A class of lightweight lenses and dielectric polarisation converters for high-gain wideband antennas

This PhD thesis addresses the characterisation of periodic layered dielectric structures, useful for the realisation of lightweight dielectric lenses and antennas designed to work at microwave frequency. Uniaxial anisotropic behaviours, related to the periodicity of thin layered structures, have been highlighted by a rigorous electromagnetic analysis which has been proven effective for the design of lightweight dielectric lenses useful for reducing the weight of radiating systems operating in the lower end of the microwave band. The developed theory has been successfully employed for the analysis and design of a large class of stacked disk dielectric lenses alternative to the massive ones currently used in applications. Experimental measurements performed on a lens antenna prototype equipped with a stacked-disk dielectric lens, whose weight is about 87% lighter than the corresponding massive benchmark lens, have been found to be in excellent agreement with the full-wave numerical simulations. Moreover, the same thin layered medium has been used to design polarisation converters useful to convert a linear polarisation into a circular one. Finally, thin layered dielectric lenses have been studied when suitable periodic metallic inclusions are introduced inside the lens body