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- Global positioning system (3)
- Antenna arrays (2)
- Backscattering (2)
- Flight control systems (2)
- Graphical user interface (2)
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- Ground clutter (2)
- Inertial navigation (2)
- Kalman filtering (2)
- R. Attri Instrumentation Design Series (Snow Hydrology) (2)
- Signal processing (2)
- Synthetic aperture radar (2)
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- Aerial cameras (1)
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- Antenna feeds (1)
- Antenna radiation patterns (1)
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- Avalanche forecast (1)
- Bistatic radar (1)
- Broadband antennas (1)
- Chi square test (1)
- Computational electromagnetics (1)
- Computer communications (1)
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Articles 1 - 28 of 28
Full-Text Articles in Signal Processing
Design Of An Instrumentation System To Record Distribution Profile Of Snow Layer Temperature For Modelling Of Snow Avalanche Forecast, Raman Attri
Raman K. Attri
The measurement of snow hydrological parameters is extremely important in developing a model for the predication of Snow avalanche as well as Snowmelt water in the rivers. When direct measurement of these parameters is practically difficult, its dependence on snow temperature is used to develop snow cover models. A robust model for avalanche forecasting requires a sophisticated instrumentation system which can measure the required temperature parameters at right data points within snow pack. A Snow Temperature Profile Sensing System along with Surface temperature Sensor has been designed to measure Snow temperature gradient, temperature distributions, and average temperature of snow pack, …
Implementation Of Linear Array Of Ultrasonic Transmitter-Receiver Transducers For Detection Of Non-Smooth Porous Surface, Raman K. Attri, Swaranjit Singh
Implementation Of Linear Array Of Ultrasonic Transmitter-Receiver Transducers For Detection Of Non-Smooth Porous Surface, Raman K. Attri, Swaranjit Singh
Raman K. Attri
Level measurements, thickness measurement or remote surface detection using ultrasonic pulse transit method require that the target surface be at 90O to the incident beam so that reflected beam comes back at 180O angel to effectively use this method. This is perfectly true in case of flat, solid surface at right angle to the incident beam. But surface irregularities of a porous, non-smooth, uneven material such as snow cause penetration of incident wave into the surface, absorption of the incident energy, scatter of energy in many directions and further attenuation of reflected signal making it difficult to detect the reflected …
Dual Channel Matched Filtering And Space-Time Adaptive Processing, Scott D. Berger
Dual Channel Matched Filtering And Space-Time Adaptive Processing, Scott D. Berger
Theses and Dissertations
We propose a dual channel matched filtering system that addresses two key challenges in the practical implementation of a single channel matched filtering system: secondary data support and computational cost. We demonstrated that the dual channel system requires half the secondary data to achieve nearly the same signal-to-interference plus noise ratio (SINR) as an equivalent single channel system. The key to the dual channel system is the block diagonalization of the interference plus noise correlation matrix with a fixed transformation. We investigated the application of this dual channel concept to the problem of space-time adaptive processing (STAP), referring to the …
Parallel Digital Signal Processing On A Network Of Personal Computers Case Study: Space-Time Adaptive Processing, Fernando Silva
Parallel Digital Signal Processing On A Network Of Personal Computers Case Study: Space-Time Adaptive Processing, Fernando Silva
Theses and Dissertations
Network based parallel computing using personal computers is currently a popular choice for concurrent scientific computing. This work evaluates the capabilities and the performance of the AFIT Bimodal Cluster (ABC); a heterogeneous cluster of PCs connected by switched fast Ethernet and using MPICH 1.1 for interprocess communication for parallel digital signal processing using Space Time Adaptive Processing (STAP) as the case study. The MITRE RT_STAP Benchmark version 1.1 is ported and executed on the ABC, as well as on a cluster of six Sun SPARC workstations connected by a Myrinet network (the AFIT NOW), and on a IBM SP for …
Bistatic Radar Cross Section (Rcs) Characterization Of Complex Objects, Robert L. Eigel Jr.
