PhDThis thesis aims to study the design and optimization of Metamaterial Ferrite (metaferrite) structures for antenna applications. These techniques are primarily focused on various forms of the Genetic Algorithm methods. The motivation for this is to provide generic design tools that will be transformed to the industry for further development of the field, especially for the design of low profile antennas. Several possible applications of this technology have been investigated. Antenna size reduction on platforms with low radar cross sections (RCS) is essential for many practical applications and through metamaterials antennas and associated platforms can be co-designed and optimized. Metamaterials are artificially designed electromagnetic materials or structures which possess properties not existing in nature. Examples include left-handed materials with simultaneous negative permittivity and permeability and zero index media etc. In this project we are particularly interested in the development of two-dimensional metamaterials or “metasurfaces” with the same function as conventional magnetic or magneto-dielectric materials. Ferrites, often used in the design of non-reciprocal microwave devices such as isolators and circulators, are bulky, heavy and lossy for antenna applications. Impedance matched media have been widely used in the design of low-profile antennas and radar absorbers with losses added. Metamaterials and metasurfaces can mimic ferrites at microwave frequencies. These “metaferrites” have attracted interest from academic and industrial communities. In this thesis, a genetic algorithm (GA) is developed incorporated with commercial electromagnetic modelling tools, namely CST Microwave Studio. Antennas with ferrites have been characterized and unique functionalities have been explored. Sample structures have been made based on conventional printed circuit board (PCB) and ink-jet printing technologies. In addition, these structures have been used to augment U-slot patch antennae and the advantages of doing so have been measured. In addition, a new concept of hyperuniform randomness has been applied to the design of metasurfaces with the intention of comparing metaferrite performance with an alternate method aimed at similar goals. It has been demonstrated by numerical simulations that superior properties such as RCS reduction can be achieved with the consideration of trade-offs between the modelling complexity and the device performance.BAE systems and Engineering and Physical Sciences Research Council
