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Articles 1 - 30 of 47
Full-Text Articles in Engineering
Performance Analysis Of Common Detectors For Shaped Offset Qpsk And Feher's Qpsk, Tom Nelson, Michael D. Rice, Erik Perrins
Performance Analysis Of Common Detectors For Shaped Offset Qpsk And Feher's Qpsk, Tom Nelson, Michael D. Rice, Erik Perrins
Faculty Publications
Sponsorship: US Air Force Grant FA9302-05-C-0001. A detector architecture capable of detecting both shaped offset quadrature phase shift keying (SOQPSK-TG) and Feher's quadrature phase shift keying (FQPSK-JR) is developed and analyzed. Both modulations are embodied as fully interoperable modulations in the Interrange Instrumentation Group (IRIG) standard IRIG-106. It is shown that the common detector achieves near optimal bit error rate performance without knowledge of which modulation is used by the transmitter. The detection 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 common pulse amplitude …
Modeling Microwave Emissions Of Erg Surfaces In The Sahara Desert, David G. Long, Haroon Stephen
Modeling Microwave Emissions Of Erg Surfaces In The Sahara Desert, David G. Long, Haroon Stephen
Faculty Publications
Sand seas (ergs) of the Sahara are the most dynamic parts of the desert. Aeolian erosion, transportation, and deposition continue to reshape the surface of the ergs. The large-scale features (dunes) of these bedforms reflect the characteristics of the sand and the long-term wind. Radiometric emissions from the ergs have strong dependence on the surface geometry. We model the erg surface as composed of tilted rough facets. Each facet is characterized by a tilt distribution dependent upon the surface roughness of the facet. The radiometric temperature (Tb) of ergs is then the weighted sum of the Tb from all the …
An Analysis Of Seawinds-Based Rain Retrieval In Severe Weather Events, David G. Long, Jeffrey R. Allen
An Analysis Of Seawinds-Based Rain Retrieval In Severe Weather Events, David G. Long, Jeffrey R. Allen
Faculty Publications
The Ku-band SeaWinds scatterometer estimates near-surface ocean wind vectors by relating measured backscatter to a geophysical model function for the near-surface vector wind. The conventional wind retrieval algorithm does not explicitly account for SeaWinds' sensitivity to rain, resulting in rain-caused wind retrieval error. A new retrieval method, termed "simultaneous wind/rain retrieval," that estimates both wind and rain from rain-contaminated measurements has been previously proposed and validated with Tropical Rain Measuring Mission data. Here, the accuracy of rains retrieved by the new method is validated through comparison with the Next Generation Weather Radar (NEXRAD) in coastal storm events. The rains detected …
A Provacative Test To Determine Brain Compliance In The Management Of Patients With Hydrocephalus, Preston K. Manwaring
A Provacative Test To Determine Brain Compliance In The Management Of Patients With Hydrocephalus, Preston K. Manwaring
Theses and Dissertations
Non-invasive techniques to explore intracranial compliance and pressure have been extensively explored in recent years. Previous techniques have used expensive technologies to make these measurements, often with difficulty. We present a novel, inexpensive provocative test to observe trends in intracranial compliance measurement targeted towards the treatment and management of hydrocephalus. Two techniques are proposed which derive data from the digital and supraorbital arteries as well as tympanic membrane displacement. This requires the use of two photo-plethysmographic sensors and a TMD sensor. A common tilt table apparatus is used to methodically and artificially increase intracranial pressure to stress the cranial system …
Highly Efficient Fluorescence Detection In Picoliter Volume Liquid-Core Waveguides, Aaron R. Hawkins, John P. Barber, Dongliang Yin
Highly Efficient Fluorescence Detection In Picoliter Volume Liquid-Core Waveguides, Aaron R. Hawkins, John P. Barber, Dongliang Yin
Faculty Publications
We report loss improvement and fluorescence detection in integrated antiresonant reflecting optical waveguides with liquid cores. The minimum waveguide loss is reduced to 0.33/cm by compensating for thickness variations in the fabrication process. We demonstrate fluorescence detection from as few as 490 molecules in a 57 pl core using these optimized waveguides. We measure angular fluorescence collection factors as high as 15% per facet in good agreement with theory. This demonstrates the potential of integrated hollow-core waveguides as optical sensors for single-molecule spectroscopy.
