Engineering Commons^™

Atmospheric Induced Errors In Space-Time Adaptive Processing, Vinod D. Naga

Theses and Dissertations

This thesis examines the effects of atmospheric turbulence-induced phase perturbations on the performance of ground-based Space-Time Adaptive Processing (STAP) systems. Both Fully Adaptive Joint Domain Optimum and Partially Adaptive Factored-Time Space processing methods are examined. This thesis concentrates on the turbulence effects on STAP applied to ground-based arrays. This thesis further focuses on the capability of STAP to resolve targets at low elevation angles in the presence of turbulence. Only clutter interference and receiver noise are considered. Turbulence effects on the EM phase-front are calculated for turbulence strength Cn(2) values ranging from 5.0 x 10(exp -14) m-2/3 to 5.0 x …

A Wire Antenna Designed For Space Wave Radiation Over The Earth Using A Genetic Algorithm, Brian S. Sandlin

Theses and Dissertations

A wire antenna is designed for optimal performance at low elevation angles in the presence of a lossy half-space. A simple genetic algorithm (GA) and GENOCOP III software are each integrated with Numerical Electromagnetics Code Version 4.1 (NEC4.1) to optimize a wire antenna geometry for multiple objectives: power gain, azimuthal symmetry, and input impedance. The performance of the two versions of the integrated GA are compared. Several of the resulting antennas are analyzed, and an antenna is proposed for use in a Remote Intrusion Monitoring System (RIMS). Simulations suggest that the proposed antenna, which is well-matched, offers a significant increase …

Analytic Transfer Function Of The Forward Propagation Of Diffuse Photon Density Waves In Turbid Media With An Embedded Spherical Inhomogeneity, Deborah L. Lasocki

Theses and Dissertations

Diffusing photons can be used to detect and localize optical inhomogeneities embedded in turbid media such as clouds, fog, paint and human tissue. This thesis shows that a transfer function derived from an analytic solution of the Helmholtz equation can completely characterize in three dimensions the perturbations in the forward propagation phenomena caused by a spherical defect object in a multiple-scattering medium. Two models of the forward propagation behavior of diffuse photon density waves in homogeneous, infinite, turbid media that contains a spherical inhomogeneity are examined. The first model is an exact analytic solution based on a modal expansion in …

Applications Of Unsupervised Clustering Algorithms To Aircraft Identification Using High Range Resolution Radar, Dzung Tri Pham

Theses and Dissertations

Identification of aircraft from high range resolution (HRR) radar range profiles requires a database of information capturing the variability of the individual range profiles as a function of viewing aspect. This database can be a collection of individual signatures or a collection of average signatures distributed over the region of viewing aspect of interest. An efficient database is one which captures the intrinsic variability of the HRR signatures without either excessive redundancy typical of single-signature databases, or without the loss of information common when averaging arbitrary groups of signatures. The identification of 'natural' clustering of similar HRR signatures provides a …

A Single Chip Low Power Implementation Of An Asynchronous Fft Algorithm For Space Applications, Bruce W. Hunt

Theses and Dissertations

A fully asynchronous fixed point FFT processor is introduced for low power space applications. The architecture is based on an algorithm developed by Suter and Stevens specifically for a low power implementation. The novelty of this architecture lies in its high localization of components and pipelining with no need to share a global memory. High throughput is attained using large numbers of small, local components working in parallel. A derivation of the algorithm from the discrete Fourier transform is presented followed by a discussion of circuit design parameters specifically, those relevant to space applications. The generic architecture is explained with …

Atmospheric Turbulence Scintillation Effects On Wavefront Tilt Estimation, James A. Louthain

Theses and Dissertations

A new atmospheric turbulence screen generator is developed for use in performance calculations of adaptive optics systems valid over a wide range of atmospheric turbulence parameters. The screen generator accounts for diffraction effects caused by weak turbulence and incorporates the phase, amplitude, and cross statistics of the perturbed optical field. The wavefront's phase and amplitude perturbations are taken from the correlation functions developed by Lee and Harp and the cross correlation of the phase and amplitude derived in this thesis. The screen generator uses a modal representation to perform a Fourier series expansion of the wavefront phase and amplitude over …

Training Strategies For Critic And Action Neural Networks In Dual Heuristic Programming Method, Christian Peter Paintz

Dissertations and Theses

This thesis discusses strategies for and details of training procedures for the Dual Heuristic Programming (DHP) methodology. This and other approximate dynamic programming approaches (HDP, DHP, GDHP) have been discussed in some detail in the literature, all being members of the Adaptive Critic Design (ACD) family. The example applications used here are the inverted pendulum problem and a fully nonlinear constant velocity bicycle steering model. The inverted pendulum has been successfully controlled using DHP, as reported in the literature. This thesis suggests and investigates several alternative D HP training procedures and compares their performance with respect to convergence speed and …

Comparison Of Fdtd Algorithms For Subcellular Modeling Of Slots In Shielding Enclosures, Kuang-Ping Ma, Min Li, James L. Drewniak, Todd H. Hubing, Thomas Van Doren

Electrical and Computer Engineering Faculty Research & Creative Works

Subcellular modeling of thin slots in the finite-difference time-domain (FDTD) method is investigated. Two subcellular algorithms for modeling thin slots with the FDTD method are compared for application to shielding end osures in electromagnetic compatibility (EMC). The stability of the algorithms is investigated, and comparisons between the two methods for slots in planes, and slots in loaded cavities are made. Results for scattering from a finite-length slot in an infinite plane employing one of the algorithms are shown to agree well with published experimental results, and power delivered to an enclosure with a slot agree well with results measured for …

Comparison Of Three Clustering Algorithms And An Application To Color Image Compression, Jihun Cha, Laurene V. Fausett

Electrical Engineering and Computer Science Faculty Publications

This paper investigates a traditional clustering algorithm (K-means) and two neural networks (SOM and ART-F). The characteristics of each algorithm are illustrated by simulating geometric space data clustering. Then each algorithm is applied to image data sets to compress the size by reducing the number of colors from 256 to 16.

New Approaches To Column Compatibility Checking And Column-Based Input/Output Encoding For Curtis Decompositions Of Completely Or Incompletely Specified Switching Functions, Michael A. Burns

Dissertations and Theses

Cube calculus is an algebraic model used to process boolean functions. Cube calculus operations are widely used in logic optimization, logic synthesis, image processing and recognition, machine learning, and other applications which require massive logic operations.

The cube calculus operations can be carried out on general-purpose computers. Since these operations can involve several levels of nested loops, this approach has poor performance.

A cube calculus machine which has a special data path designed to speed up cube calculus operations is presented in this thesis. This c-qbe calculus machine can execute cube calculus operations 10 to 25 times faster than the …