Master of Science, University of Akron, 2008, Computer Science

Fourier Transforms have wide range of applications ranging from signal processing to astronomy. The advent of digital computers led to the development of the FFT (Fast Fourier Transform) in 1965. The Fourier Transform algorithm involves many add/multiply computations involving trigonometric functions, and FFT significantly increased the speed at which the Fourier transform could be computed. A great deal of research has been done to optimize the FFT computation to provide much better computational speed. The modern advent of parallel computation offers a new opportunity to significantly increase the speed of computing the Fourier transform. This project provides a C code implementation of a new parallel method of computing this important transform. This implementation assigns computational tasks to different processors using the Message Passing Interface (MPI) library. This method involves parallel computation of the Discrete Cosine Transform (DCT) as one of the parts. Computation on two different computer clusters using up to six processors have been performed, results and comparisons with other implementations are presented.

Committee: Dale Mugler (Advisor); Tim O'Neil (Advisor) Subjects: Computer Science

Master of Science in Engineering (MSEgr), Wright State University, 2007, Electrical Engineering

Wideband digital receivers are important components used prevalently by the United States Air Force for many modern electronic warfare systems. Currently, many digital receiver architectures are designed for a specific mission requirement and are not parameterizable, modular, or reusable for varying mission requirements. Also, many designs are technology, platform, and vendor dependent which make upgrading existing fielded systems costly and difficult. Additionally, current wideband FFT-based digital receivers must wait until a number of samples equal to the size of the FFT are collected before spectral information can be updated. Achieving a high spectral update rate is important for the accurate detection of the time of arrival of radar pulses so that enemy signals can be detected and located quickly. Current methods to increase the effective spectral update rate by N require an N-fold increase in clock rate or an N-fold increase in area. For this research, a parameterizable channelized wideband digital receiver architecture is proposed that takes advantage of the tradeoffs between frequency resolution and spectral update rate while preserving bandwidth, reducing hardware requirements, and increasing throughput. The design is completely parameterizable to suit varying mission requirements, and it has been written in generic VHDL which was targeted toward FPGA and ASIC platforms with no code modification. Components developed in VHDL include the decimation filter and Parks-McClellan filter design algorithm. The FPGA implementation was fully tested, and for the parameters chosen, was able to achieve an 8x improvement in update rate.

Committee: John Emmert (Advisor) Subjects:

Ph.D., Antioch University, 2022, Antioch New England: Marriage and Family Therapy

Marriage and Family Therapists (MFTs) and Couple and Family Therapists (CFTs) engage in clinical practice from a systemic framework. This framework positions MFTs to consider the impact of social systems on the MFT/CFT field and their clients. Issues related to diversity, equity, inclusion, power, and privilege (DEIPP) impact all of the systems in which we operate. Currently, there is no consensus on a tool measuring training clinicians' competencies related to DEIPP beyond self-report. There is a need for a DEIPP competency measure because, currently, the most widely used measure is self or observer report, which may not provide a complete picture of a training clinician's competencies. This study utilized Critical Race Theory (CRT) and Feminist Family Therapy (FFT) to guide a thorough review of the literature. This process solidified domain and construct generation and then further synthesized item generation. This Delphi study was used to reach a consensus on item reduction. The survey contained 322 questions related to DEIPP. These questions were divided into three domains, attitudes self-report, multicultural knowledge questions, and clinical application vignettes. Specifically, this study's goal was to reach a consensus on item generation through two rounds of Delphi surveys sent to each participant; thus, establishing content validity. Five experts provided insight and feedback to address the domain definitions and items generated. The major contribution of this research is the completion of stage 1 for developing a measure that will address DEIPP competencies in MFT/CFT.

