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Articles 1 - 27 of 27
Full-Text Articles in Engineering
Studies On The Performance And Impact Of Channel Estimation In Mimo And Ofdm Systems, Michael David Larsen
Studies On The Performance And Impact Of Channel Estimation In Mimo And Ofdm Systems, Michael David Larsen
Theses and Dissertations
The need for reliable, high-throughput, mobile wireless communication technologies has never been greater as increases in the demand for on-the-go access to information, entertainment, and other electronic services continues. Two such technologies, which are at the forefront of current research efforts, are orthogonal frequency division multiplexing (OFDM) and multiple-input multiple-output (MIMO) systems, their union being known simply as MIMO-OFDM. The successful performance of these technologies depends upon the availability of accurate information concerning the wireless communication channel. In this dissertation, several issues related to quality of this channel state information (CSI) are studied. Specifically, the first part of this dissertation …
Compact Trench-Based Silicon-On-Insulator Rib Waveguide Ring Resonator With Large Free Spectral Range, Seunghyun Kim, Gregory P. Nordin, Weisheng Hu, Yusheng Qian, Jiguo Song, Gregory L. Wojcik
Compact Trench-Based Silicon-On-Insulator Rib Waveguide Ring Resonator With Large Free Spectral Range, Seunghyun Kim, Gregory P. Nordin, Weisheng Hu, Yusheng Qian, Jiguo Song, Gregory L. Wojcik
Faculty Publications
We demonstrate a compact trench-based silicon-on-insulator (SOI) rib waveguide ring resonator comprised of trench-based bends and splitters. It has a perimeter of 50 μm and occupies an area of only 25×25 μm. The measured free spectral range (FSR) is 13.2 nm, which the largest reported for an SOI rib waveguide ring resonator. The measured FSR, full width at half maximum, and quality factor match reasonably well with analytical calculations. Further calculation shows that a FSR of 50.8 nm is achievable for an SOI rib waveguide ring resonator with a perimeter of 15 μm.
In-Plane, All-Photonic Transduction Method For Silicon Photonic Microcantilever Array Sensors, Jong Wook Noh
In-Plane, All-Photonic Transduction Method For Silicon Photonic Microcantilever Array Sensors, Jong Wook Noh
Theses and Dissertations
We have invented an in-plane all-photonic transduction method for photonic microcantilever arrays that is scalable to large arrays for sensing applications in both bio- and nanotechnology. Our photonic transduction method utilizes a microcantilever forming a single mode rib waveguide and a differential splitter consisting of an asymmetric multimode waveguide and a Y-branch waveguide splitter. The differential splitter's outputs are used to form a differential signal that has a monotonic response to microcantilever deflection. A differential splitter using an amorphous silicon strip-loaded multimode rib waveguide is designed and fabricated to demonstrate the feasibility of the in-plane photonic transduction method. Our initial …
An Evaluation Of Quikscat Uhr Wind Product's Effectiveness In Determining Selected Tropical Cyclone Characteristics, Faozi Said
Theses and Dissertations
While the standard wind product (L2B) available operationally in near-real time from SeaWinds on QuikSCAT is only 25 km in resolution, QuikSCAT data can be enhanced to yield a 2.5 km ultra-high resolution (UHR) product. The latter can be used to help estimate Tropical Cyclone (TC) characteristics such as TC eye center and wind radii. Two studies are conducted in this thesis, in which QuikSCAT UHR wind product's effectiveness in estimating these TC characteristics is evaluated. First, a comparison is made between the analyst's choice of eye location based on UHR images and interpolated best-track position. In this analysis, the …
Slab-Coupled Optical Fiber Sensors For Electric Field Sensing Applications, Richard S. Gibson
Slab-Coupled Optical Fiber Sensors For Electric Field Sensing Applications, Richard S. Gibson
Theses and Dissertations
