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Amonson, Michael D.Multiple Charge Carrier Species and Their Effects in Photorefractive Two-Beam Coupling in Potassium Niobate
Master of Science (M.S.), University of Dayton, 2017, Electro-Optics
This thesis reports on an experiment to measure charge carrier contributions from different Fe species and their effects on beam coupling efficiency using self-pumped counter-propagating two-beam coupling in iron-doped potassium niobate KNbO3:Fe. We used multiple continuous wave lasers operating across the visual spectrum to explore charge carrier creation from various transitions. Photorefractive grating formation data was acquired and analyzed using a new theoretical model which incorporates multiple charge carrier species. Initial analysis provides supporting evidence of a multiple charge carrier model and presents new insights about the effects of various charge carriers on the photorefractive periodic space-charge fields.

Committee:

Dean Evans (Advisor)

Subjects:

Electromagnetism; Materials Science; Optics; Physics

Keywords:

Potassium Niobate; Iron Doped Potassium Niobate; Photorefractive; Multiple Charge Carriers; Two-Beam Coupling

Smith, Nathanael JNovel Closed-Loop Matching Network Topology for Reconfigurable Antenna Applications
Doctor of Philosophy, The Ohio State University, 2014, Electrical and Computer Engineering
As technology progresses, mobile devices such as laptops, tablets, cell phones, and two-way radios have become smaller in size. Consequently antennas become electrically small to fit inside aggressive packaging requirements with rapidly changing real and imaginary impedances. As such, these antennas are very narrow in bandwidth with high-Q and input impedance which is very sensitive to environmental effects. The radiation efficiency of the device is drastically decreased as the antenna is detuned and signal quality is degraded. As the number of mobile devices we use increases, adaptive impedance tuners have and will become a bigger necessity, especially as more radios are integrated into a single device. This dissertation presents novel improvements to closed loop tuning topologies from a system level perspective addressing impedance tuners, sensing techniques, and how they apply to different antennas. The biggest design hindrance to impedance tuners are losses due to small signal resistance, and loss due to circuit resonances and radiation. A detailed explanation of these loss mechanisms is developed, providing designers with the knowledge to minimize the impact of said losses and improve system efficiency. By exploiting loss mechanisms, a novel small and low cost VHF impedance synthesizer is presented to characterize impedance tuners in load pull measurements. With full consideration of circuit loss mechanisms, a new directional coupler based tuning topology is presented. Traditional tuning topologies aim to minimize |S11| of the matching network. As demonstrated in this work, such a method has the potential to maximize losses in the circuit, especially in multi-stage tuners. Alternative directional coupler based topologies are presented which maximize the system transducer gain. Furthermore, a novel method of sensing a tuned state through the use of a near field probe that detects far field radiated power is introduced. A design guide is detailed with several examples for use with different types of antennas. Concepts developed in this dissertation are demonstrated in an adaptive tuning system where mechanical means of tuning is applied as a low loss tuner. An electrically small monopole is tuned using the power sensor to provide feedback over a 2.2:1 bandwidth (180 to 400MHz) where at the lowest tunable frequency the antenna is 1/11.3 wavelengths in size.

Committee:

John Volakis, Professor (Advisor); Chi-Chih Chen, Professor (Committee Member); Chris Baker, Professor (Committee Chair)

Subjects:

Electrical Engineering; Electromagnetics; Electromagnetism

Keywords:

adaptive impedance tuning; tunable circuits and devices; Automatic tuning topology; impedance matching; load impedance tuner; impedance synthesizer; near-field probe; far-field power sensor; closed-loop tuning; antenna feed-back; small antennas

Daram, Prasanna KumarNon-Contact, Antenna-Free Probes for Characterization of THz Integrated-Devices and Components
Master of Science in Engineering (MSEgr), Wright State University, 2014, Electrical Engineering
The most common technology for electrical characterization of THz devices is DC-coupled contact probes. In this Masters thesis, a non-contact, antenna-free probe is analyzed for characterizing THz devices and integrated circuits. The probe consists of on-chip receiving or transmitting THz photomixers in a co-planar waveguide environment. Our probes are coupled to a CPW-embedded DUT by polarization current rather than conduction current and then down converted in frequency to baseband by an optically pumped photomixer. We investigated probe performance through numerical simulations using High Frequency Structure Simulator (HFSS) carried up to 1 THz and yielded a broadband design with DUT to photomixer promising coupling efficiency above -20 dB with an operational frequency range of 700 GHz between 0.3 and 1 THz, and the average increase in the coupling is ~ 8dB compared to the previous design. Several integrated-circuit techniques are necessary to achieve this performance, such as symmetric side-coupled CPW (SSC CPW), ¼ wave backshort impedance-matching. These will be addressed along with design trade offs.

Committee:

Elliott R. Brown, Ph.D. (Advisor); Mike Saville, Ph.D. (Committee Member); Yan Zhuang, Ph.D. (Committee Member)

Subjects:

Electrical Engineering; Electromagnetism

Keywords:

THz Photomixers Symmetric Side-Coupled CPW

Cumby, Brad LeeLaplace-Pressure Actuation of Liquid Metal Devices For Reconfigurable Electromagnetics
PhD, University of Cincinnati, 2014, Engineering and Applied Science: Electrical Engineering
Present day electronics are now taking on small form factors, unexpected uses, adaptability, and other features that only a decade ago were unimaginable even for most engineers. These electronic devices, such as tablets, smart phones, wearable sensors, and others, have further had a profound impact on how society interacts, works, maintains health, etc. To optimize electronics a growing trend has been to both minimize the physical space taken up by the individual electronic components as well as to maximize the number of functionalities in a single electronic device, forming a compact and efficient package. To accomplish this challenge in one step, many groups have used a design that has reconfigurable electromagnetic properties, maximizing the functionality density of the device. This would allow the replacement of multiple individual components into an integrated system that would achieve a similar result as the separate individual devices while taking up less space. For example, could a device have a reconfigurable antenna, allowing it optimal communication in various settings and across multiple communication bands, thus increasing functionality, range, and even reducing total device size. Thus far a majority of such reconfigurable devices involve connecting/disconnecting various physically static layouts to achieve a summation of individual components that give rise to multiple effects. However, this is not an ideal situation due to the fact that the individual components whether connected or not are taking up real-estate as well as electrical interference with adjacent connected components. This dissertation focuses on the reconfigurability of the metallic component of the electronic device, specifically microwave devices. This component used throughout this dissertation is that of an eutectic liquid metal alloy. The liquid metal allows the utilization of both the inherent compact form (spherical shape) of a liquid in the lowest energy state and the fact that it is resilient and shapeable to allow for reconfigurability. In this dissertation, first background information is given on the existing technology for reconfigurable microwave devices and the basic principles that these mechanisms are based upon. Then a new reconfigurable method is introduced that utilizes Laplace pressure. Materials that are associated with using liquid metals are discussed and an overall systematic view is given to provide a set of proof of concepts that are more applied and understandable by electronic designers and engineers. Finally a novel approach to making essential measurements of liquid metal microwave devices is devised and discussed. This dissertation encompasses a complete device design from materials used for fabrication, fabrication methods and measurement processes to provide a knowledge base for designing liquid metal microwave devices.

Committee:

Jason Heikenfeld, Ph.D. (Committee Chair); Michael D. Dickey, Ph.D. (Committee Member); Christopher Tabor, Ph.D. (Committee Member); Chong Ahn, Ph.D. (Committee Member); Andrew Steckl, Ph.D. (Committee Member)

Subjects:

Electromagnetism

Keywords:

Liquid metal;Laplace pressure;Microfluidics;Reconfigurable Antenna;Galinstan

Uckert, KyleHigh Temperature Resistivity and Hall Effect Measurements of Conductive and Semiconductive Thin Films
Bachelor of Science (BS), Ohio University, 2010, Astrophysics
Conducting high-temperature Hall effect measurements of various semiconductors and metals allows one to determine information regarding the carrier concentration, carrier type, and resistivity of a sample as it varies with temperature. This has an especially interesting application for military purposes and within the automotive and aerospace industries. Currently, the structural design of vehicles and industrial apparatuses is severely restricted by the limited understanding of the properties of semiconductors at high temperatures. In order to test these properties an apparatus capable of housing a conducting or semiconducting thin film sample and withstanding 1100°C with a magnetic field acting perpendicular to the direction of the flow of charge has been designed and constructed. By understanding the more fundamental characteristics of these thin films at high temperature, it may be possible to make improvements on already existing electrical components, or develop new applications entirely.

Committee:

Martin Kordesch, PhD (Advisor)

Subjects:

Electromagnetism; Materials Science; Physics

Keywords:

ITO; Hall effect; resistivity; platinum; semiconductive; thin film; high temperature;

Lee, Hwa OkNumerical Modeling of Electromagnetic Well-Logging Sensors
Doctor of Philosophy, The Ohio State University, 2010, Electrical and Computer Engineering

In this dissertation, we develop time-domain numerical algorithms to model the electromagnetic responses of logging-while-drilling (LWD) tools in complex Earth formations. The increasing need to model complex features of realistic formations calls for the development of increasingly sophisticated and flexible numerical algorithms. The new algorithms proposed in this dissertation are based upon the finite-difference time-domain (FDTD) framework. FDTD is highly suited for the purposes because it is matrix-free and discretizes Maxwell's equations directly on a discrete grid of points, providing unparalleled flexibility in handing complex Earth media.

In this dissertation, we employ FDTD directly in three-dimensional cylindrical coordinates, which suppress the staircasing error incurred when discretizing the cylindrical tool geometry, while keeping the method matrix-free. Another limitation of FDTD is its conditionally stability, which limits the maximum time increment that can be used on the marching-on-time algorithm. This maximum time increment is set up the Courant criterion and is proportional to the spatial cell size used. The Courant criteria leads to oversampling in time whenever a very fine spatial discretization is required. This implies excessive computation times. As an alternative to FDTD, the alternating direction implicit (ADI)-FDTD method offers unconditionally stability with little extra computation effort, which includes the need to solve a tridiagonal system at each time-step.

In order to properly truncate the computational domain in the modeling of open-space problems, an absorbing boundary condition is also needed. Here, a convolutional perfectly-matched-layer (CPML) absorbing boundary condition based on a complex frequency shifted (CFS) stretching and recursive convolution is developed and implemented in the 3-D cylindrical ADI-FDTD algorithm. Because the time step size in the ADI-FDTD simulations cannot be increased arbitrarily due to numerical errors such as splitting errors and numerical (grid) dispersion, a complex-envelope (CE) technique is further incorporated into the ADI-FDTD algorithm. The cylindrical CE-ADI-FDTD makes it possible to reduce the overall computation time while maintaining the dispersion error at reasonable levels.

In order to further reduce the computational time, this dissertation also develops a heterodyne approach for time-domain simulations in highly refined grids. The proposed approach is based on a complex-envelope algorithm with a carrier frequency and a complex-valued FDTD algorithm with a shifted spectrum centered at a higher simulation frequency. This corresponds to a shorter period and faster convergence for narrowband simulations. In practice, the logging tool axis is frequently misaligned with the borehole axis due to gravitational pull effects and/or mechanical vibrations. In addition, Earth media exhibits anisotropy which is represented by a full conductivity tensor during deviated drilling. The study of anisotropy and eccentricity is important for correct interpretation of logging data. A new locally-conformal (LC) FDTD based on deriving effective anisotropic tensor conductivities for partially-filled grid cells, composed of an isotropic conductive region representing the borehole and an anisotropic conductive region representing the Earth formation, is developed using a quasi-static approximation. The new LC-FDTD algorithm allows for employing coarser grids than conventional FDTD, and hence for obtaining faster simulation times, for a given required accuracy level.