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 …
Output Control Of Vertical Microcavity Light Emitting Device, James A. Lott
Output Control Of Vertical Microcavity Light Emitting Device, James A. Lott
AFIT Patents
An improved intracavity sensor based output power control for microcavity light emitting devices. An improved phototransistor transducer is both configured and physically disposed so that it passively transmits the spurious optical energy output of the microcavity light emitting device while simultaneously generating a light determined electrical signal of easily used large magnitude that is nearly free of error. The base-collector region of the transistor is disposed with a quantum well absorbing layer and produces a signal responsive to a selected emission wavelength. The configuration of the optical energy communicating transducer is arranged so that it is improved in sensitivity and …
Facial Features Localization In Front View Head And Shoulders Images, Adnan M. Alattar, Sarah A. Rajala
Facial Features Localization In Front View Head And Shoulders Images, Adnan M. Alattar, Sarah A. Rajala
Sarah A. Rajala
The computerized process of locating human facial features such as the eyes, nose and mouth in a head and shoulders image is crucial to such applications as automatic face identification and model-based video coding. A new model-based algorithm for locating these major features is developed. The algorithm estimates the parameters of the ellipse which best fits the head view in the image and uses these parameters to calculate the estimated locations of the facial features. It then refines the estimated coordinates of the eyes, mouth, and nose by exploiting the vertical and horizontal projections of the pixels in windows around …
Analysis Of The Applicability Of Video Segmentation To Unmanned Aerial Vehicle Surveillance Video, Bradley L. Pyburn
Analysis Of The Applicability Of Video Segmentation To Unmanned Aerial Vehicle Surveillance Video, Bradley L. Pyburn
Theses and Dissertations
The focus of this research is to determine if applying edge detection segmentation (proposed by Ramin Zabih, Justin Miller, and Kevin Mai) to Unmanned Aerial Vehicle (UAV) video footage can provide meaningful segments for database storage and retrieval. The edge detection segmentation algorithm is applied to fifty-four UAV video sequences containing visual effects such as abrupt camera changes, camera zooms, motion (rapid and gradual), and cloud cover while varying the frame rate from 5 fps to 30 fps. An analysis of the results is performed to compare actual versus expected outcomes, similar sequences, and scenes with motion, along with explaining …
Low Grazing Angle Terrain Backscattering Coefficient Generator, William N. O'Connor
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 …
The Effect Of Registration Errors On Tracking In A Networked Radar System, Bradley J. Mortenson
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 …
Non Co-Operative Detection Of Lpi/Lpd Signals Via Cyclic Spectral Analysis, Andrew M. Gillman
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 …
Graphical User Interface And Microprocessor Control Enhancement Of A Pseudorandom Code Generator, John M. Kos
Graphical User Interface And Microprocessor Control Enhancement Of A Pseudorandom Code Generator, John M. Kos
Theses and Dissertations
Modern digital communication techniques often require the generation of pseudorandom numbers or sequences. The ability to quickly and easily produce various codes such as maximal length codes, Gold codes, Jet Propulsion Laboratory ranging codes, syncopated codes, and non-linear codes in a laboratory environment is essential. This thesis addresses the issue of providing automated computer control to previously built, manually controlled hardware incorporating the Stanford Telecom STEL-1032 Pseudo-Random Number (PRN) Coder. By incorporating a microcontroller into existing hardware, the STEL-1032 can now be conveniently controlled from a MATLAB Graphical User Interface (GUI). The user can quickly create, save, and recall various …
Terrain Backscattering Coefficient Generator, Ricardo Mediavilla
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 …
Trade-Off Analysis Of Communications Capabilities Of Inter-Satellite Links, Andrew J. Feltman
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 …
An Empirical Prediction Model Of The Performance Impacts Of Material Tolerances In Frequency Selective Surfaces Using The Monte Carlo Method, Matthew D. Craig
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 …
Integrated Ups/Ins Precision Approach Landing With M3ae Interference Avoidance, Stephan H. Chastain
Integrated Ups/Ins Precision Approach Landing With M3ae Interference Avoidance, Stephan H. Chastain
Theses and Dissertations
Several past research efforts have developed methods to take advantage of Global Positioning System (UPS) positioning and apply it to a precision landing system (PLS). There have been proposals to phase out the current Instrument Landing System (ILS) in favor of a more cost-efficient and effective system. Accomplishments have been made in detailing a system implementing an INS aided with differential UPS, a UPS pseudolite, and a radar altimeter to handle the critical PLS requirements. This research applies the newly developed Modified Multiple Model Adaptive Estimation (M3AE) architecture in an attempt to enhance the performance of a PLS in an …
