Doctor of Philosophy, The Ohio State University, 2014, Electrical and Computer Engineering

Radar waveform design is an active research area for decades. With the advent of advanced digital signal processing, high speed computing, high frequency electronics, and solid state power amplifiers, emerging radar systems (such as UWB radar, multiple-input and multiple-output (MIMO) radar, cognitive radar, etc.) are expecting more from their waveforms. Taking advantage of the new techniques, scientists and engineers are able to implement new waveforms to achieve significantly better performance for conventional radar systems, namely target detection including range, speed, and shape. The objective of this dissertation is to exploit a practical way to build flexible waveforms for the modern radar. On the other hand, conventional radar systems detect targets or pixels of an area individually. Each target or pixel generates a set of data in real-time, which must be recorded for off-line processing. When the number of elements is increased, phased array radar is able to generate narrow beams, which can detect more targets or cover larger areas for data collection in high definition. The disadvantage is the increased time in sensing since narrow beams need more time to cover the same area than wider beams. To address this issue, the sensing mechanism needs to be studied. The objective of this dissertation is to exploit a new sensing mechanism, named transform sensing, to cover wider areas, tracking more moving objects, and providing high resolution of the target area with limited times of sensing. Because the waveform design and transform sensing in this dissertation are all based on wavelets, the dissertation introduces the wavelet basics. Then the wavelet based waveform is presented. This waveform is generated by concatenating wavelet packets, and can suppress range sidelobes more effectively than the tranditional Linear Frequency Modulated (LFM) waveform. In addition, the wavelet based waveform can de-couple its envelope and carrier for range and velocity (open full item for complete abstract)

Committee: Yuan Zheng (Advisor); Chris Baker (Committee Member); Chi-Chih Chen (Committee Member) Subjects: Electrical Engineering; Remote Sensing

Doctor of Philosophy (PhD), Wright State University, 2009, Engineering PhD

We consider the design of radar systems that are capable of using knowledge of their interference environment to dynamically design transmit waveforms that afford optimum signal-to-interference-plus-noise ratio while satisfying modulus and ambiguity function constraints. We begin by establishing the inextricable nature of modulus constraints in the waveform optimization problem. We then extend the state of the art in waveform optimization to accommodate these constraints. This is done by solving a secondary optimization problem using the method of alternating projections. We demonstrate that this approach can be a computationally efficient alternative to dynamic programming methods. We then consider the multiple-target detection problem, which is the basis for introducing ambiguity function constraints into the waveform design process. We formulate the waveform optimization problem for several receiver architectures, and solve these problems using sequential quadratic programming and interior point methods. Finally, we address the need for a more computationally tractable approach by considering a number of suboptimal formulations. This includes a novel formulation based on a parametrization of nonlinear frequency modulation.

Committee: Brian Rigling PhD (Advisor); Kefu Xue PhD (Committee Member); Zhiqiang Wu PhD (Committee Member); Michael Bryant PhD (Committee Member); Mark Oxley PhD (Committee Member) Subjects: Electrical Engineering; Engineering

Doctor of Philosophy (PhD), Wright State University, 2008, Engineering PhD

Recent studies have suggested that spectrum congestion is mainly due to the inefficient use of spectrum rather than its unavailability. Dynamic Spectrum Access (DSA) and Cognitive Radio (CR) are two terminologies which are used in the context of improved spectrum efficiency and usage. The DSA concept has been around for quite some time while the advent of CR has created a paradigm shift in wireless communications and instigated a change in FCC policy towards spectrum regulations. DSA can be broadly categorized as using a 1) Dynamic Exclusive Use Model, 2) Spectrum Commons or Open sharing model or 3) Hierarchical Access model. The hierarchical access model envisions primary licensed bands, to be opened up for secondary users, while inducing a minimum acceptable interference to primary users. Spectrum overlay and spectrum underlay technologies fall within the hierarchical model, and allow primary and secondary users to coexist while improving spectrum efficiency. Spectrum overlay in conjunction with the present CR model considers only the unused (white) spectral regions while in spectrum underlay the underused (gray) spectral regions are utilized. The underlay approach is similar to ultra wide band (UWB) and spread spectrum (SS) techniques utilize much wider spectrum and operate below the noise floor of primary users.Software defined radio (SDR) is considered a key CR enabling technology. Spectrally modulated, Spectrally encoded (SMSE) multi-carrier signals such as Orthogonal Frequency Domain Multiplexing (OFDM) and Multi-carrier Code Division Multiple Access (MCCDMA) are hailed as candidate CR waveforms. The SMSE structure supports and is well-suited for SDR based CR applications. This work began by developing a general soft decision (SD) CR framework, based on a previously developed SMSE framework that combines benefits of both the overlay and underlay techniques to improve spectrum efficiency and maximizing the channel capacity. The resultant SD-SMSE framework prov (open full item for complete abstract)