High Voltage Analog Design In A Standard Digital Cmos Process, Riley D. Beck
High Voltage Analog Design In A Standard Digital Cmos Process, Riley D. Beck
Theses and Dissertations
This thesis introduces high-voltage approaches that are implemented in an analog Hall-effect sensor interface. This interface has been realized in a modified 5V 0.6um CMOS process using 40V high-voltage MOS transistors that do not affect low-voltage device functionality. These circuits include a high-voltage, low-offset current sense amplifier, which achieves a common-mode input range that is within a Vtp of Vdd using a bulk-driven differential input stage. The amplifier also uses high voltage cascode devices to protect low-voltage devices that have been placed in critical matching areas to achieve a low input offset voltage of 500uV without the use of trim. …
Array Analysis Of Radio Frequency Interference Cancelation Requirements For A Land Mine Detection System, Devin Baker Pratt
Array Analysis Of Radio Frequency Interference Cancelation Requirements For A Land Mine Detection System, Devin Baker Pratt
Theses and Dissertations
Land mines are a major humanitarian problem with millions of active mines in place around the world. Since these mines can have little metal in them, novel detection techniques are needed. Nuclear Quadrupole Resonance (NQR) is one such technique. Unfortunately, NQR is highly succeptible to radio frequency interference (RFI). A significant contribution of this thesis is the development of a custom, experimental data acquisition system designed and built specifically for capturing RFI at frequencies significant to NQR land mine detection systems. Another major contribution is the development of data analysis techniques for determining the number of reference antennas required to …
Social Utility Functions-Part I: Theory, Wynn C. Stirling
Social Utility Functions-Part I: Theory, Wynn C. Stirling
Faculty Publications
The dominant approaches to utility-based multiagent decision theory rely on the premise of individual rationality-the doctrine that each individual is committed to achieving the best outcome for itself, regardless of the effect doing so has on others. This fundamentally asocial concept is the basis of conventional von Neumann-Morgenstern (vN-M) utilities but is inadequate to characterize truly cooperative artificial systems. Social utility functions differ from conventional vN-M utilities in that they are functions of multiple decision-maker preferences, rather than actions, and thus permit individuals to expand their spheres of interest beyond the self. A logical basis for coherent reasoning in multiagent …
Social Utility Functions-Part Ii: Applications, Wynn C. Stirling, Richard L. Frost
Social Utility Functions-Part Ii: Applications, Wynn C. Stirling, Richard L. Frost
Faculty Publications
Social utilities account for agent preferences and, thus, can characterize complex interrelationships, such as cooperation, compromise, negotiation, and altruism, that can exist between agents. Satisficing game theory, which is based on social utilities, offers a framework within which to design sophisticated multiagent systems. Key features of this approach are: a) an N-agent system may be represented by a 2N-dimensional Bayesian network, called a praxeic network; b) the theory accommodates a notion of situational altruism (a willingness to defer to others in a controlled way if so doing would actually benefit others under the condition that others wish to take advantage …
The Development Of A Small Scale Radio Astronomy Image Synthesis Array For Research In Radio Frequency Interference Mitigation, Jacob L. Campbell
The Development Of A Small Scale Radio Astronomy Image Synthesis Array For Research In Radio Frequency Interference Mitigation, Jacob L. Campbell
Theses and Dissertations
Radio astronomy synthesis imaging arrays are composed of many parabolic reflector antennas. These antennas are designed to be extremely sensitive to detect faint emissions from astronomical sources. Unfortunately, this also makes them susceptible to radio frequency interference (RFI) from man made sources such as orbiting satellites. The radio astronomy research group at Brigham Young University (BYU) is investigating methods to mitigate the effects of RFI in radio astronomy synthesis imaging. Though real-time RFI mitigation has been demonstrated for a large single dish telescope, for synthesis imaging arrays our prior work has consisted solely of algorithm development and computer simulations. To …
Static And Dynamic Obstacle Avoidance For Miniature Air Vehicles, Jeffery Brian Saunders, Brandon Call, Andrew Curtis, Randal W. Beard, Timothy W. Mclain
Static And Dynamic Obstacle Avoidance For Miniature Air Vehicles, Jeffery Brian Saunders, Brandon Call, Andrew Curtis, Randal W. Beard, Timothy W. Mclain
Faculty Publications
Small unmanned air vehicles are limited in sensor weight and power such that detection and avoidance of unknown obstacles during flight is difficult. This paper presents a low power low weight method of detection using a laser range finder. In addition, a rapidly-exploring random tree algorithm to generate waypoint paths around obstacles known a priori is presented, and a dynamic geometric algorithm to generate paths around detected obstacles is derived. The algorithms are demonstrated in simulation and in flight tests on a fixed-wing miniature air vehicle (MAV).
