Electrical and Computer Engineering Commons^™

Adaptive Space-Time Processing For Wireless Communications, Xiao Cheng Bernstein

Dissertations

Adaptive space-time processing techniques have been found to increase the capacity of two major, multiple-access wireless communication systems: Time Division Multiple Access (TDMA) and Code Division Multiple Access (CDMA).

In an IS-54 TDMA system, the frequency re-use factor has to be set to 7 so that cells with the same spectrum are separated far enough to meet a required carrier-to-interference ratio (CIR). Space processing uses multiple antennas which, in turn, provide alternative signal paths in order to cancel interferences and combat multipath fading. We have proposed the eigencanceler method and have reviewed the theoretical optimum combining and the feasible direct …

On Optimal Design And Applications Of Linear Transforms, Mehmet V. Tazebay

Dissertations

Linear transforms are encountered in many fields of applied science and engineering. In the past, conventional block transforms provided acceptable answers to different practical problems. But now, under increasing competitive pressures, with the growing reservoir of theory and a corresponding development of computing facilities, a real demand has been created for methods that systematically improve performance. As a result the past two decades have seen the explosive growth of a class of linear transform theory known as multiresolution signal decomposition. The goal of this work is to design and apply these advanced signal processing techniques to several different problems.

The …

On The Optimization Problems In Multiaccess Communication Systems, Gangsheng Wang

Dissertations

In a communication system, the bandwidth is often a primary resource. In order to support concurrent access by numerous users in a network, this finite and expensive resource must be shared among many independent contending users. Multi-access protocols control this access of the resource among users to achieve its efficient utilization, satisfy connectivity requirements and resolve any conflict among the contending users. Many optimization problems arise in designing a multi-access protocol. Among these, there is a class of optimization problems known as NP-complete, and no polynomial algorithm can possibly solve them. Conventional methods may not be efficient arid often produce …

Grain-Size Optimization And Scheduling For Distributed Memory Architectures, Jing-Chiou Liou

Dissertations

The problem of scheduling parallel programs for execution on distributed memory parallel architectures has become the subject of intense research in recent, years. Because of the high inter-processor communication overhead in existing parallel machines, a crucial step in scheduling is task clustering, the process of coalescing heavily communicating fine grain tasks into coarser ones in order to reduce the communication overhead so that the overall execution time is minimized.

The thesis of this research is that the task of exposing the parallelism in a given application should be left to the algorithm designer. On the other hand, the task of …

Investigation Of Hybrid Message-Passing And Shared-Memory Architectures For Parallel Computer : A Case Study : Turbonet, Xi Li

Dissertations

Several DSP (Digital Signal Processing) algorithms are developed for the MIT TurboNet parallel computer. In contrast to other parallel computers that implement exclusively in hardware either the message-passing or the shared-memory communication paradigm, or employ distributed shared-memory architectures characterized by inefficient implementation of the shared-memory paradigm, the hybrid architecture of TurboNet supports direct, efficient implementation of both paradigms. Three versions of each algorithm are developed, if possible, corresponding to message-passing, shared-memory, and hybrid communications, respectively. Theoretical and experimental comparisons of algorithms are employed in the analysis of performance. The results prove that the hybrid versions generally achieve better performance than …

Theory, Design And Applications Of Linear Transforms For Information Transmission, Adil Benyassine

Dissertations

The aim of this dissertation is to study the common features of block transforms, subband filter banks, and wavelets, and demonstrate how discrete uncertainty can be applied to evaluate these different decomposition techniques. In particular, we derive an uncertainty bound for discrete-time functions. It is shown that this bound is the same as that for continuous-time functions, if the discrete-time functions have a certain degree of regularity.

This dissertation also deals with spectral modeling in filter banks. It is shown, both theoretically and experimentally, that subspectral modeling is superior to full spectrum modeling if performed before the rate change. The …

Design And Micro-Fabrication Of Tantalum Silicide Cantilever Beam Threshold Accelerometer, Chang Joo Kim

Dissertations

Microfabricated threshold accelerometers were successfully designed and fabricated following a careful analysis of the electrical, mechanical, and fabrication issues inherent to micron-sized accelerometers. A uniform cantilever beam was chosen because of the simplicity of design and fabrication. New models for the electrostatic force exerted on the cantilever beam were developed and calculations were made that accurately predicted the electrical characteristics of the accelerometer. The calculations also provided design guidelines for optimizing the accelerometer dimensions. Computer simulation demonstrated that the error of the electrostatic force, calculated using the most accurate model, was within 2% of the actual force which was obtained …

Electrical Characteristics Of Novel Heterojunction Diodes Of Thin Relaxation Semiconductors/P-Si/, Hyung Joo Lee

Dissertations

The relaxation semiconductor is defined as one in which the dielectric relaxation time (τd;resistivity times permittivity) is greater than lifetime (τo). Non-hydrogenated amorphous Silicon Carbide (SiC) and KrF excimer laser induced disordered Si were used for the relaxation semiconductors. Both semiconductors have high resistivity, wide energy gap, and numerous defects. A novel diode, consisting of those semiconductors on p-type crystalline Silicon (c-Si), was fabricated. In the diode structure, an injecting contact was made on the relaxation material and a Schottky barrier contact was made on the c-Si.