Committee:

Fernando L. Teixeira, PhD (Advisor); Roberto G. Rojas, PhD (Committee Member); Joel T. Johnson, PhD (Committee Member)

Subjects:

Electromagnetism

Keywords:

numerical modeling; FDTD; well-logging

Hendricks, Jessica MarieELECTROMAGNETIC CHARACTERIZATION OF AF455 WITH DNA-CTMA IN SOLVENT BLENDS
Master of Science (MS), Wright State University, 2013, Physics
This work studies the electromagnetic properties of AF455, a two photon dye, DNA bound with cetyltrimethyl ammonium (CTMA), in liquid solvent blends for use in thin film optical filters. The liquid properties of the materials are believed to be transferred to the films. The solvent blends used are ratios of toluene (T) and dimethyl sulfoxide (DMSO). The complex permittivity and permeability of the samples are measured using the short open coaxial line technique in the frequency range of 1.0 x 107 Hz to 2.0 x 109 Hz. In this frequency range, AF455 does not act as a two photon absorber. The results show there is an interaction between AF455 and DNA-CTMA that increases the real permittivity for two solvent blends (50-50, and 60-40, T-DMSO). There is also a clear conformation change in the samples with the solvents and DNA-CTMA only that is observed in the real permittivity. In the 70-30 blend, the conformation of the DNA-CTMA is a clear helix. In the samples with less toluene the conformation of the DNA-CTMA is a coil structure. The imaginary permittivity increases with the addition DNA-CTMA. The real and imaginary permeability are constant across all samples.

Committee:

Gregory Kozlowski, Ph.D. (Advisor); Angela Campbell, Ph.D. (Committee Member); David Stewart, Ph.D. (Committee Member); Douglas Petkie, Ph.D. (Committee Member)

Subjects:

Electromagnetics; Electromagnetism

Keywords:

AF455, toluene, dimethyl sulfoxide, DNA, CTMA, optical properties, relative permittivity, relative permeability, two photon dye

Meyendorf, RobertNondestructive Determination of Case Depth in Surface Hardened Steels by Combination of Electromagnetic Test Methods
Doctor of Philosophy (Ph.D.), University of Dayton, 2011, Materials Engineering
The objective of this study was to improve the accuracy and reliability of nondestructive case depth determination from the current state of the art for application in an industrial environment. In the current state of the art only a single test method is used. In the present study simultaneous measurements were made with four independent electromagnetic test methods. The test methods used were measurement of tangential component of the magnetizing field, magnetic Barkhausen noise analysis, incremental permeability and multi-frequency eddy current measurement. The methods have different penetration depth and sensitivity to microstructure variations, thus complementing each other. The method that measures the tangential component of the magnetizing field is the only method that has a sufficiently deep depth of penetration to be useful for case depth testing. However, measurements with this method can be distorted by material variations other than the case depth. This distortion can be corrected by combining the measurement of the tangential component of the magnetizing field with a method that is mainly sensitive to the distorting effect. Such distorting effects can for example be a thin martensite layer on top of the case or a different quench oil temperature. From the 4 test methods used here 41 parameters were derived that describe the measurement signals. Multiple regression methods were used to select the most suitable parameters and build models from them. This procedure is called calibration. A separate calibration has to be performed for each different material. Models were built and the case depth testing accuracy was evaluated at 2 case hardened specimen groups. For one group the average case depth test error was in a range of ±15µm. For another group the average test error was in a range of ±100µm for case depths ranging from 1 – 2.5mm. The results of the study show that the case depth testing accuracy and robustness could be improved by combining several independent electromagnetic test methods, thus providing industry with an effective quality control method for fast and reliable quality assurance.

Committee:

Daniel Eylon, D.Sc. (Committee Chair); P. Terrence Murray, PhD (Committee Member); James Malas, PhD (Committee Member); James Snide, PhD (Committee Member); Jürgen Schreiber, PhD (Committee Member); Gerald Shaughnessy, M.S. (Committee Member)

Subjects:

Electromagnetism; Materials Science; Metallurgy

Keywords:

case depth; steel; electromagnetic; nondestructive; carburized; surface hardened

Kasemodel, Justin AllenRealization of a Planar Low-Profile Broadband Phased Array Antenna
Doctor of Philosophy, The Ohio State University, 2010, Electrical and Computer Engineering

With space at a premium, there is strong interest to develop a single ultra wideband (UWB) conformal phased array aperture capable of supporting communications, electronic warfare and radar functions. However, typical wideband designs transform into narrowband or multiband apertures when placed over a ground plane. Therefore, it is not surprising that considerable attention has been devoted to electromagnetic bandgap (EBG) surfaces to mitigate the ground plane's destructive interference. However, EBGs and other periodic ground planes are narrowband and not suited for wideband applications. As a result, developing low-cost planar phased array apertures, which are concurrently broadband and low-profile over a ground plane, remains a challenge.

The array design presented herein is based on the infinite current sheet array (CSA) concept and uses tightly coupled dipole elements for wideband conformal operation. An important aspect of tightly coupled dipole arrays (TCDAs) is the capacitive coupling that enables the following: (1) allows field propagation to neighboring elements, (2) reduces dipole resonant frequency, (3) cancels ground plane inductance, yielding a low-profile, ultra wideband phased array aperture without using lossy materials or EBGs on the ground plane. The latter, is of course, critical for retaining the aperture's wideband behavior under conformal installations.

This dissertation focuses on the realization of wideband phased array apertures using tightly coupled dipole arrays. A methodology for designing planar apertures is presented including: element selection, material loading, and unbalanced to balanced conversion for wideband feeding. Multiple solutions and practical design examples are presented to increase bandwidth, reduce height, avoid common mode excitation and retain low-cost planar PCB manufacturability. Using one of these designs, a 64 element low-profile X-band array prototype is fabricated and measured. The conformal array is capable of scanning up to 70 degrees and 60 degrees in the E- and H-planes, respectively. The active VSWR is less than 2 from 8 to 12.5 GHz (1.6:1) and the array height is only lambda/7 at the lowest frequency of operation. A unique feature of the proposed array is its planar layered PCB construction. Specifically, a single microwave laminate is used for the aperture while another supports all associated baluns and matching networks. Good agreement between simulations and measurements confirm the proposed concepts.