Impact Of Receive Amplifier Signal Coupling On Mimo System Performance, Michael A. Jensen, Matthew L. Morris
Impact Of Receive Amplifier Signal Coupling On Mimo System Performance, Michael A. Jensen, Matthew L. Morris
Faculty Publications
This paper uses a detailed model of multiple input multiple output (MIMO) systems to explore the impact of signal coupling in the receiver front end on communication capacity. The model is applied to assess the performance of a MIMO system with two transmit and receive antennas in a simulated multipath environment for different amplifier coupling levels. The results show that in practical scenarios where simple impedance matching techniques are used, the circuit coupling can reduce the signal-to-noise ratio at the receiver and therefore degrade the achievable MIMO capacity.
Superdirectivity In Mimo Systems, Michael A. Jensen, Matthew L. Morris, Jon W. Wallace
Superdirectivity In Mimo Systems, Michael A. Jensen, Matthew L. Morris, Jon W. Wallace
Faculty Publications
Multiantenna systems such as devices for multiple-input-multiple-output (MIMO) communication can theoretically use array superdirectivity to optimally exploit the propagation channel. In traditional analyses of MIMO systems, such superdirectivity is not observed due to the commonly applied constraint that limits the excitation current magnitudes. However, when an electromagnetically appropriate constraint on the power radiated by the array is applied, the computed capacity can include effects of transmit superdirectivity. A similar result occurs at the receiver for spatially colored noise. This paper formulates the MIMO system capacity under these circumstances and provides a framework for computing this capacity when the level of …
Embedded Slanted Grating Coupler For Vertical Coupling Between Fibers And Silicon-On-Insulator Planar Waveguides, Gregory P. Nordin, J. Jiang, B. Wang
Embedded Slanted Grating Coupler For Vertical Coupling Between Fibers And Silicon-On-Insulator Planar Waveguides, Gregory P. Nordin, J. Jiang, B. Wang
Faculty Publications
We propose a compact and efficient grating coupler for vertical coupling between optical fibers and planar waveguides. A grating with a parallelogram shape is designed to be etched through the entire high-index waveguide core. The coupler is optimized using a microgenetic algorithm coupled with a two-dimensional finite-difference time-domain method. Simulations show that up to 75.8% coupling efficiency can be obtained between a single-mode fiber and a 240-nm-thick silicon-on-insulator planar waveguide.
Navigation And Control Technologies For Autonomous Micro Vehicles, Randal Beard, Timothy W. Mclain
Navigation And Control Technologies For Autonomous Micro Vehicles, Randal Beard, Timothy W. Mclain
Faculty Publications
Sponsorship: Air Force Research Laboratory / Munitions Directorate. During this project we focused on four primary objectives which are listed below. 1. Magnetometer Integration. Integrate and flight test magnetometers with the current version of the autopilot (Spiral 1). 2. Height-Above-Ground Sensor Integration. Integrate and flight test height-above-ground sensors with the current version of the autopilot (Spiral 1). 3. Automatic Gain Adjustment. Develop and flight test automatic gain adjustment algorithms that automatically tune the servo loops of the autopilot. 4. Automatic Trim Seeking. Develop and flight test automatic trim seeking algorithms to recursively estimate the trim values of the UAV.