Electrical characteristics of both diodes were found to have interesting …

On Adaptive Code Division Multiple Access Detectors, Wenping Chen

Dissertations

Several variations of adaptive CDMA synchronous receiver schemes which can automatically adjust to the system parameters, are studied in this dissertation. Unlike their non-adaptive counterparts, these adaptive detectors require no knowledge of the received signals' energies and have similar or better performance.

Minimum energy and decorrelating criterion are used to update the weights. Since weights are updated according to the changes of the detector's outputs, hence no training sequence is required. The convergences of some of the aforementioned adaptive detectors are also disscussed.

The detectors proposed in this dissertation are near-far resistant,thus rendering the high-precision power control unnecessary. Among them, …

Algorithms In Fault-Tolerant Clos Networks, Hyunyeop Lee

Dissertations

No abstract provided.

Motion Estimation Using Optical Flow Field, Jingning Pan

Dissertations

Over the last decade, many low-level vision algorithms have been devised for extracting depth from intensity images. Most of them are based on motion of the rigid observer. Translation and rotation are constants with respect to space coordinates. When multi-objects move and/or the objects change shape, the algorithms cannot be used.

In this dissertation, we develop a new robust framework for the determination of dense 3-D position and motion fields from a stereo image sequence. The framework is based on unified optical flow field (UOFF). In the UOFF approach, a four frame mode is used to compute six dense 3-D …

Estimation And Cancellation Of Friction In Control Systems, Sofia Mentzelopoulou

Dissertations

The research reported in this dissertation concerns the estimation and cancellation of friction in control systems. For purposes of analysis, the Coulomb friction model, the "extended" Coulomb friction model as well as dynamic friction models are used. In addition, for systems with multiple degrees-of-freedom, a general matrix representation of friction is presented.

For the design of the friction estimators, the theory of nonlinear observers is applied. In particular, for a system with multiple degrees-of-freedom, holonomic constraints, and multiple friction sources, three different observers are presented to estimate the friction force or torque. The first (Generalized Coulomb Friction Observer) is designed …

Investigation Of Paraelectric Ptl Thin Films Using Reactive Magnetron Sputtering, Hyun Hoo Kim

Dissertations

The study of methods to prepare paraelectric perovskite PLT (Pb_1-xLa_xTi_1-x/4O₃; x=0.28) thin films has been important because thin films of this high dielectric strength material are required to make high density capacitors for dynamic random access memory. In this research, paraelectric PLT thin films were prepared on multi-layer (Pt/Ti/SiO₂/Si) and MgO substrates in a unique way by the reactive magnetron sputtering method using a multi-component metal target. The individual control of each metal area on the sputtering target had considerable influence on the stoichiometry and electrical properties of the thin …

Heart Rate Variability Study Using Phase Response Curve, Peizhuan Zhang

Dissertations

A noninvasive phase resetting experiment on human subjects was investigated. The phase response curve was estimated and was used to demonstrate cardiac phase resetting due to a vagal input. The estimated running phase response curve showed that the cardiac cycle resetting depended on the time and the amplitude of the vagal stimulation. The phase response curve was then studied using time circle analysis, topological analysis and nonlinear dynamics analysis. Also phase entrainment and stimulus frequency dependence of the phase response were evaluated. Further, the Van Der Pol model, Generalized Additive model and Knight and Peskin's model were used to simulate …

Blind Detection In Channels With Intersymbol Interference, Raafat Edward Kamel

Dissertations

In high speed digital transmission over bandlimited channels, one of the principal impairments, besides additive white Gaussian noise, is intersymbol interference. For unknown channels, adaptive equalization is used to mitigate the interference. Different types of equalizers were proposed in the literature such as linear, decision feedback equalizers and maximum likelihood sequence estimation. The transmitter embeds sequences with the data regularly to help the equalizer adapt to the unknown channel parameters.

