| Investigation of ELF Signals Associated with Mine Warfare: A University of Idaho and Acoustic Research Detachment Collaboration |
30-Jun-2009 |
69 pages |
| Authors:
Dennis Sullivan; Jeffrey L Young; Robert G Olsen; Christopher L Wagner; IDAHO UNIV MOSCOW
|
 | The questions that are being asked in this investigation are: (1) once an ELF signal is generated, how far does it propagate and still be detectable and (2) how can such signals be modeled, excited and measured? To this end, the scenario considered is one in which an ELF source of the electric or magnetic kind is located in or above water, such as a lake or ocean. This source ... |
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| Electromagnetic (EM) Wave Attachment to Laser Plasma Filaments |
May-2009 |
50 pages |
| Authors:
D C Friedman; ARMY ARMAMENT RESEARCH DEVELOPMENT AND ENGINEERING CENTER PICATINNY ARSENAL NJ WEAPONS AND SOFTWARE ENGINEERING CENTER
|
| This report explores the theoretical and experimental analysis of using plasma filaments generated by a femtosecond class laser system as a means for transmission of radio frequency (RF) electromagnetic (EM) waves. Theoretically, the plasma filaments are modeled as complex cylindrical wires in space for single and dual wire configurations. Attenuation as a function of distance is calculated for single wire transverse electric mode propagation and dual wire transverse electromagnetic (TEM) ... |
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| Signal and Image Processing Algorithms for the U.S. Army Research Laboratory Ultra-wideband (UWB) Synchronous Impulse Reconstruction (SIRE) Radar |
Apr-2009 |
68 pages |
| Authors:
Lam Nguyen; ARMY RESEARCH LAB ADELPHI MD
|
| The U.S. Army Research Laboratory (ARL), as part of a mission and customer-funded exploratory program, has developed a new low-frequency, impulse-based, ultra-wideband (UWB) synthetic aperture radar (SAR), which has been used as a test bed to support proof-of-concept demonstration for detecting concealed targets. The radar is intended to collect and process data at combat pace in an affordable, compact, and lightweight package. To achieve this, the radar is based on ... |
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| Law Enforcement Head-Borne Personal Protective Equipment Hearing Attenuation |
Apr-2009 |
48 pages |
| Authors:
Qi Li; Joshua Haijeck; Tom Burchfield; LI CREATIVE TECHNOLOGIES INC FLORHAM PARK NJ
|
| Test methods were developed to quantify and assess the effects of personal protection equipment (PPE) on hearing. The tests use a head and torso simulator that is able to don PPE and employs advanced acoustic, signal processing, and measurement techniques. The tests measure localization and speech intelligibility effects of PPE. The methods also assess the effects of noise generated by PPE fabric and/or electro/mechanical noise. Localization effects are evaluated in ... |
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| Scattering From a Lossless Sphere |
13-Mar-2009 |
53 pages |
| Authors:
Edl Schamiloglu; Thomas Hagstrom; Xi Chen; Carl E Baum; NEW MEXICO UNIV ALBUQUERQUE DEPT OF ELECTRICAL ENGINEERING AND COMPUTER SCIENCE
|
| This report describes the results of a study of the fundamental issues in electromagnetic scattering theory with an emphasis on pole behaviors of a lossless sphere arising from the singularity expansion method (SEM). Mie theory is used to solve the acoustic and electromagnetic scattering problems for spheres with lossless boundary conditions and an incident plane wave. It is shown that, for certain lossless sheet impedance boundary conditions there exist second ... |
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| Frequency Diversity for Improving Synthetic Aperture Radar Imaging |
Mar-2009 |
151 pages |
| Authors:
Jawad Farooq; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH GRADUATE SCHOOL OF ENGINEERING AND MANAGEMENT
|
| In this work, a novel theoretical framework is presented for using recent advances in frequency diversity arrays (FDAs). Unlike a conventional array, the FDA simultaneously transmits a unique frequency from each element in the array. As a result, special time and space properties of the radiation pattern are exploited to improve cross-range resolution. The idealized FDA radiation pattern is compared with and validated against a full-wave electromagnetic solver, and it ... |
