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Articles 1 - 30 of 41
Full-Text Articles in Engineering
Estimating Tmr Reliability On Fpgas Using Markov Models, Daniel Mcmurtrey, Keith S. Morgan, Brian Pratt, Michael J. Wirthlin
Estimating Tmr Reliability On Fpgas Using Markov Models, Daniel Mcmurtrey, Keith S. Morgan, Brian Pratt, Michael J. Wirthlin
Faculty Publications
This paper summarizes several reliability models for modeling FPGA reliability using Markov models.
Decentralized Perimeter Surveillance Using A Team Of Uavs, Randal Beard, David Casbeer, Derek Kingston
Decentralized Perimeter Surveillance Using A Team Of Uavs, Randal Beard, David Casbeer, Derek Kingston
Faculty Publications
Sponsorship: NASA, AFOSR. This paper develops a distributed algorithm to maintain a current estimate of the state of the perimeter using a team of UAVs. Using notions of consensus, an algorithm is developed and shown to distribute a UAV team uniformly around the perimeter.
A C-Band Scatterometer Simultaneous Wind/Rain Retrieval Method, David G. Long, Congling Nie
A C-Band Scatterometer Simultaneous Wind/Rain Retrieval Method, David G. Long, Congling Nie
Faculty Publications
Using collocated ERS scatterometer (ESCAT), Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR), and European Centre for Medium-Range Weather Forecasts (ECMWF) data, the effects of rain on ESCAT wind-only retrieval are evaluated. Additional scattering from rain causes estimated wind speeds to appear higher than expected. Selected directions of the rain-corrupted wind vectors are biased toward along-track directions under conditions of heavy rain, which is regardless of the true wind direction. Rain becomes more significant for data acquired at a high incidence angle. To compensate for rain-induced backscatter, a simultaneous wind/rain retrieval (SWRR) method, which simultaneously retrieves wind velocity and surface …
Surface Relief D-Fiber Bragg Gratings For Sensing Applications, Tyson Lee Lowder
Surface Relief D-Fiber Bragg Gratings For Sensing Applications, Tyson Lee Lowder
Theses and Dissertations
This dissertation presents the novel creation of a surface relief fiber Bragg grating on the flat surface of a D-shaped optical fiber. In order to produce an efficient surface relief grating the grating must be etched into the surface of the glass fiber close to the core. A short etch that removes the cladding above the core is performed in order to decrease the core-to-flat distance and allow the light to interact with the grating on the flat surface. Due to the unique D-shape of the optical fiber the mechanical integrity of the fiber remains high even after the fabrication …
Theory And Application Of Motion Compensation For Lfm-Cw Sar, David G. Long, Evan C. Zaugg
Theory And Application Of Motion Compensation For Lfm-Cw Sar, David G. Long, Evan C. Zaugg
Faculty Publications
Small low-cost high-resolution synthetic aperture radar (SAR) systems are made possible by using a linear frequency-modulated continuous-wave (LFM-CW) signal. SAR processing assumes that the sensor is moving in a straight line at a constant speed, but in actuality, an unmanned aerial vehicle (UAV) or airplane will often significantly deviate from this ideal. This nonideal motion can seriously degrade the SAR image quality. In a continuous-wave system, this motion happens during the radar pulse, which means that existing motion compensation techniques that approximate the position as constant over a pulse are limited for LFM-CW SAR. Small aircraft and UAVs are particularly …
A Low-Cost Open-Hardware Wideband Multiple-Input-Multiple-Output (Mimo) Wireless Channel Sounder, Michael A. Jensen, Jon W. Wallace, B. T. Maharaj, Louis P. Linde
A Low-Cost Open-Hardware Wideband Multiple-Input-Multiple-Output (Mimo) Wireless Channel Sounder, Michael A. Jensen, Jon W. Wallace, B. T. Maharaj, Louis P. Linde
Faculty Publications
Due to the complexity of multiple-input-multiple- output (MIMO) wireless channels, direct measurement is the main viable option for accurate characterization. Details on a new low-cost wideband channel sounder are presented, which was mainly constructed from conventional instruments and components. This switched architecture system is similar to commercial channel sounders and has modest cost (< US$ 50000). The sounder operates in the 2- to 8-GHz range with up to 100 MHz of instantaneous bandwidth and supports eight transmitters and receivers, which are sufficient to support the development and assessment of current and future MIMO wireless systems. In this "open-hardware" project, the hardware design and software components are openly available to other researchers interested in developing or enhancing the MIMO measurement capability. The actual systems built at the University of Pretoria, Pretoria, South Africa, and Brigham Young University, Provo, UT, are presented, as are some example studies.