Committee: Arnab Shaw PhD (Committee Co-Chair); Zhiqiang Wu PhD (Committee Co-Chair); Fred Garber PhD (Committee Member); Michael Temple PhD (Committee Member); Michael Bryant PhD (Committee Member) Subjects: Electrical Engineering

Master of Science in Electrical Engineering (MSEE), Wright State University, 2024, Electrical Engineering

This research illustrates a high-security wireless communication method using a joint radar/communication waveform, addressing the vulnerability of traditional low probability of detection (LPD) waveforms to hostile receiver detection via cyclostationary processing (CSP). To mitigate this risk, RF steganography is used, concealing communication signals within linear frequency modulation (LFM) radar signals. The method integrates reduced phase-shift keying (RPSK) modulation and variable symbol duration, ensuring secure transmission while evading detection. Implementation is validated through software-defined radios (SDRs), demonstrating effectiveness in covert communication scenarios. Results include analysis of message reception and cyclostationary features, highlighting the method's ability to conceal messages from hostile receivers. Challenges encountered are discussed, with suggestions for future enhancements to improve real-world applicability.

Committee: Zhiqiang Wu Ph.D. (Advisor); Xiaodong Zhang Ph.D. (Committee Member); Bin Wang Ph.D. (Committee Member) Subjects: Electrical Engineering

Master of Science (MS), Ohio University, 2023, Physics and Astronomy (Arts and Sciences)

The Neutral Particle Spectrometer (NPS) at Jefferson Lab enables a suite of experiments for the study of the internal structure of nucleons. It is a new dedicated apparatus made up of a sweeping magnet and an Electro-Magnetic (EM) calorimeter. Data-taking is scheduled to start in the summer of 2023. This thesis reports on the assembly and initial testing of the calorimeter that took place in the summer and fall of 2022. Initial checkouts of the NPS detector component, integrated trigger paddles, and calorimeter Photo-Multipliers Tubes (PMTs) performance were done. Initial gain calibration procedures for the NPS detector were developed. Analysis scripts and the Data Acquisition System were exercised focusing on the PMT waveform data.

Committee: Julie Roche (Advisor); Gang Chen (Committee Member); Chaden Djalali (Committee Chair) Subjects: Physics

Doctor of Philosophy, The Ohio State University, 2022, Physics

The success of modern digital electronics relies on compartmentalizing logical functions into individual gates, and controlling their order of operations via a global clock. In the absence of such a timekeeping mechanism, systems of connected logic gates can quickly become chaotic and unpredictable -- exhibiting analog, asynchronous, autonomous dynamics. Such recurrent circuitry behaves in a manner more consistent with neural networks than digital computers, exchanging and conducting electricity as quickly as its hardware allows. These physics enable new forms of information processing that are faster and more complex than clocked digital circuitry. However, modern electronic design tools often fail to measure or predict the properties of large recurrent networks, and their presence can disrupt other clocked architectures. In this thesis, I study and apply the physics of complex networks of self-interacting logic gates at sub-ns timescales. At a high level, my unique contributions are: 1. I derive a general theory of network dynamics and develop open-source simulation libraries and experimental circuit designs to re-create this work; 2. I invent a best-in-class digital measurement system to experimentally analyze signals at the trillionth-of-a-second (ps) timescale; 3. I introduce a network computing architecture based on chaotic fractal dynamics, creating the first `physically unclonable function' with near-infinite entropy. In practice, I use a digital computer to reconfigure a tabletop electronic device containing millions of logic gates (a field-programmable gate array; FPGA) into a network of Boolean functions (a hybrid Boolean network; HBN). From within the FPGA, I release the HBN from initial conditions and measure the resulting state of the network over time. These data are transferred to an external computer and used to study the system experimentally and via a mathematical model. Existing mathematical theories and FPGA simulation tools produce in (open full item for complete abstract)

