Signal Processing Commons^™

Forward Looking Radar: Interference Modelling, Characterization, And Suppression, James T. Caldwell

Theses and Dissertations

This research characterizes forward looking radar performance while noting differences with traditionally examined sidelooking radar. The target detection problem for forward looking radar is extremely difficult due to the severe, heterogeneous and range dependent ground clutter. Consequently, forward looking radar detection represents an important but overlooked topic because of the increased difficulty compared to sidelooking radar. This void must be filled since most fighter aircraft use forward looking radar, making this topic intensely interesting to the Air Force. After characterizing forward looking radar performance, basic radar concepts along with advanced adaptive interference suppression techniques improve the output Signal-to-Interference-plus-Noise Ratio (SINR) …

A Fast And Simple Algorithm For Computing M-Shortest Paths In State Graph, M. Sherwood, Laxmi P. Gewali, Henry Selvaraj, Venkatesan Muthukumar

Electrical & Computer Engineering Faculty Research

We consider the problem of computing m shortest paths between a source node s and a target node t in a stage graph. Polynomial time algorithms known to solve this problem use complicated data structures. This paper proposes a very simple algorithm for computing all m shortest paths in a stage graph efficiently. The proposed algorithm does not use any complicated data structure and can be implemented in a straightforward way by using only array data structure. This problem appears as a sub-problem for planning risk reduced multiple k-legged trajectories for aerial vehicles.

Phase-Sensitive Detection Electronics For Wavelength Modulation Spectroscopy Experiments, Tyrone Pate

Electrical & Computer Engineering Theses & Dissertations

Wavelength modulation spectroscopy (WMS) is a non-intrusive detection technique, which enables the measurement of several parameters such as pressure, concentration, and temperature of a species of interest by analyzing the latter's absorption lineshape profile. The method employs a synchronous modulation and detection apparatus to increase the signal to noise ratio and hence the sensitivity of the measurement. Phase-sensitive detection and demodulation of the signal is performed at the modulation frequency and its harmonics. Research at ODU demonstrates that each particular measurement can be performed optimally at an appropriate harmonic of the modulation frequency. The most suitable harmonic depends on many …

Wavelet-Based Audio Embedding & Audio/Video Compression, Michael J. Mendenhall

Theses and Dissertations

With the decline in military spending, the United States relies heavily on state side support. Communications has never been more important. High-quality audio and video capabilities are a must. Watermarking, traditionally used for copyright protection, is used in a new and exciting way. An efficient wavelet-based watermarking technique embeds audio information into a video signal. Several highly effective compression techniques are applied to compress the resulting audio/video signal in an embedded fashion. This wavelet-based compression algorithm incorporates bit plane coding, first difference coding, and Huffman coding. To demonstrate the potential of this audio embedding audio/video compression system, an audio signal …

Bistatic Radar Cross Section (Rcs) Characterization Of Complex Objects, Robert L. Eigel Jr.

Theses and Dissertations

This research addresses some phenomenological aspects of bistatic scattering from a complex object with an emphasis on specular, shadowing, dihedral, and cavity effects. Five targets are investigated for their simplicity and ability to highlight certain scattering phenomena. Direct measurements of scattered electromagnetic energy and simulation data is gathered for a frequency bandwidth of 6-18 GHz. Both ray tracing and scattering center approaches are used to describe the bistatic mechanisms. An appraisal of the effectiveness and utility of the monostatic-to-bistatic equivalence theorems (Kell's and Crispin's) and several commercial scattering prediction codes is also accomplished. Simulation data is generated from two different …

Stability Analysis And Augmentation Of A Closed-Loop Computer Control System Subject To Electromagnetic Disturbances, Mustafa Doğan

Electrical & Computer Engineering Theses & Dissertations

Most electronic and electrical equipment is not only a potential source of electromagnetic interference (EMI) but can also malfunction when exposed to certain levels of ambient EMI. This phenomena becomes more significant for digital control-computers automating the command and control performances in complex plants. Such EM disturbances can introduce transient signals on analog sensor and actuator lines, change data values on digital buses and in memory, or even produce logic changes in the CPU. The result of these so called computer upsets is the introduction of some degree of degradation in the quality of the control signal ranging from a …