Optimal Estimation Of Calibration Parameters In Polarimetric Microwave Radiometers, David G. Long, Derek Hudson
Optimal Estimation Of Calibration Parameters In Polarimetric Microwave Radiometers, David G. Long, Derek Hudson
Faculty Publications
Methods for internal calibration of a certain class of microwave polarimetric radiometers are presented by Piepmeier. In that work, the calibration parameters are estimated algebraically. We demonstrate that Bayesian estimation decreases the root-mean-square error of the estimates by a factor of two. This improvement is obtained by using knowledge of the noise structure of the measurements and by utilizing all of the information provided by the measurements. Drawbacks are the increased complexity of the method and an increase in computation. We also extend the method to estimate several hardware component parameters of interest in system calibration.
Estimation Of Hurricane Winds From Seawinds At Ultrahigh Resolution, David G. Long, Brent A. Williams
Estimation Of Hurricane Winds From Seawinds At Ultrahigh Resolution, David G. Long, Brent A. Williams
Faculty Publications
Although the SeaWinds scatterometer was not specifically designed to observe tropical cyclones, new high-resolution wind products resolve much of the horizontal structure of these storms. However, these higher resolution products (2.5 km) are inherently noisier than the standard 25-km near-surface wind products. These noise levels combined with rain contamination complicate high-resolution wind estimation-particularly in tropical cyclones. Fortunately, tropical cyclones have structures that can be exploited by using a wind field model. This paper develops a new procedure for hurricane wind field estimation from the SeaWinds instrument at ultrahigh resolution. A simplified hurricane model is developed to provide prior information to …
Reduced-Feedback Linear Precoding With Stable Performance For The Time-Varying Mimo Broadcast Channel, Michael A. Jensen, Adam L. Anderson, James R. Zeidler
Reduced-Feedback Linear Precoding With Stable Performance For The Time-Varying Mimo Broadcast Channel, Michael A. Jensen, Adam L. Anderson, James R. Zeidler
Faculty Publications
This work explores the performance of a multiple-input multiple-output broadcast channel where both the transmitter and receivers have outdated channel knowledge due to node motion or other time-variations in the communication channel. A performance analysis based on measured channel responses reveals significant throughput degradation for optimal linear and nonlinear precoding strategies unless the channel state information (CSI) is frequently fed back to the transmitter. The paper then develops a linear beamforming precoding strategy based on channel distribution information in the form of a full spatial correlation matrix for each user. This algorithm is shown to provide highly stable communication, with …
A Detailed Look At The Omega-K Algorithm For Processing Synthetic Aperture Radar Data, Matthew A. Tolman
A Detailed Look At The Omega-K Algorithm For Processing Synthetic Aperture Radar Data, Matthew A. Tolman
Theses and Dissertations
In this thesis, the Omega-k algorithm used for processing stripmap synthetic aperture radar (SAR) data is explored in detail. While the original Omega-k algorithm does not achieve the same SNR as a matched filter, a modification is presented which enables the algorithm to nearly achieve that SNR. It is shown that the focused point spread function obtained when the Omega-k algorithm is used differs in important ways from the output of a modified version of the matched filter. Spread out sidelobes and a stretched mainlobe are observed when the data is processed by the Omega-k algorithm. These differences may increase …
Windsat Passive Microwave Polarimetric Signatures Of The Greenland Ice Sheet, David G. Long, Li Li, Peter Gaiser, Mary R. Albert, Elizabeth M. Twarog
Windsat Passive Microwave Polarimetric Signatures Of The Greenland Ice Sheet, David G. Long, Li Li, Peter Gaiser, Mary R. Albert, Elizabeth M. Twarog
Faculty Publications