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| Blind Deconvolution Through Polarization Diversity of Long Exposure Imagery |
Mar-2009 |
51 pages |
| Authors:
Steven P James; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH GRADUATE SCHOOL OF ENGINEERING AND MANAGEMENT
|
| The purpose of the algorithm developed in this thesis was to create a post processing method that could resolve objects at low signal levels using polarization diversity and no knowledge of the atmospheric seeing conditions. The process uses a two-channel system, one unpolarized image and one polarized image, in a GEM algorithm to reconstruct the object. Long exposure images were simulated and a single Kolmogorov model used. This allowed for ... |
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| A Computational Tool for Evaluating THz Imaging Performance in Brownout Conditions at Land Sites Throughout the World |
Mar-2009 |
65 pages |
| Authors:
Seth L Marek; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH GRADUATE SCHOOL OF ENGINEERING AND MANAGEMENT
|
| This study quantifies terahertz (THz) or sub-millimeter imaging performance during simulated rotary-wing brownout or whiteout environments based on geographic location and recent/current atmospheric weather conditions. The atmospheric conditions are defined through the Air Force Institute of Technology Center for Directed Energy (AFIT/CDE) Laser Environmental Effects Definition and Reference or LEEDR model. This model enables the creation of vertical profiles of temperature, pressure, water vapor content, optical turbulence, and atmospheric particulates ... |
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| Production and Characterization of High Repetition Rate Terahertz Radiation in Femtosecond-Laser-Induced Air Plasma |
Mar-2009 |
79 pages |
| Authors:
Michael L Dexter; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH GRADUATE SCHOOL OF ENGINEERING AND MANAGEMENT
|
| The purpose of this research was to produce and characterize high repetition rate terahertz radiation in ionized air plasma. An 800 nanometer, 50 femtosecond, 0.35 Watt, 40 KHz, pulsed Ti:Sapphire laser system was used as the source infrared beam. This beam was focused onto a second harmonic generation crystal to produce a collinear, perpendicularly polarized secondary beam at 400 nm. After realigning the polarization of the fundamental to the second ... |
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| Design and Development of a Single Channel RSNS Direction Finder |
Mar-2009 |
95 pages |
| Authors:
Jessica A Benveniste; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| This thesis carried out the design and development of a single channel Robust Symmetrical Number System (RSNS) virtual spacing direction finding (DF) system. This was based on previous work on a three-channel RSNS virtual spacing DF system. Various moduli sets were chosen and run through MATLAB simulations. The results showed unacceptably large errors at low signal-to-noise ratios (SNRs) for all sets. Large dynamic range moduli sets yielded relatively high errors ... |
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| Radar Imaging with a Network of Digital Noise Radar Systems |
Mar-2009 |
168 pages |
| Authors:
Ashley L Schmitt; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING AND MANAGEMENT
|
| Due to the threat of terrorism, today's enemy can be anyone and they can exist anywhere even in populated cities. Monitoring human activities in an urban environment is a difficult problem due walls, clutter, and other obstructions. This thesis discusses the development of a network of digital noise radars that operate simultaneously to track humans and non-human targets inside rooms and through walls. Each individual noise radar works by cross ... |
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| Designing an Ultrasonic Modem for Robotic Communications |
Mar-2009 |
26 pages |
| Authors:
Justin Shumaker; ARMY RESEARCH LAB CLEVELAND OH VEHICLE TECHNOLOGY DIRECTORATE
|
| An ultrasonic modem is a device that can transmit information acoustically. One was designed for the 2008 FIRST Robotics League competition to provide short-range communications with the robot. The creation of this device was the result of a regulation that inhibited any use of electromagnetic-based communications technology in the competition. The ultrasonic modem consists of easily attainable and low-cost parts and was designed to attenuate ambient noise in the audible ... |