It is not always appropriate or feasible to send training sequences; in such cases, self adaptive or blind equalizers are used. The past ten years have witnessed an interest in …

Human Visual System Modelling : Analysis Of Evoked Potential Dynamics, Zongqi Hu

Dissertations

The visual evoked potential (VEP) reflects the electrical activity in the cerebral cortex due to visual stimulation. It contains information on signal processing in the visual pathways from the retina, through the lateral geniculate nucleus (LGN) to the cortical level. Although the VEP is generated by various sources in the multi-layer neural network, the functions of some neuronal mechanisms and the transfer characteristics of particular pathways can be revealed and analyzed by use of carefully designed stimuli (Zemon & Ratliff, 1984; Zemon, Victor & Ratliff, 1986). This dissertation focuses on studies of the visual evoked potential as a composite of …

On Generalized Adaptive Neural Filter, Zhiqiang Zhang

Dissertations

Linear filters have historically been used in the past as the most useful tools for suppressing noise in signal processing. It has been shown that the optimal filter which minimizes the mean square error (MSE) between the filter output and the desired output is a linear filter provided that the noise is additive white Gaussian noise (AWGN). However, in most signal processing applications, the noise in the channel through which a signal is transmitted is not AWGN; it is not stationary, and it may have unknown characteristics.

To overcome the shortcomings of linear filters, nonlinear filters ranging from the median …

Minimum Redundancy Array Structure For Interference Cancellation, Wan-Ling Chen

Dissertations

Adaptive antenna arrays are widely used in many advanced radar, sonar, and communication systems because of their effectiveness in cancelling intentional or unintentional interferers. A uniformly spaced linear array, referred to as a Uniform Regular Array (URA), is the usual structure used for interference cancellation. The Minimum Redundancy Array (MRA) structure proposed in this work is a special kind of thinned array whose application was limited in the past to direction finding. MRAs with the same number of array elements can resolve directions of much more closely spaced signals than URAs.

The URA structure is customarily utilized for interference cancellation, …

Characterization Of Advanced Etching Reactors Using Novel Diagnostic Tools, Vipulkumar Patel

Dissertations

Plasma etching equipment used for sub-micron integrated circuit fabrication at present are exclusively based on 13.56 MHz, capacitively coupled, parallel-plate geometry. The underlying mechanisms of plasma processes in these reactors are not well understood and there is even less understanding of how the etch-tool parameters relate to the plasma discharge characteristics which actually determine the etch process. In this thesis, new diagnostic techniques were applied for the characterization and optimization of plasma etching processes in various reactor configurations.

Specifically, diode and triode configurations were studied extensively using tuned scanning Langmuir probes. Both radial and axial distributions of plasma density were …

Investigation Of The Consumer Electronics Bus, Jaesoo Yang

Dissertations

The objectives of this dissertation are to investigate the performance of the Consumer Electronics Bus (CEBus) and to develop a theoretical formulation of the Carrier Sense Multiple Access with Contention Detection and Contention Resolution (CSMA/CDCR) with three priority classes protocol utilized by the CEBus

A new priority channel assigned multiple access with embedded priority resolution (PAMA/PR) theoretical model is formulated. It incorporates the main features of the CEBus with three priority classes. The analytical results for throughput and delay obtained by this formulation were compared to simulation experiments. A close agreement has been found thus validated both theory and simulation …

On Adaptive Censored Cfar Detection, Loizos Anastasiou Prastitis

Dissertations

In an automatic radar detection system the received signal in every range resolution cell is compared with a threshold to test for the presence of a target. A Neyman-Pearson type test is used which maximizes the probability of detection for a fixed probability of false alarm. For the simple case where the noise is homogeneous a fixed threshold is chosen to achieve the designed constant false alarm rate (CFAR). In the more realistic case the noise background is non-stationary due to clutter and interference. In this situation, the threshold used for testing a particular cell is usually set adaptively using …

Fabrication And Characterization Of Gated Silicon Field Emission Micro Triodes, Nanchou Liu

Dissertations

This dissertation describes the fabrication technology and characterization of a gated silicon field emission micro triode that is a novel electron tunneling device for generating electron emission into a vacuum. Conic (point) and wedge field emitter structures with nm-scale radii were fabricated in silicon and GaAs by etching, MOCVD and dry oxidation. A new self-aligned process was developed for fabrication of vertical field emission triodes. This process allows control of gate opening to less than 0.5 μm diameter without the need of electron-beam writing. It also provides a planar gate electrode and a thick dielectric layer for reduction of the …

Performance Evaluation Of Spread Spectrum System With Cochannel Interference Through A Nonlinear Channel, Yong H. Kim

Dissertations

This thesis deals with the problem of more than one subscriber transmitting data signals through a common satellite repeater using code division multiplexing to separate the signals. We are concerned with the problem of amplifying two DS spread spectrum signals, both QPSK or BPSK modulated, in a common device in which limiting occurs. One signal is considered the signal we desire to receive, and the other, having the same nominal carrier frequency with a small random offset, is considered to be a cochannel interferer. The case of a cochannel interferer on the uplink and downlink in QPSK signalling and BPSK …

Process Technology And Characterization For Field Emission Devices, Jong Min Kim

Dissertations

Vacuum microelectronics is a new research field which applies semiconductor process technology to the fabrication of micron-dimensioned electron devices. Vacuum microelectronics is made possible by advances in microstructures and nanofabrication technology. Vacuum microelectronic devices are further characterized by a wide operating temperature range, nuclear radiation immunity, higher emission current density potential, and lower power consumption than that of thermionic emitters. The low mass of the electron provides a higher carrier mobility than GaAs or any solid state device. These features offer the potentials for wide variety of applications.

