Engineering Commons^™

Structurally Integrated Reconfigurable Wideband Array For Conformal Applications, Michael Damon Wright

Theses and Dissertations

Structurally integrated conformal antennas offer significant advantages over traditional bolt on antennas, especially for air vehicle applications. The ability to leverage the entire structure allows for unconventionally large antennas and arrays to be implemented in a manner which does not detract from the aerodynamic, structural or aesthetic qualities of the vehicle. Works along this line have included Slotted Waveguide Antenna Stiffened Structures (SWASS), conformal helix and spiral antennas, Log Periodic Dipole Arrays (LPDA), and other antennas.

An area which has not been investigated to date is the possibility of implementing reconfigurable antennas in a structural environment. There are inherent challenges …

Novel Wideband Ebg Structures For Isolation Improvement Between Cosite Antennas, Paul John Czeresko Iii

Theses and Dissertations

As the number of installed antennas increases on a structure, the available real estate to do so without each antenna interfering with the others diminishes. Electromagnetic band gap (EBG) structures are one way to mitigate this cosite interference with compact antenna installations. While a host of EBG structures and types (3-D, planar etc.) have been proposed and studied historically, it has been found that planar EBG structures tend to provide very narrow bandwidths for both antenna design and cosite interference reduction. This research focuses on the design of EBG structures intended to achieve greater than 20 dB of isolation improvement …

Multifunction Radio Frequency Composite Structures, David L. Zeppettella

Theses and Dissertations

There has been recent interest in the development of multifunction structures for weight-critical applications. A multifunction structure is a load-bearing structure that also allows one or more additional functions such as RF communication, energy storage, sensing etc. The focus of this dissertation is to analyze, design, develop, and test new high performance (broadband, high gain, circularly polarized) internal antennas that are structural and integral to the aircraft. It is demonstrated that antennas with more bandwidth and higher efficiency could be developed if the space and materials available in an aircraft structure could be judiciously exploited for multifunctional usage. This is …

High Resolution Radiation Detectors Based On 4h-Sic N-Type Epitaxial Layers And Pixilated Cdznte Single Crystal Devices, Cihan Oner

Theses and Dissertations

Silicon Carbide (SiC) is an indirect wide bandgap semiconductor with high thermal conductivity, high breakdown electric field, high carrier saturation drift velocity, and large displacement energy making it a suitable candidate for replacing conventional radiation detectors based on Si, Ge, CdTe, and CdZnTe (CZT). In this dissertation, fabrication and characterization of high-resolution Schottky barrier detectors for alpha particles using 20 µm thick n-type 4H-SiC epitaxial layers are reported. Schottky barriers were obtained by depositing circular nickel contacts of ~10 mm2 area.

Room temperature current-voltage (I-V) measurements revealed Schottky barrier heights of the order of 1.7 eV, ideality factor of ~1.1, …

Study Of 4h-Sic And Alxga1-Xn Based Heterojunction Devices For Ultraviolet Detection Applications, Venkata Surya Naga Raju Chava

Theses and Dissertations

Ultraviolet (UV) detectors are important for their applications in flame detection, furnace gas control systems, plume monitoring etc. Due to their wide band-gap, 4H-SiC (Eg=3.26eV) and III-V semiconductors such as GaN (Eg=3.4eV), AlxGa1-xN (Eg=3.4eV to 6.2eV) etc., are excellent candidates for visible(��cut-0ff=400nm) and solar blind(��cut-0ff=290nm) UV detectors. Conventional SiC UV detectors suffer from poor UV responsivities due to reflection/absorption/transmission losses caused by the metal electrodes used in those detectors.

In the first part, a novel bipolar transistor with epitaxial graphene(EG)/p-SiC (30μm)/n+-SiC substrate was fabricated and characterized. The 2-3 ML thick, transparent and conducting, EG used in this work was grown …

Study Of Ultra Wide Band Gap Alxga1-Xn Field Effect Transistors For Power Electronic Applications, Sakib Mohammed Muhtadi

Theses and Dissertations

High Aluminum content Al_xGa_1-xN (x > 30%) has attracted intense research interest nowadays as “Ultra Wide Band Gap (UWBG)” material due to large band gap (> 3.4 eV). The critical electric field (EC) of UWBG semiconductor AlGaN is significantly higher than GaN. Moreover, electron saturation velocity is also comparable to GaN. These attractive material properties are the needs for getting large breakdown voltage and high thermal stability which are the requirements for next generation power semiconductor devices. Theoretical possibilities show UWBG AlGaN based devices are an emerging class and can outperform conventional GaN based devices even at …

Growth And Characterization Of Anisotropic Gase Semiconductor For Radiation Detection And Thz Applications, Haseeb Nazir

Theses and Dissertations

Anisotropic wide-bandgap gallium selenide (GaSe) crystals were grown using high purity (7N) Ga and zone refined (ZR) Se precursor materials. The crystal growth was performed using a modified vertical Bridgman method (VBM) with a slow crystallization from the melt and with a pre-determined temperature profile. The structure, surface morphology, and the composition of the grown crystals were characterized using x-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive analysis by x-rays (EDAX), respectively. Optical absorption and transmission properties were characterized and optical bandgap was determined. Electrical resistivity has been determined using current-voltage (I V) measurements using van der Pauw …

Integrating Nano-Patterned Ferromagnetic And Ferroelectric Materials For Smart Tunable Microwave Applications, Tengxing Wang

Theses and Dissertations

The wireless communication market has been ever-growing in the recent decades. Radios with high performance and capabilities to support wireless connections are increasingly demanded. Recent developments in wireless communications targeting ubiquitous connections have resulted in ever more complex system structures for supporting multiple frequency bands and standards. Reconfigurable and tunable RF/microwave technologies have the potential to significantly simplify the systems. The main objective of this dissertation is to develop tunable technologies and design concepts, and propose a new design methodology to implement dually electrically tunable microwave components by integrating both selectively patterned ferromagnetic and ferroelectric materials.

The first part of …

Software Modelling For Real World Faults On Ac Transmission Protective Systems Analysis And Effects, Iandale Tualla

Theses and Dissertations

The Electric Power Utilities serves many diverse customers from regular households to major processing plants that develop parts for gasoline vehicles. Those varying customer usages has adverse effects on the Electric Grid in many ways, that requires continuing analysis by the engineers and technical skills specialists who keep the Electric Grid stable. Several papers have been written about harmonics and Non- Sinusoidal waveforms and its effect on the Electric Grid. This thesis will exam a realworld fault event on a transmission line, its effects on the AC Transmission Protection Systems (TPS) that provides electrical energy to a nonlinear load, specifically …

Cable Health Monitoring System Built Into Power Converter Using Time Domain Reflectometry, Hossein Baninajar

Theses and Dissertations

Aging cables are a critical reliability concern for many electrical systems. Cables run over long distances, are often exposed to harsh environments and are intended to work for several decades. Cable faults can be a serious problem because cables are usually hard to repair or replace. Condition based maintenance is a popular approach that provides high reliability and low maintenance cost at the same time. This is a non-destructive method that collects information about the health condition of the cable under test without causing any potential damage.

Nowadays, in several applications power cables are connected to power converters and it …

Fault Protection In Dc Microgrids Based On Autonomous Operation Of All Components, Qiu Deng

Theses and Dissertations

DC power distribution systems (or so called DC microgrids) are of wide interest for various power applications due to their advantages over traditional AC power distribution systems with respect to power density and power distribution efficiency. On the other hand, short-circuit faults present formidable hazards in these systems. It is difficult to extinguish these arc faults via conventional circuit breakers due to the lack of natural zero-crossing of DC current. Also the DC breakers are usually more bulky and costly. Today, fault protection in these systems – to the extent that it exists – relies on over-current time-out limits in …

Evaluation Of Multicarrier Air Interfaces In The Presence Of Interference For L-Band And C-Band Air-Ground Communications, Hosseinali Jamal

Theses and Dissertations

The use of aeronautical vehicles and systems is continuously growing, and this means current aeronautical communication systems, particularly those operating in the very high frequency (VHF) aviation band, will suffer from severe congestion in some regions of the world. For example, it is estimated that air-to-ground (AG) communication traffic density will at least double by 2035 over that in 2012, based on the most-likely growth scenario for Europe. This traffic growth (worldwide) has led civil aviation authorities such as the FAA in the USA, and EuroControl in Europe, to jointly explore development of future communication infrastructures (FCI). According to international …

High Gain Pattern Reconfigurable Antenna Arrays For Portable And Body-Centric Wireless Applications, Nowrin Hasan Chamok

Theses and Dissertations

Wireless devices such as smartphones, tablet computers, smartwatches etc. have become ubiquitous. With that, the demand for high speed data has increased tremendously. Designing antennas for such applications is challenging because of limited availability of space, shadowing or blockage from the human body, and signal loss from multipath fading. Conventional broad, fixed beam low gain antennas result in poor reception, faster battery drainage, and low data rate. Compressed footprint high gain pattern reconfigurable antenna arrays can solve these problems which is the focus of this dissertation. Two innovative high gain pattern reconfiguration techniques, the switched beam parasitic array and the …

Positive Feedforward Control Design For Stabilization Of A Single-Bus Dc Power Distribution System Using An Improved Impedance Identification Technique, Silvia Arrúa

Theses and Dissertations

Due to recent advances in power electronics technology, DC power distribution systems offer distinct advantages over traditional AC systems for many applications such as electric vehicles, more electric aircrafts and industrial applications. For example, for the All-Electric ship proposed by the U.S. Navy the preferred design option is the adoption of a Medium Voltage DC power distribution system, due to the high power level required on board and the highly dynamic nature of the electric loads.

These DC power distribution systems consist of generation units, energy storage systems and different loads connected to one or more DC busses through switching …

Simulation Of Gan Based Mis Varactor, Bojidha Babu

Theses and Dissertations

This work deals with novel microwave switches based on III-Nitride varactors. RF switches, power limiters and other control devices are important components of various RF systems, such as wireless modules of laptops, tablets, cell phones etc., satellites communication systems, radars, multi-band wireless and aerospace communications, phased array antennas and so worth. Traditional RF switches are fabricated using pin diodes or MEMS, Si MOSFETs or GaAs HEMTs. These devices have a number of fundamental limitations. Si or GaAs based devices suffer from a low breakdown voltage and cannot handle high RF power. Pin-diodes require large forward currents and do not allow …

Miniaturized Rf Components With A Novel Tunable Engineered Substrate For Wireless Communication Systems, Yujia Peng

Theses and Dissertations

There is an increasing demand for reliable sensor system capable of remote sensing and measuring interesting data. Although large communication range can be achieved, active wireless communication systems are still suboptimal in longtime applications due to their harmful battery supply. Inductively coupled passive devices, with the advantages in safe long-term implanting, structural simplicity, small fabrication footprint and low-cost production, are preferred in chronic monitoring, but little work has been done to optimize the performance of these systems, especially under some design constraints.

The model and optimization of an inductively coupled wireless pressure sensor system is presented in this dissertation. With …

Applications Of Impedance Identification To Electric Ship System Control And Power Hardware-In-The-Loop Simulation, Jonathan Siegers

Theses and Dissertations

Recent advances in semiconductor technology, controls, and switching converter topologies have resulted in the increasing application of power electronics in power distribution systems. Power electronic enabled distribution systems have inspired a renewed interest in DC distribution architectures as an appealing alternative to traditional AC methods due to the significant performance and efficiency gains they offer. However, the notional power electronic based DC distribution system is a complex and extensively interconnected system consisting of multiple power converters. As a result, a number of system-level challenges related to stability arise due to interaction among multiple power converters. In addition, the power distribution …

Estimating Local Average Power In A Line-Of-Sight Indoor Channel: Spatial Sampling And Processing, Israt Jahan Disha

Theses and Dissertations

Modeling of indoor radio channels has been a dynamic area of research in recent years because of the increasing demand for indoor wireless communications. In order to efficiently deploy such indoor systems, a good knowledge of the indoor wireless channel’s characteristics are required. One important characteristic is an accurate propagation path loss model. For developing such models various measurements have been carried out. In modeling propagation path loss in complex indoor environments, accurate and fast algorithms for estimating the local mean signal level are essential; these are also of use for power control and handoff decisions. These local mean power …

A Comparison Of Fpga Implementation Of Latency-Based Solvers For Power Electronic System Real-Time Simulation, Matthew Aaron Milton

Theses and Dissertations

In the design of power systems, real-time simulation is a powerful tool to evaluate and validate designs before dedicating resources to develop such systems. Through use of real-time simulation, one can study the behavior of a power system in interaction with real, physical elements, all while avoiding the cost and risk in constructing and testing such systems before a design is finalized. In recent decades, effort has been made in the industry and academia to apply real-time simulation to that of switching power converters through use of high-speed digital signal processors (DSPs) and field programmable gate array (FPGA) devices. With …

Engineering Model Of Iii-Nitride Power Heterostructure Field Effect Transistor On Silicon Substrate, Mohammad Mirwazul Islam

Theses and Dissertations

In modern society, the demand for power consumption is increasing rapidly and the need of energy savings is now an issue of global importance. Highly efficient power converters and power conditioning systems operating with wide range of traditional as well as novel renewable and clean energy sources, are playing crucial role in energy saving. Si converters have already reached their limitation in terms of switching frequency and breakdown voltage/on-resistance ratio. Research is going on all around the world and it is now well accepted that significant improvement in power conversion efficiency and speed can only be achieved using beyond Si …

Investigation Of Wide Bandgap Semiconductor Devices For Radiation Detection Applications, Rahmi Orhon Pak

Theses and Dissertations

Radioactive materials, as they decay, generate different high-frequency electromagnetic radiation such as alpha particles, beta particles, x-rays, gamma-rays, and neutrons. Nuclear detectors could stop these high-energy ionizing radiations, collect and transport the charges generated to an external circuit, and produce an electrical signal which is amplified by readout electronics to measure the energy of nuclear interaction. Thus, nuclear detectors are important tools for accounting of radioactive materials and have widespread applications in nuclear power plants, nuclear waste management, in national security, in medical imaging such as x-ray mammography, digital chest radiography, CT scan, and in high energy astronomy for NASA …

Distributed Optimization And Control Of Islanded Microgrids, Md Rishad Hossain

Theses and Dissertations

A microgrid may have numerous multi-functional power electronic converters connecting sources, loads, and storage to the system. Systems where converters are the interface between many of the main sources of energy and load centers have the ability to direct the flow of energy if the control of the converters is coordinated. The influence of energy flow in a microgrid by coordinated action of converters is referred to here as ‘energy routing’. Energy routing allows for reduction of systems losses by optimizing source operating points and reducing transmission and distribution path losses. Energy ramp rates at various points in the system …

Wireless Channel Modeling For Networks On Chips, William Rayess

Theses and Dissertations

The advent of integrated circuit (chip) multiprocessors (CMPs) combined with the continuous reduction in device physical size (technology scaling) to the sub-nanometer regime will result in an exponential increase in the number of processing cores that can be integrated within a single chip. Today’s CMPs already support tens to low hundreds of cores and both industry and academic roadmaps project that future chips will have thousands of cores. Therefore, while there are open questions on how to harness the computing power offered by CMPs, the design of power-efficient and compact on-chip interconnection networks that connects cores, caches and memory controllers …

System Level Analysis And Design For Wireless Inter-Chip Interconnection Communication Systems By Applying Advanced Wireless Communication Technologies, Xin Zheng

Theses and Dissertations

As the dramatic development of high speed integrated circuits has progressed, the 60 GHz silicon technology has been introduced to enable much faster computer systems and their corresponding applications. However, when signals are propagating at 60 GHz or higher frequencies on a PCB (Printed Circuit Board), the crosstalk among signal buses and devices, trace losses, and introduced parasitic capacitance and inductance between high density traces, become significant and may be severe enough such that the inter-chip communications will not be able to meet computer system signal specifications. High speed circuit signal integrity researchers in both electronic industries and academia have …