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| Electronic Warfare in Operations |
25-Feb-2009 |
115 pages |
| Authors:
DEPARTMENT OF THE ARMY WASHINGTON DC
|
| FM 3-36 provides Army commanders and their staff guidance on how the electromagnetic spectrum can impact their operations and how friendly EW operations can be used to gain an advantage. This manual describes the application of EW in support of full spectrum operations and provides a baseline for ensuring a common understanding and operational consistency. Although new equipment, tactics, techniques, and procedures continue to be developed, the physics of electromagnetic ... |
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| A New Approach to the Characterization and Detection of Nonstationary Environments and Channels |
20-Feb-2009 |
25 pages |
| Authors:
Leon Cohen; HUNTER COLL NEW YORK
|
| A new method to study nonstationary systems and channels that applies to both the time-variant and time-invariant case has been developed. It is shown that a significant simplification occurs when systems are formulated in phase space. The phase space can be time-frequency for the usual formulation of channels/systems, or position-wave number for dispersive channels and pulses. In the standard textbook approach of input-output relations and system functions, the relations are ... |
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| New Magnetic Materials and Phenomena for Radar and Microwave Signal Processing Devices - Bulk and Thin Film Ferrites and Metallic Films |
15-Feb-2009 |
38 pages |
| Authors:
Carl E Patton; COLORADO STATE UNIV FORT COLLINS DEPT OF PHYSICS
|
| ONR Grant ONR N00014-07-1-0597 has supported a four phase program. Under Phase (1), there were three materials thrusts, (a) hybrid pulse laser deposited and liquid phase epitaxy films of low loss cubic yttrium iron garnet (YIG) and uniaxial barium hexaferrite, (b) bulk and thick film ultra-dense fine grain pol) crystalline YIG materials, and (c) high magnetization metallic films, notably of Permalloy, iron, and FeTiN. Under Phase (2), the focus was ... |
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| Nonlinear Wave Propagation |
12-Feb-2009 |
27 pages |
| Authors:
Mark J Ablowitz; COLORADO UNIV AT BOULDER DEPT OF APPLIED MATHEMATICS
|
| The objective of this basic research project is to derive and interrogate mathematical models of the propagation of ultrashort pulses in mode locked lasers (particularly Ti:sapphire), the nonlinear propagation of light in certain optical waveguides and photonic lattices, and the nonlinear propagation of light in chi(2) media. The PI and his research team will study the nonlinear partial differential equations that arise from the full nonlinear Maxwell equations under various ... |
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| A Frequency Domain Approach to Pretest Analysis Model Correlation and Model Updating for the Mid-Frequency Range |
Feb-2009 |
21 pages |
| Authors:
Daniel C Kammer; Aaron Nimityongskul; WISCONSIN UNIV-MADISON BOARD OF REGENTS/RESEARCH SPONSORED PROGRAMS
|
| Large, high-performance space vehicles will require test-validated finite element models for accurate response predictions. The models of these precision spacecraft must be valid to a higher frequency range, referred to as the mid-frequency range, which is characterized by high modal density. The product of this research project is a complete finite element model validation procedure for the mid-frequency range, or any system with high modal density. The procedure includes sensor ... |
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| Architectures and Devices for Millimeter Wave Imaging |
Feb-2009 |
18 pages |
| Authors:
Mark Mirotznik; David A Wikner; Joseph N Mait; ARMY RESEARCH LAB ADELPHI MD SENSORS AND ELECTRON DEVICES DIRECTORATE
|
| A research effort was conducted to explore the ways in which sub-wavelength gratings can be used to reduce the reflections from the optics of millimeter-wave imaging systems. A moth-eye lens is sometimes used at optical and infrared frequencies for this purpose, but it is too fragile to be applied directly to the plastic lenses used in the millimeter-wave. A modification of this structure, called the inverse moth-eye lens, was designed, ... |