Solid-State Current Amplifier Based On Impact Ionization, Aaron R. Hawkins, Hong-Wei Lee
Solid-State Current Amplifier Based On Impact Ionization, Aaron R. Hawkins, Hong-Wei Lee
Faculty Publications
The operation principle, fabrication, and measurement results for a stand-alone amplifier based on impact ionization are reported. The device was built in silicon using standard microelectronic processes. Testing was performed by connecting the device to both silicon and indium-gallium-arsenide photodiodes to demonstrate its compatibility with arbitrary current sources. Preamplified leakage currents of less than 1 nA were measured along with current gains greater than 100.
Effects Of Mutual Coupling On Interference Mitigation With A Focal Plane Array, Michael A. Jensen, Karl F. Warnick
Effects Of Mutual Coupling On Interference Mitigation With A Focal Plane Array, Michael A. Jensen, Karl F. Warnick
Faculty Publications
A focal plane array feed of electrically small elements has been proposed as a means for achieving high sensitivity for radio astronomy applications in the presence of radio frequency interference (RFI). For a broadband system, mutual coupling effects become significant as the array element spacing becomes small relative to the electromagnetic wavelength. We present a theoretical framework for modeling the effects of mutual coupling and for determining the optimal multiport matching network between array elements and front-end transistor low-noise amplifiers for maximum signal-to-noise ratio (SNR). Numerical results are given for a model scenario including spillover and amplifier thermal noise and …
The Impact Of Antenna And Rf System Characteristics On Mimo System Capacity, Matthew Leon Morris
The Impact Of Antenna And Rf System Characteristics On Mimo System Capacity, Matthew Leon Morris
Theses and Dissertations
The recent growth in demand for wireless services coupled with the limited spectrum available for these services has spawned new efforts to increase the spectral efficiency of wireless links. Recent research has shown that in multipath propagation environments, the spatial characteristics of the propagation channel can be exploited to increase spectral efficiency through the use of multiple antennas at the transmitting and receiving nodes. Such multiple-input multiple-output (MIMO) systems show promise for dramatic performance gains over their single-antenna counterparts. However, MIMO system performance is influenced by many different factors. Antenna array configuration directly contributes to MIMO system performance. The ability …
Reduced Complexity Detection Methods For Continuous Phase Modulation, Erik Samuel Perrins
Reduced Complexity Detection Methods For Continuous Phase Modulation, Erik Samuel Perrins
Theses and Dissertations
Continuous phase modulation (CPM) is often plagued by high receiver complexity. One successful method of dealing with this is the well-known pulse amplitude modulation (PAM) representation of CPM, which was first proposed by Laurent. It is shown that the PAM representation also applies to multi-h CPM and ternary CPM, two previously unconsidered cases. In both cases it is shown that many PAM components may be required to exactly represent the signal. This is especially true of partial-response systems where the memory of the signal is long. Therefore, approximations are proposed which require only a limited number of terms. These extensions …
A Flexible Infrastructure For Multi-Agent Systems, Gerrit Addison N Sorensen
A Flexible Infrastructure For Multi-Agent Systems, Gerrit Addison N Sorensen
Theses and Dissertations
Multi-Agent coordination and control has been studied for a long time, but has recently gained more interest because of technology improvements allowing smaller, more versatile robots and other types of agents. To facilitate multi-agent experiments between heterogeneous agents, including robots and UAVs, we have created a test-bed with both simulation and hardware capabilities. This thesis discusses the creation of this unique, versatile test-bed for multi-agent experiments, also a unique graph creation algorithm, and some experimental results obtained using the test-bed.