Terrain Backscattering Coefficient Generator, Ricardo Mediavilla

Theses and Dissertations

Using already available data, a backscattering coefficient generator (BCG) for several types of terrain and measurement conditions is developed. The types of terrain are: (1) soils and rocks, (2) trees, (3) grasses, (4) shrubs, (5) short vegetation, (6) roads, (7) urban areas, (8) dry snow, and (9) wet snow. These data sets typically cover incidence angles ranging between 0 and 80 degrees where 0 is normal to the terrain. Measurement conditions are defined by: (1) incidence angle, (2) wave polarizations configuration (HH, HV, or VV), and (3) radar band (L, C, S, X, Ku, Ka, or W). The BCG output …

Ultra-Wideband Tem Horns, Transient Arrays And Exponential Curves: A Fdtd Look, Troy S. Utton

Theses and Dissertations

This research investigates the possibility of applying exponentially curved conducting plates to single-element Transverse Electromagnetic (TEM) horns and their transient arrays to enhance the UWB characteristics already experienced by these radiators. The first part of this study demonstrates the Finite-Difference Time-Domain (FDTD) method's ability to duplicate experimental data, and establishes the baseline models used throughout the remainder of the research. The baseline models consist of the typical flat-triangle shaped conducting plates. The exponential taper models incorporate the exponential curves in the height, the width, and both the height and width directions. One, two- and four-element baseline configurations are compared to …

An Empirical Prediction Model Of The Performance Impacts Of Material Tolerances In Frequency Selective Surfaces Using The Monte Carlo Method, Matthew D. Craig

Theses and Dissertations

Standard computational tools predicting frequency selective surface (FSS) performance model periodic structures as an infinite-by-infinite array of perfectly placed elements with perfect, identical dimensions, and with dielectric layers of uniform thickness and material composition. These models do not address perturbations caused by manufacturing tolerances of elements and dielectric layers, nor do they address edge effects caused by finite-by-finite dimensional arrays. The Monte Carlo Method was used to determine the effects of random variations in element dimension, placement, dielectric thickness, and dielectric material on FSS performance. A full-factorial experimental design was applied, and eight hundred twenty-five unique finite arrays of elements …

A Climatology-Based Model For Long-Term Prediction Of Radar Beam Refraction, Todd S. Pittman

Theses and Dissertations

The National Air Intelligence Center, WPAFB, OH, needs more accurate predictions of radar beam refraction. A new mode was developed for this thesis replacing the standard atmosphere approach with raytracing and climatology. Usually a microwave radio beam bends towards the earth with a radius of curvature greater than the earth's surface. However, seasonal and climatic variations influence the bending, and at times create temperature or moisture inversions that redirect the energy along the earth's surface leaving radio holes where there is no coverage. This model uses iterative raytracing to determine the most direct path from radar to target through the …

Trade-Off Analysis Of Communications Capabilities Of Inter-Satellite Links, Andrew J. Feltman

Theses and Dissertations

This thesis designs, develops, and uses software Graphical User Interfaces (GUIs) to analyze the communications capabilities of Radio Frequency (RF) Inter-Satellite Links (ISLs). The GUIs are geared towards analyzing the proposed ISLs of the Discoverer II program, but are general enough to permit analysis of any free-space RF ISLs. Discoverer II is a demonstration program of low-earth orbiting satellites and is primarily focused on satellite-based sensor technology. This thesis shows RF ISLs can meet the program requirement to broadcast the sensor data back to CONUS in near-real-time. The GUIs operate in real-time and explore trade-offs in the communications capability by …

Non Co-Operative Detection Of Lpi/Lpd Signals Via Cyclic Spectral Analysis, Andrew M. Gillman

Theses and Dissertations

This research proposes and evaluates a novel technique for detecting LPI/LPD communication signals using a digital receiver primarily designed to detect radar signals, such as a Radar Warning Receiver (RWR) or an Electronic Support Measures (ESM) receiver. The proposed Cyclic Spectrum Analysis (CSA) receiver is a robust detector that takes advantage of the spectral correlation properties of second-order cyclostationary signals. A computationally efficient algorithm is used to estimate the Spectral Correlation Function (SCF). Using state-of-the-art FFT processing, it is expected that the proposed CSA receiver architecture could estimate the entire cyclic spectrum m approximately 0.6 ms. The estimate is then …