Committee: Lucy Byno Ph.D (Committee Chair); Kevin Lyness Ph.D (Committee Member); Bryson Greaves Ph.D (Committee Member) Subjects: Mental Health; Psychology; Therapy

Master of Science in Engineering, Youngstown State University, 2020, Department of Civil/Environmental and Chemical Engineering

In any civil engineering structure, damage resulted from the construction phase or developed over time affects the structural performance and may result in its failure. Early-stage damage detection is necessary for maintaining structural safety, serviceability, and minimizing the cost throughout the structural operation. Various destructive and conventional non-destructive damage detection techniques employed over the years are either laborious or, uneconomical, and require access to the entire structure. These limitations were addressed by developing the vibration-based methods for regular structural health monitoring. This holistic approach includes analyses of vibration signals and the related modal parameters. The change in these parameters may be used for detection of damage. In this research, modal frequency was used as a parameter to detect damage. The objective is to identify damage using natural frequency. To achieve this objective, several tests were conducted on simply supported steel beams having an open transverse crack with varying depths and locations. The analytical, numerical, and experimental approaches generate frequencies for the first three vibrating modes. The analytical approach considered the beam as the Euler-Bernoulli beam. Analytical frequencies were found from the solution of a partial differential equation by applying the boundary conditions. Vibration signals collected from the portable digital vibrometer (PDV 100) were analyzed using the Fast Fourier Transform (FFT) technique to achieve modal frequencies of the steel beam. In ANSYS (ANSYS, 2017), the finite element models of the beams were calibrated using the experimental results. The frequency from the analytical approach depends on the crack depth. Therefore, this method cannot produce the actual frequency of a beam with varying damage locations and depths. The graphical plots of the normalized frequency with varying damage depth and damage location was used to study the impact o (open full item for complete abstract)

Committee: AKM Anwarul Islam PhD (Advisor); Shakir Husain PhD (Committee Member); Richard Deschenes PhD (Committee Member) Subjects: Civil Engineering; Engineering

Master of Science (M.S.), University of Dayton, 2020, Aerospace Engineering

Velocity measurement inside of a wind tunnel is an extremely useful quantitative data for a multitude of reasons. One major reason is that velocity has a mathematical relationship with dynamic pressure which in turn influences all the aerodynamic forces on the test model. Many devices and methods exist for measuring velocity inside wind tunnels. At the same time, Doppler wind lidar (light detection and ranging) has been used for decades to make air speed measurements outdoors at long ranges. Lidar has been proven effective for many applications, and it has the potential to solve many of the problems faced by current velocimetry techniques inside wind tunnels. Despite this, minimal research has been performed with Doppler wind lidars inside wind tunnels. While multiple commercial systems exist for making air speed measurements at longer ranges, there are currently no widely available commercial devices designed to work well inside wind tunnels. In this research, initial work is described for the design and development of a continuous wave (CW), coherent wind lidar system. The system is for use as an alternative non-intrusive velocimetry method inside wind tunnels relying on the Doppler effect. A scaled down wind lidar designed to operate at much shorter ranges than current commercial wind lidars can be simpler, less expensive, and require less power. A first iteration of the design was constructed for proof of concept testing with a small-scale wind tunnel at low speeds (7.5-9 m/s). Testing showed that the lidar system could take one-dimensional speed measurements of seeded flow that closely matched Pitot static tube data. When not adding tracer particles to the flow, the lidar return signal was not strong enough for the photodetector used to measure the beat frequency. This research is focused on the process for designing the Doppler wind lidar system, constructing the experimental setup, and studying methods for data analysis. Results of testing presente (open full item for complete abstract)

Committee: Sidaard Gunasekaran (Advisor); Aaron Altman (Committee Member); Paul McManamon (Committee Member) Subjects: Aerospace Engineering; Atmosphere; Atmospheric Sciences; Engineering; Optics; Technology

Master of Science in Engineering, University of Akron, 2019, Electrical Engineering

This thesis proposes a technique for identifying deteriorated or contaminated electrical equipment. The technique uses the harmonic components of demodulated radio frequency (RF) and ultrasonic emissions to detect partial discharge (PD) events from faulty or contaminated components. The technique uses the sum-of-squares of the magnitudes of the first five 60-Hz harmonic components of the demodulated RF signal to detect the presence of faulty power system components. A parabolic acoustic noise detector captures ultrasonic emissions to pinpoint the physical location of the faulty power system component or components that causes the detected RF emissions. The proposed technique is capable of detecting all emissions detected, as well as others not detected, by the current industry standard – The Exacter Trigger. It is also more compact and portable, and it uses less data, requires fewer computations, and consumes less power. Single-chip digital signal processor implementations of the proposed technique are extensively validated via laboratory and field tests.