WindSat has systematically collected the first global fully polarimetric passive microwave data over both land and ocean. As the first spaceborne polarimetric microwave radiometer, it was designed to measure ocean surface wind speed and direction by including the third and fourth Stokes parameters, which are mostly related to the asymmetric structures of the ocean surface roughness. Although designed for wind vector retrieval, WindSat data are also collected over land and ice, and this new data has revealed, for the first time, significant land signals in the third and fourth Stokes parameter channels, particularly over Greenland and the Antarctic ice sheets. …
Ultracompact Awg Using Air-Trench Bends With Perfluorocyclobutyl Polymer Waveguides, Seunghyun Kim, Gregory P. Nordin, John Ballato, Yongbin Lin, Nazli Rahmanian, Dennis W. Smith, Chris Topping
Ultracompact Awg Using Air-Trench Bends With Perfluorocyclobutyl Polymer Waveguides, Seunghyun Kim, Gregory P. Nordin, John Ballato, Yongbin Lin, Nazli Rahmanian, Dennis W. Smith, Chris Topping
Faculty Publications
Using air-trench bends, an ultracompact 8 8 arrayed waveguide grating (AWG) demultiplexer (200-GHz channel spacing) for wavelength-division multiplexing (WDM) has been designed and fabricated with perfluorocyclobutyl (PFCB) core and clad co-polymers on a polyimide substrate. Compared to a conventional AWG in the same material system, the air-trench bend AWG shrinks the required chip area by a factor of 20. The decreased size is a factor in reducing the measured thermal shift to -0.012 nm/ C and decreasing the polarization-dependent wavelength shift to 1.3 nm.
In-Plane Photonic Transduction Of Silicon-On-Insulator Microcantilevers, Ryan Anderson, Seunghyun Kim, Gregory P. Nordin, Jong Wook Noh, Jaime Cardenas
In-Plane Photonic Transduction Of Silicon-On-Insulator Microcantilevers, Ryan Anderson, Seunghyun Kim, Gregory P. Nordin, Jong Wook Noh, Jaime Cardenas
Faculty Publications
We demonstrate an in-plane photonic transduction method for microcantilevers, which have been widely investigated for sensor applications. In our approach the microcantilever is etched to form a single mode rib waveguide. Light propagates down the microcantilever and crosses a small gap at the free end of the microcantilever, some of which is captured by an asymmetrical multimode waveguide that terminates in a Y-branch. The Y-branch outputs are used to form a differential signal that is monotonically dependent on microcantilever deflection. The measured differential signal matches simulation when microcantilever rotation is properly accounted for. The measured differential signal sensitivity is 1.4 …
Planning Continuous Curvature Paths Using Constructive Polylines, Joshua H. Henrie
Planning Continuous Curvature Paths Using Constructive Polylines, Joshua H. Henrie
Theses and Dissertations
Previous methods for planning clothoid based continuous curvature paths aim at minimizing path length. However, minimal length paths are not always smooth, natural, and drivable. A method of generating clothoid-based trajectories is discussed using constructive polylines. The goal of the motion planner is to create a path for a large car-like vehicle in human driving environments. Thus, the trajectories generated by the motion planner must be smooth, drivable, and natural such that the vehicle can follow the planned path on human roadways. Several examples are shown of trajectories developed for a DARPA Urban Challenge vehicle and a method of testing …
Nineteen-Element Phased-Array Feed Development And Analysis On Effects Of Focal Plane Offset And Beam Steering On Sensitivity, Jacob S. Waldron
Nineteen-Element Phased-Array Feed Development And Analysis On Effects Of Focal Plane Offset And Beam Steering On Sensitivity, Jacob S. Waldron
Theses and Dissertations
Presented herein is the design and construction process in the expansion of BYU's seven-element experimental platform to a nineteen-element platform for phased array feed experiments. The nineteen-element system was deployed at the National Radio Astronomy Observatory (NRAO) in Green Bank West Virginia for use on the Green Bank 20-Meter Telescope. Numerical simulations were performed to determine how sensitivity was affected by electronic beam steering and offset of the phased array feed (PAF) relative to the focal plane of the reflector. These simulated results were then compared to experimental data.