Improved Network Analysis Of Coupled Antenna Diversity Performance, Michael A. Jensen, Matthew L. Morris
Improved Network Analysis Of Coupled Antenna Diversity Performance, Michael A. Jensen, Matthew L. Morris
Faculty Publications
This paper presents a new framework for the analysis of mutually coupled diversity antennas based on network theory. The network model incorporates the matching network between the antennas and front-end amplifiers and uses a realistic model for the amplifier noise. The resulting analysis includes the impact of the coupled-antenna radiation patterns and impedance characteristics in determining the branch signal-to-noise ratios (SNRs). Application of the formulation to coupled dipole antennas characterized using full-wave electromagnetic analysis illustrates that a matching network providing a minimum amplifier noise figure achieves significantly better diversity performance than one providing maximum power transfer.
A Pam Decomposition Of Weak Cpm, Mason B. Wardle
A Pam Decomposition Of Weak Cpm, Mason B. Wardle
Theses and Dissertations
The Enhanced Flight Termination System uses weak CPM as its modulation scheme and a limiter-discriminator as its demodulation scheme. A PAM representation of weak CPM was developed which representation provided the necessary componenents to build a simplified PAM-based receiver that outperformed the EFTS limiter-discriminator, even in the presence of phase noise. The PAM representation also provided a new perspective into the negative characteristics of weak CPM.
Correlation Of Fault-Injection To Proton Accelerator Persistent Cross Section Measurements, Keith S. Morgan, Michael J. Wirthlin
Correlation Of Fault-Injection To Proton Accelerator Persistent Cross Section Measurements, Keith S. Morgan, Michael J. Wirthlin
Faculty Publications
Sponsorship: Los Alamos National Laboratory. Field Programmable Gate Arrays (FPGAs) are an attractive solution for space system electronics. Unfortunately, FPGAs are susceptible to radiation-induced single-event upsets (SEU). As such, the FPGA Reliability Studies research group (http://reliability.ee.byu.edu) at Brigham Young University has studied ways to effectively measure the static, dynamic and persistent cross sections of an FPGA desgin; each of which are characterized in some way by how the part reacts to an SEU. One such method is to actually radiate an FPGA and monitor how it reacts to SEUs. A cheaper, more efficient solution is to use fault-injection to emulate …
Predicting On-Orbit Seu Rates, Keith S. Morgan, Michael J. Wirthlin
Predicting On-Orbit Seu Rates, Keith S. Morgan, Michael J. Wirthlin
Faculty Publications
As process geometry sizes continue to decrease, microelectronics are becoming more vulnerable to the effects of radiation. Of particular concern are the effects of Single-Event Upsets (SEU) in Field Programmable Gate Arrays (FPGA). An SEU causes a dynamic memory element, such as a flip-flop or latch, to unwantedly change state. Since FPGAs are becoming an increasingly attractive solution for space system electronics, it is desirable to predict static on-orbit SEU rates likely to be encountered by a particular device for any particular orbit. Mean Time Between Failure (MTBF) can directly be calculated from a static SEU rate, allowing a system …
The Hybrid Architecture Parallel Fast Fourier Transform (Hapfft), Joseph M. Palmer
The Hybrid Architecture Parallel Fast Fourier Transform (Hapfft), Joseph M. Palmer
Theses and Dissertations
The FFT is an efficient algorithm for computing the DFT. It drastically reduces the cost of implementing the DFT on digital computing systems. Nevertheless, the FFT is still computationally intensive, and continued technological advances of computers demand larger and faster implementations of this algorithm. Past attempts at producing high-performance, and small FFT implementations, have focused on custom hardware (ASICs and FPGAs). Ultimately, the most efficient have been single-chipped, streaming I/O, pipelined FFT architectures. These architectures increase computational concurrency through the use of hardware pipelining. Streaming I/O, pipelined FFT architectures are capable of accepting a single data sample every clock cycle. …
Differentiation Between Melt And Freeze Stages Of The Melt Cycle Using Ssm/I Channel Ratios, David G. Long, Ivan S. Ashcraft
