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Electrical and Computer Engineering Faculty Research & Creative Works

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Full-Text Articles in Electrical and Computer Engineering

Mocvd Of Cds Onto (111) Silicon Substrates, Jack L. Boone, Scott A. Howard, Don D. Martin, Gene Cantwell Sep 1989

Mocvd Of Cds Onto (111) Silicon Substrates, Jack L. Boone, Scott A. Howard, Don D. Martin, Gene Cantwell

Electrical and Computer Engineering Faculty Research & Creative Works

Thin films of CdS were grown onto (111) silicon substrates (wafers 2 in in diameter) by employing a horizontal, low-pressure MOCVD system. The observed growth of heteroepitaxial films occurred in the temperature range of 275-325 ±5 °C. The growth of polycrystalline samples with a high degree of preferred orientation occurred at temperatures above 325 ± 5 °C. The later films exhibited irregularly shaped surface pits about 1 μm in depth. These pits were observed by sectioning the substrates and examining them with an SEM; no significant crystallinity was apparent. X-ray analysis of an heteroepitaxial and a polycrystalline film via a …

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Convergence Properties Of The Waveform Relaxation Method As Applied To Electric Power Systems, Marija D. Ilić, J. K. White, Mariesa Crow May 1989

Convergence Properties Of The Waveform Relaxation Method As Applied To Electric Power Systems, Marija D. Ilić, J. K. White, Mariesa Crow

Electrical and Computer Engineering Faculty Research & Creative Works

Several theoretical results are presented and simple examples examined in order to determine the suitability of waveform relaxation for transient power system simulation. This examination leads to two practical suggestions that can easily be satisfied for power systems. The first is to break the simulation interval into sections, the first of which should be narrow and be used to kill off errors in the initial guess that activate the stiff modes. The second is to partition the system into subsystems that are stable, as this not only aids convergence but ensures multirate numerical stability.

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Anserlin. A Broad-Band, Low-Profile, Circularly Polarized Antenna, James L. Drewniak, P. E. Mayes Mar 1989

Anserlin. A Broad-Band, Low-Profile, Circularly Polarized Antenna, James L. Drewniak, P. E. Mayes

Electrical and Computer Engineering Faculty Research & Creative Works

A technique is presented for improving the performance of low-profile, circularly polarized (CP) radiating-line antennas. The essential elements of the technique pertain to establishing a single traveling wave on an annular sector of conducting strip that is positioned parallel and close to a large conducting surface. The antenna is named the annular sector, radiating-line (ANSERLIN) antenna. Using this technique, the impedance bandwidth becomes so large that it no longer has any bearing on the operating bandwidth. Instead, the pattern shape and axial ratio become the factors that limit the bandwidth. Both senses of circular polarization can be transmitted or received …

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Algorithms For Multi-Channel Dtmf Detection For The We Dsp32 Family, Steven L. Grant, J. Hartung, G. L. Smith Jan 1989

Algorithms For Multi-Channel Dtmf Detection For The We Dsp32 Family, Steven L. Grant, J. Hartung, G. L. Smith

Electrical and Computer Engineering Faculty Research & Creative Works

The authors describe two DTMF (dual-tone multiple frequency) detection algorithms that are highly efficient in the use of both real time and memory. The first algorithm is based on linear prediction (LP) and can be used to implement up to 32 DTMF detectors on a single 25-MHz NMOS WE DSP32. Using a 50-MHZ WE CMOS DSP32C, up to 45 detectors can be implemented. The second algorithm is based on a slight modification of the Goertzel algorithm and can be used to implement up to 16 DTMF detectors on a single DSP32 and up to 32 detectors on a DSP32C. In …

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Central-Station Photovoltaic Plant With Energy Storage For Utility Peak Load Leveling, Badrul H. Chowdhury Jan 1989

Central-Station Photovoltaic Plant With Energy Storage For Utility Peak Load Leveling, Badrul H. Chowdhury