In this dissertation. electron field emission structures applicable to a variety of …

Investigation Of Epitaxial Lift-Off Gaas And Langmuir-Blodgett Films For Optoelectronic Device Applications, Divyang M. Shah

Dissertations

Epitaxial lift-off (ELO), a technique of removing an epitaxially grown GaAs layer from its growth substrate by selective etching of an AlAs sacrificial layer, is described for field-effect transistor fabrication independent of the GaAs growth substrate. Metal Semiconductor Field-Effect Transistors (MESFETs) and High Electron Mobility Transistors (HEMTs) fabricated on silicon and sapphire substrates using ELO are investigated. A 0.1 μm gate length depletion mode MESFET made on silicon exhibited a unity current gain frequency f_t = 34 GHz. Excellent device isolation with subpicoampere leakage currents is obtained. A high input impedance amplifier has been implemented on silicon substrate using …

A Generalized, Parametric Pr-Qmf/Wavelet Transform Design Approach For Multiresolution Signal Decomposition, Hakan Caglar

Dissertations

This dissertation aims to emphasize the interrelations and the linkages of the theories of discrete-time filter banks and wavelet transforms. It is shown that the Binomial-QMF banks are identical to the interscale coefficients or filters of the compactly supported orthonormal wavelet transform bases proposed by Daubechies.

A generalized, parametric, smooth 2-band PR-QMF design approach based on Bernstein polynomial approximation is developed. It is found that the most regular compact support orthonormal wavelet filters, coiflet filters are only the special cases of the proposed filter bank design technique.

A new objective performance measure called Non-aliasing Energy Ratio(NER) is developed. Its merits …

The Theory Of Bootstrapped Algorithms And Their Applications To Cross Polarization Interference Cancelation, Abdulkadir Dinc

Dissertations

Dual-polarized transmission has become an important method for frequency re-use, particularly in satellite and microwave radio communication. Nevertheless, cross-polarization interference, which is inherent to this method, may cause degradation in system performance.

Different canceler [sic] structures have been proposed to mitigate the effect of cross-polarization. Among these are the diagonalizer, the least mean square (LMS) canceler [sic] and the bootstrapped cancelers [sic]. Bootstrapped canceler [sic] schemes have been proposed and implemented in different applications, such as satellites, tactical communications, and quadrature amplitude madulation [sic] (QAM) dual polarized microwave radio. Nevertheless, no attempt was made in the past to quantify the …

Computer Aided Localization Of Neurological Diseases, Yusuf Parlar

Dissertations

Computers in medicine has brought new dimensions and better understanding of uncertainties in the field of medical sciences in the last decade. This thesis is focused upon the localization of neurological lesions in the human nervous system. It relates clinical neurological test outcomes to pathways of function or malfunction. Certain methods are proposed-empirical. stochastic. Deterministic-to estimate the spatial distributions of lesion probabilities.

First. a Bayesian model is presented to estimate the posterior probability of lesion from a priori information, based on the test outcomes. Due to unavailable data alternative methods and models are presented: Regression Analysis. Monte Carlo simulation, and …

On The Performance Of Minimum Redundancy Array For Multisource Direction Finding, Byung-Seub Lee

Dissertations

As an application of power spectrum estimation, the multi-source direction finding has been evolved from conventional FFT method to Superresolution methods such as Multiple Signal Classification(MUSIC) algorithm. Uniform Regular Array(URA) was mainly used in all these approaches.

The Minimum Redundancy array(MRA); a non-uniform thinned array which results in an input signals covariance matrix with minimum redundancy has been shown to have certain interesting properties for spectrum estimation. Only recently it was suggested to use the MRA for spatial estimation. The purpose of this research was to study the performance of this array in multi-source direction finding estimation and compare it …

Computer Modeling And Analysis Of Biological Rhythms, Shi Xiong Yang

Dissertations

Biological rhythms are an important phenomenon and feature of physiologic systems. Indirect means have to be employed for their description and exploration due to the unclear internal nature of the system. This study analyzed and developed several possible mathematical models using single or multidimensional nonlinear differential equations to approach the experimental circadian data. The numerical solutions of the models were obtained by computer simulation and the simulated and experimental acquired circadian data were analyzed in both the time and frequency domains. Phase plane plots, phase response curves and power spectrum analysis were employed to determine the nonlinearity of the system …