Committee: J. Alexis De Abreu Garcia (Advisor); Robert Veillette (Advisor); Michael French (Committee Member) Subjects: Electrical Engineering

Master of Science in Engineering, University of Akron, 2018, Electrical Engineering

This thesis discusses a detailed study of the design and performance analysis of patch antenna arrays at different frequencies. A linear hybrid array of 16 elements is built using patch antennas integrated with an RF front-end using commercial off-the-shelf (COTS) components. A well organized receiver chain that can work at a frequency in the range of 5 - 6 GHz is built using chip level components on a printed circuit board (PCB). This study mainly emphasizes the design and implementation of the comprehensive receiver beamforming systems using fast Fourier transform (FFT) algorithm and approximate - discrete Fourier transform (a-DFT). A low complexity 32-beam multi-beamformer at 5.8 GHz is designed, built and implemented in real time using optimized digital FPGA cores as the digital back-end which is collaborated work with Viduneth Ariyarathna. The emanating beams were measured and verified using the FPGA - based 32-element 5.8 GHz array setup which can generate 120 MHz bandwidth per channel. The beams corresponding to the approximate DFT are in good agreement with the beams corresponding to the FFT with negligible error approximately less than -14 dB. This setup can be used as a test bed to measure and evaluate various signal processing algorithms up to 32 linear array elements.

Committee: Arjuna Madanayake Dr (Advisor); Nghi Tran Dr (Committee Member); Ryan Christopher Toonen Dr (Committee Member) Subjects: Computer Engineering; Electrical Engineering

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

Doctor of Philosophy, The Ohio State University, 2016, Materials Science and Engineering

Metallic glasses represent a relatively new class of materials that have demonstrated enormous potential for functional and structural applications due to the unique set of properties attributed to them as a result of the disordered isotropic structure with metallically bonded elements. Amorphous metals benefit from the strong nature of the metallic bonds, but lack the crystallographic structure and polycrystalline nature of traditional metals which unsurprisingly has huge implications on the material properties, as all deformation mechanisms associated with a lattice are suppressed. This results in excellent strength, a high elastic strain limit, exceptional hardness, and improved corrosion and wear resistance. "Bulk" metallic glasses (BMG) represent the amorphous metals which can be produced at the cm length-scale, thus greatly expanding their applicability for structural applications. However, due to the catastrophic nature of the failure produced upon yielding, monolithic metallic glasses are seldomly used for structural applications. Bulk metallic glass-matrix composites (BMGMCs), however, are able to combine the excellent strength, hardness, and elastic strain limit of amorphous metallic glass with a ductile crystalline phase to achieve extraordinary toughness with minimal degradation in strength. In order to explore the mechanical interactions between the amorphous and crystalline phases, a full-field micromechanical model which couples the free-volume based constitutive behavior for the matrix phase with standard rate-dependent crystal plasticity for the dendrites, and its implementation via an elastic-viscoplastic Fast-Fourier Transform (FFT) solver. The model is calibrated to macroscale stress-strain data for Ti-Zr-V-Cu-Be BMGMCs with varying composition and furthermore by comparing the deformation behavior associated with the shear bands predicted by the model, to the artifacts observed from characterization microscopy analysis on the same failed BMGMC (open full item for complete abstract)

Committee: Wolfgang Windl (Advisor); Stephen Niezgoda (Advisor); Maryam Ghazisaeidi (Committee Member) Subjects: Aerospace Materials; Materials Science

Doctor of Philosophy (Ph.D.), University of Dayton, 2016, Electrical Engineering

The goal of this research is to develop a method for affordable and reliable sampling and coherent processing of measurement data collected via a modified magnetron oscillator based marine radar system. Non-coherent low-priced marine radar systems offer limited surveillance in clutter rich environments as compared to more expensive and complex coherent solid state radar systems. The approach used herein leverages modern analog to digital converters (ADC) and field programmable gate array (FPGA) technology to affordably and effectively sample the radiated and received signals for further analysis using FFT-based Doppler processing or cross correlation analysis. Track processing of moving targets is fundamental to any advanced radar and is a further focus of this research. The marine radar hardware is modified to capture the transmit signal at the source, and the receive signal at the aperture, for processing via FPGAs. The receive pulse train is cross-correlated with the transmit pulse train reference to remove the uncertainties in the phase history of the collected data. This operation ultimately makes the radar fully coherent on receive. Once the receive signal is made coherent, classical Doppler processing is used to differentiate moving targets from clutter and electromagnetic interference. A real time system has been built on a board with ADCs, FPGAs, and a microprocessor. Mixing of the Transmit (TX) and the Receive (RX) signals, Fourier transform analysis, and Pulse Compression are all executed digitally in the FPGA whereas Doppler Processing is performed on the microprocessor. This paper presents the underlying principles of cohering signals on receive, and it will show a real-time implementation of such algorithms using FPGAs.