This dissertation presents the creation of slab coupled optical sensors (SCOS) for electric field sensing applications. SCOS devices utilize the benefits of an optical fiber system for high bandwidth and low electromagnetic interference. These sensors are fabricated by means of mode coupling between a small section of D-shaped optical fiber (D-fiber) with a multi-mode electro-optic slab waveguide. Electric field detection is accomplished by monitoring the behavior of the resonances, seen as transmission dips in the D-fiber transmission, as they shift with electric fields. The novelties of SCOS devices include their small compact nature, potential for sensor multiplexing and a dielectric …
Improving Accuracy In Microwave Radiometry Via Probability And Inverse Problem Theory, Derek Lavell Hudson
Improving Accuracy In Microwave Radiometry Via Probability And Inverse Problem Theory, Derek Lavell Hudson
Theses and Dissertations
Three problems at the forefront of microwave radiometry are solved using probability theory and inverse problem formulations which are heavily based in probability theory. Probability theory is able to capture information about random phenomena, while inverse problem theory processes that information. The use of these theories results in more accurate estimates and assessments of estimate error than is possible with previous, non-probabilistic approaches. The benefits of probabilistic approaches are expounded and demonstrated. The first problem to be solved is a derivation of the error that remains after using a method which corrects radiometric measurements for polarization rotation. Yueh [1] proposed …
In-Plane All-Photonic Transduction With Differential Splitter Using Double-Step Rib Waveguide For Photonic Microcantilever Arrays, Ryan Anderson, Seunghyun Kim, Gregory P. Nordin, Jong Wook Noh, Weisheng Hu
In-Plane All-Photonic Transduction With Differential Splitter Using Double-Step Rib Waveguide For Photonic Microcantilever Arrays, Ryan Anderson, Seunghyun Kim, Gregory P. Nordin, Jong Wook Noh, Weisheng Hu
Faculty Publications
We report a differential splitter consisting of an asymmetric double-step multimode rib waveguide and a Y-branch splitter for in-plane photonic transduction of photonic microcantilever deflection. Arrays of photonic microcantilevers are integrated with differential splitters and an optical waveguide network to demonstrate uniformity and sensitivity of transduction. Measurement results from multiple arrays indicate a sensitivity of 0.32 x 10-3 nm-1 and minimum detectable deflection of 141 pm for a 3.5 Hz measurement bandwidth.
Low Cost/ High Precision Flight Dynamics Estimation Using The Square-Root Unscented Kalman Filter, Trevor H. Paulsen
Low Cost/ High Precision Flight Dynamics Estimation Using The Square-Root Unscented Kalman Filter, Trevor H. Paulsen
Theses and Dissertations
For over a decade, Brigham Young University's Microwave Earth Remote Sensing (MERS) team has been developing SAR systems and SAR processing algorithms. In order to create the most accurate image reconstruction algorithms, detailed aircraft motion data is essential. In 2008, the MERS team purchased a costly inertial measurement unit (IMU) coupled with a high precision global positioning system (GPS) from NovAtel, Inc. In order to lower the cost of obtaining detailed motion measurements, the MERS group decided to build a system that mimics the capability the NovAtel system as closely as possible for a much lower cost. As a first …
New Low-Complexity Equalizers For Offset Qpsk, Qiang Lei, Michael D. Rice
New Low-Complexity Equalizers For Offset Qpsk, Qiang Lei, Michael D. Rice
Faculty Publications
Reduced-complexity linear and decision-feedback equalizers for use with offset QPSK are described and analyzed. The analysis and simulations show that reduced-complexity equalizers have 1/4 the complexity and achieve this at a loss that depends on the channel. As an example, the loss for the “Proakis B” channel is 2.7 dB for the linear equalizer and 0.8 dB for the decision feedback equalizer.
