Design of Low-Profile Multi-Band Microwave Antennas and Components Using Metamaterial-Based Electromagnetic Bandgap Structures

Abstract

This thesis investigates applications of metamaterial-based electromagnetic bandgap structures, or MTM-EBGs. MTM-EBGs are uniplanar, compact, and often fully printable, making them ideal candidates for integration into planar topologies. This differs from many other metamaterial-based structures that have been proposed in the last couple of decades, many of which have shown great potential but have suffered from drawbacks including difficult integration into existing structures, poor operating characteristics, and expensive fabrication. Along with its useful physical and electrical properties, the recent development of MTM-EBG theory based on multiconductor transmission line techniques has rendered its properties predictable and designable, and this presents an excellent opportunity to fully explore how they can be used to improve performance and reduce the size of commonly used microstrip-based structures. In particular, embedding MTM-EBG unit cells directly into the metallic features of microstrip-based circuit components and antennas is an efficient way to produce multi-band operation without taking up any extra circuit board space. A general approach is taken that further allows the same technology to be used in a multitude of different applications. This is demonstrated with the design of many different circuit components, including dual- and tri-band microstrip stub filters, dual- and tri-band matching networks for arbitrary impedances, and a dual-band Wilkinson power divider. There are diverse uses in antenna applications as well; a dual-band antenna is first presented, followed by a simultaneously dual-band and dual-polarized antenna, as well as a GPS antenna with increased bandwidth. A tunable version of the dual-band dual-polarized antenna demonstrates further possibilities of what can be achieved with the MTM-EBG. Most devices were fabricated for comparison to simulation and excellent agreement is consistently seen between both sets of results, further suggesting that the MTM-EBG is a versatile and extremely useful tool for creating the next generation of miniaturized and multi-functional microwave systems.