Committee:

John Volakis, PhD (Advisor); Chi-Chih Chen, PhD (Advisor); Joel Johnson, PhD (Committee Member)

Subjects:

Electrical Engineering; Electromagnetism

Keywords:

phased array; broadband antenna; wide-angle scanning

O’Donnell, Andrew NickersonOn the Electromagnetic Scattering from Small Grooves in a Conical Surface
Master of Science, The Ohio State University, 2011, Electrical and Computer Engineering
Rapid generation of radar signatures is of particular interest for the missile defense community. These radar signautres are normally found through predictive methods. The two classes of predictive methods are Full-Wave Numerical Solutions and High-Frequency Asymptotic Solutions. Full-Wave Numerical Solutions solve problems in a numerically exact fashion, but are inefficient for electrically large targets. High-Frequency solutions work quickly but rely on the assumption that the target is made up of simple canonical shapes, which is not often the case. Real world objects contain many small features that greatly contribute to the radar signature. One such small feature is a groove on a cone. In this thesis, the scattered fields of a groove around a conical surface is derived. In the high frequency case, the scattering from the groove will reduce to an analytic solution of one or two point scatterers, using the method of stationary phase.

Committee:

Robert Burkholder, PhD (Advisor); Prabhakar Pathak, PhD (Committee Member)

Subjects:

Applied Mathematics; Electrical Engineering; Electromagnetics; Electromagnetism

Keywords:

Electromagnetics; High Frequency Asymptotics; Point Scattering Models; Stationary Phase Approximation

Kung, Christopher W.Development of a Time Domain Hybrid Finite Difference/Finite Element Method For Solutions to Maxwell’s Equations in Anisotropic Media
Doctor of Philosophy, The Ohio State University, 2009, Electrical and Computer Engineering

The finite difference time domain (FDTD) and finite element numerical methods are two popular time domain computational methods in electromagnetics, but the two numerical methods have certain tradeoffs. FDTD is a fast explicit method with second order accuracy, but the method’s accuracy is reduced when analyzing structures that are not conforming to a Cartesian grid. The finite element method on the other hand excels at examining domains with non-conforming structures, but its method of solution usually requires a matrix inverse operation, which is computationally expensive. Fortunately, research in hybrid methods have shown that the FDTD method for isotropic materials can be viewed upon as a subset of finite elements, and from this viewpoint, the FDTD and finite element method in the time domain can be hybridized together to the advantages of both methods while mitigating the disadvantages.

With the recent rise in the study of metamaterials, which contain anisotropic media, having a hybridized method to study anisotropic media is a desirable tool as, for example, the effects of these materials combined with antennas are being examined. However, the hybridization approach combining the FDTD and finite element method for isotropic media does not extend to anisotropic media since the anisotropic FDTD equation cannot be recovered from the finite element formulation in this fashion. In this dissertation, a hybridized FDTD/finite element method for anisotropic materials will be developed. In the derivation of the hybridized method, a new finite element method will be formulated which incorporates the constitutive relation in a finite element point of view. This new finite element method will also be used to construct new anisotropic FDTD stencils in a systematic manner for certain interface and boundary conditions that the traditional anisotropic FDTD update fails to handle. Numerical tests will be performed to demonstrate the accuracy of the both the hybridized anisotropic FDTD/finite element method as well as the new FDTD stencils that are derived from the new finite element method.

Committee:

Robert Lee, PhD (Advisor); Fernando Teixeira, PhD (Committee Member); Prabhakar H. Pathak, PhD (Committee Member)

Subjects:

Electrical Engineering; Electromagnetism

Keywords:

finite difference; finite element; anisotropic materials; hybrid numerical methods; time domain; electromagnetics

Evers, ChrisNovel Techniques for Enhancing SAR Imaging using Spatially Variant Apodization
Master of Science, The Ohio State University, 2011, Electrical and Computer Engineering
Conventional radar imaging techniques have long been plagued by problematic sidelobes and poor resolution. Indeed, numerous algorithms exist for combating these two issues. In tackling the first problem the technique spatially variant apodization (SVA) has been utilized for quite some time with tremendously positive results. A more recent enhancement to this technique known as Super-SVA has potential for tackling the second problem. In this thesis, a method is developed for utilizing Super-SVA to enhance down-range and cross-range resolution while minimizing sidelobes without distorting scatterer mainlobes.

Committee:

Robert Burkholder (Committee Member); Eric Walton (Committee Member)

Subjects:

Electrical Engineering; Electromagnetics; Electromagnetism; Engineering

Keywords:

Radar Imaging

Vabbilisetty, PratimaFabrication and Characterization of Substrate Materials for Trace Analytical Measurements by Surface Enhanced Raman Scattering (SERS) Spectroscopy Technique
Master of Science in Chemistry, Youngstown State University, 2008, Department of Chemistry
The detection of various compounds using Surface enhanced Raman Scattering (SERS) from colloidal suspensions of silver and gold colloids has been attempted. Different substrates have been utilized and SERS spectra for R6G, creatinine, imidazole and benzoic acid have been evaluated as a function of time. SERS investigations have been performed using model compounds to allow comparison between the substrates. Different concentrations of R6G have been used for the valuation of the analytical capabilities. Silver and gold colloids have been prepared and used for SERS measurements and for the fabrication of substrates having a layer of immobilized metal nanoparticles.

Committee:

Josef B. Simeonsson, PhD (Advisor); Daryl W. Mincey, PhD (Committee Member); Timothy R. Wagner, PhD (Committee Member)

Subjects:

Analytical Chemistry; Chemistry; Electromagnetism; Materials Science

Keywords:

SERS; Raman scattering; fabrication and characterization; substrate materials; trace analytical measurements

Mumcu, GokhanEM Characterization of Magnetic Photonic / Degenerate Band Edge Crystals and Related Antenna Realizations
Doctor of Philosophy, The Ohio State University, 2008, Electrical and Computer Engineering

Extraordinary properties found in engineered metamaterials have drawn great interest as they can address industry demands for small, light-weight, and multifunctional devices. It is not therefore surprising that a variety of artificial materials are being widely considered for various radio frequency (RF) applications. Among these metamaterials, a recently introduced class of anisotropic photonic crystals, namely magnetic photonic (MPC) and degenerate band edge (DBE) crystals, has been shown to exhibit unique propagation modes as compared to regular periodic assemblies. For the first time, this dissertation carries out computational and experimental analysis of these new crystals for specific RF applications. Our ultimate goal is to develop high gain antenna apertures and miniature footprint antennas. In this context, this dissertation begins by establishing an understanding of the fundamental electromagnetic properties of 1D DBE and MPC crystals using the transfer matrix and spectral domain method of moments (MoM) computations. This is followed by numerical characterization of 3D DBE crystals via surface integral equations. Upon successful demonstration of the DBE mode for improved antenna performance, a measurement setup is presented to characterize low loss uniaxial materials. Subsequently, Specifically, a finite DBE assembly is built and shown to exhibit large aperture efficiency for conformal high gain antenna applications.