A System Level Approach To D-Fiber Electric Field Sensing, Joshua Monroe Kvavle
A System Level Approach To D-Fiber Electric Field Sensing, Joshua Monroe Kvavle
Theses and Dissertations
This dissertation presents the novel creation of a hybrid D-fiber electro-optic polymer electric field sensor. The sensor is made by removing a portion of the cladding from a D-shaped optical fiber, thus exposing the core to interaction with external stimulus. Then, an electro-optic polymer is deposited, partially replacing the core of the fiber. Next, the polymer is poled to endow it with electro-optic properties. This sensor is packaged in order to restore its mechanical strength. Because D-fiber is not intrinsically compatible with standard optical equipment it is fusion spliced to standard polarization maintaining fiber. Finally the sensor is tested for …
Construction Of Large Geo-Referenced Mosaics From Mav Video And Telemetry Data, Benjamin Kurt Heiner
Construction Of Large Geo-Referenced Mosaics From Mav Video And Telemetry Data, Benjamin Kurt Heiner
Theses and Dissertations
Miniature Aerial Vehicles (MAVs) are quickly gaining acceptance as a platform for performing remote sensing or surveillance of remote areas. However, because MAVs are typically flown close to the ground (1000 feet or less in altitude), their field of view for any one image is relatively small. In addition, the context of the video (where and at what orientation are the objects being observed, the relationship between images) is unclear from any one image. To overcome these problems, we propose a geo-referenced mosaicing method that creates a mosaic from the captured images and geo-references the mosaic using information from the …
Offset Qpsk In Siso And Mimo Environments, Xiaoyu Dang
Offset Qpsk In Siso And Mimo Environments, Xiaoyu Dang
Theses and Dissertations
We demonstrate how the performance of offset quadrature phase-shift keying (OQPSK) and its variants of Feher-patented QPSK (FQPSK) and Shaped Offset QPSK (SOQPSK) (collectively known as the ARTM Tier-1 waveforms) in single input single output (SISO) system could change with the channel fading parameters. The bit error rate expression of offset QSPK and ATRM Tier-1 waveforms over the aeronautical telemetry multipath channel has been derived. Simulations show that for the case of a single multipath ray, the BER gets worse with increasing Γ for a fixed delay, and that the BER has a quasi-periodic property for fixed Γ and increasing …
Obstacle Avoidance, Visual Automatic Target Tracking, And Task Allocation For Small Unmanned Air Vehicles, Jeffery Brian Saunders
Obstacle Avoidance, Visual Automatic Target Tracking, And Task Allocation For Small Unmanned Air Vehicles, Jeffery Brian Saunders
Theses and Dissertations
Recent developments in autopilot technology have increased the potential use of micro air vehicles (MAVs). As the number of applications increase, the demand on MAVs to operate autonomously in any scenario increases. Currently, MAVs cannot reliably fly in cluttered environments because of the difficulty to detect and avoid obstacles. The main contribution of this research is to offer obstacle detection and avoidance strategies using laser rangers and cameras coupled with computer vision processing. In addition, we explore methods of visual target tracking and task allocation. Utilizing a laser ranger, we develop a dynamic geometric guidance strategy to generate paths around …
Design And Analysis Of A Dual-Mode Cascaded-Loop Frequency Synthesizer, Xiongliang Lai
Design And Analysis Of A Dual-Mode Cascaded-Loop Frequency Synthesizer, Xiongliang Lai
Theses and Dissertations
A new architecture for a frequency synthesizer with adjustable output frequency range and channel spacing is introduced. It is intended for the generation of closely spaced frequency channels in the GHz range while producing minimal spurious phase noise components. The architecture employs two independent phase-locked loops that are driven in cascade by a single reference oscillator. The approach provides fine resolution and wide bandwidth as well as low phase noise and should find application in many contemporary communication systems. The synthesizer can be operated in either of two different modes: nonfractional and mini-denominator fractional modes. The architecture produces no fractional …
Radio Frequency Interference Mitigation On The Very Small Array, Alan Joseph Stemmons
Radio Frequency Interference Mitigation On The Very Small Array, Alan Joseph Stemmons
Theses and Dissertations
Radio astronomical synthesis imaging arrays can create images with resolution much higher than can single dish telescopes. However, one of the biggest problems that imaging arrays face is radio frequency interference (RFI). This interference corrupts signals and prevents accurate image creation. Therefore, it is necessary to remove this interference. This thesis discusses the synthesis imaging procedure and array spatial filtering methods to remove interference, including Multiple Sidelobe Canceller (MSC), Subspace Projection (SP), and Cross-Subspace Projection (CSP). The CLEAN algorithm, an image restoration technique, is also discussed. Various improvements to the VSA are discussed, including upgrades to the hardware and software …
Dynamics And Control Of Cable-Drogue System In Aerial Recovery Of Micro Air Vehicles Based On Gauss's Principle, Liang Sun, Randal W. Beard, Mark B. Colton, Timothy W. Mclain
