Electrical and Computer Engineering Commons^™

Passive And Electronically Steered Array Planar Feeds For Satellite Communications, Kyle C. Browning

Theses and Dissertations

As the need for more bandwidth increases, satellite communication (SatCom) terminals are forced to climb higher in frequency. Higher frequency means greater propagation losses, and so antenna gain and sensitivity have to increase. The higher the gain, the more difficult it is to point the antenna. To make matters even more challenging, consumers are requesting satellite links in harsher environments and on moving vehicle and planes. In order to meet today's challenges and improve on dish feeds, research is ongoing to replace fixed-beam feedhorns with smaller, cheaper, and lighter PCB based antennas and to develop low-cost electronically steered array feeds …

Application Improvements Of Slab-Coupled Optical Fiber Sensors, Spencer L. Chadderdon

Theses and Dissertations

This dissertation explores techniques for improving slab-coupled optical fiber sensor (SCOS) technology for use in specific applications and sensing configurations. SCOS are advantageous for their small size and all-dielectric composition which permit non-intrusive measurement of electric fields within compact environments; however, their small size also limits their sensitivity. This work performs a thorough analysis of the factors contributing to the performance of SCOS and demonstrates methods which improve SCOS, while maintaining its small dimensions and high level of directional sensitivity. These improvements include increasing the sensitivity by 9x, improving the frequency response to include sub 300 kHz frequencies, and developing …

Modulation And Synchronization For Aeronautical Telemetry, Christopher G. Shaw

Theses and Dissertations

Aeronautical telemetry systems have historically been implemented with constant envelope modulations like CPM. Shifts in system constraints including reduced available bandwidth and increased throughput demands have caused many in the field to reevaluate traditional methods and design practices. This work examines the costs and benefits of using APSK for aeronautical telemetry instead of CPM. Variable rate turbo codes are used to improve the power efficiency of 16- and 32-APSK. Spectral regrowth in nonlinear power amplifiers when driven by non-constant envelope modulation is also considered. Simulation results show the improved spectral efficiency of this modulation scheme over those currently defined in …

Gps Multipath Reduction With Correlator Beamforming, Jason M. Barhorst

Theses and Dissertations

This research effort investigates the feasibility of beamforming using a single Global Positioning System (GPS) front end. Traditional methods of beamforming use multiple front ends, typically one per antenna element. By enabling a receiver to sample a switched antenna array, the hardware cost of implementing a GPS antenna array can be significantly reduced. Similar techniques of reducing the number of receivers have been used by Locata Corporation in the design of their non-GPS positioning systems. However, Locata Corporation's local transmitters provide a signal strength much higher than GPS's signal strength. For this reason, the inclusion of low-noise amplifiers into the …

Contact Resistance Evolution And Degradation Of Highly Cycled Micro-Contacts, Christopher L. Stilson

Theses and Dissertations

Reliable microelectromechanical systems (MEMS) switches are critical for developing high performance radio frequency circuits like phase shifters. Engineers have attempted to improve reliability and lifecycle performance using novel contact metals, unique mechanical designs and packaging. Various test fixtures including: MEMS devices, atomic force microscopes (AFM) and nanoindentors have been used to collect resistance and contact force data. AFM and nanoindentor test fixtures allow direct contact force measurements but are severely limited by low resonance sensors, and therefore low data collection rates. This thesis reports the contact resistance evolution results and fabrication of thin film micro-contacts dynamically tested up to 3kHz. …

Characterization And Performance Comparison Of Low-Voltage, High-Speed, Push-Pull And Traveling-Wave Silicon Mach-Zehnder Modulators, Tristan A. Latchu

Theses and Dissertations

The well-known power and memory walls are recognized as the current bottlenecks in computing performance, and with the increasing computational load of commonly run applications, it is necessary to nd ways to alleviate the issues presented by the aforementioned bottlenecks. It is therefore necessary to not focus solely on extracting performance improvement by way of changes to the processing architecture, but rather by holistically improving the computing platform, namely the communications backbone. This work focuses on the characterization and performance comparison of two families of optical data modulators, both fundamentally Mach{Zehnder modulators (MZMs); namely, a modulator with a Push-Pull (PP) …