Compact Trench-Based Silicon-On-Insulator Rib Waveguide 90-Degree And 105-Degree Bend And Splitter Design, Jiguo Song
Compact Trench-Based Silicon-On-Insulator Rib Waveguide 90-Degree And 105-Degree Bend And Splitter Design, Jiguo Song
Theses and Dissertations
This thesis presents a theoretical and numerical investigation of silicon-on-insulator trench based passive optical components, bend and splitter, respectively. Compact 90 degree and 105 degree bend and splitter are designed with high index-contrast rib waveguide at wavelength 1550nm and serve as building blocks of splitting network in micro-cantilever biosensing application. The main characteristic of trench based bend and splitter structures is their miniature size and their low radiation loss due to the strong light confinement in high index-contrast systems. Thus large scale, high density optical integrated splitting network becomes possible with the associated advantages of compactness. With FDTD simulation, we …
Inverse Scattering Image Quality With Noisy Forward Data, Thomas J. Sorensen
Inverse Scattering Image Quality With Noisy Forward Data, Thomas J. Sorensen
Theses and Dissertations
Image quality metrics for several inverse scattering methods and algorithms are presented. Analytical estimates and numerical simulations provide a basis for poor image quality diagnostics. The limitations and noise behavior of reconstructed images are explored analytically and empirically using a contrast ratio. Theoretical contrast ratio estimates using the canonical PEC circular cylinder are derived. Empirical studies are conducted to confirm theoretical estimates and to provide examples of image quality vs SNR for more complex scatterer profiles. Regularized sampling is shown to be more noise sensitive than tomographic reconstructive methods.
Optically Powered Logic Transistor, Hanho Cho
Optically Powered Logic Transistor, Hanho Cho
Theses and Dissertations
This thesis presents the modeling and fabrication of a new solid-state device meant to be used for digital logic circuits. Most current logic circuits are based on MOSFETs. The new logic device uses some of the same operating principles, but also relies on optical illumination to provide input power. In order to obtain the desired current-voltage behavior of the new device, the Silvaco (Atlas) device simulation was used to give some insight into the correct doping levels in the semiconductor and device geometries. Prototypes were fabricated on p-type silicon wafers using CMOS fabrication processes including oxide growth, photolithography, precise plasma …
Characterization Of A Phased Array Feed Model, David A. Jones
Characterization Of A Phased Array Feed Model, David A. Jones
Theses and Dissertations
Creating accurate software based models of phased array feeds (PAFs) is one of many steps to successfully integrating PAFs with current and future radio telescopes, which is a goal of many groups around the globe. This thesis characterizes the latest models of a 19 element hexagonal PAF of dipoles used by the BYU radio astronomy research group and presents comparisons of these models with experimental data obtained using a prototype array. Experiments were performed at the NRAO site in Green Bank, West Virginia, and utilized the outdoor antenna test range and 20 meter radio telescope. Accurate modeling of the PAF …
A Satisficing Approach To Aircraft Conflict Resolution, Wynn C. Stirling, James K. Archibald, Nicholas A. Jepsen, Richard L. Frost, Jared C. Hill
A Satisficing Approach To Aircraft Conflict Resolution, Wynn C. Stirling, James K. Archibald, Nicholas A. Jepsen, Richard L. Frost, Jared C. Hill
Faculty Publications