A Trade-Off Analysis For Quality Of Service In Real-Time Voice Over Ip, Tuncel Altunbasak
A Trade-Off Analysis For Quality Of Service In Real-Time Voice Over Ip, Tuncel Altunbasak
Theses and Dissertations
During the past several years, there has been a significant increase in interest in the use of packetized audio over packet-switched networks due to economic and technical feasibility. However, distribution of real-time voice traffic is basically different from traditional reliable data transfer since continuous voice is sensitive to end-to-end delays and variations of delays. The distribution of continuous voice across a packet-switched network requires consideration of encoding schemas, end-to-end network delays, delay variations, and packet loss, all of which significantly affect the playback quality at the receiving side. There is a trade-off among these factors that affects the quality of …
Target Pose Estimation From Radar Data Using Adaptive Networks, Andrew W. Learn
Target Pose Estimation From Radar Data Using Adaptive Networks, Andrew W. Learn
Theses and Dissertations
his research investigates and extends recent work by J.C. Principe at the University of Florida in target pose estimation using adaptive networks. First, Principe's technique is successfully extended to estimate both azimuth and elevation using SAR images. A network trained and tested using MSTAR data yields mean errors of less than six degrees in azimuth and five degrees in elevation. Second, the technique is applied to high-range resolution radar (HRR) signatures. Ground target (azimuth only) testing yields mean errors of less than 11 degrees for most classes. Air target testing for networks trained and tested on the same aircraft class …
Optimal Wavelet Denoising For High Range Resolution Radar Classification, Brian M. Huether
Optimal Wavelet Denoising For High Range Resolution Radar Classification, Brian M. Huether
Theses and Dissertations
Noncooperative identification (NCTI) of airborne targets is a top priority for the Air Force and this thesis makes a significant contribution to that area. High range resolution radar (HRR) provides an attractive means to perform NCTI. When measured HRR data is used, classification performance is excellent. However, it is often not feasible to acquire measured HRR signatures for a wide set of targets, thus necessitating the use of synthetically generated HRR data. Classification performance suffers severe degradation when using synthetic data. This thesis suggests that a large portion of HRR signature content is non-discriminatory and that this content is a …
Antenna Gain Enhancement Using A Photonic Band Gap Reflector, Karl C. Schloer
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 …
Application Of The Finite Element Method To The Scattering Of A Two-Dimensional, Semi-Infinite Periodic Structure, Perry N. Villanueva
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 …
Incorporating Scene Mosaics As Visual Indexes Into Uav Video Imagery Databases, Timothy I. Page
Incorporating Scene Mosaics As Visual Indexes Into Uav Video Imagery Databases, Timothy I. Page
Theses and Dissertations
The rise of large digital video archives has strengthened the need for more efficient ways of indexing video files an accessing the information contained in them. Reconnaissance platforms, such as the Predator UAV, are contributing thousands of hours of video footage that require analysis, storage, and retrieval. A process is proposed for converting a video stream into a series of mosaic and selected still images that provide complete coverage of the original video. The video mosaic images can be utilized as visual indexes into a video database. In addition, mosaic images contain information from an entire sequence of video frames …
A Climatology-Based Model For Long-Term Prediction Of Radar Beam Refraction, Todd S. Pittman
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 …
Modulation Of Electrostatic Microelectromechanical Mirrors Using A Cmos Controller, Paul C. Rounsavall
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 …
Loop Gain Estimation For Adaptive Control, Jamey P. Sillence
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.
Ultra-Wideband Tem Horns, Transient Arrays And Exponential Curves: A Fdtd Look, Troy S. Utton
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 Integrated Synthetic Aperture Radar/Global Positioning System/Inertial Navigation System For Target Geolocation Improvement, Brian J. Young
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 …
Analysis Of Radio Frequency Interference Effects On A Modern Coarse Acquisition Code Global Positioning System (Gps) Receiver, Kenneth D. Johnston
Analysis Of Radio Frequency Interference Effects On A Modern Coarse Acquisition Code Global Positioning System (Gps) Receiver, Kenneth D. Johnston
Theses and Dissertations
The purpose of this thesis was to investigate the performance of a twelve channel Standard Positioning Service (SPS) based (Global Positioning System (GPS) receiver using an eight state Kalman filter in a hostile radio frequency (RF) environment and to develop instructional tools for teaching RF interference on GPS receivers. The two types of jamming signals generated included Continuous Wave (CW) and Swept CW. Actual GPS and jamming signals were used in the research. The signals received from GPS satellites exhibit a Doppler shift which vary between approximately plus six Kilohertz. The Doppler shift frequency can be reasonably predicted for a …