The second half of the dissertation introduces a novel coupled transmission line concept capable of emulating DBE mode on otherwise uniform microwave substrates. Using this novel dual transmission line concept, we present examples of several small antennas on low and high contrast substrates, and fabricate a prototype to experimentally verify the printed slow wave concepts. The measured DBE antenna is shown to perform better than other recently published metamaterial antennas. It is therefore very attractive for several RF applications requiring small and efficient antennas (such as RF identification (RFID) tags or mobile communications). The last chapter presents a lumped circuit DBE model and suggest improvement to existing DBE antennas by introducing lumped elements into the transmission lines.

Committee:

John Volakis, L (Advisor); Jin-Fa Lee (Committee Member); Roberto Rojas, G (Committee Member); Kubilay Sertel (Committee Member)

Subjects:

Electrical Engineering; Electromagnetism

Keywords:

magnetic photonic crystals; MPC; degenerate band edge crystals; DBE; anisotropic media; metamaterials; printed antennas; miniature antennas; equivalent circuit model; surface integral equation; SIE; uniaxial medium; dyadic Green's function

Hansen, Matthew Martin KennethOptimization of Conformal Joints in Axial Tension
Master of Science, The Ohio State University, 2012, Mechanical Engineering

Electromagnetic forming uses high current to form conductive material. It has been a possible manufacturing technique for joining materials since the 1960s. In the past decade the process has seen a resurgence due to the desire for lightweight manufacturing. The process provides a means to join dissimilar metals, reduce material costs, and the potential for energy savings in manufacturing. One issue that the process faces is the lack of a model to predict the forming process and effectiveness of resulting joints. There has been work done to characterize high strain rate deformation and to couple electro-mechanical systems, but there are still opportunities to provide better and more specific models of joint formation and behavior. A model was developed to describe the process of electromagnetically compressing aluminum tubes onto a steel mandrel. The model was then used to assess potential mandrel geometries for a tensile joint.

The process of characterizing the joint formation uses a combination of a numerical code to describe the tube compression pressure and an LS-DYNA computer model to describe the tube compression. The resulting conformal joint predicted by the model was experimentally verified and compared to three purposed mandrel geometries. The purposed mandrel designs were an attempt to evenly distribute the tensile load using three gradually increasing groove depths. The simulation then tested the tensile strength of the joints, verified with physical testing, and identified possible improvements in groove design. A test matrix was used to assess the effect of groove radius and groove depth on joint strength. The results showed that, in terms of strength, the groove depth is the most critical dimension and that the groove entry radius had little effect. The final optimized joint had a rectangular groove profile, with a groove entry radius the same size as the depth. The joint evenly distributed the tensile load and was shown to be more resistant to a reduction in friction than previously purposed geometries.

Committee:

Anthony Luscher, PhD (Advisor); Gary Kinzel, PhD (Committee Member); Glenn Daehn, PhD (Committee Member)

Subjects:

Automotive Engineering; Electromagnetism; Engineering; Materials Science; Mechanical Engineering; Mechanics

Keywords:

electromagnetic forming; EMF; LS-DYNA; mechanical joints; lightweight structures; joining methods;

Esfahani, PedramA Study of the Frequency Dependence of Permittivity and Permeability in Lossless One-Dimensional Composite Right/Left Handed Metamaterials by the Equivalent Circuit Model
Master of Science, University of Akron, 2016, Physics
A medium with a negative permittivity and permeability was first proposed in the 1960s; developments of such a medium did not occur until the late 1990s. Different and new electromagnetic metamaterials have been suggested since 2000. Due to the unusual properties of metamaterials, as a bridge between theory and experiment, computer simulation methods are essential for researchers. The frequency dependence of the permittivity and permeability in an electromagnetic metamaterial constructed of arrays of long thin wires (TWs) and split-ring resonators (SRRs) is presented to demonstrate the effects of macroscopic properties on the electromagnetic properties of the medium. Also, the response of three different materials (Aluminum, Copper, and Silver) is presented to show how material properties of components affect the permittivity and its frequency domain where permittivity and permeability are negative. Based on these designs, a computer simulation model to study one-dimensional lossless metamaterials is presented as well. This simulation model is based on RLC equivalent circuits. Finally, the necessary conversion equations are presented to compare the LC model with the theoretical results.

Committee:

Sergei F. Lyuksyutov (Advisor); Jutta Luettmer-Strathmann (Committee Chair); Alper Buldum (Committee Member)

Subjects:

Electrical Engineering; Electromagnetics; Electromagnetism; Engineering; Physics; Theoretical Physics

Cao, QianPropagation Dynamics of Spatio-Temporal Wave Packets
Master of Science (M.S.), University of Dayton, 2014, Electro-Optics
We measured the three-dimensional (3D) propagation dynamics of the Airy-Bessel wave packet, inculding its intensity and phase evolution. Its non-diffraction and non-dispersive feature were verified. Meanwhile, we built a spatial-light-modulator (SLM) based wave packet shaping system to generate other types of wave packets such as Airy-Airy-Airy and dual-Airy-Airy-rings. These wave packets were also measured in 3D. The abrupt 3D autofocusing effect was observed on dual-Airy-Airy-rings.