Bayesian Methods And Confidence Intervals For Automatic Target Recognition Of Sar Canonical Shapes, Richard W. Rademacher

Theses and Dissertations

This research develops a new Bayesian technique for the detection of scattering primitives in synthetic aperture radar (SAR) phase history data received from a sensor platform. The primary goal of this research is the estimation of size, position, and orientation parameters defined by the “canonical” shape primitives of Jackson. Previous Bayesian methods for this problem have focused on the traditional maximum a posteriori (MAP) estimate based on the posterior density. A new concept, the probability mass interval, is developed. In this technique the posterior density is partitioned into intervals, which are then integrated to form a probability mass over that …

Selectively Tuning A Buckled Si/Sio2 Membrane Mems Through Joule Heating Actuation And Mechanical Restriction, Kyle K. Ziegler

Theses and Dissertations

This research followed previous work and attempted to modify the spring in two ways. First, a Ti/Au meander resistor was deposited atop the membrane in an effort to actuate the membrane and change the spring constant. Secondly, a series of overhanging cantilevers were attached to the bulk substrate surrounding the membrane in an effort to constrain the membrane buckling deflection to the negative stiffness region. Membrane buckling was investigated through Finite Element analysis (FEA) and analytical equations. Deflections were measured using an interferometric microscope (IFM) and force/deflection measurements were captured using a unique measurement scheme. The results concluded that by …

The Design, Implementation, Assessment, And Evaluation Of A Power Systems Protection Laboratory Curriculum, Jennifer Ferris

Dissertations and Theses

Over the last the last three decades, there has been a significant and documented decrease of power engineering curriculum within U.S. electrical engineering programs. Development of lifelong learners capable of critical and independent thinking is required to replace the large number of upcoming retirees from the industry and to prepare for the engineering challenges new technologies, laws and regulations are bringing to the electrical power system. In response to these challenges, Portland State University redesigned its BSEE and MSECE power engineering programs in order to create a launching pad for successful power engineering careers. A course series on power system …

Electrical Characterization Of Spherical Copper Oxide Memristive Array Sensors, James P. Orta

Theses and Dissertations

A new System Protection (SP) technology is explored by using electrical and mechanical interference-sensing devices that are implemented with granular memristive material. The granular materials consist of oxide-coated copper spheres with radii of about 700 µm that are placed in contact to produce thin oxide junctions which exhibit memristive behavior. Processes for etching, which compared acetic acid and nitric acid etches, and thermal oxidation at 100°C are performed and compared to produce copper spheres with a copper oxide layer over the sphere surface. Oxidized copper spheres are tested as sensor arrays by loading into a capillary tube in an aligned …

Memristive Responses Of Jammed Granular Copper Array Sensors To Mechanical Stress, Gary A. Willey

Theses and Dissertations

A granular memristive device with the end goal of creating a novel system protection device is introduced in a 1-Dimension array. The electromechanical network will lay the groundwork for future 2-Dimensional and 3-Dimensional devices for simultaneous protection from intrusion. Off the shelf copper spheres with diameter of 710 ± 11microns were found through nano-indentation measurements to have elastic modulus of 106GPa, and compressive yield strength of 729MPa, these spheres were prepared for test in a 1-Dimensional array device. The arrays response to mechanical perturbations modeled by Hertz contact mechanics can be monitored by simultaneous electrical measurements across the multiple metal-insulator-metal …

Removing Parallax-Induced False Changes In Change Detection, Karmon M. Vongsy

Theses and Dissertations

Accurate change detection (CD) results in urban environments is of interest to a diverse set of applications including military surveillance, environmental monitoring, and urban development. This work presents a hyperspectral CD (HSCD) framework. The framework uncovers the need for HSCD methods that resolve false change caused by image parallax. A Generalized Likelihood Ratio Test (GLRT) statistic for HSCD is developed that accommodates unknown mis-registration between imagery described by a prior probability density function for the spatial mis-registration. The potential of the derived method to incorporate more complex signal proccessing functions is demonstrated by the incorporation of a parallax error mitigation …

Airborne Wireless Communication Modeling And Analysis With Matlab, Matthew J. Vincie