Committee: Michael Wicks PhD (Advisor); Lorenzo Lo Monte PhD (Committee Chair); Guru Subramanyam PhD (Committee Chair); Eric Balster PhD (Committee Chair) Subjects: Electrical Engineering; Engineering

MS, University of Cincinnati, 2014, Engineering and Applied Science: Aerospace Engineering

Fast Poisson solvers using the Fast Fourier Transform on uniform grids are especially suited for parallel implementation, making them appropriate for portability on graphical processing unit (GPU) devices. The goal of the following work was to implement, test, and evaluate a fast Poisson solver for periodic boundary conditions for use on a variety of GPU configurations. The solver used in this research was FLASH, an immersed-boundary-based method, which is well suited for complex, time-dependent geometries, has robust adaptive mesh refinement/de-refinement capabilities to capture evolving flow structures, and has been successfully implemented on conventional, parallel supercomputers. However, these solvers are still computationally costly to employ, and the total solver time is dominated by the solution of the pressure Poisson equation using state-of-the-art multigrid methods. FLASH improves the performance of its multigrid solvers by integrating a parallel FFT solver on a uniform grid during a coarse level. This hybrid solver could then be theoretically improved by replacing the highly-parallelizable FFT solver with one that utilizes GPUs, and, thus, was the motivation for my research. In the present work, the CPU-utilizing parallel FFT solver (PFFT) used in the base version of FLASH for solving the Poisson equation on uniform grids has been modified to enable parallel execution on CUDA-enabled GPU devices. New algorithms have been implemented to replace the Poisson solver that decompose the computational domain and send each new block to a GPU for parallel computation. One-dimensional (1-D) decomposition of the computational domain minimizes the amount of network traffic involved in this bandwidth-intensive computation by limiting the amount of all-to-all communication required between processes. Advanced techniques have been incorporated and implemented in a GPU-centric code design, while allowing end users the flexibility of parameter control at runtime (open full item for complete abstract)

Committee: Kirti Ghia Ph.D. (Committee Chair); Bracy Elton Ph.D (Committee Member); Shaaban Abdallah Ph.D. (Committee Member); Urmila Ghia Ph.D. (Committee Member) Subjects: Aerospace Materials

Doctor of Philosophy (PhD), Wright State University, 2013, Environmental Sciences PhD

Time series that exhibit multiple scaling properties in the frequency domain are common in natural systems (e.g., temperature through geologic time). NOAA verified hourly water level data ranging from 20 to 30 years in duration for nine stations in the North American Great Lakes is converted to the frequency domain using a complex discrete fast Fourier transform (FFT) and then expressed as a power spectrum in terms of frequency versus power. To quantify power law scaling behavior, a scaling exponent (β) is determined by fitting a power function to a log-log plot of frequency (f ) or period (T) versus power in the frequency domain. For water level fluctuations in the Great Lakes, the frequency domain exhibits four distinct regions of power law scaling. The mathematical relationship of the scaling exponent (β) to 1/f time series behavior is examined employing Bode analysis. Variations in scaling behavior of water level data, indicated by the patterns of change in amplitude and phase across frequencies, can be expressed through transfer functions. The transfer functions are created using Laplace transforms. Each Laplace term (s) has a fractional exponent based on the scaling exponent (β) derived from the Bode magnitude plot. Convolution of the transfer function in the time domain is equivalent to multiplication in the frequency domain (Laplace space). Combining the transfer functions for all frequencies yields a Frequency Response Model and provides a basis to determine how the system that created the time series will respond to any given input over all frequencies. For water level fluctuations in the Great Lakes, the scaling behavior pattern is well approximated by a combination of four linear differential equations or transfer functions, one primary equation for each distinct scaling region. The collective interactions of all equations over all frequencies create the Great Lakes Frequency Response Model and represent the underlying physical dynamics of the Great La (open full item for complete abstract)

