<p>Recent advances in electromagnetics introduced tools that enable the creation of arti-</p><p>cial electromagnetic structures with exotic properties such as negative material pa-</p><p>rameters. The ability to express these parameters has experimentally demonstrated</p><p>using passive metamaterial structures. These structures, based on their passivity and</p><p>resonant properties, are typically associated with high loss and signicant bandwidth</p><p>limitations.</p><p>Enhancing and further exploring novel electromagnetic properties can be done</p><p>through embedding active circuits in the constitutive unit cells. Active elements</p><p>are able to supplement the passive inclusions to mitigate and overcome loss and</p><p>bandwidth limitations. The inclusion of these circuits also signcantly expands the</p><p>design space for the development of functional metamaterials and their potential</p><p>applications.</p><p>Due to the relative diculty of designing active circuits compared with passive</p><p>circuits, using active circuits in the construction of metamaterials is still an under-</p><p>developed area of research. By combining the two elds of active circuit design and</p><p>metamaterial design, we aim ll the functional active metamaterial design space.</p><p>This document provides the basis for understanding the design and synthesis of</p><p>functional active metamaterials.</p><p>To provide necessary background matter, chapter 1 will function as an introduc-</p><p>tion chapter, discussing how active electromagnetic metamaterials are created and characterized. There are also several required design techniques necessary to suc-</p><p>cessfully engineer a functional active metamaterial. The introduction will emphasize</p><p>on linking metamaterial unit cell response with RF/analog circuit design with a brief</p><p>introduction to the semiconductor physics important to aid in the understanding of</p><p>the full active metamaterial design and fabrication process.</p><p>The subsequent chapters detail our specic contributions to the eld of func-</p><p>tional active RF metamaterials. Chapter 2 introduces and characterizes a meta-</p><p>material designed to have a tunable quality factor (tunable resonant bandwidth).</p><p>This metamaterial is essentially passive but demonstrates the transistor's versatility</p><p>as a combination of tunable elements, motivating the use of embedding transistors</p><p>in metamaterials. After establishing a simple application of a transistor in a pas-</p><p>sive metamaterial, chapter 3 outlines the design and characterization of an active</p><p>metamaterial exhibiting the properties of loss cancellation and gain. Chapter 4 in-</p><p>troduces another active metamaterial with the ability to self-adapt to an incident</p><p>signal. Within the self-adapting system, several complex RF circuit systems are</p><p>simulatenously developed and implemented such as a self-oscillating mixer and a</p><p>phase locked loop. Conclusions and additional suggested future research directions</p><p>are discussed in chapter 5.</p><p>There are also several appendices attached at the end of this document that are</p><p>meant to assist future graduate students and other readers. The additional topics</p><p>include the experimental verication of a passive magnetic metamaterial acting as a</p><p>near eld parasitic, the stabilization and measurement of a tunnel diode, a discussion</p><p>on the challenges of realizing active inductors from discrete components, and a basic</p><p>strategy for creating a non-volatile metamaterial. It is my aim for these appendices</p><p>to help provide additional inspiration for future studies within the eld.</p> / Dissertation
| Identifer | oai:union.ndltd.org:DUKE/oai:dukespace.lib.duke.edu:10161/9912 |
| Date | January 2015 |
| Creators | Barrett, John |
| Contributors | Cummer, Steven |
| Source Sets | Duke University |
| Detected Language | English |
| Type | Dissertation |
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