Theses and Dissertations

Over the past decade, there has been a dramatic increase in the use of unmanned aerial vehicles (UAV) for military, commercial, and private applications. Critical to maintaining control and a use for these systems is the development of wireless networking systems [1]. Computer simulation has increasingly become a key player in airborne networking developments though the accuracy and credibility of network simulations has become a topic of increasing scrutiny [2-5]. Much of the inaccuracies seen in simulation are due to inaccurate modeling of the physical layer of the communication system. This research develops a physical layer model that combines antenna …

Blind Demodulation Of Pass Band Ofdma Signals And Jamming Battle Damage Assessment Utilizing Link Adaptation, Nicholas A. Rutherford

Theses and Dissertations

This research focuses on blind demodulation of a pass band OFDMA signal so that jamming effectiveness can be assessed; referred to in this research as BDA. The research extends, modifies and collates work within literature to perform a new method of blindly demodulating of a passband OFDMA signal, which exhibits properties of the 802.16 Wireless MAN OFDMA standard, and presents a novel method for performing BDA via observation of SC LA. Blind demodulation is achieved by estimating the carrier frequency, sampling rate, pulse shaping filter roll off factor, synchronization parameters and CFO. The blind demodulator's performance in AWGN and a …

Influence Of Reduction Promoters On Stability Of Cobalt/Γ-Alumina Fischer-Tropsch Synthesis Catalysts, Gary Jacobs, Wenping Ma, Burtron H. Davis

Center for Applied Energy Research Faculty and Staff Publications

This focused review article underscores how metal reduction promoters can impact deactivation phenomena associated with cobalt Fischer-Tropsch synthesis catalysts. Promoters can exacerbate sintering if the additional cobalt metal clusters, formed as a result of the promoting effect, are in close proximity at the nanoscale to other cobalt particles on the surface. Recent efforts have shown that when promoters are used to facilitate the reduction of small crystallites with the aim of increasing surface Co⁰ site densities (e.g., in research catalysts), ultra-small crystallites (e.g., < 2–4.4 nm) formed are more susceptible to oxidation at high conversion relative to larger ones. The choice of promoter is important, as certain metals (e.g., Au) that promote cobalt oxide reduction can separate from cobalt during oxidation-reduction (regeneration) cycles. Finally, some elements have been identified to promote reduction but either poison the surface of Co⁰ (e.g., Cu), or produce excessive light gas selectivity (e.g., Cu and Pd, or Au at …

A Cavity-Backed Spiral Slot Antenna With Wide Axial Ratio Beamwidth For Gps System, Xiulong Bao, Max Ammann

Articles

A monofilar spiral slot antenna with a cavity-backed reflector is described. presented, which can achieve the performance of the wide Axial Ratio beamwave for Global Positioning System GPS system. It comprises an arrangement of a single printed spiral slots fed by a 50 Ω microstrip line. By using cavity-backed covering the slot structure, a wide axial ratio beamwidth performance is achieved in the GPS L1 frequency. The angle with less than 3 dB axial ratio at 1.575 GHz in the YoZ plane is about 215 degree. The measured results show that the HPWB beamwidths at 1.575 GHz are 100 degree …

Parameter Identification Of Micro-Grid Control System, Ning Gao

Electronic Theses and Dissertations

Micro-grid provides an effective means of integrating distributed energy resource (DER) units into the power systems. A micro-grid is defined as an independent low- or medium-voltage distribution network comprising various DER units, power-electronic interfaces, controllable loads, and monitoring and protection devices. Following the development of the renewable energy, micro-grid has attracted much attention.