Committee:

Andy Chong (Advisor); Joseph Haus (Committee Member); Partha Banerjee (Committee Member)

Subjects:

Electromagnetism; Optics; Physics

Keywords:

ultrafast measurements, phase measurement, 3D wave packet generation

Hussaini, SheenaIntegrated Magnetic Components for RF Applications
Doctor of Philosophy (PhD), Wright State University, 2015, Engineering PhD
Integrated r-f passive components such as inductors, transmission lines, transformers etc, form the basic building blocks in r-f integrated circuits (RFICs) such as matching networks, low noise amplifiers (LNAs), synthesizers and r-f mixers. One main challenge faced by current technology developers in integrating r-f components on integrated chip (IC) are related to operation and size. Tremendous efforts were made for overcoming challenges of r-f integrated circuits to meet growing technology demands. In general, r-f devices utilize magnetic materials such as ferrites for their operation for improving device performance and scaling. However, due to material properties and size ferrite materials are poor choices when attempting to scale r-f components. The main focus of this work has been to explore new material properties and investigate applications of ferromagnetic (FM) films as potential solution for device scaling. One attractive property of ferromagnetic materials is low processing temperature and high magnetic saturation which eliminates the need for continuous application of magnetic (d-c) field and are compatible with CMOS technology. The disadvantage of ferromagnetic films is high conductivity which induces ohmic losses and affects r-f device performance. In this work a novel concept of low-loss conductor has been introduced whose conductivity can be modeled by utilizing multilayered superlattice structure. The low-loss conductor is made of artificial layered metamaterial (ARLYM) consisting Ni80Fe20/Cu superlattice. By modeling thickness ratio between superlattice layers the skin effect has been suppressed by increasing skin depth at r-f frequencies. The experimental results presented in this work indicates significant improvement in r-f device characteristics such as inductance, quality factor (85%), loss reduction ratio (70%) etc, operating at r-f frequencies. In addition, application of continuous magnetic field was not required in this work due to magnetic anisotropy property in ferromagnetic materials. Further, a new approach for studying magneto-dynamics in thin ferromagnetic films has been investigated in this work by modeling r-f solenoid single-turn inductor fabricated using thin ferromagnetic core. The effect of magnetic resonances in thin ferromagnetic films has been calculated using magneto-static thin film approximation and Greens function. Therefore, these newly developed concepts of artificial low-loss conductor and magneto-dynamics in thin ferromagnetic structures can be applied for improving speed, clock frequency, power dissipation etc in r-f integrated circuits, microprocessor applications etc, and are fully compatible with CMOS technology.

Committee:

Yan Zhuang, Ph.D. (Advisor); Marian Kazimierczuk, Ph.D. (Committee Member); Henry Chen, Ph.D. (Committee Member); Robert C. Fitch, Ph.D. (Committee Member); Guru Subramanyam, Ph.D. (Committee Member); Robert E. W. Fyffe, Ph.D. (Other); Ramana V. Grandhi, Ph.D. (Other)

Subjects:

Electrical Engineering; Electromagnetics; Electromagnetism; Engineering; Nanotechnology; Physics; Quantum Physics; Radiation

Keywords:

Radio-frequency integrated circuits;Magnetic films; Passive devices;transmission lines;Coplanar waveguides;Inductors;Permeability;Ferromagnetic resonance;Magnetic anisotropy;Magnetic Materials;Low-loss conductors;Resistance;Quality factor;Skin effect; RF

Zemba, Michael JSite Characterization of Phase Instability via Interferometer Measurement
Master of Science in Engineering, University of Akron, 2013, Electrical Engineering
Single-dish reflector antennas are often used for their ability to produce a highly directive (narrow beam) radiation pattern which increases in directivity as the diameter of the reflector increases. However, as reflectors grow larger in the pursuit of more directivity, they become more expensive and unwieldy to construct, maintain, and operate. A more practical solution is to employ an array of elements which are smaller individually, but which can yield similar or better gains when arrayed together. However, one trade-off associated with this approach is that antenna arrays are subject to losses introduced by atmospheric turbulence. Inhomogeneous cells of water vapor in the troposphere change the refractivity of the air along the path of the propagating wave, distorting the wavefront and introducing a phase error between the elements of the array. These losses are stochastic and site-dependent. Techniques have been developed over the past several decades to compensate for such losses on the receiving end, but uplink arraying remains challenging as it requires prediction of atmospheric conditions to effectively compensate the signal before transmitting. This is especially true at higher frequencies such as Ka-band given that atmospheric phase noise increases with frequency. Thus, a critical first step in system planning is to determine the losses a particular array configuration will experience based on the phase statistics of a given site. To this end, NASA Glenn Research Center has deployed site test interferometers to three ground-station sites with the intent to characterize their phase instability ahead of upgrades to Ka-Band operation. The sites to be studied are Goldstone, California; White Sands, New Mexico; and the island of Guam. Using three years of data collected from these campaigns, the primary goal of this thesis is to develop a thorough characterization of the phase statistics of each site which may then be used to determine the sites’ suitability for uplink arraying. In addition, a secondary goal is the development of the data analysis software suite that was used to process the data, which it is hoped will facilitate easy analysis of future sites for system designers.

Committee:

Nathan Ida, Dr. (Advisor); Igor Tsukerman, Dr. (Committee Member); Subramaniya Hariharan, Dr. (Committee Member)

Subjects:

Aerospace Engineering; Electrical Engineering; Electromagnetics; Electromagnetism; Engineering

Keywords:

Antenna Arrays; Phase Noise; Atmospheric Phase Instability; Propagation Measurements; Interferometry; NASA; Ka-Band; Radio Frequency; Electrical Engineering; Electromagnetics; Antennas; Propagation; Site Test Interferometer

Chakrabarti, SuryarghyaModeling of 3D Magnetostrictive Systems with Application to Galfenol and Terfenol-D Transducers
Doctor of Philosophy, The Ohio State University, 2011, Mechanical Engineering

Magnetostrictive materials deform in response to applied magnetic fields and change their magnetic state when stressed. Because these processes are due to moment realignments, magnetostrictive materials are ideally suited for sensing and actuation mechanisms with a bandwidth of a few kHz. Significant research effort has been focused on two magnetostrictive alloys: Terfenol-D (an alloy of terbium, iron and dysprosium) and Galfenol (an iron gallium alloy), for their ability to produce giant magnetostrictive strains at moderate fields. Terfenol-D has higher energy density and magnetomechanical coupling factor than Galfenol but it is brittle and suffers from poor machinability. Galfenol on the other hand has excellent structural properties. It can be machined, welded, extruded into complex shapes for use in transducers with 3D functionality.