Committee: Daniel Gauthier (Advisor); Emre Koksal (Committee Member); Gregory Lafyatis (Committee Member); Antonio Boveia (Committee Member) Subjects: Applied Mathematics; Computer Engineering; Computer Science; Condensed Matter Physics; Electrical Engineering; Electromagnetics; Electromagnetism; Engineering; Experiments; High Temperature Physics; Information Science; Information Systems; Information Technology; Low Temperature Physics; Materials Science; Mathematics; Medical Imaging; Nanotechnology; Particle Physics; Physics; Quantum Physics; Scientific Imaging; Solid State Physics; Systems Design; Technology; Theoretical Physics

Doctor of Philosophy, The Ohio State University, 2020, Electrical and Computer Engineering

A new design methodology providing optimal mixed-mode operation for dual-input class-F outphasing Chireix amplifiers is presented. The design starts with single-transistor class-F simulations at the intrinsic I-V reference planes to directly select the optimal peak and backoff resistive loads Rmin and Rmax and input RF gate drives yielding the best combination of efficiencies and output powers without needing to perform a load pull simulation or measurement. New analytic equations expressed only in terms of Rmin and Rmax are given for designing the Chireix combiner at the current source reference planes. Nonlinear embedding is then used to predict the incident power and multi-harmonic source and load impedances required at the package reference planes to physically implement the power amplifier (PA). An analytic formula solely expressed in terms of Rmin and Rmax is reported for the peak and backoff outphasing angles required at the PA input reference planes. A Chireix outphasing PA designed with two 15-W GaN HEMTs exhibits a peak efficiency of 72.58% with peak power of 43.97 dBm and a 8-dB backoff efficiency of 75.22% at 1.9 GHz. Measurements with 10-MHz LTE signals with 9.6-dB PAPR yield 59.4% average drain efficiency at 1.9 GHz while satisfying the 3GPP linearity requirements. A novel frequency-agile PA designed with a modified class-J theory enforcing constant maximum and minimum instantaneous drain voltages for all frequencies is presented. The resulting high efficiency class-J mode which requires a reconfigurable drain supply exhibits clockwise fundamental and second harmonic load impedance trajectories versus frequency facilitating the PA design. This clockwise-loaded class-J (CLCJ) mode enables frequency-agile capability with enhanced efficiency when the proper drain supply voltage co-designed with the clockwise fundamental and harmonic loads is applied. A broadband power amplifier designed with a clockwise-loaded class-J theory is selected for demo (open full item for complete abstract)

Committee: Patrick Roblin (Advisor); Ayman Fayed (Committee Member); Waleed Khalil (Committee Member) Subjects: Electrical Engineering

Master of Science (M.S.), University of Dayton, 2019, Mechanical Engineering

Toe walking is often considered an undesirable gait deviation seen in pathological populations. The heterogeneous nature within and between these populations make it difficult to understand the biomechanics of pathological toe walking. Thus, previous studies have often analyzed healthy individuals performing non-habitual toe walking in hopes to understand this gait abnormality. Studies have found biomechanical deviations in kinematics, muscle activity levels, and kinetics between heel-toe and toe walking. However, these findings have focused primarily on sagittal plane discrete metrics of more proximal joints. Because toe walking involves increased activity of the distal foot, and these joints are often thought to have multi-planar tendencies, we believe further investigation is needed. The purpose of this study was to examine biomechanical differences in rearfoot strike walking (RFSW) and non-rearfoot strike walking (NRFSW). We hypothesized that previously seen increased ankle plantarflexion would be accompanied by increased ankle inversion and adduction, commonly referred to as supination, during NRFSW, and the MT joint would supinate with the ankle because of their parallel axes. Twenty-four healthy females walked overground with both walking patterns. Motion capture, electromyography (EMG), and force plate data were collected. A validated multi-segment foot model was used along with mean difference waveform analyses to study differences in the walking conditions during stance. Most differences occurred in early stance. NRFSW exhibited increased ankle supination at IC compared to RFSW, indicating ankle supination is needed for forefoot contact. Increased supination creates increased pronation excursion and pronation is a mechanism for shock absorption. This advantageous phenomenon was apparent in NRFSW as the loading rate was reduced despite a larger peak vertical ground reaction force and would not have been found if waveform analyses were not performed. The (open full item for complete abstract)