Committee: Sarah Tebbens Ph.D. (Advisor); Christopher Barton Ph.D. (Committee Member); John Flach Ph.D. (Committee Member); Paul Seybold Ph.D. (Committee Member); Brian Tsou Ph.D. (Committee Member) Subjects: Applied Mathematics; Environmental Science; Geophysical; Geophysics; Hydrologic Sciences; Mathematics; Systems Design; Systems Science; Water Resource Management

Master of Science in Engineering (MSEgr), Wright State University, 2010, Electrical Engineering

Digital microwave receivers play a critical role in many of today's modern radar tracking systems. The need for these digital receivers to push the boundaries in terms of bandwidth and input dynamic ranges (DR) is vital for their use in radar signal tracking. Significant research has been conducted in the area of the fast Fourier transform (FFT) to aid in continuing to enhance the performance capabilities of digital microwave receivers. However, with the advancement and increased complexity of these systems, the need for an efficient and effective adaptive thresholding technique is becoming ever more present. The proposed adaptive thresholding technique utilizes signal magnitude evaluations and multi-stage signal scaling throughout a 128-point FFT in order to effectively determine the optimal threshold for the microwave receiver. The incorporation of a 10-bit dynamic kernel function, as well as 14-bit word size between FFT stages is used to aid in increasing receiver sensitivity, multi-tone instantaneous dynamic range (IDR) and spurious free dynamic range (SFDR) performance. With the implementation of our adaptive thresholding technique, our receiver's maximum IDR is maintained between 34dB down to 24dB for input signal strengths ranging from -4dBm down to -32dBm. From simulation results incorporating the use of digitized data from our 10-bit Atmel ADC our Multi-Stage Scaling (MSS) receiver design is capable of obtaining an SFDR of 35.91dB using an input signal strength of -7dBm.

Committee: Henry Chien-In PhD (Advisor); Marian Kazimierczuk PhD (Committee Member); Saiyu Ren PhD (Committee Member) Subjects: Electrical Engineering

Master of Science in Engineering (MSEgr), Wright State University, 2008, Electrical Engineering

Digital receivers involve fast Fourier transform (FFT) computations that require a large amount of arithmetic operations. The implementation of a FFT processor is one of the most challenging parts in the realization of a wideband receiver and its hardware complexity is very high. Hence, kernel function FFT processors have been proposed to meet real-time processing requirements and to reduce hardware complexity by rounding the kernel function to predetermined kernel points so as to eliminate the multipliers and use only shifters and adders or subtractors. Because of the nonlinear nature of this approximation by the rounding errors, spurious responses are generated and reduce the two signal instantaneous dynamic range (IDR) of the receiver in comparison with ideal FFT. Furthermore, there is a need to increase the resolution bits of the analog-to-digital converter (ADC) for FFT to improve the receiver performance by reducing the false alarm and increasing the spur-free dynamic range (SFDR). In this research, architecture for an FPGA-based 2.56 giga sample per second (GSPS) fixed kernel function FFT, using a truncated 10-bit ADC, is implemented. The FFT can produce an averaged single signal SFDR using the ideal ADC, of 22.8 dB with the ability to produce a two-signal IDR using the ideal ADC with a performance of 20.8 dB. With the ADC utilizing the eight most significant bit (MSB) values, the FPGA-based FFT can detect a weak input signal at -17.6 dBm at a full scale amplitude of 3.6 dBm. The resulting spurious-free dynamic range (SFDR) has a performance of 21.2 dB, which is very close to the ideal realization. The eight least significant bit (LSB) values where evaluated as well, generating a low signal detection of -22.7 dBm for a full scale amplitude of -9.3 dBm. This truncation scheme resulted in an SFDR performance of 13.4 dB. There was also a reduction in the hardware utilization with the FPGA implementation. With the employment of a folding technique the available r (open full item for complete abstract)

Committee: Chien-In Henry Chen PhD (Advisor); John M. Emmert PhD (Committee Member); Raymond E. Siferd PhD (Committee Member) Subjects: Electrical Engineering