Future generations of air traffic management systems may give appropriately equipped aircraft the freedom to change flight paths in real time. This would require a conflict avoidance and resolution scheme that is both decentralized and cooperative. We describe a multiagent solution to aircraft conflict resolution based on satisficing game theory. A key feature of the theory is that satisficing decision makers form their preferences by taking into consideration the preferences of others, unlike conventional game theory that models agents that maximize self-interest metrics. This makes possible situational altruism, a sophisticated form of unselfish behavior in which the preferences of another …
A Surveillance System To Create And Distribute Geo-Referenced Mosaics Using Suav Video, Evan D. Andersen
A Surveillance System To Create And Distribute Geo-Referenced Mosaics Using Suav Video, Evan D. Andersen
Theses and Dissertations
Small Unmanned Aerial Vehicles (SUAVs) are an attractive choice for many surveillance tasks. However, video from an SUAV can be difficult to use in its raw form. In addition, the limitations inherent in the SUAV platform inhibit the distribution of video to remote users. To solve the problems with using SUAV video, we propose a system to automatically create geo-referenced mosiacs of video frames. We also present three novel techniques we have developed to improve ortho-rectification and geo-location accuracy of the mosaics. The most successful of these techniques is able to reduce geo-location error by a factor of 15 with …
Monitoring The Antarctic Ice Sheet From Space, Benjamin Rule Lambert
Monitoring The Antarctic Ice Sheet From Space, Benjamin Rule Lambert
Theses and Dissertations
The Antarctic ice sheet is a geophysically - and in an age of growing concern about global warming, geopolitically - important portion of Earth. The composition and dynamics of the Antarctic ice sheet influence global climate patterns, global sea level and the planet's radiation budget. Recent evidence also suggests that the long term stability of portions of the ice sheet may be in jeopardy. In this thesis I use data from three Ku-band space-borne scatterometers to monitor changes in the backscatter signature of the Antarctic ice sheet from 1978 through 2007. Significant changes in backscatter, which result from geophysical changes …
Minimizing The Noise Penalty Due To Mutual Coupling For A Receiving Array, Karl F. Warnick, Leonid Belostotski, Peter Russer
Minimizing The Noise Penalty Due To Mutual Coupling For A Receiving Array, Karl F. Warnick, Leonid Belostotski, Peter Russer
Faculty Publications
For phased array receivers, mutual coupling leads to beam-dependent effective impedances at array element ports. Front end amplifiers can be matched for optimal noise performance for one beam steering direction, but noise performance becomes poor at other steering directions. We analyze this noise penalty in terms of beam equivalent noise temperature for various amplifier noise matching conditions, and develop a new matching condition that minimizes the average beam equivalent receiver noise temperature over multiple beams. For non-beamforming applications such as MIMO communications, we show that noise performance for coupled arrays can be quantified using the spectrum of an available receiver …
Efficiencies And System Temperature For A Beamforming Array, Karl F. Warnick, Brian D. Jeffs
Efficiencies And System Temperature For A Beamforming Array, Karl F. Warnick, Brian D. Jeffs
Faculty Publications
For an active beamforming array, standard definitions for efficiencies and system temperature are not available. We use noise considerations to generalize the single-antenna conventions for aperture efficiency, spillover efficiency, radiation efficiency, and system temperature to arrays. The treatment leads to a new noise matching efficiency that quantifies the effect of mutual coupling on amplifier noise. Numerical results for a phased array feed indicate that the noise increase caused by mutual coupling can be significant.
Quadrotor Dynamics And Control Rev 0.1, Randal Beard
Quadrotor Dynamics And Control Rev 0.1, Randal Beard
Faculty Publications
These notes outline quadrotor dynamics, state estimation, and control using a camera as the primary sensor.