Committee: Allison Kinney Dr. (Advisor); Joaquin Barrios Dr. (Committee Co-Chair); Reissman Timothy Dr. (Committee Member) Subjects: Biomechanics

PhD, University of Cincinnati, 2019, Arts and Sciences: Geography

Thermokarst lakes are the most conspicuous features in the Arctic coastal regions that cover roughly 15% - 40 % percent of the area. Those lakes play as a critical niche in the local environment system and provide habitats for a great number of species. In the context of global warming, lakes are experiencing dramatic changes in recent decades. The lake water level and the snow cover atop the ice in the winter are two sensitive indicators of the local and global climate change. Monitoring the variations in lake water level and snow accumulation in Arctic regions could provide more insights of the global climate change and facilitate our understanding of their influences on local hydrological and ecological systems. However, there are very rare in situ observations of lake water levels and lake snow accumulations for the Arctic regions due to the remote locations and also the harsh environmental conditions. Satellite radar and laser altimetry measures elevation profiles of Earth's surface at the global scale and offers an alternative to achieve the purpose. Most previous studies have focused on the application of satellite radar and laser altimetry on lakes at low or middle latitudes, with few of them discussing the applicability of these data to high-latitude lakes. In this research, I explored the capability of satellite radar and laser altimetry missions to monitor lake water levels and snow accumulation on frozen lakes in the Arctic coastal regions. The performances of Sentinel-3, the most recent satellite radar altimetry, on the retrieval of lake water levels were assessed particularly for high-latitude ice-covered lakes. The results showed that lake ice can greatly reduce the accuracy of Sentinel-3 observations. I developed a new empirical retracking algorithm that significantly improves the measurements and provide more reliable and consistent water level estimates for the ice-covered lakes. I examined the performances of ICESat/GLAS, the first and until now (open full item for complete abstract)

Committee: Hongxing Liu Ph.D. (Committee Chair); Richard Beck Ph.D. (Committee Member); Kenneth Hinkel Ph.D. (Committee Member); Emily Kang Ph.D. (Committee Member); Tomasz Stepinski Ph.D. (Committee Member) Subjects: Geography

Master of Science (M.S.), University of Dayton, 2018, Electro-Optics

In this thesis, Electro-Optic (EO) range signatures are obtained with a Short-Wave Infrared Super-Continuum Laser (SWIR-SCL) source. 3D printed canonical targets of interest are illuminated by the SWIR-SCL pulsed laser. The scattered laser light from the target is directly detected in mono-static and bi-static configurations with a fast, high bandwidth Indium Gallium Arsenide (InGaAs) PIN photodiode. Temporal pulse returns provide target shape, orientation, and surface roughness information. Spatial and temporal analysis of the collected intensity distribution is performed in MATLAB. Macro and micro surface properties are identified from the collected data by correlating pulse amplitude variations with known range scenes. Finally, range resolution improvement is investigated by means of Tomographic Reconstruction using Radon Transforms and by image processing techniques such as Deconvolution.