The Effect Of Registration Errors On Tracking In A Networked Radar System, Bradley J. Mortenson

Theses and Dissertations

To successfully combine information from distributed radar sensors, it is essential that each sensor be correctly referenced in a global coordinate system. If there are biases in the reported position of these sensors, the reported target position will also be biased and the ensuing global estimate of the target position will be degraded. Furthermore, any biases in range or azimuth measurements of these sensors will likewise be reflected in the degradation of global estimate of target position. Registration is the process of ensuring that these errors do not result in the creation of an additional redundant target when only a …

Low Grazing Angle Terrain Backscattering Coefficient Generator, William N. O'Connor

Theses and Dissertations

A near-horizon probabilistic terrain backscatter coefficient generator is introduced, combining modified sea-state curves with Weibull-type probability density functions. A total of nine terrain type classifications (soils & rocks, trees, grasses, shrubs, short vegetation, roads, urban areas, dry snow, and wet snow) are supported, for seven radar bands (L, S, C, X, Ku, Ka, and W), and both linear (HH, VV) and cross (HV, VH) polarizations. The Weibull functions are based on measured sigma and match the published data. The functions also provide a probabilistic nature to the generator. Modified sea state curves are used in place of the Weibull functions …

Modulation Of Electrostatic Microelectromechanical Mirrors Using A Cmos Controller, Paul C. Rounsavall

Theses and Dissertations

Microelectromechanical Systems (MEMS) is a rapidly growing technology that lends itself particularly well to optical applications. An example of an optical MEMS device is the piston-action mirror that modulates the phase of reflected light. The phase of reflected light can be varied using thermal or electrostatic actuation to control the position of the mirror. In previous research, a modulation method to control thermally actuated mirrors was developed. This thesis presents the development, implementation, fabrication, and testing of a complimentary metal oxide semiconductor (CMOS) controller capable of directly interfacing between a digital system, such as a computer, and an electrostatically actuated …

Antenna Gain Enhancement Using A Photonic Band Gap Reflector, Karl C. Schloer

Theses and Dissertations

Scientists have long known that periodic structures can filter electromagnetic (EM) waves. In the last decade, extension of one- and two-dimensionally periodic structures into a third periodic dimension has produced photonic band gap (PBG) structures. A PBG structure is characterized by its omnidirectional stop band at a set of frequencies determined by the structure's periodicity and permittivity. In the present research, we investigate such a structure as an antenna reflector. We aim to develop a modeling approach that provides accurate computations of PBG behavior without relying on massively parallel processing. We also construct and measure the bulk reflection and transmission …

Loop Gain Estimation For Adaptive Control, Jamey P. Sillence

Theses and Dissertations

The identification of a linear discrete-time control system's loop gain is addressed. The classical Kalman filter theory for state estimation in linear control systems is extended, and the control system's loop gain and state are jointly estimated. A rigorous analysis of the measurement situation under consideration yields explicit formulae for the loop gain's unbiased estimate and estimation error's covariance.

Application Of The Finite Element Method To The Scattering Of A Two-Dimensional, Semi-Infinite Periodic Structure, Perry N. Villanueva

Theses and Dissertations

Infinite periodic structures have been studied heavily because of their efficient filtering capabilities. They generally exhibit sharp frequency roll-offs at the frequency band of interest. In the RF region of the electromagnetic spectrum, periodic structures find applications such as radomes and photonic bandgap materials. Most studies have been done with infinitely periodic arrays because it is convenient to collapse an infinite array into one representative period using Floquet Analysis. Truncating an infinite array introduces an edge and invalidates Floquet analysis over the entire array. This thesis formulates a Finite Element Method (FEM) solution of a semi-infinite periodic array consisting of …

An Integrated Synthetic Aperture Radar/Global Positioning System/Inertial Navigation System For Target Geolocation Improvement, Brian J. Young

