involved in a communication system in order to find additional room for further exploitation of the theoretical gains of Multiple-Input Multiple-Output (MIMO) wireless communication systems. As shown, important extra gains can be obtained as a result of combining the use of reconfigurable antennas and specifically designed Space-Time Coding schemes. It is also shown that once these extra gains are available they could be used to further improve the performance of current MIMO systems or they can be traded to reduce the implementation cost of current MIMO systems. Several novel reconfigurable antennas using MicroElectroMechanical Switches (MEMS) exploiting different types of diversity techniques and new coding schemes which were able to take advantage of the reconfigurable capabilities of these antennas were developed. The powerful capabilities of these systems (to improve capacity, diversity order, signal resistance to multipath, dramatic cost reduction, etc.) are demonstrated analytically, and also through simulations and measurements. These findings came as a result of a strong team work collaboration and through an efficient integration of the abovementioned disciplines, which otherwise would have not been obtained by working in an individual manner. |