Dynamics And Control Of Cable-Drogue System In Aerial Recovery Of Micro Air Vehicles Based On Gauss's Principle, Liang Sun, Randal W. Beard, Mark B. Colton, Timothy W. Mclain
Faculty Publications
This paper presents a new concept for aerial recovery of Micro Air Vehicles (ARMAVs) using a large mothership and a recovery drogue. The mothership drags a drogue attached to a cable and the drogue is controlled to match the flight patten of the MAV. This paper uses Gauss’s Principle to derive the dynamic model of the cable-drogue systems. A controllable drogue plays a key role in recovering MAVs in windy conditions. We develop a control approach for the drogue using its drag coefficient. Simulation results based on multilink cable-drogue systems present the feasibility of the aerial recovery concept and the …
An Internal Representation For Adaptive Online Parallelization, Koy D. Rehme
An Internal Representation For Adaptive Online Parallelization, Koy D. Rehme
Theses and Dissertations
Future computer processors may have tens or hundreds of cores, increasing the need for efficient parallel programming models. The nature of multicore processors will present applications with the challenge of diversity: a variety of operating environments, architectures, and data will be available and the compiler will have no foreknowledge of the environment until run time. Adaptive Online Parallelization (ADOPAR) is a unifying framework that attempts to overcome diver sity by separating discovery and packaging of parallelism. Scheduling for execution may then occur at run time when diversity may best be resolved. This work presents a compact representation of parallelism based …
Real-Time Optical Flow Sensor Design And Its Application On Obstacle Detection, Zhaoyi Wei
Real-Time Optical Flow Sensor Design And Its Application On Obstacle Detection, Zhaoyi Wei
Theses and Dissertations
Motion is one of the most important features describing an image sequence. Motion estimation has been widely applied in structure from motion, vision-based navigation and many other fields. However, real-time motion estimation remains a challenge because of its high computational expense. The traditional CPU-based scheme cannot satisfy the power, size and computation requirements in many applications. With the availability of new parallel architectures such as FPGAs and GPUs, applying these new technologies to computer vision tasks such as motion estimation has been an active research field in recent years. In this dissertation, FPGAs have been applied to real-time motion estimation …
Payload Directed Flight Of Miniature Air Vehicles, Randal W. Beard, Clark Taylor, Jeff Saunders, Ryan Holt, Timothy W. Mclain
Payload Directed Flight Of Miniature Air Vehicles, Randal W. Beard, Clark Taylor, Jeff Saunders, Ryan Holt, Timothy W. Mclain
Faculty Publications
This paper describes three applications of payload directed flight using miniature air vehicles: vision-based road following, vision-based target tracking, and vision-based mapping. A general overview of each application is given, followed by simulation and flight-test results. Results demonstrate the viability of utilizing electo-optical video imagery to directly control the air vehicle flight path to enhance performance relative to the sensing objective.
Compact Trench Based Bend And Splitter Devices For Silicon-On-Insulator Rib Waveguides, Yusheng Qian
Compact Trench Based Bend And Splitter Devices For Silicon-On-Insulator Rib Waveguides, Yusheng Qian
Theses and Dissertations
Bends and splitters are typically the fundamental limiting waveguide components in reducing the size of planar lightwave circuits (PLCs) based on waveguides that have a low core/clad refractive index contrast, such as silicon-on-insulator (SOI) rib waveguides. This dissertation presents a solution to this problem in the form of trench-based bends (TBBs) and trench-based splitters (TBSs). Emphasis is placed on experimental demonstration of these components and their integration into practical devices exhibiting significant size reduction. First, a compact and low loss silicon-on-insulator rib waveguide 90◦ TBB is demonstrated based on an etched vertical interface and total internal reflection (TIR) realized by …
Design Of A Continuous-Wave Synthetic Aperture Radar System With Analog Dechirp, Matthew C. Edwards
Design Of A Continuous-Wave Synthetic Aperture Radar System With Analog Dechirp, Matthew C. Edwards
Theses and Dissertations
This thesis presents a design methodology for continuous wave (CW) synthetic aperture radar (SAR) systems. The focus is on design considerations specific to small, low-power systems suitable for operation on small aircraft and unmanned aerial vehicles (UAVs). Well-known results which have been derived in other works, such as the radar equation, are explained in the context of low-power, CW systems. Additionally, design issues unique to CW SAR are addressed and the results generalized. A method for controlling feedthrough between antennas is developed, and the resulting limitations on swath width are discussed. Methods are developed which allow an engineer to design …
An Optical Flow Implementation Comparison Study, John M. Bodily
An Optical Flow Implementation Comparison Study, John M. Bodily
Theses and Dissertations
