Thesis (M.S.)--Ohio University, August, 1996. / Title from PDF t.p.

Thesis (M. S.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2009. / Committee Member: John Cressler; Committee Member: John Papapolymerou; Committee Member: Joy Laskar; Committee Member: Thomas Morley; Committee Member: William Hunt.

Dielectric properties play an influential role in the development of medical devices. Understanding the behavior of these properties and how they respond to external stimuli, such as heat, over an extended frequency has yet to be researched. The focus of this study is to examine the impact of temperature on dielectric properties from 500 MHz to 10 GHz in order to better match the antenna properties of medical applications to the dielectric properties of biological tissue in question; more specifically, microwave ablation, microwave hyperthermia, and thermal modeling of brown adipose tissue’s metabolic processes. The dielectric properties of biological tissue samples from porcine lung, liver, heart, skin, fat, and muscle as well as brown adipose tissue and white adipose tissue from rat have been tested. These results have then been used to develop medical applications involving microwave antennas.

Millimeter waves, corresponding to the frequency range 30 to 300 GHz, have characteristics which make them ideal for many applications. Antennas at these frequencies have the advantage of reduced size and weight and can be fabricated as an integral part of the system they are used in. Millimeter wave microstrip antennas have been extensively researched over the past decade. The purposed of this report was to build and test 35 GHz microstrip antennas as well as put into operation a high voltage klystron power supply, Micro-Now Model 756. The antennas were fabricated and tested in the lab and the results obtained are reported. The operation of the Model 756 power supply is also outlined in detail.

by Chong Man Yuen. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1997. / Includes bibliographical references (leaves 125-128). / Dedication / Acknowledgements / List of Figure / List of Table / List of Appendix / Chapter 1. --- Introduction / Chapter 1.1 --- Background / Chapter 1.2 --- Ultra-Wide Band Antenna / Chapter 1.3 --- Finite Element Method (FEM) / Chapter 1.3.1 --- Domain Discretization / Chapter 1.3.2 --- Formulation of Variational Method / Chapter 2 --- Theory / Chapter 2.1 --- Variational principles for electromagnetics / Chapter 2.1.1 --- Construction of Functional / Chapter 2.2 --- Artificial Boundary / Chapter 2.2.1 --- Absorbing Boundary Conditions / Chapter 2.2.2 --- Perfectly Matched Layer (PML) / Chapter 2.3 --- Edge Basis Function / Chapter 2.4 --- Slotline Analysis / Chapter 3 --- Implementation of FEM / Chapter 3.1 --- Formulation of Element matrix / Chapter 3.2 --- Mesh Generation / Chapter 3.3 --- Assembly / Chapter 3.4 --- Incorporation of Boundary Conditions / Chapter 3.5 --- Code Implementation / Chapter 4 --- Finite Element Simulations / Chapter 4.1 --- Slotline / Chapter 4.2 --- Artificial Boundary of the domain / Chapter 4.3 --- Slotline Taper Junction / Chapter 4.4 --- Slotline Bowtie Junction / Chapter 5 --- Conclusion / Appendix A1 / Appendix A2 / Appendix A3 / Bibliography

Transmitarrays have been shown to be viable architectures for achieving high-directivity reconfigurable apertures. The existing work on reconfigurable transmitarrays is sparse, with only a few experimental demonstrations of reconfigurable implementations. Furthermore, of the designs that have been presented, different approaches have been proposed, but the advantages and drawbacks of these approaches have not been compared. Therefore, in this thesis we present a systematic study of the different approaches to designing reconfigurable transmitarrays, and present designs following these approaches with experimental validation. First, we investigate the distributed-scatterer approach, which is modeled with layers of identical scattering surfaces. We characterize the beamforming capabilities and then present a Method of Moments technique for analyzing and optimizing designs that follow this approach. Then, we present experimental results for a unit cell with varactor-loaded dipoles following this approach. From these results, we demonstrate that the structure thickness following this approach is problematic for beamforming applications. Taking the coupled-resonator approach, we next present a slot-coupled patch design that is significantly thinner and easier to fabricate than designs that follow the first approach. Implementing this design in a fully reconfigurable transmitarray, we demonstrate two-dimensional beamforming. An advantage of this design is that it can also operate as a reflectarray. Next, following the guided-wave approach, we present a transmitarray design that uses a bridged-T phase shifter and proximity-coupled differentially-fed stacked patches. Not only does this design not require vias, it is has a large fractional bandwidth of 10 percent, which is unprecedented in reconfigurable transmitarrays. Implementing this design in a full transmitarray, we experimentally demonstrate reconfigurable two-dimensional beamsteering, as well as shaped-beam synthesis. The main contributions of this thesis are two-fold. First, we thoroughly and systematically compare the transmitarray approaches, which has not been previously done in literature. Secondly, we experimentally demonstrate a reconfigurable array design that achieves better bandwidth, scan angle range, and beam-shaping capability, than existing designs, with reduced fabrication complexity and physical profile.

Transmitarrays have been shown to be viable architectures for achieving high-directivity reconfigurable apertures. The existing work on reconfigurable transmitarrays is sparse, with only a few experimental demonstrations of reconfigurable implementations. Furthermore, of the designs that have been presented, different approaches have been proposed, but the advantages and drawbacks of these approaches have not been compared. Therefore, in this thesis we present a systematic study of the different approaches to designing reconfigurable transmitarrays, and present designs following these approaches with experimental validation. First, we investigate the distributed-scatterer approach, which is modeled with layers of identical scattering surfaces. We characterize the beamforming capabilities and then present a Method of Moments technique for analyzing and optimizing designs that follow this approach. Then, we present experimental results for a unit cell with varactor-loaded dipoles following this approach. From these results, we demonstrate that the structure thickness following this approach is problematic for beamforming applications. Taking the coupled-resonator approach, we next present a slot-coupled patch design that is significantly thinner and easier to fabricate than designs that follow the first approach. Implementing this design in a fully reconfigurable transmitarray, we demonstrate two-dimensional beamforming. An advantage of this design is that it can also operate as a reflectarray. Next, following the guided-wave approach, we present a transmitarray design that uses a bridged-T phase shifter and proximity-coupled differentially-fed stacked patches. Not only does this design not require vias, it is has a large fractional bandwidth of 10 percent, which is unprecedented in reconfigurable transmitarrays. Implementing this design in a full transmitarray, we experimentally demonstrate reconfigurable two-dimensional beamsteering, as well as shaped-beam synthesis. The main contributions of this thesis are two-fold. First, we thoroughly and systematically compare the transmitarray approaches, which has not been previously done in literature. Secondly, we experimentally demonstrate a reconfigurable array design that achieves better bandwidth, scan angle range, and beam-shaping capability, than existing designs, with reduced fabrication complexity and physical profile.

Thesis (Ph. D.)--University of Missouri--Rolla, 2007. / Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed November 16, 2007) Includes bibliographical references (p. 134-136).

Thesis(M.S.)--Auburn University, 2006. / Abstract. Vita. Includes bibliographic references (p.47-50).

Thesis (Ph. D.)--University of Texas at Austin, 1998. / Vita. Includes bibliographical references (leaves 86-94). Available also in a digital version from Dissertation Abstracts.