Advanced modeling tools are necessary for analyzing magnetostrictive transducers because these materials exhibit nonlinear coupling between the magnetic and mechanical domains. Also, system level electromagnetic coupling is present through Maxwell's equations. This work addresses the development of a unified modeling framework to serve as a design tool for 3D, dynamic magnetostrictive transducers. Maxwell's equations for electromagnetics and Navier's equations for mechanical systems are formulated in weak form and coupled using a generic constitutive law. The overall system is approximated hierarchically; first, piecewise linearization is used to describe quasistatic responses and perform magnetic bias calculations. A linear dynamic solution with piezomagnetic coefficients computed at the bias point describes the system dynamics for moderate inputs. Dynamic responses at large inputs are obtained through an implicit time integration algorithm. The framework simultaneously describes the effect of magneto-structural dynamics, flux leakages, eddy currents, and transducer geometry. Being a fully coupled formulation, it yields system level input-output relationships and is applicable to both actuators and sensors.

An anhysteretic 3D discrete energy-averaged constitutive law for Galfenol is incorporated into the framework to describe the dynamic performance of Galfenol transducers. A parameter identification algorithm is developed which takes as input the 1D material characterization curves and calculates the 3D constitutive model parameters. The algorithm is embedded within the finite element model such that the only inputs required are the constitutive parameters for passive materials (permeability, conductivity, Young's modulus etc.), the transducer geometry, and the 1D magnetostrictive material characterization curves. A case study on a Galfenol unimorph actuator illustrates the model's ability to accurately describe the dynamic mechanical and magnetic response of Galfenol transducers. A new energy-averaged model is formulated for Terfenol-D based on an implicit definition of domain volume fractions and a weighted anisotropy energy. The model is shown to simultaneously describe the strain-field and magnetization-stress behavior of Terfenol-D. The 3D finite element model is reduced to a 2D axisymmetric form to exploit the axisymmetric geometry of Terfenol-D transducers. The model describes the dynamic mechanical and electrical response of a hydraulically amplified Terfenol-D mount actuator. A parametric study on the actuator shows the applicability of the model to transducer design optimization.

Committee:

Marcelo Dapino, PhD (Advisor); Ahet Kahraman, PhD (Committee Member); Junmin Wang, PhD (Committee Member); Rajendra Singh, PhD (Committee Member)

Subjects:

Electromagnetics; Electromagnetism; Mechanical Engineering; Mechanics

Keywords:

magnetostriction; electromagnetism; eddy currents; finite element modeling; magnetostrictive transducers; engine mount actuator; nonlinear constitutive modeling; magnetomechanical coupling

Raines, Bryan DennisSystematic Design of Multiple Antenna Systems Using Characteristic Modes
Doctor of Philosophy, The Ohio State University, 2011, Electrical and Computer Engineering

Complex multiple antenna systems are emerging today as market pressures to improve link capacity and reliability on complex integrated platforms. Complexity is therefore inherent in both the analysis and design of such systems. Modal analysis of various types has been used in a variety of fields to manage this inherent complexity. For single antenna systems, the Theory of Characteristic Modes (CM) has been used to great success in designing single antennas. In this dissertation, four interconnected topics are discussed, which are crucial to the proper extension of Characteristic Modes to complex antenna systems, especially multiple antenna systems.

First, existing characteristic mode systems are reviewed and their common properties examined. A software architecture is then discussed which enables the computation of characteristic modes in general, requiring only that the particular system definition satisfies those common properties. The software is used to perform all computations, analyses, and designs in this dissertation.

Second, a general, high-performance, wideband mode tracking system is proposed. It is shown to be efficient and robust through several challenging examples. It is the first robust tracker proposed in connection with Characteristic Modes.

Third, a procedure is proposed to compute the number, location, and even voltages of ports on a given antenna or antennas using a CM description of the problem. Its mathematical construction is inspired by results from the emerging field of Compressed Sensing. Its generality is demonstrated through a number of simulated designs.

Lastly, two new modal systems related to CM are proposed. One modal system, Subsystem Classical Characteristic Modes, produces modes which successively optimize the ratio of stored power to radiated power for an antenna embedded in a multistructure system. The other modal system, Target Coupling Characteristic Modes, produces modes which successively optimize the ratio of induced current intensity on a target structure to the current intensity on a source antenna. The modal systems are related through a projection matrix, which demonstrates the tradeoff between mutual coupling and radiation properties for a given multiple antenna system. The two modal systems are applied to several examples to validate their properties. Then, they are used in a new design procedure to systematically reduce the mutual coupling between two parallel dipoles. It is found that through loading an intermediate structure suggested by the proposed modal systems, the mutual coupling may be reduced, also predicted by the modal coupling analysis. The resulting designs generally improve upon designs available in the literature.

The dissertation concludes with a summary and discussion of future work. The appendices discusses various definitions, including a novel derivation of Classical Characteristic Modes from the starting point of orthogonal eigenpatterns.

Committee:

Roberto Rojas, PhD (Advisor); Robert Garbacz, PhD (Committee Member); Fernando Teixeira, PhD (Committee Member)

Subjects:

Electrical Engineering; Electromagnetics; Electromagnetism

Keywords:

antennas; characteristic modes; MIMO; mode tracking; antenna feed design

Lei, FeiranHomogenization of Heterogeneous Composites by Using Effective Electromagnetic Properties
Master of Science, The Ohio State University, 2011, Electrical and Computer Engineering
Nowadays, multi-scale or multi-physics modeling plays a very important role in many important problems. In the past few years, there have been increasingly growing research activities aiming at developing novel multi-scale computational methods. In this thesis, we will focus on one computational electromagnetics method (CEM) which is based on the homogenization theory and considers the microscopically heterogeneous system to be a macroscopically homogeneous system by averaging the local electromagnetic fields and current distributions. The averaging process adopted here is to replace the original inhomogeneous structure by a homogeneous material with effective anisotropic permittivity and permeability tensors.