Electrical and Computer Engineering Faculty Research & Creative Works

The impact of photovoltaic (PV) power generation with energy storage on the electric utility's load shape for load leveling purposes is explored. Results show that utilities employing battery storage for peak load shaving might benefit from use of photovoltaic power, the extent of its usefulness being dependent on the specific load shapes as well as the photovoltaic array orientations. Typical utility load shapes both in the eastern and in the western parts of the US are examined for this purpose. Although photovoltaic power generation seems to have a bigger impact on the load of the western utility, utilities in both …

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The Effect Of Cable Terminations On Emi Measurements, Todd H. Hubing Jan 1989

The Effect Of Cable Terminations On Emi Measurements, Todd H. Hubing

Electrical and Computer Engineering Faculty Research & Creative Works

The effects of using uncontrolled or undefined cable terminations during electromagnetic interference (EMI) measurements was investigated. Several different models are described along with corresponding measurements in order to illustrate how specific terminations can be used to achieve particular measurement goals. It is noted that until a well-defined method of terminating power and signal cables is introduced, the best the EMI test engineer can do is to be aware of the significance of common-mode terminations and try to avoid situations where the common-mode termination impedance is completely undefined or not repeatable.

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Lqg/Ltr Controller Design Using A Reduced Order Model, Rajiva Prakash, Vittal S. Rao Jan 1989

Lqg/Ltr Controller Design Using A Reduced Order Model, Rajiva Prakash, Vittal S. Rao

Electrical and Computer Engineering Faculty Research & Creative Works

A specific robust controller design procedure, linear quadratic Gaussian with loop transfer recovery (LQG/LTR), is studied. LQG/LTR design using a reduced-order model is performed. The error due to the use of the reduced model is accounted for by computing multiplicative error. All closed right half plane modes of the given system are included in the reduced-order model. The reduced-order LQG/LTR controller design procedure is applied to the problem of lateral attitude control of a drone aircraft. The case study demonstrates the reduction/design steps for a practical problem.

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Automatic Color Segmentation Of Images With Application To Detection Of Variegated Coloring In Skin Tumors, Scott E. Umbaugh, Randy Hays Moss, William V. Stoecker Jan 1989

Automatic Color Segmentation Of Images With Application To Detection Of Variegated Coloring In Skin Tumors, Scott E. Umbaugh, Randy Hays Moss, William V. Stoecker

Electrical and Computer Engineering Faculty Research & Creative Works

A description is given of a computer vision system, developed to serve as the front-end of a medical expert system, that automates visual feature identification for skin tumor evaluation. The general approach is to create different software modules that detect the presence or absence of critical features. Image analysis with artificial intelligence (AI) techniques, such as the use of heuristics incorporated into image processing algorithms, is the primary approach. On a broad scale, this research addressed the problem of segmentation of a digital image based on color information. The algorithm that was developed to segment the image strictly on the …

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Modeling The Electromagnetic Radiation From Electrically Small Table-Top Products, Todd H. Hubing, J. Frank Kaufman Jan 1989

Modeling The Electromagnetic Radiation From Electrically Small Table-Top Products, Todd H. Hubing, J. Frank Kaufman

Electrical and Computer Engineering Faculty Research & Creative Works

It is noted that the most difficult radiated electromagnetic interference (EMI) problems with table-top products often occur at frequencies where the maximum dimensions of the product are much smaller than a wavelength. Electrically small table-top products tend to be much more efficient radiation sources than dipole source models would predict, and the radiation is generally much more difficult to contain than other types of EMI source models indicated. The ways in which electrically small sources radiate are investigated, and a technique for modeling electrically small table-top products that have power or signal cables is proposed. The end-driven wire model is …

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Free Carrier Density Profiling By Scanning Infrared Absorption, Jack L. Boone, Michael D. Shaw, Gene Cantwell, William C. Harsch Dec 1988

Free Carrier Density Profiling By Scanning Infrared Absorption, Jack L. Boone, Michael D. Shaw, Gene Cantwell, William C. Harsch

