Design of isofrequency reconfigurable repeaters

Abstract

The advances in the communications systems has brought new requirements and challenges in terms of compactness and efficient systems that looking for increase the signal coverage area. The reconfigurable antennas are a promising solution for the communication systems when looking to improve the channel capacity and/or to extend the signal coverage. The main advantages of the reconfigurable antennas are the capabilities to change their frequency, polarization and radiation beam steering at a low cost. The reconfigurable antennas can be designed to operate in a determined changing environment keeping good electromagnetic characteristics. The design of reconfigurable RF repeaters is a relevant application of this reconfigurable antenna principle. This thesis is devoted to study and propose new repeater architectures in which a set of reconfigurable parasitic elements as part of the repeater are used for reducing the electromagnetic coupling between the Rx and Tx antennas. It is shown that the use of the parasitic elements as a reconfigurable mechanism gives the flexibility to adapt the repeater electromagnetic characteristics to changing environments while keeping a good system performance. The determination of the minimum number of parasitic elements is an important parameter and it is determined by a modal analysis to define the minimum number of parasitic elements able to fulfill specific repeater electromagnetic characteristics. In order to validate the analytical results, different reconfigurable repeater prototypes controlled electronically are manufactured. A reconfigurable repeater prototype that is using eight reconfigurable parasitic elements has been designed for operating at different scatterer environments. The repeater reconfigurable capabilities are studied to evaluate the repeater performance in realistic indoor locations. Finally, in order to obtain a repeater with reconfigurable frequency isolation capabilities between the Rx and Tx antennas over a wide frequency range, a repeater prototype based on a pixeled layer as reconfigurable mechanism has been designed and measured.