Theses and Dissertations

This thesis explores a potential integration technique to fuse information from an inertial navigation system (INS) and global positioning system (GPS) with synthetic aperture radar target measurements. Using Kalman filtering techniques, an INSIGPS/SAR integrated system was simulated in a single Kalman filter to analyze the SAR target geolocation accuracy benefits. Three different GPS receiver models were used in the integrated system: stand-alone (SGPS), differential (DGPS), and carrier-phase differential GPS (CPGPS). Each of these GPS models were integrated with a common INSISAR combination to determine the target geolocation accuarcy improvements due only to GPS receiver type. Thesis results show that SAR …

Coupled Electrodynamic-Monte Carlo Simulations Of Nanoscale Gaas Terahertz Optical Mixers, Jiang Li

Electrical & Computer Engineering Theses & Dissertations

The concept of mixing or heterodyning has traditionally been used for microwaves and for radio frequency communications. However, the concept can easily be extended into the optical frequency regime. By doing so, the photomixing process can serve as a very versatile tool for both the generation of ultrahigh frequency (terahertz) and the detection of weak optical signals.

The aim of this thesis is to perform a theoretical study of the photomixing process inside GaAs devices as the non-linear elements. A coupled approach which combines the Monte Carlo simulation scheme for the carrier transport, with Maxwell's equation for the electrodynamics, has …

Joint Map Registration And High Resolution Image Estimation Using A Sequence Of Undersampled Images, Russell C. Hardie, Kenneth J. Barnard, Ernest E. Armstrong

Electrical and Computer Engineering Faculty Publications

n many imaging systems, the detector array is not sufficiently dense to adequately sample the scene with the desired field of view. This is particularly true for many infrared focal plane arrays. Thus, the resulting images may be severely aliased. This paper examines a technique for estimating a high-resolution image, with reduced aliasing, from a sequence of undersampled frames. Several approaches to this problem have been investigated previously. However, in this paper a maximum a posteriori (MAP) framework for jointly estimating image registration parameters and the high-resolution image is presented. Several previous approaches have relied on knowing the registration parameters …

Fetal Heart Rate Detection With A Passive Acoustic Sensor System, Zongyao Zhou

Electrical & Computer Engineering Theses & Dissertations

Research and development is presented of real time signal processing methodologies for the detection of fetal heart tones from noise contaminated signals obtained from passive acoustic sensors. A nonlinear Teager energy operator is utilized for detection of the fetal heart tone event. Autocorrelation and a parallel redundancy correction algorithm derives fetal heart rates. A real time monitoring system is described which records and plots the time history of both the fetal heart rate and the acoustic fetal heart signal. The system is validated in the context of the fetal nonstress test. Comparisons are made with ultrasonic nonstress tests on a …

A General Approach To Boolean Function Decomposition And Its Application In Fpgabased Synthesis, Tadeusz Luba, Henry Selvaraj

Electrical & Computer Engineering Faculty Research

An effective logic synthesis procedure based on parallel and serial decomposition of a Boolean function is presented in this paper. The decomposition, carried out as the very first step of the .synthesis process, is based on an original representation of the function by a set of r-partitions over the set of minterms. Two different decomposition strategies, namely serial and parallel, are exploited by striking a balance between the two ideas. The presented procedure can be applied to completely or incompletely specified, single- or multiple-output functions and is suitable for different types of FPGAs including XILINX, ACTEL and ALGOTRONIX devices. The …

Development Of A 4-Bit Parallel Analog-To-Digital Converter And A Four- Quadrant Double-Balanced Mixer Using Heterojunction Bipolar Transistor Technology, Scott F. Jokerst

Theses and Dissertations

A 4-bit parallel analog-to-digital converter (ADC) and a four- quadrant double-balanced mixer were designed and simulated using heterojunction bipolar transistor (HBT) technology to test the dc and high-frequency characteristics of HBTs. HSPICE simulations of small-scale components and the large-scale ADC operated within expected ranges. The ADC implemented with the Rockwell HBT model operated at a sampling rate of over 1 GHz, and the Fellows model also operated at a 1 GHz sampling rate. The mixer produced an intermediate frequency (IF) signal using radio frequency (RF) and local oscillator (LO) inputs. The circuit produced a +9 dB power gain with less …