Electrical and Computer Engineering Faculty Research & Creative Works

A prototype instrument for making contactless measurements of free carrier concentration as a function of the surface coordinates has been developed. The instrument requires minimal sample preparation, and the measurements are nondestructive. Measurements are based upon the free carrier absorption of photons at a wavelength of 10.6 μm. The measurement sensitivity is determined by the ability to resolve small variations in the transmitted wave. These variations can be significantly influenced by changes in sample thickness. A scheme has been devised which eliminates thickness variations by rotating the sample through small angles to achieve a transmission maximum at each data point. …

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Estimation Of X-Band Scattering Properties Of Tree Components, David E. Pitts, Gautam D. Badhwar, Eddie Reyna, R. Zoughi, Linkim Wu, Richard K. Moore Sep 1988

Estimation Of X-Band Scattering Properties Of Tree Components, David E. Pitts, Gautam D. Badhwar, Eddie Reyna, R. Zoughi, Linkim Wu, Richard K. Moore

Electrical and Computer Engineering Faculty Research & Creative Works

An X-band FM-CW very fine range resolution scatterometer was used to acquire backscattering data for individual branches for a number of tree species. Using a model to describe the scattering source function, dσ/dR = f(η, κ), and an experimental procedure for selected removal of plant parts, allows the estimation of η, the volume backscatter coefficient, and κ, the volume extinction coefficient. It is found that 1) leaves are strong attenuators as well as scatterers, 2) the albedo, ω = η/κ, at a given angle of incidence, is nearly independent of the tree type, 3) the tree …

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Measurements Of Radar Backscatter From An Artificial Tree An Indication Of Azimuthal Variations And Polarisation Sensitivity Of Trees, Richard K. Moore, M. S. Osman, R. Zoughi Sep 1988

Measurements Of Radar Backscatter From An Artificial Tree An Indication Of Azimuthal Variations And Polarisation Sensitivity Of Trees, Richard K. Moore, M. S. Osman, R. Zoughi

Electrical and Computer Engineering Faculty Research & Creative Works

Measurements of radar backscatter from an artificial tree were made in the laboratory at 6 and 10 GHz at horizontal incidence. The system has resolution cylinder 18 cm in diameter and 11 cm long. The tree itself was only 30.5 cm high so about half the tree was within the beam. The scattering was azimuthally uniform. Tilted polarizations gave results favoring an angle corresponding with that of the branches. Measurements were made with and without leaves.

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Simulation Of Photovoltaic Power Systems And Their Performance Prediction, S. Rahman, Badrul H. Chowdhury Jan 1988

Simulation Of Photovoltaic Power Systems And Their Performance Prediction, S. Rahman, Badrul H. Chowdhury

Electrical and Computer Engineering Faculty Research & Creative Works

A number of photovoltaic (PV) performance-analysis models are tested for their ability to estimate the AC power output and validated against historical observations from a PV test facility. A method to estimate meteorological parameters is developed for use in PV performance models for predicting future AC power output from a PV test site. Twelve such PV performance models are examined, and the PVFORM system analysis program and lifetime cost and performance models are extensively tested. These two models are tested using the typical meteorological year and the VPI model-generated estimates of long-term data. Performance prediction results are compared against actual …

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Still-Frame Image Transmission Using Dpcm/Interpolative Coding, Brindala Mallappa, Norman R. Cox Jan 1988

Still-Frame Image Transmission Using Dpcm/Interpolative Coding, Brindala Mallappa, Norman R. Cox

Electrical and Computer Engineering Faculty Research & Creative Works

Two methods of combining DPCM (differential pulse-code modulation) and interpolation are proposed for compressing still-frame teleconferencing signals. The first method uses horizontal subsampling, DPCM, and interpolation to achieve a 4:1 compression. The other method is similar but uses vertical subsampling instead. Simulation results indicate that either method can easily achieve the required 2-b/pel data rate with negligible degradation in image quality. Conventional DPCM is shown to perform slightly better in quantitative terms when fixed-wordlength coding is used. However, the two DPCM/interpolation methods offer other advantages when used with a variable-wordlength coder