Master of Science in Engineering (MSEgr), Wright State University, 2008, Electrical Engineering

The purpose of this research was to investigate the feasibility of using broadband electronic warfare (EW) receivers for Global Position System (GPS) tracking. These are pulse-oriented receivers, typically with input bandwidths of 1 Ghz or larger, and so by definition do not have the same characteristics and processing of continuous wave (CW) receivers like GPS devices, FM radios, etc. For example, the spectral output of the Fast Fourier Transform (FFT) used in broadband signal processing updates on the frequency of the FFT input sample size, versus a CW receiver which updates on a more continuous basis. The foundation of this potential broadband application of GPS hinges on the ability to accurately detect the GPS Satellite Coarse Acquisition (C/A) Code, which is phase modulated onto the GPS L1 carrier signal. This study uses the high speed Monobit FFT approximation technique developed by Dr. A. Despain [1] and Dr. Jim Tsui as the core signal processor, of which Dr. Tsui holds patents [2,3]. The cyclical C/A Code FFT spectral bin components are processed and compared to a known good C/A code for a given satellite to determine the accuracy of the correlation. The novel EW GPS technique developed in this thesis indicates that GPS satellite C/A codes can indeed be reasonably processed with broadband techniques, at least with the Monobit FFT, and that this foundational work can be built upon in the future so that broadband devices can ultimately be used for GPS applications. Synthesizable deliverables include a phase detector, a hardware signal condenser, and a correlation module. A robust Hardware Description Language (HDL) Test Bench, several signal generators, and various Matlab support tools were also developed.

Committee: John Emmert PhD (Advisor); Fred Garber PhD (Committee Member); Stephen Hary PhD (Committee Member); Raymond Siferd PhD (Committee Member) Subjects: Electrical Engineering

Master of Science in Engineering (MSEgr), Wright State University, 2007, Electrical Engineering

The advent of field-programmable gate array (FPGA) has provided an excellent platform to market prototyping of full receiver-on-chip designs in a short time. The design of multi-tone wideband receiver has always been a challenge because of the difficulty to detect weak signals in the presence of noise in the frequency spectrum and also the presence of general spurs generated by the receiver. In this research, architecture for a FPGA-based 2.56-GSPS digital wideband receiver with multi-tone signal detection and tracking is designed to demonstrate the capability of replacing more expensive analog components into their cheaper digital design counterparts. Novel hardware implementations of a Hamming window function, a fast Fourier transform (FFT), and an encoder algorithm is presented. This receiver can distinguish four-tone signals for a bandwidth of 1.20 GHz at a 20 MHz interval, has an average of four-tone signal spurious-free dynamic range (SFDR) of 22 dB, two-tone signal SFDR of 39 dB, and single signal SFDR of 45.5 dB. The digital receiver can also track the input signals and distinguish if they are continuous or a pulse wave signals.

Committee: Chien-In Chen (Advisor) Subjects:

Master of Science (MS), Ohio University, 1989, Electrical Engineering & Computer Science (Engineering and Technology)

Hypercube machine implementation of a 2-D FFT algorithm for object recognition

Committee: Mehmet Celenk (Advisor) Subjects:

Doctor of Philosophy (PhD), Ohio University, 2002, Electrical Engineering & Computer Science (Engineering and Technology)

GPS receivers spend much of their time on acquisition and tracking. Slow acquisition is due to the large computation time of the correlation function. The correlation function searches for the code phase between the GPS receiver signal arrival time and the GPS satellite's signal transmission time. The computation of the correlation function in frequency domain is speed up N/logN times compared with the time domain implementation. The long computation time for the correlation function is due to the computation of the FFT functions. One possible solution to speed up the calculations of the correlation function is by replacing the FFTs with simpler transforms. Two transforms were studied in this work. A real transform called the Fermat number transform (FNT) was presented. The FNT-based convolution algorithm was shown. However, the FNT-based convolution has a sequence length restriction that makes it not applicable to the GPS case. A binary transform called the Walsh Hadamard transform (WHT) was also investigated. The WHT-based correlation algorithm was presented and verified. This method shows a significant reduction in the computing time of the correlation function by approximately 20 times compared to the FFT method. The Walsh Hadamard method is not directly applicable to the GPS C/A code, so was not used for GPS signal acquisition. This dissertation also illustrates a realistic solution to the slow acquisition of the GPS receivers. It uses the FPGA technology along with an averaging method to speed up the calculations of the FFT-based correlation function and to reduce the hardware requirements. The developed method approximated the correlation function by using a modified version of the C/A code. This approximation was accurate enough to use in the acquisition process while maintaining an acceptable level of signal power. This algorithm was used to guide three serial correlators to zoom-in around the correlation peak and provide refined versions of the acquisition (open full item for complete abstract)