Optical flow is the apparent motion of brightness patterns within an image scene. Algorithms used to calculate the optical flow for a sequence of images are useful in a variety of applications, including motion detection and obstacle avoidance. Typical optical flow algorithms are computationally intense and run slowly when implemented in software, which is problematic since many potential applications of the algorithm require real-time calculation in order to be useful. To increase performance of the calculation, optical flow has recently been implemented on FPGA and GPU platforms. These devices are able to process optical flow in real-time, but are generally …
Near-Optimal Antenna Design For Multiple Antenna Systems, Daniel N. Evans
Near-Optimal Antenna Design For Multiple Antenna Systems, Daniel N. Evans
Theses and Dissertations
Multiple-input-multiple-output (MIMO) wireless systems use multiple antenna elements at the transmitter and receiver to offer improved spectral efficiency over traditional single antenna systems. In these systems, properties of the transmit and receive antenna arrays play a key role in determining the overall performance of the system. This thesis derives an upper bound on ergodic (average) channel capacity which formally links good antenna diversity performance with good ergodic capacity. As a result of this derivation, antenna arrays with good ergodic capacity performance are designed in this thesis by designing antenna arrays with near-optimal diversity gain. Several approaches are developed to design …
Real-Time Wind Estimation And Video Compression Onboard Miniature Aerial Vehicles, Andres Felipe Rodriguez Perez
Real-Time Wind Estimation And Video Compression Onboard Miniature Aerial Vehicles, Andres Felipe Rodriguez Perez
Theses and Dissertations
Autonomous miniature air vehicles (MAVs) are becoming increasingly popular platforms for the collection of data about an area of interest for military and commercial applications. Two challenges that often present themselves in the process of collecting this data. First, winds can be a significant percentage of the MAV's airspeed and can affect the analysis of collected data if ignored. Second, the majority of MAV's video is transmitted using RF analog transmitters instead of the more desirable digital video due to the computational intensive compression requirements of digital video. This two-part thesis addresses these two challenges. First, this thesis presents an …
Real-Time Carrier Frequency Estimation Using Disjoint Pilot Symbol Blocks, Joseph M. Palmer
Real-Time Carrier Frequency Estimation Using Disjoint Pilot Symbol Blocks, Joseph M. Palmer
Theses and Dissertations
Three new and efficient carrier frequency offset estimators are created for the case of disjoint pilot symbol blocks. The estimators are efficient in both a statistical sense and a computational sense. They are formulated to reduce computational cost for use in real-time applications, such as FPGA (field programmable gate array) devices. A reduced cost maximum likelihood (ML) frequency estimator is described. It is a generalization of the approximate ML estimator for a single block of pilot symbols. A number of recent ML estimation techniques are integrated with the purpose of reducing the computational cost while preserving estimation performance. The estimator …
Decentralized Estimation Using Information Consensus Filters With A Multi-Static Uav Radar Tracking System, David W. Casbeer
Decentralized Estimation Using Information Consensus Filters With A Multi-Static Uav Radar Tracking System, David W. Casbeer
Theses and Dissertations
This dissertation lays out a multi-static radar system with mobile receivers. The transmitter is at a known location emitting a radar signal that bounces off a target. The echo is received by a team of UAVs that are capable of estimating both time-delay and Doppler from the received signal. Several methods for controlling the movement of mobile sensor platforms are presented to improve target tracking performance. Two optimization criteria are derived for the problem, both of which require some type of search procedure to find the desired solution. Simulations are used to show the benefit of using closed-loop sensor control …
Demonstration Of Microcantilever Array With Simultaneous Readout Using An In-Plane Photonic Transduction Method, Seunghyun Kim, Gregory P. Nordin, Ryan Anderson, Weisheng Hu, Yusheng Qian, Jiguo Song, Jong Wook Noh
Demonstration Of Microcantilever Array With Simultaneous Readout Using An In-Plane Photonic Transduction Method, Seunghyun Kim, Gregory P. Nordin, Ryan Anderson, Weisheng Hu, Yusheng Qian, Jiguo Song, Jong Wook Noh
Faculty Publications
We demonstrate a microcantilever array with an in-plane photonic transduction method for simultaneous readout of each microcantilever. The array is fabricated on a silicon-on-insulator substrate. Rib waveguides in conjunction with a compact waveguide splitter network comprised of trench-based splitters and trench-based bends route light from a single optical input to each microcantilever on the chip. Light propagates down a rib waveguide integrated into the microcantilever and, at the free end of the microcantilever, crosses a small gap. Light is captured in static asymmetric multimode waveguides that terminate in Y-branches, the outputs of which are imaged onto an InGaAs line scan …