| Antenna miniaturization and bandwidth improvements have always been a challenge for antenna engineers. Antenna miniaturization approaches generally fall into two basic categories, namely, material loading and shape design. However, by and large, material loading has been limited to uniform substrates (from a select set of constants and thicknesses). This is due to the limited availability of material constants and associated fabrication techniques for antenna substrates, particularly non-uniform.; With this in mind, the focus of this dissertation is to introduce antenna designs beyond uniform substrates and superstrates and to consider materials which entail arbitrary dielectric distributions. Such materials are manufactured using novel fabrication techniques and lead to a new class of composites whose properties may not be the same as those of the original constituent components. Such materials are often referred to as metamaterials (meaning "after or beyond materials"), and provide original design possibilities. More specifically, because they allow additional degrees of freedom, they can yield miniaturizations with concurrent bandwidth enhancements that are far beyond those available today.; In this dissertation we explore the potential of metamaterials in antenna design by introducing material modifications in the overall volume of the antenna with particular emphasis on high contrast low loss ceramics developed from a combination of two or more material components. Emphasis is given on UHF antennas since a great need exists in miniaturizing such antennas. Specifically, by looking at various novel metallic and material texture designs, we pursue a design process that achieves larger bandwidth using smaller size aperture than ever before. Among the examples considered are textured substrates for patch antenna designs, and selected implantation of materials in the design of bow-tie and cavity-backed UHF apertures. |