Kalman Filter Tracking Of A Ballistic Missile Using Forward Looking Infrared Measurements And Doppler Returns, Michael L. Ching

Theses and Dissertations

The Air Force Institute of Technology (AFIT) has been involved in developing Kalman Filter trackers for airborne targets for the last 14 years. The goal of this particular thesis was to track a ballistic missile in the boost phase at ranges up to 2000 km, in order to control a high energy laser weapon designed to destroy the target The filter developed combined an existing 'FLIR' filter, which estimated location of the plume intensity centroid based on measurements from a forward looking infrared sensor (FLIR), and an existing center-of-mass filter, which estimated the offset between the plume and missile center-of-mass …

An Analytical And Experimental Investigation Of Fm-By-Noise Jamming, Charles J. Daly

Theses and Dissertations

Among the jamming waveforms used in Electronic Warfare, FM-by-noise is the least understood, and no exhaustive analytical and experimental investigation of the subject exists. This investigation presents a thorough review, consolidation, and elucidation of the theory of FM-by-noise. To explain and predict the behavior of FM-by-noise at RF and IF, three useful ratios, namely the deviation-to-victim ratio, the noise-to-victim ratio, and the sweep- to-victim ratio, are developed. To complement the theory, results of FM-by-noise jamming experiments conducted using commercial test and measurement equipment are presented. Specifically, the time- and frequency-domain behavior of FM-by- noise at RF and IF is studied …

Cepstral And Auditory Model Features For Speaker Recognition, John M. Colombi

Theses and Dissertations

The TIMIT and KING databases, as well as a ten day AFIT speaker corpus, are used to compare proven spectral processing techniques to an auditory neural representation for speaker identification. The feature sets compared were Linear Predictive Coding (LPC) cepstral coefficients and auditory nerve firing rates using the Payton model. This auditory model provides for the mechanisms found in the human middle and inner auditory periphery as well as neural transduction. Clustering algorithms were used to generate speaker specific codebooks - one statistically based and the other a neural approach. These algorithms are the Linde-Buzo-Gray (LBG) algorithm and a Kohonen …

High Range Resolution Radar Target Identification Using The Prony Model And Hidden Markov Models, Mark R. Dewitt

Theses and Dissertations

Fully polarized Xpatch signatures are transformed to two left circularly polarized signals. These two signals are then filtered by a linear FM pulse compression ('chirp') transfer function, corrupted by AWGN, and filtered by a filter matched to the 'chirp' transfer function. The bandwidth of the 'chirp' radar is about 750 MHz. Range profile feature extraction is performed using the TLS Prony Model parameter estimation technique developed at Ohio State University. Using the Prony Model, each scattering center is described by a polarization ellipse, relative energy, frequency response, and range. This representation of the target is vector quantized using a K-means …

Applications Of Digital Signal Processing With Cardiac Pacemakers, Merry Thi Tran

Dissertations and Theses

Because the voltage amplitude of a heart beat is small compared to the amplitude of exponential noise, pacemakers have difficulty registering the responding heart beat immediately after a pacing pulse. This thesis investigates use of digital filters, an inverse filter and a lowpass filter, to eliminate the effects of exponential noise following a pace pulse. The goal was to create a filter which makes recognition of a haversine wave less dependent on natural subsidence of exponential noise.

Research included the design of heart system, pacemaker, pulse generation, and sensor system simulations. The simulation model includes the following components:

• Signal source, …

An Investigation To Improve Linear Predictive Vocoder Pulse/Noise Excitation Models, Elizabeth Annella Martina Effer

Electrical & Computer Engineering Theses & Dissertations

The quality of synthetic speech from Linear Predictive (LP) vocoders is known to be degraded due to the lack of detail in the commonly used pulse/noise excitation model. In this investigation, it was hypothesized that this degradation is due to the lack of precise timing information in the pulses and to the constraint that each short-time segment of excitation be either an impulse train or white noise. Accordingly, more complex excitation models were implemented using precise timing from peaks in the residual and a mixture of pulses and noise. Since the LP residual is known to be the perfect excitation …