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A Rule-Based Dynamic Economic Dispatch For Power Systems, Badrul H. Chowdhury Jan 1988

A Rule-Based Dynamic Economic Dispatch For Power Systems, Badrul H. Chowdhury

Electrical and Computer Engineering Faculty Research & Creative Works

The author introduces a novel operation tool for economic dispatch. It deals with the development and implementation of a new approach-a dynamic rule-based dispatch algorithm that takes into account the major problems faced by the dispatch operator during a dispatch interval and channels those into a database for use by a rule-based system. The algorithm is very fast and can be used effectively in interconnected systems. It can also handle renewable technologies and is therefore considered useful for major electric power utilities contemplating adding a significant amount of these new generation sources to their existing mix

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A Discussion On The Diversity In The Applications Of Photovoltaic Systems, S. Rahman, Badrul H. Chowdhury, M. A. Khallat Jan 1988

A Discussion On The Diversity In The Applications Of Photovoltaic Systems, S. Rahman, Badrul H. Chowdhury, M. A. Khallat

Electrical and Computer Engineering Faculty Research & Creative Works

References on the diverse applications of photovoltaic (PV) systems around the world are classified. The classes presented are (i) stand-alone, (ii) grid-connected, (iii) PV-thermal, (iv) PV-wind, and (v) dedicated applications. 73 papers are cited and classified into these five categories including a brief summary of each paper. Out of these, 42 papers relate to grid-connected applications in many industrialized countries of the world. These papers reflect the importance given to such applications. Due to the rapidly changing nature of PV and related industries, only papers published during the last ten years are considered.

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A Practical C Language Compiler/Optimizer For Real-Time Implementations On A Family Of Floating Point Dsps, J. Hartung, Steven L. Grant, S. G. Haigh Jan 1988

A Practical C Language Compiler/Optimizer For Real-Time Implementations On A Family Of Floating Point Dsps, J. Hartung, Steven L. Grant, S. G. Haigh

Electrical and Computer Engineering Faculty Research & Creative Works

Digital signal processors (DSPs) have traditionally been used in real-time applications with very high data throughput. For this reason, system designers have been reluctant to accept the degradation in performance inherent in machine code compiled from high-level languages such as C. The problem is compounded by the fact that DSPs use pipelined architectures to achieve their high data throughput, resulting in hazards and latencies between instructions. Simple compiler implementation cannot take advantage of latent instructions, resulting in a conservative and inefficient executable program. This problem has been addressed in the C compiler package for the AT&T WE DSP32 by the …

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Linear State Variable Dynamic Model And Estimator Design For Allison 1406 Gas Turbine Engine, Vittal S. Rao, D. Moellenhoff, J. A. Jaeger Jan 1988

Linear State Variable Dynamic Model And Estimator Design For Allison 1406 Gas Turbine Engine, Vittal S. Rao, D. Moellenhoff, J. A. Jaeger

Electrical and Computer Engineering Faculty Research & Creative Works

This paper describes a procedure for developing a State Variable Model for the Allison T406 gas turbine engine. This linear model is useful for designing controllers using modern control techniques. The engine and V-22 rotor system is modeled around an operating point by using four state variables and one input variable. For a given power setting, it is observed that two linear models are sufficient to represent the engine dynamics over the entire flight envelope. A relationship between surge margin and the state variables is also developed. It is demonstrated that these linear models are useful in designing an estimator …

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Distribution Automation For The Association Of Missouri Electric Cooperatives—A Statewide Evaluation Of Load Management, Jack F. Morris, Frank J. Kern Jan 1988

Distribution Automation For The Association Of Missouri Electric Cooperatives—A Statewide Evaluation Of Load Management, Jack F. Morris, Frank J. Kern

Electrical and Computer Engineering Faculty Research & Creative Works

Presented is an in-depth technical and economic feasibility study utilizing one- and two-way management systems for statewide load control and distribution automation. Included are 1) an evaluation of the generation and transmission load patterns of the state cooperatives and the determination of the amount of controllable load for use by a load management system, 2) an in-depth economic cost-benefit study as a result of implementing a load management system on a statewide basis, 3) communication alternatives for implementing the statewide load management and distribution automation system, 4) an investigation into using an existing statewide microwave communications system for direct load …

