Application of Metamaterials to the Optimization of Smart Antenna Systems

Recent developments in engineered electromagnetic materials called metamaterials have opened the door to a whole new class of devices and improved performance in existing systems using electromagnetic properties that are beyond those found in nature. These materials can be designed to have spatially varying anisotropic electromagnetic properties which include positive and negative permeability and permittivity values. The objective of this research was to explore how these newly available degrees of freedom in material parameters can be exploited to improve the performance of smart antenna systems.;In this dissertation, we examined adaptive null/beam forming phased array systems in the presence of metamaterial superstrates. While these systems have been studied extensively from a system engineering point-of-view, understanding the system from a material engineering prospective will help define the role that these new materials can play in these systems and how they maybe designed to enhance the overall system performance. One specific area further explored is how to steer the available performance of these systems, preferentially to regions of the scan space where interferers/jammers are most likely to occur, thus improving the system's anti-jamming or interference mitigation capabilities. New performance gains can also be suggested by including the behavior of sources and accompanying material properties in the transformations optics methodology to modify space through material design. This can be achieved using source transformations.;Chapter 1 introduces the basic theory of phased array systems and radomes, background of previous work carried out, Controlled Radiation Pattern Antennas, Global Position Systems and a short overview of transformation optics and metamaterials. In Chapter 2, we present analytical, ray tracing and full-wave electromagnetic simulation models to analyze the effect of a quasi-optical element on the array performance. We use these models to show how changing geometry and materials characteristics of the radome affects the density and distribution of nulls for a given linear phased array. We also analytically showed how the concept of scan space null density is related to the overall system performance through null steepness (signal coverage), noise susceptibility and Signal-to-Interference-plus-Noise Ratio. Chapter 3 discusses different strategies such as optimization of material parameters to design a practical quasi-optical lens and presents results for a simple device design that was fabricated and experimentally measured. In Chapter 4, we show using theoretical simulations how source transformations can be used to modify the radiation patterns of antennas and how this might be applied in phased array systems for enhancing existing capabilities. In Chapter 5, achievements of the research and directions for future work are discussed.