Committee:

Jin-Fa Lee (Advisor); Fernando L. Teixeira (Committee Member)

Subjects:

Electrical Engineering; Electromagnetics; Electromagnetism

Keywords:

electromagnetic scattering; homogenization; hybrid FE/BE method; multi-scale problem

Whelan, Jedidiah J.Diverse Polarization Extension to MUSIC Applied to a Circular Array of H-Plane Horns
Master of Science (M.S.), University of Dayton, 2010, Electrical Engineering
Shown herein is a specific application to an existing algorithm and technique: the advantages of using a diversely polarized antenna array to perform direction finding on multiple narrow-band signals co-located in frequency via an extension to the MUSIC algorithm. The original MUSIC algorithm has been extended to support diverse polarization and is applied here to a circular array of H-plane sectoral horn antennas. The results clearly show that direction finding on multiple signals simultaneously is not only possible in the scenario described, but can resolve differently-polarized, very closely spaced signals better than a uniformly polarized array. The MUSIC algorithm with the diverse polarization extension are described mathematically and discussed in detail for the purposes of this specific application.

Committee:

Robert P Penno, PhD (Committee Chair); Guru Subramanyam, PhD (Committee Member); Daniel Reuster, PhD (Committee Member)

Subjects:

Aerospace Engineering; Electrical Engineering; Electromagnetism; Engineering; Radiation

Keywords:

MUSIC; polarization; circular array; angle of arrival; direction of arrival; aoa; df; horn antenna; horn antennas; schmidt; ferrera; pseudospectrum; diverse polarization; diversely polarized; RADAR; radiation pattern

Wroblewski, Adam C.Model Identification, Updating, and Validation of an Active Magnetic Bearing High-Speed Machining Spindle for Precision Machining Operation
Doctor of Engineering, Cleveland State University, 2011, Fenn College of Engineering
High-Speed Machining (HSM) spindles equipped with Active Magnetic Bearings (AMBs) are envisioned to be capable of autonomous self-identification and performance self-optimization for stable high-speed and high quality machining operation. High-speed machining requires carefully selected parameters for reliable and optimal machining performance. For this reason, the accuracy of the spindle model in terms of physical and dynamic properties is essential to substantiate confidence in its predictive aptitude for subsequent analyses. This dissertation addresses system identification, open-loop model development and updating, and closed-loop model validation. System identification was performed in situ utilizing the existing AMB hardware. A simplified, nominal open-loop rotor model was developed based on available geometrical and material information. The nominal rotor model demonstrated poor correlation when compared with open-loop system identification data. Since considerable model error was realized, the nominal rotor model was corrected by employing optimization methodology to minimize the error of resonance and antiresonance frequencies between the modeled and experimental data. Validity of the updated open-loop model was demonstrated through successful implementation of a MIMO µ-controller. Since the µ-controller is generated based on the spindle model, robust levitation of the real machining spindle is achieved only when the model is of high fidelity. Spindle performance characterization was carried out at the tool location through evaluations of the dynamic stiffness as well as orbits at various rotational speeds. Updated model simulations exhibited high fidelity correspondence to experimental data confirming the predictive aptitude of the updated model. Further, a case study is presented which illustrates the improved performance of the µ-controller when designed with lower uncertainty of the model’s accuracy.

Committee:

Jerzy T. Sawicki, PhD (Advisor); Stephen F. Duffy, PhD (Committee Member); James A. Lock, PhD (Committee Member); Taysir H. Nayfeh, PhD (Committee Member); Ana V. Stankovic, PhD (Committee Member)

Subjects:

Electromagnetism; Engineering; Industrial Engineering; Mechanical Engineering

Keywords:

rotordynamics; modeling; spindle; high speed; active magnetic bearing; AMB; machining; high speed machining; system identification; open loop model; model updating; optimization; robust control; mu-synthesis; mu-control;

Murad, Mark RichardRadiation View Factors Between A Disk And The Interior Of A Class Of Axisymmetric Bodies Including Converging Diverging Rocket Nozzles
Master of Science in Mechanical Engineering, Cleveland State University, 2008, Fenn College of Engineering

A general symbolic exact analytic solution is developed for the radiation view factors including shadowing by the throat between a divergence thin gas disk between the combustion chamber and the beginning of the rocket nozzle radiating energy to the interior downstream of the nozzle contour for a class of coaxial axisymmetric converging diverging rocket nozzles. The radiation view factors presented in this thesis for the projection which are blocked or shadowed through the throat radiating downstream to the contour have never been presented before in the literature.

It was found that the curvature of the function of the contour of the nozzle being either concave up or down and the slope of the first derivative being either positive or negative determined the values used for the transformation of the Stokes Theorem into terms of x, r (radius) and f(x) for the evaluation of the line integral.

The analytical solutions from the view factors of, for example, the interior of a combustion chamber, or any radiating heat source to a disk may then be applied to the solution of the view factor of the disk to the interior of the rocket nozzle contour presented here. This modular building block type approach is what the author desires to allow the development of an interstellar matter antimatter rocket engine. The gases of this type of reaction shall approach those towards the speed of light, which shall involve a transport phenomena, which the author is looking forward to researching the solution.

Committee:

Asuquo Ebiana, PhD (Advisor); Majid Rashidi, PhD (Committee Member); John Frater, PhD (Committee Member); John Oprea, PhD (Committee Member)

Subjects:

Aerospace Materials; Astrophysics; Chemical Engineering; Computer Science; Electromagnetism; Engineering; Gases; Materials Science; Mathematics; Mechanical Engineering; Nuclear Chemistry; Nuclear Physics; Radiation; Radiology; Scientific Imaging; Transportation

Keywords:

shadowing; radiation view factor; rocket nozzle: cooling; radiation heat transfer; differential geometry; configuration factor

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