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Simulation Of Communication Systems Using Personal Computers, William H. Tranter, Carl R. Ryan Jan 1988

Simulation Of Communication Systems Using Personal Computers, William H. Tranter, Carl R. Ryan

Electrical and Computer Engineering Faculty Research & Creative Works

Microcomputer simulation provides a powerful tool for computer-aided design and analysis of communication systems and requires a minimum of investment. Two different simulation examples are presented: a fixed topology simulation program for digital data links written in Pascal; and a simulation of an analog link using Fortran. These examples are followed by a consideration of the new 32-bit single-board computers and their potential impact on microcomputer simulation. © 1988 IEEE

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Analysis Of Interrelationships Between Photovoltaic Power And Battery Storage For Electric Utility Load Management, Badrul H. Chowdhury, S. Rahman Jan 1988

Analysis Of Interrelationships Between Photovoltaic Power And Battery Storage For Electric Utility Load Management, Badrul H. Chowdhury, S. Rahman

Electrical and Computer Engineering Faculty Research & Creative Works

The impact of photovoltaic power generation on an electric utility's load shape under supply-side peak load management conditions is explored. Results show that some utilities utilizing battery storage for peak load shaving might benefit from use of photovoltaic (PV) power, the extent of its usefulness being dependent on the specific load shapes as well as the photovoltaic array orientations. Typical utility load shapes both in the eastern (at Rayleigh, NC) and in the western (at Hesperia, CA) parts of the USA are examined for this purpose. It is concluded that while photovoltaic power generation seems to present a bigger impact …

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Is Central Station Photovoltaic Power Dispatchable?, Badrul H. Chowdhury, S. Rahman Jan 1988

Is Central Station Photovoltaic Power Dispatchable?, Badrul H. Chowdhury, S. Rahman

Electrical and Computer Engineering Faculty Research & Creative Works

An operational tool for integrating a photovoltaic system into the utility's generation mix is introduced. The development and implementation of a new approach-a dynamic rule-based (RB) dispatch algorithm-is presented. A Box-Jenkins time-series method is used to model the subhourly solar irradiance. The model is extended to yield forecast parameters which are then used to predict the photovoltaic output expected to occur at certain lead times coinciding with the economic dispatch intervals. The RB dispatch algorithm is introduced to operate as either a substitute for or an aid to the dispatch operator. It is concluded that results depend on the time …

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Implementation Of Dsp Applications Using The At&T Dsp32 C Compiler And Application Library, J. Tow, J. Hartung, Steven L. Grant Jan 1988

Implementation Of Dsp Applications Using The At&T Dsp32 C Compiler And Application Library, J. Tow, J. Hartung, Steven L. Grant

Electrical and Computer Engineering Faculty Research & Creative Works

The authors briefly introduce the C compiler and the application library for the DSP32 digital signal processor (DSP). Several examples are shown that illustrate the ease of writing C programs for some common filtering applications. In most cases, a small real-time penalty is incurred by using C, rather than assembly language coding. Programming in C, however, allows a dramatic improvement in programmer productivity in terms of implementing, testing, and maintaining an application

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New Directions In Subband Coding, Y. Shoham, Steven L. Grant, N. Seshadri, R. V. Cox, S. R. Quackenbush, N. S. Jayant Jan 1988

New Directions In Subband Coding, Y. Shoham, Steven L. Grant, N. Seshadri, R. V. Cox, S. R. Quackenbush, N. S. Jayant

Electrical and Computer Engineering Faculty Research & Creative Works

Two very different subband coders are described. The first is a modified dynamic bit-allocation-subband coder (D-SBC) designed for variable rate coding situations and easily adaptable to noisy channel environments. It can operate at rates as low as 12 kb/s and still give good quality speech. The second coder is a 16-kb/s waveform coder, based on a combination of subband coding and vector quantization (VQ-SBC). The key feature of this coder is its short coding delay, which makes it suitable for real-time communication networks. The speech quality of both coders has been enhanced by adaptive postfiltering. The coders have been implemented …