Dual-Band Non-Stationary Channel Modeling For The Air-Ground Channel, Ruoyu Sun

Theses and Dissertations

Multiple air-to-ground (AG) radio propagation channels are experimentally characterized for two frequency bands, C-band and L-band. These characterizations are aimed to support the specification of the control and non-payload communication (CNPC) links being designed for civil unmanned aircraft systems (UAS). The use of UAS is expected to grow dramatically in the coming decades. In the United States, UAS will be monitored and guided in their operation within the national airspace system (NAS) via the CNPC link. The specifications of the CNPC link are being designed by government, industries, academia and standards bodies such as the Radio Technical Commission for Aeronautics …

Technology Development And Characterization Of Aiinn/Gan Hemts For High Power Application, Mahbuba Sultana

Theses and Dissertations

AlInN has attracted much attention only recently as a material due to its unique and superior material properties, which is however known to be difficult to be grown among the III-nitride ternary compounds. The electrons confined at the heterointerface of coherently grown AlInN on GaN buffer layers determine crucial electronic properties. This dissertation has been designed targeting the lattice matched AlInN/GaN investigation with very detail to optimize the design, fabrication process, and electronic properties to realize AlInN/GaN HEMTs. Each single step of this process was optimized in order to improve device performance.

The work started with establishing the main features …

Investigation Of Modular Multilevel Converter Performance Under Non-Ideal Distribution System Conditions, Rostan Rodrigues

Theses and Dissertations

The Modular Multilevel Converter (MMC) is an emerging power converter technology that has caught widespread attention mainly because of several technical and economic benefits such as modular realization, easy scalability, low total harmonic distortion, fail-safe operations etc. The MMC is comprised of a series connection of sub-modules (SM). A sub-module is made by either a half-bridge or a full-bridge IGBT device and a capacitor as a source of energy connected across the bridge. This modular structure allows for the possibility to design high-voltage converters handling hundreds of kilo-volts without direct series connection of the power semiconductor devices.

Due to its …

Iii-V Nitride Based Microcantilever Heaters For Unique Multimodal Detection Of Volatile Organic Compounds At Low Temperature, Ifat Jahangir

Theses and Dissertations

Detection of volatile organic compounds (VOCs), which are widely used in industrial processes and household products, is very important due to significant health hazards associated with them. VOCs are commonly detected using photo-ionization detectors (PIDs), suspended hot bead pellistors, or heated metal oxide semiconductor functionalization layers. However, these techniques used for detecting VOCs often suffer from one or more of the following issues - high power consumption, limited selectivity, complicated functionalization technique and expensive characterization tools. On the other hand, microcantilevers offer excellent avenues for molecular sensing that arises out of their high sensitivity to various physical parameter changes induced …

Fabrication And Characterization Of Graphene Based Biocompatible Ion-Sensitive Field Effect Transistor (Isfet), Rina Patel

Theses and Dissertations

Graphene, a two-dimensional material with a high surface to volume ratio, has drawn extensive research enthusiasm for applications in the field of electronic sensors. The special material properties that make graphene a highly promising material include its biocompatibility, very high mobility, low 1/f and thermal noise, modulation of carrier concentration and fermi level by electrical, optical, and chemical means. To exploit these properties for practical applications a large area high quality graphene, transferred on appropriate substrates, is required. In this work, high quality single monolayer graphene (determined from Raman spectroscopy) has been synthesized by chemical vapor deposition (CVD) technique for …

Inn Nems And Heterojunction Devices For Sensing Applications, Alina Wilson

Theses and Dissertations

Recent research trends in chemical and biological sensing have been geared toward developing molecular sensor devices that are fast, inexpensive, miniaturized, have low power consumption and are portable. The performance of these devices can be dramatically improved by utilizing multimodal detection techniques, new materials and nanofabrication technologies. To develop such sensor devices, we utilized Indium Nitride (InN) nanowires (NWs) to fabricate nanoelectromechanical system (NEMS) based sensors and Graphene/InN NW heterojunctions, and InN thin films to fabricate Graphene/InN thin film heterojunction based sensors. InN NWs, which exhibit interesting properties including high carrier density, superior electron mobility, strong surface charge accumulation, and …