This thesis emphasizes on the parameter identification of the control system of the micro-grid. The control system plays an important role in the stable operation of the micro-grid. The micro-grid has two operation modes, which are grid-connected operation mode and islanded operation mode. The transition between two …

Numerical Analysis Of First-Order Acousto-Optic Bragg Diffraction Of Profiled Optical Beams Using Open-Loop Transfer Functions, Monish Ranjan Chatterjee, Fares S. Almehmadi

Electrical and Computer Engineering Faculty Publications

In standard acousto-optic Bragg analysis, the incident light and sound beams are assumed to be uniform plane waves (with constant profiles) leading to the results based on standard weak interaction theory. As a follow-up to earlier work dealing with nonuniform incident optical beams, we revisit the problem of Bragg diffraction under nonuniform profiles, and include Gaussian, third-order Hermite–Gaussian, and zeroth-order Bessel profiles in our investigation, along with a few others. The first-order diffracted beam is examined (using a transfer function formalism based on angular spectra) under several parametric limits [such as the Klein–Cook parameter Q, the effective profile width, and …

Addressing User Requirements In Open Source Software: The Role Of Online Forums, Arif Raza, Luiz Fernando Capretz

Electrical and Computer Engineering Publications

User satisfaction has always been important in the success of software, regardless of whether it is closed and proprietary or open source software (OSS). OSS users are geographically distributed and include technical as well as novice users. However, it is generally believed that if OSS was more usable, its popularity would increase tremendously. Hence, users and their requirements need to be addressed in the priorities of an OSS environment. Online public forums are a major medium of communication for the OSS community. The research model of this work studies the relationship between user requirements in open source software and online …

Boosty-Bit: Power For Pint-Sized Projects, Timothy Grijalva

Electrical Engineering

In order to make it easier for hobbyists to create small portable microcontroller based electronics projects, I have created Boosty-bit, a tiny DC-DC boost convert that runs off a single alkaline battery cell (AA or AAA). The Boosty-bit converter can source up to 250mA @ 3.3v, making it ideal for many microcontroller based projects. In addition to power management, Boosty-bit is also physically small, allowing it to fit inside pen/marker-sized enclosures along with a AAA battery and a microcontroller. Boosty-bit aims to be the ideal solution for “makers” who desire portability and compact form factors in their projects.

Imu Based Tracking And Stabilization System, Aaron Barton

Electrical Engineering

The objective of this project is to develop a system that can track a user selected point in space given displacement, vibration and rotation of the device. Stabilization systems are used in various forms over the years, with the military amongst the foremost adopters. More recently, with the increasing popularity of quad-copters for RC hobbyists, and small cameras capable of take high quality video during recreational sports such as skiing or mountain biking, the need has emerged for a cheaper, more accessible version of stabilization systems for use in photography. Additionally, while some devices do exist for hobbyists can take …

The Garage Band Lightshow, Jason Descenzo

Electrical Engineering

The expenses musicians accrue make it hard to afford all the different equipment needed to perform and very unlikely that the average start up band or artist can afford the luxury of a musical light show in their early performances. The Garage Band Lightshow provides an easily set up and affordable way for musicians to use concert lighting in their performances. The Garage Band Lightshow provides one LED box. The light box responds to an audio signal and provides varying pulses and colors of light depending on the high, mid, and low frequencies of the audio signal. The Garage Band …

Learning About Led Lighting Technology Through Patents, Joe C. Liu

Master's Theses

Patents and published patent applications are valuable resources to students, engineers, and researchers for learning about technology. This thesis investigated the ability to learn about a technology through the disclosures that are made in published patent applications and issued patents.

This thesis first provides an overview of U.S. patent law, system, and resources that are available to the public. It is through an understanding of U.S. patent law and system that one can appreciate that patents and patent applications are a resource for learning about technology.

By providing the basic building blocks of LED lighting technology as learned through the …

Investigation Of Degradation Effects Due To Gate Stress In Gan-On-Si High Electron Mobility Transistors Through Analysis Of Low Frequency Noise, Michael Curtis Meyer Masuda

Master's Theses

Gallium Nitride (GaN) high electron mobility transistors (HEMT) have superior performance characteristics compared to Silicon (Si) and Gallium Arsenide (GaAs) based transistors. GaN is a wide bandgap semiconductor which allows it to operate at higher breakdown voltages and power. Unlike traditional semiconductor devices, the GaN HEMT channel region is undoped and relies on the piezoelectric effect created at the GaN and Aluminum Gallium Nitride (AlGaN) heterojunction to create a conduction channel in the form of a quantum well known as the two dimensional electron gas (2DEG). Because the GaN HEMTs are undoped, these devices have higher electron mobility crucial for …