Committee: Janusz Starzyk (Advisor) Subjects:

Doctor of Philosophy (PhD), Ohio University, 2007, Electrical Engineering & Computer Science (Engineering and Technology)

A transform-domain, instrumentation Global Positioning System (GPS) receiver is developed for high-fidelity signal quality monitoring (SQM), GPS anomalous event monitoring (GAEM), and GPS software-defined radio (SDR) research. Features of the receiver include: a radio frequency front-end with 24 MHz bandwidth on the GPS L1 (1575.42 MHz) and L2 (1227.6 MHz) frequencies with 14-bit sampling capability to capture and analyze high-dynamic-range signals such as in-band interference; An integrated GPS/Inertial Measurement Unit (IMU) data collection capability at 105 Mbytes/sec sustained transfer rate and 2-Terabyte capacity, with a novel, sub-microsecond resolution IMU time stamping method that significantly simplifies GPS/IMU deeply-integrated processing; a continuous-processing transform-domain engine that computes 1024-point complex parallel-code-correlation functions in less than 15 microseconds for 1-ms blocks of data; A runtime-configurable serial engine containing several hundred ‘split-sum' coarse/acquisition (C/A) code correlators operating on 14-bit input samples; A realtime transform-domain GPS receiver with full message decoding, range measurement, and position-velocity-time solution updates up to a 1 kHz rate. The receiver's graphical user interface allows runtime interaction via a set of software controls, and realtime internal-parameter graphing capabilities similar in function to a combined digital storage oscilloscope and spectrum analyzer. High-fidelity capabilities of the receiver include 55 points per C/A-chip SQM, and 10-correlator Precise-code SQM. The instrument's unique GPS/IMU interleaved data collection capability enabled a flight test where GPS carrier phase tracking was maintained for signals with carrier-to-noise ratios (CNR) at the 15 dB-Hz level. The receiver's application layer is built using a custom-developed, object-oriented applications programming interface that supports customization to suit a variety of applications. The instrument's (open full item for complete abstract)

Committee: Frank van Graas (Advisor) Subjects:

Master of Science (MS), Ohio University, 2000, Electrical Engineering & Computer Science (Engineering and Technology)

The Global Positioning System represents the pinnacle of navigation technology for the 21st century. As new technologies integrate GPS services, the limited availability of GPS in environments where the signal is severely attenuated, subject to strong multipath or high dynamics becomes an obstacle to a rapidly growing industry. A novel scheme for processing the GPS signal, namely a software radio employing block-processing techniques similar to those used for image processing has proven to enhance the usability of GPS in such environments. However, these techniques have huge computational requirements that are impossible to meet with a microprocessor. Custom designed hardware, such as an application specific integrated circuit (ASIC) would handle the processing requirement, but defeats the philosophy of a software radio since the algorithms cannot be changed. Field programmable gate arrays (FPGAs) are beginning to replace ASICs in certain applications since they feature software-like re-programmability while approaching ASIC-like performance. FPGAs are excellent candidates for research since they lack the NRE costs associated with ASICs. Hence, FPGAs are the most attractive implementation platform for developing a real-time block-processing GPS receiver. This work lays the groundwork for the implementation of a real-time block-processing GPS receiver in FPGA hardware. It is a feasibility study since the problem is approached at a high-level of abstraction. The original block-processing approach is re-analyzed for implementation in FPGA hardware. Implementing the 5000-point FFTs in finite-precision hardware represents one of the biggest challenges in this work. This requires analysis of the FFT error bound to determine the minimum precision required that would yield acceptable results while minimizing hardware cost. Even though the analytical error bound for finite-precision FFTs is well documented in past literature, its direct application to the block-processing pr (open full item for complete abstract)

Committee: Janusz Starzyk (Advisor) Subjects: