Digital Commons Network^™

Dispersion Comparison For Dsi- And Tensor-Based Nonorthogonal Fdtd, Hao Shi, James L. Drewniak

Electrical and Computer Engineering Faculty Research & Creative Works

An explicit formulation of the finite-difference time-domain-discrete surface integral (FDTD-DSI) technique has allowed a rigorous study of numerical dispersion for the method. The study shows that the DSI- and tensor-based FDTD methods do not have the same numerical dispersion relation. It also clarifies the recently reported discrepancies in the dispersion relation between the two approaches. This study also shows that the tensor-based FDTD algorithm exhibits better dispersion properties for a two-dimensional uniformly skewed mesh.

In Situ And Ex Situ Optical Characterization Of Electro Deposited Magneto-Optic Materials, James N. Hilfiker, Darin W. Glenn, Scott W. Heckens, John A. Woollam, Kurt W. Weirman

Department of Electrical and Computer Engineering: Faculty Publications

Electrodeposition is being investigated as a novel and low-cost method to prepare magneto-optic thin film and nanostructured materials. This deposition method allows precise control over thin-film properties and permits deposition of novel magnetic geometries. Multilayers and alloys can be deposited and controlled by adjusting deposition potentials and ion concentrations in the bath. Nickel/cobalt alloys have been electrodeposited from sulfamate, sulfate, and chloride solutions onto Au substrates. The optical properties were monitored in situ with a real-time spectroscopic ellipsometer measuring simultaneously at 44 wavelengths in the 410–750 nm spectral range. In situ measurements have the advantage of determining the material microstructural …

United States Patent: System And Method For Compensating Polarization-Dependent Sensitivity Of Dispersive Optics In A Rotating Analyzer Ellipsometer System, Blaine D. Johs, Shakil A. Pittal, Steven E. Green, John A. Woollam, David W. Doerr, Reed A. Christenson

Department of Electrical and Computer Engineering: Faculty Publications

An ellipsometer system which includes a pivotal dispersive optics positioned to receive polychromatic light from an analyzer thereof, without further focusing after reflection from a substrate system, is presented. In addition, a stationary compensator, positioned between an analyzer and the dispersive optics, which serves to reduce detector element polarization dependent sensitivity to light entering thereto after it interacts with the dispersive optics, is disclosed. The use of a light fiber to carry light from a source thereof, to a polarization state generator, is also disclosed. The method of the present invention can include application of mathematical correction factors to, for …

Using An Evolutionary Strategy To Solve Frequency Allocation Problems, Min Chen

Masters Theses

Frequency allocation problem (F AP) is to assign radio frequencies to a number of stations subject to a number of constraints, so that the minimum interference is suffered. FAP is NP-complete. In order to solve FAPs, there are interference constraints to be satisfied. There are two constraints of FAP which were the focus of this study: (1) co-channel interference, (2) adjacent channel interference.

Evolutionary Strategies (ESs) are very efficient optimization algorithms based upon the principles of adaptive selection found in nature. In this study, a (μ,A)ES algorithm was implemented to solve instances of FAP.

This thesis has demonstrated that …

Frequency Response Enhancement Of A Flow Sensor Using Diamond Thin Films Synthesized By Plasma Cvd, John Curren Hagwood

Electrical & Computer Engineering Theses & Dissertations

Theoretical modeling conducted previously in our Microelectronics Laboratory has shown that a layer of diamond film inserted between a metal film and a substrate will enhance the frequency response of a conventional thin film flow sensor. This thesis involved fabricating and testing a conventional thin film sensor of nickel on quartz (Ni/Q) and a diamond enhanced sensor (Ni/D/Q) for comparative frequency response analysis to validate the theory. Diamond films were grown onto quartz substrates using a microwave plasma enhanced chemical vapor deposition process. Conditions were established to synthesize continuous diamond films on quartz substrates. These films were characterized by scanning …

Wavelength Modulation Spectroscopy With Diode Lasers, Ying Lu

Electrical & Computer Engineering Theses & Dissertations

Wavelength Modulation Spectroscopy is a non-intrusive technique which enables several parameters such as concentration, velocity, and temperature of a target specie to be measured. The method involves a modulation of a probe laser beam and detection at the fundamental, or any harmonic frequency, by a phase-sensitive apparatus. The theory of wavelength modulation is discussed. Effects of the finite value of the wavelength modulation index, together with the effects of any residual amplitude modulation that often occurs simultaneously in a diode laser, are included. It is shown that there are several advantages in using detection harmonics orders greater than the second. …

Adaptive Integration Of Audio And Visual Information Using Discrete And Semi-Continuous Hidden Markov Models In Audiovisual Automatic Speech Recognition, Qin Su

Electrical & Computer Engineering Theses & Dissertations

An audiovisual semi-continuous hidden Markov model (HMM)-based Automatic Speech Recognition (ASR) system and an improved method of integrating audio and visual information in an audiovisual discrete HMM-based ASR system are investigated.

In the audiovisual discrete HMM, an adaptive integration formulation is employed, which incorporates the integration into the HMM at a pre-categorical stage. A visual weighting parameter is determined automatically, which allows the relative contribution of audio and visual information to be adjusted adaptively. Using an adaptive weight, the accuracy increased by 13% compared to the same model with no adaptive weight.

The semi-continuous HMM is a class of models …

Variable Step Size Lms Adaptive Filters With Delayed Coefficient Updating, Guixian Xu

Electrical & Computer Engineering Theses & Dissertations

A new approach to delayed LMS adaptive filtering is presented, which uses a variable step size for coefficient updating to increase convergence speed and improve tracking characteristics. The new algorithm, called delayed variable step size LMS (DVLMS), is explained, analyzed, and simulated to experimentally determine performance characteristics. Three different strategies for adjusting the step size are examined, and their performance is compared. Also, simulation results are presented to show that the proposed DVLMS systems provide faster convergence and lower mis-adjustment than previously proposed DLMS systems.

Speech Feature Computation For Visual Speech Articulation Training, Stefan Auberg

Electrical & Computer Engineering Theses & Dissertations

A new version of the Visual Speech Articulation Training Aid was implemented which provides real-time visual feedback for speech articulation training. This version was migrated to a Windows Multimedia PC from a previous version which used a Personal Computer (PC) system and additional specialized and expensive custom hardware. This new version will make the system more available to schools and private users. A new method was developed for computing spectral/temporal features which characterize the speech sounds. In addition to the typical frame-based spectral analysis parameters, the new method represents temporal changes of the spectrum with a small number of features. …

An Enhanced Signal Processing Strategy For Fetal Heart Rate Detection, Charles Brewton

Electrical & Computer Engineering Theses & Dissertations

The goal of the research was to improve the signal processing strategy for an acoustic fetal heart rate monitor. The theory, implementation, and testing of several possible signal processing strategies for fetal heart rate detection are presented. The enhanced signal processing strategy implemented is discussed and justified with off-line Matlab simulations and real-time experiments. A FIR matched filter was used as a preprocessor to increase the SNR of the acoustic fetal heart signal. The Teager energy operator and autocorrelation, used in the previous version of the monitor, were combined with a matched filter. Linear prediction and quadratic energy detection were …

Similarity-Based Learning For Pattern Classification, Laurene V. Fausett

Electrical Engineering and Computer Science Faculty Publications

Several standard neural networks, including counterpropagation networks, predictive ART networks, and radial basis function networks, are based on a combination of clustering (unsupervised learning) and mapping (supervised learning). A comparison of the characteristics of these networks for pattern classification problems is presented.

Calibration Of Spaceborne Scatterometers Using Tropical Rain Forests, David G. Long, Gary B. Skouson

Faculty Publications

Wind scatterometers are radar systems designed specifically to measure the normalized radar backscatter coefficient (O) of the ocean's surface in order to determine the near-surface wind vector. Postlaunch calibration of a wind scatterometer can be performed with an extended-area natural target such as the Amazon tropical rain forest. Rain forests exhibit a remarkably high degree of homogeneity in their radar response over a very large area though some spatial and temporal variability exist. The authors present a simple technique for calibrating scatterometer data using tropical rain forests, Using a polynomial model for the rolloff of O with incidence angle, the …

Generalized Hidden Filter Markov Models Applied To Speaker Recognition, John M. Colombi

Theses and Dissertations

Classification of time series has wide Air Force, DoD and commercial interest, from automatic target recognition systems on munitions to recognition of speakers in diverse environments. The ability to effectively model the temporal information contained in a sequence is of paramount importance. Toward this goal, this research develops theoretical extensions to a class of stochastic models and demonstrates their effectiveness on the problem of text-independent (language constrained) speaker recognition. Specifically within the hidden Markov model architecture, additional constraints are implemented which better incorporate observation correlations and context, where standard approaches fail. Two methods of modeling correlations are developed, and their …

Studies Of Thin Strained Inas, Alas, And Alsb Layers By Spectroscopic Ellipsometry, C. M. Herzinger, Paul G. Snyder, F. G. Celii, Y.-C. Kao, D. Chow, B. Johs, John A. Woollam

Department of Electrical and Computer Engineering: Faculty Publications

The optical constants for thin layers of strained InAs, AlAs, and AlSb have been investigated by spectroscopic ellipsometry and multi-sample analyses. These materials are important for high-speed resonant tunneling diodes in the AlAs/InAs/In_0.53Ga_0.47As and AlSb/InAs material systems. Understanding the optical properties for these thin layers is important for developing in situ growth control using spectroscopic ellipsometry. Ex situ room-temperature measurements were made on multiple samples. The resulting fitted optical constants are interpreted as apparent values because they are dependent on the fit model and sample structure. These apparent optical constants for very thin layers can be …

A Crosstalk Correcting Router That Uses Online Noise Simulation To Route High-Speed Multichip Modules, Kenneth J. Mcclellan Jr.

Theses and Dissertations

Existing Multi Chip Module (MCM) auto-routers either ignore crosstalk or use over-simplified crosstalk approximations. Of the routers that do consider crosstalk, very few have the capability to correct crosstalk problems after they occur. This dissertation describes a router that not only has an internal crosstalk model for high speed MCMs which is more accurate than that of other existing routers, but also has the capability to use an online simulator to more accurately determine noise levels. After crosstalk problems occur, the router has the ability to correct these problems. Through memory usage reductions and routing efficiency improvements, this maze router …

Text-Independent, Open-Set Speaker Recognition, Stephen V. Pellissier

Theses and Dissertations

Speaker recognition, like other biometric personal identification techniques, depends upon a person's intrinsic characteristics. A realistically viable system must be capable of dealing with the open-set task. This effort attacks the open-set task, identifying the best features to use, and proposes the use of a fuzzy classifier followed by hypothesis testing as a model for text-independent, open-set speaker recognition. Using the TIMIT corpus and Rome Laboratory's GREENFLAG tactical communications corpus, this thesis demonstrates that the proposed system succeeded in open-set speaker recognition. Considering the fact that extremely short utterances were used to train the system (compared to other closed-set speaker …

An Investigation Of Preliminary Feature Screening Using Signal-To-Noise Ratios, David B. Sumrell

Theses and Dissertations

A new saliency metric and a new saliency screening method are developed. This new metric, the SN saliency metric, is based upon signal-to-noise ratios, where the signal is provided by a sum of squared weights associated with a given feature, and the noise is based upon a sum of squared weights associated with a reference noise feature which is injected into the data. The resultant metric allows for a direct comparison of the feature of interest with a reference noise feature which is known to be nonsalient. The SN saliency screening method, which uses the SN saliency metric, offers the …

Variable-Complexity Trellis Decoding Of Binary Convolutional Codes, David W. Matolak, S. G. Wilson

Faculty Publications

Considers trellis decoding of convolutional codes with selectable effort, as measured by decoder complexity. Decoding is described for single parent codes with a variety of complexities, with performance "near" that of the optimal fixed receiver complexity coding system. Effective free distance is examined. Criteria are proposed for ranking parent codes, and some codes found to be best according to the criteria are tabulated, Several codes with effective free distance better than the best code of comparable complexity were found. Asymptotic (high SNR) performance analysis and error propagation are discussed. Simulation results are also provided.

On The Adaptive Multi-Stage Detector For Cancellation Of Multiuser Interference In Cdma Wireless Communication Systems, Nadir Sezgin

Dissertations

The classical multiple access techniques such as Frequency Division Multiple Access (FDMA) and Time Division Multiple Access (TDMA) schemes are band limited in terms of their capacity to be used for mobile radio communication. Recent developments in the area of digital signal processing, makes Code Division Multiple Access (CDMA) as a possible solution to the demand of capacity for the mobile radio communication. The capacity of CDMA is limited by multiuser interference, that is the interference from the other users.

The goal of this dissertation is to improve the multiuser CDMA detector with high Bit Error Rate (BER) performance, low …

Implementation Of A Friction Estimation And Compensation Technique, Jayesh N. Amin

Theses

This thesis reports implementation of a friction estimation and compensation technique on a special laboratory apparatus. In this work, experimental results are reported for the Coulomb friction observer.

The Coulomb friction observer estimates the total friction present in a system, assuming it to be a constant function of velocity. An extension of the observer, utilizing a coupled velocity observer, is used when velocity is not measurable. A modification to the velocity observer is also implemented. Experimental results show a remarkable improvement in the friction estimates which are also compared to the actual friction measurements. The estimates are qualitatively similar to …

Design And Development Of Four To Sixteen Channel Video Multiplexers, Ronan Rahimi

Theses

Video multiplexer series were successfully designed and built for prototype and evaluation both in terms of hardware and software. The hardware platform was designed to accommodate up to sixteen color video input channels for time lapse or real time recording on a single video cassette recorder. This product implements four modes of operation; Live, Record, Playback and Menu mode, which is not a full mode of operation. Menu mode is a series of on-screen programming menus which appears on Live, Record and Playback modes. Menu mode enables the user to program the machine to work under specific modes of application. …

The Development Of An Embedded Wireless Modem Conforming To Advanced Mobile Phone System And Cellular Digital Packet Data Standards, Xin Ren

Theses

Introduced by AT&T Bell Labs in 1970s, today Advanced Mobile Phone Systems (AMPS) - a first generation analog cellular system serve millions of customers in the United States and 55 other countries, and the number of subscribers is still rapidly increasing. Although digital cellular systems are emerging in recent years, research efforts are still being made to the enhancement of AMPS systems because of their popularity. An example is the new Cellular Digital Packet Data (CDPD) standard announced in 1994. CDPD is an overlay of the existing AMPS, and has the capability of transmitting data packets over such an analog …

Numerical Simulation Of Clipping Distortion In Lightwave Catv Systems, Luay Al-Nadi

Theses

Clipping induced distortion is an essential limit for modulation depth and number of channels in subcarrier multiplexed lightwave video transmission systems. Two different types of laser clipping are compared (single-clipping vs. double-clipping). In this work, the distortion limits imposed by clipping effects, in both directly (single-clipping) and externally (double-clipping) modulated systems, are examined. Numerical simulations were performed to test the efficiency of Saleh's Model. A comparison of results with clipping induced distortion in directly modulated lightwave systems (single-clipping) and clipping induced distortion in externally modulated lightwave systems (double-clipping) is presented, it is shown through numerical simulation that the total non-linear …

Configuring The Radial Basis Function Neural Network, Insoo Sohn

Theses

The most important factor in configuring an optimum radial basis function (RBF) network is the training of neural units in the hidden layer. Many algorithms have been proposed, e.g., competitive learning (CL), to train the hidden units. CL suffers from producing "dead-units." The other major factor Which was ignored in the past is the appropriate selection of the number of neural units in the hidden layer. The frequency sensitive competitive learning (FSCL) algorithm was proposed to alleviate the problem of dead-units, but it does not alleviate the latter problem. The rival penalized competitive learning (RPCL) algorithm is an improved version …

Coded Modulation For Satellite Broadcasting, Robert H. Morelos-Zaragoza, Oscar Y. Takeshita, Hideki Imai, Marc P. C. Fossorier, Shu Lin

Faculty Publications

In this paper, three-level block coded 8-PSK modulations, suitable for satellite broadcasting of digital TV signals, are presented. A design principle to achieve unequal error protection is introduced. The coding scheme is designed in such a way that the information bits carrying the basic definition TV signal have a lower error rate than the high definition information bits. The large error coefficients, formally associated with standard mapping by set partitioning, are reduced by considering a nonstandard partition of an 8-PSK signal set. The bits-to-signal mapping induced by this partition allows the use of suboptimal low-complexity soft-decision decoding of binary block …

An Atm-Based Intelligent Optical Backplane Using Cmos-Seed Smart Pixel Arrays And Free- Space Optical Interconnect Modules, Dominic J. Goodwill, Kent E. Devenport, Harvard Scott Hinton

Electrical and Computer Engineering Faculty Publications

The architecture, smart pixel array chip design, and optical design of an intelligent free-space digital optical backplane for ATM switching are presented. The smart pixel chip uses reflective SEED (self-electrooptic effect device) optical modulators and detectors flip-chip bonded to CMOS circuitry. This chip is one of the most complex designs ever reported in this technology, and it operates at a simulated backplane clock rate of 125 MHz. The low-loss optical system employs f/4 diffractive minilenses and microlenses to interconnect clusters of smart pixels, and it is shown to allow 2060 connections per chip if 1-cm2 -sized smart pixel chips are …

Cavity Model Analysis Of Microstrip Ring Antennas Using Green's Functions, Javier Gomez Tagle Rangel

Retrospective Theses and Dissertations

Microstrip ring antennas have been experimentally tested by several researchers due to their specific radiation characteristics that make them very suitable for many applications, from medical uses to mobile communications. Ring antennas have been found to have a larger bandwidth compared to other conventional types of microstrip patch antennas. Further more, their size is smaller when compared to circular and rectangular resonant structures. The TM1m modes (m = 2,4,6 .. , where m represents radial variations) radiate conical beams in the broadside direction, while TM nl modes (n = 2,4,6 .. , where n represents azimuthal variations) have a radiation …

A Self-Consistent Numerical Method For Simulation Of Quantum Transport In High Electron Mobility Transistor; Part 1: The Boltzmann-Poisson-Schrodinger Solver, Rahim Khoie

Electrical & Computer Engineering Faculty Research

A self-consistent Boltzmann-Poisson-Schrödinger solver for High Electron Mobility Transistor is presented. The quantization of electrons in the quantum well normal to the heterojunction is taken into account by solving the two higher moments of Boltzmann equation along with the Schrödinger and Poisson equations, self-consistently. The Boltzmann transport equation in the form of a current continuity equation and an energy balance equation are solved to obtain the transient and steady-state transport behavior. The numerical instability problems associated with the simulator are presented, and the criteria for smooth convergence of the solutions are discussed. The current-voltage characteristics, transconductance, gate capacitance, and unity-gain …

A Simulation Environment For Cdma Wireless Communication Systems In Awgn Channels, Muzaffer Kanaan

Theses

The goal of this work is the development of a, wireless communication system simulator. The simulator has been developed primarily to aid in the studies of Code Division Multiple Access (CDMA) digital cellular systems. We begin by introducing the fundamentals of spread spectrum communications and the motivation for this work. We then take a detailed look at CDMA systems and their structure. We then verify the accuracy of the simulator by using it to simulate some familiar system scenarios. We end this work by presenting conclusions and suggestions for further work.

Asynchronous Multiuser Decorrelating Detector For Awgn Channel, Ashwini A. Borkar

Theses

Decorrelating detector is one of the sub-optimum detectors for CDMA applications that generally has better performance than the conventional detector and is near-far resistant. Synchronous decorrelating detector employing DPSK modulation is considered and its simulation results are presented.

Attention is focussed on one-shot decorrelating detector for a two user case for asynchronous transmission, where each symbol interval is considered seperately. Initially the performance of the detector with exact estimation of the relative delay is analyzed and then the effect of inaccurate estimation on the probability of error is discussed.