An Experimental Evaluation Of Image Quality For Various Scenarios In A Chromotomographic System With A Spinning Prism, Kyle J. Dufaud

Theses and Dissertations

A lab and eld based hyperspectral chromotomographic imager has been developed at the Air Force Institute of Technology. It is a prototype used to study the requirements for a space-based system. The imager uses a high speed visible band camera behind a direct-vision prism to image both spatial dimensions and the spectral dimension at the same time. Capturing all 3 simultaneously allows for the hyperspectral imaging of transient events. The prism multiplexes the spectral and spatial information, so tomographic reconstruction algorithms must be used to separate hyperspectral channels. Experiments were conducted to compare reconstructed image quality as a function of …

Neutral Nitrogen Acceptors In Zno: The 67Zn Hyperfine Interactions, Eric M. Golden, S. M. Evans, Larry E. Halliburton, Nancy C. Giles

Faculty Publications

Electron paramagnetic resonance (EPR) is used to characterize the ⁶⁷Zn hyperfine interactions associated with neutral nitrogen acceptors in zinc oxide. Data are obtained from an n-type bulk crystal grown by the seeded chemical vapor transport method. Singly ionized nitrogen acceptors (N⁻) initially present in the crystal are converted to their paramagnetic neutral charge state (N⁰) during exposure at low temperature to 442 or 633 nm laser light. The EPR signals from these N⁰ acceptors are best observed near 5 K. Nitrogen substitutes for oxygen ions and has four nearest-neighbor cations. The zinc ion …

Singing Arc, Justin Kis

Electrical Engineering

This project aims to develop a singing arc. A singing arc is commonly, though mistakenly, referred to as a plasma speaker. Whereas a traditional speaker uses a pulse width modulated (PWM) signal to move an electromagnet, which in turn moves a cone, which generates sound waves, the singing arc sends a PWM signal through a standing spark, which vibrates, which generates sound waves.

Several plans for the singing arc are readily available online. This project will analyze the similarities between a selection of them, try to eliminate any faults in design, and improve the function of the circuit. The final …

Polarimetric Calibration And Characterization Of The Telops Field Portable Polarimetric-Hyperspectral Imager, Joel G. Holder

Theses and Dissertations

The Telops polarimetric-hyperspectral imager combines polarimetric and hyperspectral technologies to enable enhanced scene characterization. The Defense Threat Reduction Agency funded research at AFIT to leverage this capability to provide more accurate scene information to radiation transport models that will allow for more effective location of radiation sources within a region of interest. To support the objectives of the DTRA effort, there is a requirement for highly accurate radiometric, polarimetric, and spectral data on a pixel-by-pixel basis. The complex nature of the Telops instrument combined with working in the thermal IR waveband makes achieving this accuracy a challenge. This thesis develops …

Analytical Models For Distribution Of The Envelope And Phase Of Linearly Modulated Signals In Awgn Channel, Taleb Moazzeni, Yingtao Jiang, Henry Selvaraj, Tianding Chen

Electrical & Computer Engineering Faculty Research

In this paper, analytical expressions for the distribution of the envelope and phase of linearly modulated signals such as BPSK, M-PSK, and M-QAM in AWGN are presented. We perform numerical simulations for different orders of signal constellations. The results show that the proposed theoretical models are in excellent agreement with the estimated distributions from various numerical experiments.

A Review Of Active Management For Distribution Networks: Current Status And Future Development Trends, Junhui Zhao, Bo Zhao, Feng Lin, Quan Zhou, Yang Wang, Caisheng Wang

Electrical & Computer Engineering and Computer Science Faculty Publications

Driven by smart distribution technologies, by the widespread use of distributed generation sources, and by the injection of new loads, such as electric vehicles, distribution networks are evolving from passive to active. The integration of distributed generation, including renewable distributed generation changes the power flow of a distribution network from unidirectional to bi-directional. The adoption of electric vehicles makes the management of distribution networks even more challenging. As such, an active network management has to be fulfilled by taking advantage of the emerging techniques of control, monitoring, protection, and communication to assist distribution network operators in an optimal manner. This …