Committee: Edward Watson Ph.D. (Advisor); Paul McManamon Ph.D. (Committee Member); Joe Haus Ph.D. (Committee Member) Subjects: Computer Engineering; Electrical Engineering; Engineering; Experiments; Optics; Physics; Scientific Imaging

Master of Science, Miami University, 2017, Geology and Environmental Earth Science

North Texas has seen an increase in seismic activity around the Dallas/Fort Worth area since the early 2000's, with activity in Johnson County in particular culminating in magnitude 3 and 4 events in 2011 and 2015 respectively. Previous analysis of the Johnson County sequence between 2009 and 2011 concluded that many of the events were induced by wastewater injection (Frohlich, 2012), however the earthquake database was small during this time period, and the differences between inducing and non-inducing injection wells were not clearly identified. This study addresses the causes of recent seismicity in Johnson County through an in depth characterization of the seismicity, industry operations, and regional and local geology in North Texas from 2009 to 2011. Seismic template matching using 3 USArray Transportable Array station recordings of all previously cataloged earthquakes in the study area provide a more complete temporal history of seismicity, identifying 977 additional events. Earthquakes from the largest burst in activity, in June 2011, were relocated using hypoDD and seem to align along NNE-SSW trends consistent with regional stress orientations and pre-existing structures related to the adjacent Ouachita thrust front. Relocated seismicity outlines a fault plane in the Precambrian basement that extends approximately 4 km in vertical extent, and is consistent with the hypothesis that seismicity is occurring on reactivated, pre-existing, critically stressed faults. Monthly injected volumes from 9 wastewater disposal wells suggest a correlation with background levels of seismicity throughout the study timeframe, however they do not correlate with distinct spikes in seismic activity. Temporal patterns of seismicity during the June 2011 sequence resemble patterns seen in previously documented cases of hydraulically fractured induced seismicity in Ohio. While a complete stimulation database is not available from this time frame, the vast number of active hydraulic (open full item for complete abstract)

Committee: Mike Brudzinski (Advisor); Brian Currie (Committee Member); Jonathan Levy (Committee Member) Subjects: Geology; Geophysics

Doctor of Philosophy, Case Western Reserve University, 2017, EECS - Computer Engineering

In this era of technological transformation in medicine, there is need to revolutionize the approach and procedures involved in the treatment of diseases to have a restructured understanding of the role of data and technology in the medical industry. Data is a key factor in diagnosis, management, and treatment of patients in any medical institution. Proper management and usage of patient's data will go a long way in helping the society save money, time and life of the patient. Having data is one thing and providing a system or means of translating the data is another issue. This dissertation is proposing a design of a Point of Care system for the Intensive Care Unit (a.k.a ICU_POC), which is a system that integrates the capabilities of the bedside monitors, bedside eFlowsheet and the Electronic Medical Records in such a manner that the clinicians interact with one another in real time from different locations, to view, analyze, and even make necessary diagnoses on patients' ailment based on their medical records. It demonstrates how patient data from the monitors can be imported, processed, and transformed into meaningful and useful information, stored, reproduced and transferred automatically to all necessary locations securely and efficiently without any human manipulation. ICU_POC will grant physicians the remote capability in managing patients properly by providing accurate patient data, easy analysis and fast diagnosis of patient conditions. It creates an interface for physicians to query historical data and make proper assumptions based on previous medical conditions. The problem lies in managing data transfer securely between one hospital EMR database and the other for easy accessibility of data by the physicians. This work is challenged by designing a system that could provide a fast, accurate, secure and effective (FASE) diagnosis of medical conditions of the patients in the ICU. The proposed system has the potential of reducing patients' length of stay i (open full item for complete abstract)

Committee: Kenneth Loparo (Advisor); Farhad Kaffashi (Committee Member); Vira Chankong (Committee Member); Michael Degeorgia (Committee Member) Subjects: Computer Engineering; Computer Science; Engineering

Doctor of Philosophy (PhD), Wright State University, 2016, Engineering PhD

Today's radars face an ever increasingly complex operational environment, intensified by the numerous types of mission/modes, number and type of targets, non-homogenous clutter and active interferers in the scene. Thus, the ability to adapt ones transmit waveform, to optimally suit the needs for a particular radar tasking and environment, becomes mandatory. This requirement brings with it a host of challenges to implement including the basic decision of what to transmit. In this dissertation, we discuss six original contributions, including the development of performance prediction models for constrained radar waveforms, that aid in the decision making process of an adaptive radar in selecting what to transmit. It is critical that the algorithms and performance prediction models developed be robust to varying radio frequency interference (RFI) environments. However, the current literature only provides toy examples not suitable in representing real-world interference. Therefore, we develop and validate two new power spectral density (PSD) models for interference and noise, derived from measured data, that allow us to ascertain the effectiveness of an algorithm under varying conditions. We then investigate the signal-to-interference-and-noise ratio (SINR) performance for a multi-constrained waveform design in the presence of colored interference. We set-up and numerically solve two optimization problems that maximize the SINR while applying a novel waveform design technique that requires the signal be an ordered subset of eigenvectors of the interference and noise covariance matrix. The significance of this work is the observation of the non-linearity in the SINR performance as a function of the constraints. This inspires the development of performance prediction models to obtain a greater understanding of the impact practical constraints have on the SINR. Building upon these results, we derive two new performance models, one for the constraine (open full item for complete abstract)