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Aircraft Vertical Profile Implementation Using Directed-Graph Methods, L. T. Brewster, Paul D. Stigall Jan 1988

Aircraft Vertical Profile Implementation Using Directed-Graph Methods, L. T. Brewster, Paul D. Stigall

Electrical and Computer Engineering Faculty Research & Creative Works

Aircraft Vertical Profile Simulation is Realized using a Demand-Driven Minimal-Calculation Directed Graph Structure to Reduce Calculation Time and to Force Synchronization of the Performance Measurement Functions with the System State Variables. Performance-Directed Model Adaptation Makes Dynamic Vertical Profile Path Corrections, in the Presence of Fixed Drag Variations, Possible. Drag Variations Ranging from + 10 Percent to - 10 Percent Yielded Fuel Consumption Improvements of Less Than 1 Percent in the Majority of the Cases. Calculation Time Improvement for Path Simulation Ranges from a Factor of 1.19 in the Worst Case to 1.5 in the Best Case. © 1988 IEEE

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A Stochastic Model For Dielectric Breakdown In Thin Capacitors, D. A. Willming, Cheng-Hsiao Wu Jan 1988

A Stochastic Model For Dielectric Breakdown In Thin Capacitors, D. A. Willming, Cheng-Hsiao Wu

Electrical and Computer Engineering Faculty Research & Creative Works

A nontrivial two-dimensional stochastic model for dielectric breakdown within a parallel plate capacitor is presented for the first time. The model has been used to determine geometric properties of parallel plate discharges. Comparisons are made between these properties and known fractal properties of electrostatic discharges within cylindrical geometries. As the spacing between the plates of a capacitor increases, the value of the fractal dimension of the associated discharge structure increases from the minimum value of unity and approaches the limiting value corresponding to the case of infinite spacing. For any given spacing, this fractal exponent is equal to the exponent …

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Transient Stability Simulation By Waveform Relaxation Methods, Marija D. Ilić, M. A. Pai, Mariesa Crow Nov 1987

Transient Stability Simulation By Waveform Relaxation Methods, Marija D. Ilić, M. A. Pai, Mariesa Crow

Electrical and Computer Engineering Faculty Research & Creative Works

In this paper, a new methodology for power system dynamic response calculations is presented. The technique known as the waveform relaxation has been extensively used in transient analysis of VLSI circuits and it can take advantage of new architectures in computer systems such as parallel processors. The application in this paper is limited to swing equations of a large power system. Computational results are presented.

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Power Division By Element Design In A Circularly Polarized, Series-Fed Array, James L. Drewniak, P. E. Mayes Jun 1987

Power Division By Element Design In A Circularly Polarized, Series-Fed Array, James L. Drewniak, P. E. Mayes

Electrical and Computer Engineering Faculty Research & Creative Works

The feasibility of designing a wideband circular polarized (CP) array of series-fed elements using the element geometry to control the array excitation has been demonstrated. The simple array of wideband, low-profile CP elements requires no phase-shifters and only sufficient feed lines for the interconnection of the elements in a series-fed array. A complicated network is not required to obtain the excitation coefficients for a specified design. Rather, the excitation coefficients can be realized by utilizing the geometric parameters of the individual elements.

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A Dual Circular Polarization Radiating-Line Antenna, James L. Drewniak, P. E. Mayes, D. Tanner, J. Woodruff Jun 1987

A Dual Circular Polarization Radiating-Line Antenna, James L. Drewniak, P. E. Mayes, D. Tanner, J. Woodruff

Electrical and Computer Engineering Faculty Research & Creative Works

No abstract provided.

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Current That Kills., Burns E. Hegler Jan 1987

Current That Kills., Burns E. Hegler

Electrical and Computer Engineering Faculty Research & Creative Works

The authors point out the hazards associated with electricity. Several methods for preventing or coping with inadvertent shocks are described.

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