Antennes reconfigurables en diagramme de rayonnement à base de surfaces sélectives de fréquence / Reconfigurable Radiation Pattern Antennas Based on Frequency Selective Surfaces.

摘要

Reconfigurable antennas have recently formed a popular research topic. They are attracting the interest of many industry professionals. This is basically due to the growing demands for more functionality while occupying the same or even smaller physical volume. Using various antennas for wireless applications is no longer effective because having several antennas take too much space. Reconfigurable antennas are the best solution to provide a better performance in terms of flexibility, efficiency and combination of several electromagnetic spectrum applications. Frequency selective surfaces are exploited in many communication applications, especially in designing reconfigurable antennas due to their ability to control the electromagnetic field. A frequency selective surface is an important figure concept in reconfigurable antenna structures and has developed rapidly due to their unique properties in suppressing the surface wave propagation.udThe main topic of this research is to design new reconfigurable radiation pattern antennas with enhanced performance by using switchable frequency selective surfaces. The antenna consists of a central radiating source surrounded by switchable frequency selective surface unit cells to give the antenna beam, shaping capability to scan 360 degree in the azimuth plane. Novel switchable frequency selective surface unit cells with various structures are designed and their characteristics are compared in both the reflective and transparent states. The reconfigurable response is the basic concept in the antenna design. This is achieved by adding PIN diodes to the lines that will connect or disconnect the unit cells and transform the frequency selective surface to be either a reflective or a transparent surface. As a consequence, switching the frequency selective surface PIN diodes leads to control the antenna beam direction.udIn this thesis, two novel reconfigurable antennas with frequency selective surface unit cells are presented, each antenna works at a different frequency band. The switchable frequency selective surface utilized in the proposed antennas operates at different frequency bands. The research topic in this thesis includes investigations and techniques to increase the bandwidth and improve the radiation characteristics of the reconfigurable antennas by using new switchable frequency selective surface unit cells. Experimental results show the preference of the proposed antennas over those presented in the literature. Thus, two new reconfigurable antennas are implemented and their enhanced performances in terms of bandwidth are proven.