Committee: Brian Rigling Ph.D. (Advisor); Muralidhar Rangaswamy Ph.D. (Committee Member); Christopher Baker Ph.D. (Committee Member); Fred Garber Ph.D. (Committee Member); Wu Zhiqiang Ph.D. (Committee Member) Subjects: Aerospace Engineering; Electrical Engineering

Doctor of Philosophy, The Ohio State University, 2016, Electrical and Computer Engineering

Multiple-input multiple-output (MIMO) radar is an emerging set of technologies designed to extend the capabilities of multi-channel radar systems. While conventional radar architectures emphasize the use of antenna array beamforming to maximize real-time power on target, MIMO radar systems instead attempt to preserve some degree of independence between their received signals and to exploit this expanded matrix of target measurements in the signal-processing domain. Specifically the use of sparse “virtual” antenna arrays may allow MIMO radars to achieve gains over traditional multi-channel systems by post-processing diverse received signals to implement both transmit and receive beamforming at all points of interest within a given scene. MIMO architectures have been widely examined for use in radar target detection, but these systems may yet be ideally suited to real and synthetic aperture radar imaging applications where their proposed benefits include improved resolutions, expanded area coverage, novel modes of operation, and a reduction in hardware size, weight, and cost. While MIMO radar's theoretical benefits have been well established in the literature, its practical limitations have not received great attention thus far. The effective use of MIMO radar techniques requires a diversity of signals, and to date almost all MIMO system demonstrations have made use of time-staggered transmission to satisfy this requirement. Doing so is reliable but can be prohibitively slow. Waveform-diverse systems have been proposed as an alternative in which multiple, independent waveforms are broadcast simultaneously over a common bandwidth and separated on receive using signal processing. Operating in this way is much faster than its time-diverse equivalent, but finding a set of suitable waveforms for this technique has proven to be a difficult problem. In light of this, many have questioned the practicality of MIMO radar imaging and whether or not its theoretical ben (open full item for complete abstract)

Committee: Joel Johnson (Advisor); Robert Burkholder (Committee Member); Emre Ertin (Committee Member) Subjects: Electrical Engineering; Remote Sensing

Doctor of Philosophy, Case Western Reserve University, 2015, EECS - Electrical Engineering

This project has developed an energy-efficient, high data-rate, impulse radio ultra wideband (IR-UWB) transceiver, operating in three channels within 3–5 GHz for centimeter-to-meter range biotelemetry. Fabricated in 90 nm 1P/9M CMOS, the transceiver integrates an all-digital transmitter with a waveform-synthesis pulse generator and a timing generator for pulse modulation and phase scrambling that, as well as a noncoherent receiver with front-end RF amplification/filtering, self-correlation for energy detection and digital synchronization of the baseband clock and data. The transmitter provides great flexibility in reconfiguring the UWB pulse waveform in the time domain (e.g., overall shape, amplitude, duration) as well as its power spectral density (PSD) in the frequency domain (e.g., center frequency, bandwidth, peak level). A fully integrated receiver would also significantly reduce its power consumption as compared to that of a discrete implementation, addressing another limitation for true portability of the centimeter-range transceiver and greatly enhancing energy efficiency per received bit in the wireless link. The receiver RF front-end can provide up to 37 dB of gain with adjustable bandwidth, sharp roll-off and tunable center frequency at 3.5, 4 and 4.5 GHz for channel selection and robustness against out-of-band noise/interference. Employing a miniaturized, UWB, chip antenna for the transmitter and receiver, wireless transmission of pseudo-random binary sequence (PRBS) data at rates up to 75 Mb/s over 10 cm–1 m is shown for portable application. Further, employing a high gain horn antenna for the receiver, wireless transmission of PRBS data at rates up to 125 Mb/s over 50 cm–4 m is shown for stationary application with transmitter and receiver energy consumption of 14 pJ/pulse and 0.15 nJ/b, respectively, from 1.2 V. To address the problem of data rate in high-channel-count neurochemical monitoring, we demonstrated proof-of-concept feasibility of utilizin (open full item for complete abstract)