Differentiation Between Melt And Freeze Stages Of The Melt Cycle Using Ssm/I Channel Ratios, David G. Long, Ivan S. Ashcraft
Faculty Publications
Microwave remote sensing detection of snow melt and ablation generally focuses on the detection of liquid moisture in the snow-pack. For ablation estimation, it is important to determine if wet snow is in the process of melting or freezing. The different stages of the melt cycle are observed in the diurnal variation of Tb measurements from the Special Sensor Microwave Imager (SSM/I) over Greenland. SSM/I channel ratios exhibit patterns indicating that they are sensitive to melt and freeze stages of the daily melt cycle. The horizontal to vertical polarization ratio is sensitive to surface wetness associated with melting. The 19-37-GHz …
Higher Radix Floating-Point Representations For Fpga-Based Arithmetic, Bryan Christopher Catanzaro
Higher Radix Floating-Point Representations For Fpga-Based Arithmetic, Bryan Christopher Catanzaro
Theses and Dissertations
Field Programmable Gate Arrays (FPGAs) are increasingly being used for high-throughput floating-point computation. It is forecasted that by 2009, FPGAs will provide an order of magnitude greater sustained floating-point throughput than conventional processors. FPGA implementations of floating-point operators have historically been designed to use binary floating-point representations, as do general purpose processors. Binary representations were chosen as the standard over three decades ago because they provide maximal numerical accuracy per bit of floating-point data. However, the unique nature of FPGA-based computation makes numerical accuracy per unit of FPGA resources a more important measure of the usefulness of a given floating-point …
Stratified Waveguide Grating Coupler For Normal Fiber Incidence, Gregory P. Nordin, D. M. Chambers, J. Jiang, B. Wang
Stratified Waveguide Grating Coupler For Normal Fiber Incidence, Gregory P. Nordin, D. M. Chambers, J. Jiang, B. Wang
Faculty Publications
We propose a new stratified waveguide grating coupler (SWGC) to couple light from a fiber at normal incidence into a planar waveguide. SWGCs are designed to operate in the strong coupling regime without intermediate optics between the fiber and the waveguide. Two-dimensional finite-difference time-domain simulation in conjunction with microgenetic algorithm optimization shows that about 72% coupling efficiency is possible for fiber (core size of 8.3 μm and ∆=0.36%) to slab waveguide (1.2- μm core and ∆=3.1%) coupling. We show that the phase-matching and Bragg conditions are simultaneously satisfied through the fundamental leaky mode.
Estimating The Dynamic Sensitive Cross Section Of An Fpga Design Through Fault Injection, Darrel E. Johnson
Estimating The Dynamic Sensitive Cross Section Of An Fpga Design Through Fault Injection, Darrel E. Johnson
Theses and Dissertations
A fault injection tool has been created to emulate single event upset (SEU) behavior within the configuration memory of an FPGA. This tool is able to rapidly and accurately determine the dynamic sensitive cross section of the configuration memory for a given FPGA design. This tool enables the reliability of FPGA designs and fault tolerance schemes to be quickly and accurately tested. The validity of testing performed with this fault injection tool has been confirmed through radiation testing. A radiation test was conducted at Crocker Nuclear Laboratory using a proton accelerator in order to determine the actual dynamic sensitive cross …
A Flexible Circuit-Switched Communication Network For Fpga-Based Soc Design, Clint Richard Hilton
A Flexible Circuit-Switched Communication Network For Fpga-Based Soc Design, Clint Richard Hilton
Theses and Dissertations
As FPGA densities continue to improve, single chips are becoming capable of implementing larger and more complex systems. Even today these systems may include several processors working in conjuction with a handful of other standard interfaces or custom modules. Additional system complexity naturally leads to added complexity throughout the different design and implementation stages. Attempting to design such a system while maintaining high performance and within a reasonable time frame is becoming more and more difficult. Architectural design approaches ranging from direct module interconnection to sophisticated bus schemes have been used to build such systems, all with their own trade-offs. …