Digital Commons Network^™

Radar Image Processing For The Afit Anechoic Chamber, Brian K. Sanders

Theses and Dissertations

The purpose of this study was to begin development of an Inverse Synthetic Aperture Radar imaging capability for the AFIT anechoic chamber. This began with an evaluation of the capabilities and limitations of the existing radar system and the chamber itself for this application. Then, after deciding on the image processing approach, software had to be written to collect the data necessary for image processing. This constituted the majority of this study, and resulted in a versatile, user-friendly program that automates the process of collecting data for high-resolution radar images. The program checks that the data to be collected will …

Characterization Of An Air-To-Air Optical Heterodyne Communication System, Rebecca N. Seeger

Theses and Dissertations

The primary goal of this research was to determine the feasibility of air-to-air optical communications systems using coherent detection in a turbulent environment. Secondary goals were to determine (1) the signal-to-noise ratio (SNR) degradation due to turbulence and (2) the effect of varying the wavelength (1.5, 830, 904 nm), altitude (5000-12500 m), path length (40-160 km) and aperture side length (1-15 cm) on the turbulence affected SNR. The research was conducted under the following assumptions: (1) ideal transmitter and receiver, (2) equally sized, uniformly weighted, square transmitter and receiver apertures, (3) ideal tracking by the receiver, and (4) zero losses …

Establishment Of A Fabrication And Measurement Capability For Aperture-Fed Stacked Patch Microstrip Antennas At The Air Force Institute Of Technology, Christopher I. Terry

Theses and Dissertations

Much time and effort has been applied to accurately model aperture- fed stacked patch microstrip antennas at the Air Force Institute of Technology (AFIT). The results of this study provide AFIT with the capability to fabricate and measure these antennas for comparison of measured radiation characteristics to the predicted characteristics. Basic microstrip patch antenna theory is reviewed, as well as the motivation leading to the development of aperture-fed stacked patch microstrip antennas. The fabrication process used to produce the two antennas manufactured for this study is described in detail. The construction of a small anechoic chamber for pattern measurements is …

Te Scattering From A Dielectric Coated Conducting Strip, William D. Wood Jr.

Theses and Dissertations

Consider a plane wave incident on a conducting strip of infinite length coated on one side with a thin, uniform coating of lossless dielectric, and let the incident magnetic field vector be parallel to the edges of the strip. From first principles we develop the integral equations relating the total, incident, and scattered fields in the dielectric. We expand the fields in the dielectric slab as the sum of three plane waves (the 'forced' wave and two oppositely-directed surface waves). The phase constants in the x and y directions are known and the wave amplitudes are found using least-squared- error-point-matching. …

An Evaluation Of An Ada Implementation Of The Rete Algorithm For Embedded Flight Processors, F. Jesse Fanning

Theses and Dissertations

The purpose of this thesis was to design and develop an expert system shell in Ada, and to evaluate the shell's execution and size performance to determine its suitability for real-time operation on the MIL-STD-1750A embedded flight processor. The expert system shell uses the CLIPS/Ada inference engine, a forward-chaining Ada implementation of Rete. The expert system shell design is presented along with an overview of the target environment--the MIL-STD-1750A VHSIC Avionic Modular Processor (VAMP) running under the Ada Avionics Real-Time Software (AARTS) Operating System. Theoretical and empirical complexity analyses of the inference engine are presented and discussed in view of …

Model-Based Reasoning In The Detection Of Satellite Anomalies, Ralph W. Dries

Theses and Dissertations

Automatic fault detection and recovery would be a mandatory requirement for a satellite where some degree of autonomy is required. This thesis reviews some AI techniques used for the detection of satellite anomalies, and concludes that the model-based reasoning paradigm is best suited for automated on-board fault detection because it can cope with situations not necessarily programmed into the knowledge base. Using the Scheme language and its SCOOPS object oriented extension, development of software is described that models the pitch control channel in the attitude and velocity control subsystem of a typical geo-stationary communications satellite. This model is used by …

Oscillation Frequency In High-Gain Lasers, Lee W. Casperson

Electrical and Computer Engineering Faculty Publications and Presentations

The calculation of the oscillation frequency of a single-mode laser oscillator is examined systematically. Mode-pulling formulas are developed for a variety of laser systems, and the limitations of a standard approximation are explored.

Evaluation Of An Interdigitated Gate Electrode Field-Effect Transistor For Detecting Organophosphorus Compounds, Charles P. Brothers Jr.

Theses and Dissertations

This study used integrated circuit microsensors to detect organophosphorus compounds. Chemically-sensitive thin films, copper phthalocyanine, DFPase, succinyl chloride, succinylcholine chloride, 2- naphthol(B), and L-histidine dihydrochloride,were deposited on interdigitated gate electrode (IGE) structures, with an average thickness of 2000A. Thin film electrical performance characteristics were measured for several parameters, including: DC resistance, AC impedance, time-domain, and spectral responses from 10 Hz to 1 MHz. Each microsensor contained nine IGEs; each IGE possessed an in situ field-effect transistor amplifier. After purging each sensor with filtered air, it was exposed to one or two of the following gases: diisopropyl fluorophosphate (DFP), diisopropyl methylphosphonate, …

Characterization Of Sige/Si Heterostructures Formed By Ge+ And C+ Implantation, Akira Fukami, Ken-Ichi Shoji, Takahiro Nagano, Cary Y. Yang

Electrical and Computer Engineering

Formation of SiGe/Si heterostructures by germanium ion implantation was investigated. A germanium‐implanted layer was grown epitaxially in the solid phase by thermal annealing. Two kinds of crystalline defects were observed. One is a misfit dislocation, and the other is a residual dislocation caused by ion bombardment. The p‐n junction formed in the SiGe layer has a leakage current three orders of magnitude larger than that of a pure Si p‐n junction fabricated with an identical process except for the Ge+ implantation. Carbon doping in the SiGe layer improves its crystalline quality and the junction characteristics.

A 512 X 512 Random Addressable Variable Resolution Image Sensor, Chakravarthy Yarlagadda

Theses

This thesis presents the design and layout of a 512 x 512-element with 20μm x 20μm pixels image sensor that emulates the properties of the human eye and is useful in high speed processing of visual data for machine vision applications. The imager will be able to operate with random-address selection in variable resolution or with multiple regions of interest to reduce the number of pixels readout. The selection of the pixels is done by x-y addressing the MOS switches which connect the photodiode pixel to the output through the sense lines. The design of column decoder and row decoder …

Photo-Induced Electrochemical Etching Of Inp Semiconductor In A Thin Film Cell, Bungsu Iskandar

Theses

The Photo-Induced Electrochemical Etching of n-InP wafer in aqueous solution is investigated for both reservoir and capillary systems. A sinusoidal spatial variation of light intensity pattern is directly illuminated and promoting etching on an InP semiconductor wafer. The etching process is time-efficient, and produces highly isotropical and a promising high resolution pattern. It gives a good reproducibility and has less contaminating features. Its features may be explained by a non-linear relationship between the electrolyte concentration and the photo-generated holes density at the interaction surface. An optimal reaction rate is determined by the ratio of the reactivity to ionic diffusion, either …

Rotary Micromotor Design With Ic-Compatible Processing, Hong Yu

Theses

Several microelectromechanical rotary motors have been designed and simulated with varying rotor and stator configurations. All of these micromotors operate with an electrostatic power source and have rotor diameters varying from 0.2 to 0.4 mm. These micromotors develop torques in the range 8 to 50 picoNewtons with rotors of polysilicon with 2 micron film thickness based on the detailed simulations of this thesis using a 3-phase voltage power source. The geometries modelled in this work are side-drive and vertical-drive configurations. These micromotors obtain drive torque from the fringe-field differential at the periphery of the rotor poles.

Unlevitated micromotors (with bearings) …

Integrated Control Of Thermally Distorted Large Space Antennas, Robert H. Tolson

Mechanical & Aerospace Engineering Theses & Dissertations

Studies on controlling the thermal distortion of large space antennae have generally investigated a single orbital position and have optimized actuator locations based on minimizing the RMS surface deviation from the original parabolic shape. One study showed the benefits of directly using far zone electric field characteristics as the performance measure; but, this approach resulted in a nonlinear programming problem. The objective of the current study is to develop an approach to designing a control system that (1) recognizes the time dependence of the distortion and (2) controls variables that are directly related to far field performance in a quadratic …

Measurement Of Thermal Noise In Condenser Microphones In A Vacuum-Isolation Vessel, Kim Chi Thi Ngo

Electrical & Computer Engineering Theses & Dissertations

The electrical noise generated by thermal agitation of the air molecules impinging upon the membrane of a condenser microphone and from its associated preamplifier has been studied analytically and experimentally over a wide bandwidth. These background noise levels constitute one of the most important specifications of a microphone for they determine the lowest sound pressure that can be detected. Therefore, a new method for measuring the thermal agitation noise within a bandwidth of 1-25600 Hz has been developed. The theoretical and experimental measurements of thermal agitation noise in a condenser microphone by enclosing the microphone in a vessel which is …

Optical And High Electric Field Effects In Bulk Gallium Arsenide Switches, Randy Roush

Electrical & Computer Engineering Theses & Dissertations

During the past few years, bulk, photoconductive switching has become recognized as a viable topic for future research on moderate and high power switches. The two-pulse, or BOSS, concept relies on an excitation laser pulse, and a separate de-excitation pulse in conjunction with silicon doped, copper compensated, GaAs to create a variable temporal electrical pulse width. The research contained in this document provides information concerning the feasibility of the BOSS concept, as the switch is scaled to larger sizes, and higher voltage and current. The major concern will be the high voltage and current effects. The absorption length for 1064 …

The Modeling Of The Interactions Of Pellets With Magnetic Fusion Plasmas For Alpha Particle Diagnostics, Abdel-Ghafar Mahmood El-Cashlan

Electrical & Computer Engineering Theses & Dissertations

A model for the interactions of hydrogen and carbon pellets with thermonuclear fusion plasmas has been developed and solved to determine the charge-state spatial distributions in the ablation cloud surrounding the pellet. The ionization is treated in a self-consistent manner in the energy balance and the collisional radiative (CR) model is used to calculate the ionization levels. External plasma electron effects on ionization are included. The electron heat flux is modeled as a multigroup distribution. The channelling of the flow along the field line is treated phenomenologically by restricting the cross-sectional area of the flow. The predictions of the model …

Deep Level Characterization Studies In Gaas, Gordhan R. Barevadia

Electrical & Computer Engineering Theses & Dissertations

The goal of this research was to investigate deep levels in different types of GaAs, a material for high power optically controlled bulk semiconductor switches. For low resistivity semiconductors, such as silicon doped GaAs material (p =0.054 Ω cm), deep level transient spectroscopy (DLTS) was used to characterize deep levels. Three deep levels (EL6, EL3, and EL2) have been detected in this material. For high resistivity semiconductors (p > 10⁴ Ω cm), difficulty of electrical carrier injection and of making a junction does not permit the use of DLTS technique. Therefore, an experimental set-up of the photo-induced current transient spectroscopy …

Monolithic Induction-Sourced Ac-To-Dc Power Supply Design, Jianhua Chen

Theses

This thesis describes techniques with design nomographs for supplying power to CMOS and microelectromechanical implanted devices. These applications require voltages in the range of 5 to 50 volts. Different kinds of voltage multiplier circuits were used to achieve high voltage output. The AC-to-DC and DC-to-DC capacitive bootstrap voltage multipliers are designed and analyzed. The AC-to-DC and DC-to-DC inductive bootstrap voltage multiplier circuits are presented and the SPICE simulations are done with those circuits. Four different options of inductive link high voltage power supply are presented, analyzed and compared. The link parameters of two VLSI-compatible square-shaped coils are calculated in both …

Investigation Of Micromechanical Properties Of Tungsten Silicide Thin Films, Bharat Pathak

Theses

Micromechanics is a field which is maturing. Recent research interest in micromechanical structures has focussed on the fabrication of microactuators and microsensors. These microsensors and actuators can sense very small changes in the environment without disturbing the equilibrium of the environment. The refractory silicides are some of the compatible materials used to integrate the micromechanical structures and the interfacing electronic circuits on the same chip. As a result of this, the thermodynamic, electrical and mechanical properties of transition metal silicides should be given a closer look for micromechanical applications.

This thesis details the design and fabrication of tungsten silicide moveable …

Simulation And Analysis Of Priority Classes In Extended Token Based Local Area Networks, Bhavinkumar R. Pathak

Theses

Recently, Local Area Networks carrying multiple priority classes of messages have received considerable attention. The IEEE 802.5 token ring standard defines an optional priority scheme to handle different priority classes of messages. A simulation model of symmetric priority based networks, consisting of token ring networks interconnected by a bridge is considered. Messages are divided into two priority classes, namely, high priority traffic and low priority traffic. High priority traffic is guaranteed access on the channel, whereas low priority messages are served when the system determines that no high priority messages are currently waiting. The simulation results are used to evaluate …

A Self Testing Strategy For The Wafer Scale Hierarchical Memory Architecture, Maremanda V. R. Rao

Theses

Since the early 1960's, semiconductor chips have matured from single transistor devices to one million transistors per chip. The integration has been achieved by reducing transistor dimensions, and by increasing chip sizes. However, physical limits are being reached as submicrometre dimensions are approached. Fault tolerance has to be used to maintain the increase in the chip complexity. Yield improvement is only one of the many possible gains of fault tolerance. The dense integration of logic on a single chip also creates a huge test problem. in recent years a great deal of effort has gone into the development of yield …

The Interconnection Network Analysis Package, Nadeem Sabbar

Theses

This thesis focuses on the development of the Interconnection Network Analysis Package (INAP), and the use of INAP to analyze minimal permutation networks. The INAP code is written in C language using Turbo C compiler. Although the INAP has been used to analyze the subject networks it is not a dedicated system. It gives the user the freedom to create the permutation network from scratch (1-8 inputs and 1-7 stages), and then to process it for any number of stages.

The INAP made the analysis of five input networks easy and efficient. The networks have been analyzed stage by stage. …

A Novel Schottky Barrier Mosfet For Vlsi Applications, Venkata S. Simhadri

Theses

Schottky barrier MOSFETs are expected to offer certain fabrication advantages, low series resistance and the feasibility to go into sub-micron technology without having short-channel effects. A p-channel MOSFET using Schottky contacts as source and drain is reviewed theoritically. The limitations of the device arising from the oxide offset between source/channel is studied with the help of one dimensional simulation SEDAN. The process sequence leads to an offset between source and channel. The performance of the SBMOSFETs with and without offset is estimated using two dimensional device simulation program PISCES-II for PtSi and IrSi as source and drain material. A novel …

Microengineered Thermal Conductivity Vacuum Pressure Sensor, Sanjay Talreja

Theses

This thesis details the first designs for microengineered vacuum pressure gauges based on silicon microelectronic technology. A monolithic polysilicon air-bridge structure (supported at both ends), within a Wheatstone bridge circuit, is used as a pressure sensor. The device utilizes the change of the thermal conductivity of a gas with ambient gas pressure. The doubly supported beam functions as a temperature sensitive resistor with a negative temperature coefficient of resistivity. Thermal change of resistance monitored as a measure of ambient pressure constitutes the basis of operation for this sensor. The sensor operates over the pressure ranging from 1 Torr to 10 …

Reflection And Transmission Through Achiral-Chiral Interface, Jia-Feng Wang

Theses

Electromagnetic wave propagation through an achiral-chiral interface is analyzed via Maxwell's equations using the appropriate boundary conditions. Experimental data for reflected power from achiral-chiral interface was found to be in qualitative agreement with the analytical results. In addition, coupled mode equations for chiral cladding waveguides were derived and solved for weak coupling. The experimental results of chiral cladding waveguides show that an average of about 0.2° per cm in polarization rotation occurred. These waveguides were fabricated by using spin-coating deposition. The sense of the rotation was found to be independent of the handness of the cladding chirality, which was predicted …

Measurement Of Cluster Size By Retarding Potential And Time-Of- Flight Methods In An Ionized Cluster Beam Deposition System, Yung-Kuan Wang

Theses

The goal of this research was to study the mass distribution of ions generated in the Ionized Cluster Beam (ICB) deposition system. The ICB deposition method has been used to form high quality films of metals and other materials. It was postulated that the clusters consisting of hundreds and thousands of atoms produced by vapor expansion in the ICB source are responsible for the superior film properties. However, consistent experimental evidence concerning the cluster mass distribution, or even the existence of such clusters in the ICB apparatus, was lacking.

Two methods of cluster ion mass spectroscopy were used in this …

Modeling And Analysis Of Electrical Properties Of Polycrystalline Silicon Films, Yunsheng Wang

Theses

In recent years, investigations on polysilicon grain structures have shown that all polysilicon films by LPCVD which are most used in today's integrated circuits are columnar in structure. In this work, a square columnar grain structure has been considered to model electrical properties of polycrystalline silicon films instead of all previous one-dimensional grain structure models. By solving Poisson's equation with certain boundary conditions, we find that the barrier height at the corners of the grain is lower than that in the one-dimensional case. Assuming the trapping state energy level as constant, we also find that this level has a value …

Optimization Of Bandwidth Allocation In Atm Nets Through Simulated Annealing, Chien-Long Hou

Theses

Optimization of Bandwidth Allocation in ATM network is considered in this thesis. We address the problem of determining optimal bandwidth allocation in such BISDN's that adopt ATM as their basic switching. technique by using Simulated Annealing. Computer simulation shows that this optimal policy leads to the configuration which yields the minimum average packet delay.

An Optically Powered Cmos On-Chip Power Supply, Jaeyong Jeong

Theses

This thesis presents an optically powered CMOS on-chip power supply for CMOS IC applications. There exists a need for specialized chips that are located remotely and are powered by light supplied through fiber-optic cabling. An optically powered CMOS on-chip power supply circuit described in this thesis is composed of three subcircuits; light to voltage converter circuit, clock pulse generator circuit, and voltage multiplier circuit. Each subcircuit has been analyzed and designed, and simmulated using SPICE 2G.5/6 with 3pm CMOS SPICE parameters from the MOSIS. The circuits layout has been done using MAGIC according to the MOSIS scalable CMOS design rules. …

A Transputer Based Distributed Graphics Display, Ramana V. Kattula

Theses

The design of a transputer based graphics display is discussed. The problems associated with the single processor graphics systems are described. A solution based on multiple transputers is proposed. The transputer based graphics display described is a general purpose graphics system which can achieve any required compute performance and drawing performance without using special hardware. The display resolution and color depth can be enhanced as per the user requirements with little or no change in hardware.