Committee: Pedram Mohseni (Advisor); Dominique Durand (Committee Member); Francis Merat (Committee Member); Soumyajit Mandal (Committee Member) Subjects: Biomedical Engineering; Electrical Engineering

Master of Science (MS), Wright State University, 2014, Earth and Environmental Sciences

The Horizontal to Vertical Spectral Ratio (HVSR) of broadband seismometer recordings, was explored in this study as a means of characterizing the varying depth to bedrock beneath a glacial drift surface layer. Data were collected using fifteen Guralp CMG-3ESPCD 3-component seismometers deployed from January 15, 2010 to March 16, 2010 over the Stark-Summit gas storage field of Dominion East Ohio. Using Antelope seismic analysis software, I used the HVSR of these seismic data to evaluate the apparent resonance frequency of the glacial drift surface layer and its dependency upon the thickness and shear velocity of the glacial drift. I also constructed a glacial drift thickness contour map in Arcview using bedrock depth information from the Ohio DNR, which was supplemented with additional new bedrock depth data in the area. The bedrock depths vary significantly in the study area but the surface layer resonance appears to be a useful tool to map depth to bedrock.

Committee: Ernest Hauser Ph.D. (Advisor); Doyle Watts Ph.D. (Committee Member); David Dominic Ph.D. (Committee Chair) Subjects: Environmental Geology; Geology; Geophysics; Petroleum Geology

Master of Science in Engineering (MSEgr), Wright State University, 2011, Electrical Engineering

Typical radar systems are limited to energy distribution characteristics that are range independent. However, operators are generally interested in obtaining information at particular ranges and discarding elsewhere. It seems appropriate then to attempt to put energy solely at the range(s) of interest, thus minimizing exposure to clutter, jammers and other range-dependent interferences sources. The frequency diverse array (FDA) can provide a mechanism to achieve range-dependent beamforming and the spatial energy distribution properties are investigated on transmit and receive for different architectures herein. While simplified FDA receive architectures have been explored, they exclude the return signals from transmitters that are not frequency matched. This practice neglects practical consideration in receiver implementation and has motivated research to formulate a design that includes all frequencies. We present several receiver architectures for a uniform linear FDA, and compare the processing chain and spatial patterns in order to formulate an argument for the most efficient design to maximize gain on target. It may also be desirable to beamsteer in higher dimensionalities than a linear array affords, thus, the transmit and receive concept is extended to a generic planar array. This new architecture allows 3-D beamsteering in angle and range while maintaining practicality. The spatial patterns that arise are extremely unique and afford the radar designer an additional degree of freedom to develop operational strategy. The ability to simultaneously acquire, track, image and protect assets is a requirement of future fielded systems. The FDA architecture intrinsically covers multiple diversity domains and, therefore, naturally lends it self to a multi-mission, multi-mode adar scheme. A multiple beam technique that uses coding is suggested to advance this notion.

Committee: Brian Rigling PhD (Advisor); Douglas Petkie PhD (Committee Member); Fred Garber PhD (Committee Member) Subjects: Electrical Engineering

Master of Science in Engineering (MSEgr), Wright State University, 2011, Mechanical Engineering