Near Optimal Common Detection Techniques For Shaped Offset Qpsk And Feher's Qpsk, Tom Nelson, Michael D. Rice, Erik Perrins
Near Optimal Common Detection Techniques For Shaped Offset Qpsk And Feher's Qpsk, Tom Nelson, Michael D. Rice, Erik Perrins
Faculty Publications
This paper compares three candidate detection techniques for shaped offset QPSK (SOQPSK-TG) and Feher's QPSK (FQPSK-JR) modulations which are embodied as fully interoperable modulations in the Interrange Instrumentation Group standard IRIG-106. The techniques are based on a common trellis-coded modulation representation and a common continuous phase modulation (CPM) representation for these two modulations. In addition the pulse amplitude modulation (PAM) decomposition of the common CPM representation is developed. All three techniques achieve near-optimal bit error rate performance. The PAM-based detector offers the best performance-complexity trade-off.
Real-Time Implementation Of Vision Algorithm For Control, Stabilization, And Target Tracking For A Hovering Micro-Uav, Beau J. Tippetts
Real-Time Implementation Of Vision Algorithm For Control, Stabilization, And Target Tracking For A Hovering Micro-Uav, Beau J. Tippetts
Theses and Dissertations
A lightweight, powerful, yet efficient quad-rotor platform was designed and constructed to obtain experimental results of completely autonomous control of a hovering micro-UAV using a complete on-board vision system. The on-board vision and control system is composed of a Helios FPGA board, an Autonomous Vehicle Toolkit daughterboard, and a Kestrel Autopilot. The resulting platform is referred to as the Helio-copter. An efficient algorithm to detect, correlate, and track features in a scene and estimate attitude information was implemented with a combination of hardware and software on the FPGA, and real-time performance was obtained. The algorithms implemented include a Harris feature …
Stabilization And Control Of A Quad-Rotor Micro-Uav Using Vision Sensors, Spencer G. Fowers
Stabilization And Control Of A Quad-Rotor Micro-Uav Using Vision Sensors, Spencer G. Fowers
Theses and Dissertations
Quad-rotor micro-UAVs have become an important tool in the field of indoor UAV research. Indoor flight poses problems not experienced in outdoor applications. The ability to be location- and movement-aware is paramount because of the close proximity of obstacles (walls, doorways, desks). The Helio-copter, an indoor quad-rotor platform that utilizes a compact FPGA board called Helios has been developed in the Robotic Vision Lab at Brigham Young University. Helios allows researchers to perform on-board vision processing and feature tracking without the aid of a ground station or wireless transmission. Using this on-board feature tracking system a drift stabilization control system …
Compact Waveguide Splitter Networks, Seunghyun Kim, Gregory P. Nordin, Weisheng Hu, Yusheng Qian, Jiguo Song
Compact Waveguide Splitter Networks, Seunghyun Kim, Gregory P. Nordin, Weisheng Hu, Yusheng Qian, Jiguo Song
Faculty Publications
We demonstrate compact waveguide splitter networks in siliconon-insulator (SOI) rib waveguides using trench-based splitters (TBSs) and bends (TBBs). Rather than a 90° geometry, we use 105° TBSs to facilitate reliable fabrication of high aspect ratio trenches suitable for 50/50 splitting when filled with SU8. Three dimensional (3D) finite difference time domain (FDTD) simulation is used for splitter and bend design. Measured TBB and TBS optical efficiencies are 84% and 68%, respectively. Compact 105° 1 x 4, 1 x 8, and 1 x 32 trench-based splitter networks (TBSNs) are demonstrated. The measured total optical loss of the 1 x 32 TBSN …
Satisficing Theory And Non-Cooperative Games, Matthew S. Nokleby
Satisficing Theory And Non-Cooperative Games, Matthew S. Nokleby
Theses and Dissertations
Satisficing game theory is an alternative to traditional non-cooperative game theory which offers increased flexibility in modeling players' social interactions. However, satisficing players with conflicting attitudes may implement dysfunctional behaviors, leading to poor performance. In this thesis, we present two attempts to "bridge the gap" between satisficing and non-cooperative game theory. First, we present an evolutionary method by which players adapt their attitudes to increase raw payoff, allowing players to overcome dysfunction. We extend the Nash equilibrium concept to satisficing games, showing that the evolutionary method presented leads the players toward an equilibrium in their attitudes. Second, we introduce the …