Typical vibration analysis of turbine engine components incorporates the use of a function generator to produce a signal that is routed to an excitation source as the forcing function of the test specimen. These waveforms are constructed by varying the amplitude of the signal over time with a fixed update rate (time increment between samples). This research investigates generating chirp waveforms by storing only one sinusoid of points and using an external timing signal to repetitively send out these stored data points. This results in varying the amplitude of the signal over time as well as the update rate. The update rate varies linearly as the frequency varies throughout the chirp. The number of samples stored is fixed as only one sinusoid is stored in memory. This results in a degraded waveform with step changes in the voltages of the analog output signal. This research incorporates a high speed analog output device from National Instruments used to generate the waveform built from user inputs for sweep range, time, and desired samples/cycle. For this research, both single and multiple degree of freedom systems were used to analytically predict the response of the system to the degraded waveforms. A series of experimental tests was conducted using a cantilevered beam to validate the analytical predictions. The response of the test article was captured using a scanning laser vibrometer from which the frequency response function (FRF) was calculated, and in turn, the natural frequencies, mode shapes, and damping characteristics were determined. The differences in the responses of the test article were quantified to determine the effect of the degraded waveform and the minimum number of samples/cycle in a waveform necessary to generate a signal sufficient for accurate modal analysis. A simulated bladed disk was modeled in state space to quantify the accuracy of modal analysis implementing the variable update rate waveforms with traveling wave excitation.

Committee: Joseph Slater PhD, PE (Advisor); Joseph Slater PhD, PE (Committee Chair); Fred Garber PhD (Committee Member); Tommy George PhD (Committee Member) Subjects: Aerospace Engineering; Engineering; Mechanical Engineering

Master of Science in Engineering (MSEgr), Wright State University, 2011, Electrical Engineering

With more users populating the RF spectrum and hence less available contiguous bandwidth, radar and communication waveforms are slowly forced to become more efficient at using their available frequencies. Two scenarios are considered: operation in a colored interference environment and operation in discontiguous spectral bands. Unconstrained algorithms for designing transmit waveforms and receive filters are evaluated, wherein varying a convex weight trades performance between spectral flatness and side lobe levels. An empirical study provides performance bounds for constrained radar waveform designs for an instantiation of the interference spectrum. Closed-form predictions for integrated sidelobe ratio (ISLR) and peak-to-sidelobe ratio (PSLR) for radar waveforms designed to operate in discontiguous spectral bands are derived and validated against two spectrally-disjoint waveform designs. These spectrally-disjoint waveform designs must also consider constraints imposed by hardware, such as modulus and phase restrictions. In the final part of this thesis, four spectrally-disjoint waveform designs are subjected to hardware-in-the-loop tests. Experimental results are shown and compared to computer simulations.

Committee: Brian Rigling PhD (Advisor); Fred Garber PhD (Committee Member); Zhiqiang Wu PhD (Committee Member) Subjects: Electrical Engineering

Doctor of Philosophy (PhD), Wright State University, 2011, Engineering PhD

Modern frequency modulated continuous wave (FMCW) radar technology provides the ability to modify the system transmission frequency as a function of time, which in turn provides the ability to generate multiple output waveforms from a single radar unit. Current low-power multi-waveform FMCW radar techniques lack the ability to reliably associate measurements from the various waveform sections in the presence of multiple targets and multiple false detections within the field-of-view. Two approaches are developed here to address this problem. The first approach takes advantage of the relationships between the waveform segments to generate a weighting function for candidate combinations of measurements from the waveform sections. This weighting function is then used to choose the best candidate combinations to form polar-coordinate measurements. Simulations show that this approach provides a ten to twenty percent increase in the probability of correct association over the current approach while reducing the number of false alarms in generated in the process, but still fails to form a measurement if a detection form a waveform section is missing. The second approach models the multi-waveform FMCW radar as a set of independent sensors and uses distributed data fusion to fuse estimates from those individual sensors within a tracking structure. Tracking in this approach is performed directly with the raw frequency and angle measurements from the waveform segments. This removes the need for data association between the measurements from the individual waveform segments. A distributed data fusion model is used again to modify the radar tracking systems to include a video sensor to provide additional angular and identification information into the system. The combination of the radar and vision sensors, as an end result, provides an enhanced roadside tracking system.

Committee: Lang Hong PhD (Advisor); Michael Temple PhD (Committee Member); Kefu Xue PhD (Committee Member); Zhiqiang (John) Wu PhD (Committee Member); Arthur Goshtasby PhD (Committee Member) Subjects: Electrical Engineering; Engineering