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| Analysis of Plasma Communication Schemes for Hypersonic Vehicles: Final Report |
Feb-2009 |
71 pages |
| Authors:
David V Rose; Carsten H Thoma; Vladimir Sotnikov; VOSS SCIENTIFIC LLC ALBUQUERQUE NM
|
| We summarize progress in our analysis of proposed communication schemes for hypersonic vehicles in flight. Investigations into the electron-acoustic wave (EAW) communication scheme have yielded a dispersion analysis indicating that EAW modes can be generated and propagate in the plasma layer. Furthermore, we have demonstrated that these modes can be coupled to EM waves at the plasma layer boundary for the assumption of a sharp density boundary. We discuss results ... |
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| Embedded Meta-Material Antennas |
31-Jan-2009 |
21 pages |
| Authors:
Dennis W Prather; DELAWARE UNIV NEWARK
|
| With the dawn of the Digital Battlefield, a critical capability in the modern warfare environment is the miniaturization of electronic warfare signal and information processing systems. To realize such systems, the key is to miniaturize antennas that transmit and receive signals. In particular, by introducing reconfigurable antennas, one can combine multiple antennas operating at various frequency bands into a single aperture, which can provide significant miniaturization and flexibility to the ... |
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| Genesis of Infrared Decoy Flares: The Early Years from 1950 into the 1970s. First Edition |
26-Jan-2009 |
186 pages |
| Authors:
Bernard E Douda; NAVAL SURFACE WARFARE CENTER CRANE DIV IN
|
| The evolution of decoy flares did not follow a direct or pre-planned path. Instead, the development was influenced by many factors and requirements existing at the time. One of the most important of these is that the Naval Ordnance Test Station (NOTS), Inyokern China Lake, California had an assigned mission to develop rockets and missiles. This mission became the basis for the requirement that drove flare developments. Fortunately there were ... |
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| Imaging Near-Earth Electron Densities Using Thomson Scattering |
15-Jan-2009 |
33 pages |
| Authors:
Christoph R Englert; R R Meier; Jonathan F Krall; Steven P Slinker; Joseph D Huba; William S Vincent; Dennis G Socker; Damien H Chua; J M Picone; M T Carter; NAVAL RESEARCH LAB WASHINGTON DC
|
| An innovative observational concept to image the electron density in the near-Earth environment or geospace, which includes the plasmasphere, the magnetosphere, and their boundary regions, was studied. The concept is based on the broadband detection of Thomson-scattered sunlight by the geospace electrons. This study shows that the proposed measurement is feasible with currently available technology. The major challenge of this novel type of measurement is to achieve a suitable temporal ... |
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| Characterising the Ionosphere (La caracterisation de l'ionosphere) |
Jan-2009 |
266 pages |
| Authors:
G Wyman; NATO RESEARCH AND TECHNOLOGY ORGANIZATION NEUILLY-SUR-SEINE (FRANCE)
|
| This report is a compilation of papers from academic and other research institutes that describe ionospheric phenomena and parameters that affect electromagnetic propagation. The report addresses both mid-latitude and high-latitude effects. The first chapter describes the morphology of the ionosphere, briefly covers the neutral atmosphere and expands on the influence of the geomagnetic field, ionospheric electric field and currents, and particle precipitation at high latitudes. Chapter 2 looks at the ... |
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| EMI/RFI Survey at Detachment K |
Jan-2009 |
68 pages |
| Authors:
Wilbur R Vincent; Andrew A Parker; Richard W Adler; George F Munsch; Carlo Melnick; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| During this survey several new and major sources of radio interference were encountered. While the brief visit did not allow time for the identification of all sources of interference, several were identified. Major sources were the insufficient dynamic range of the site's multicouplers and their inability to cope with the normal ambient signal environment as well as intermodulation components generated from the operation of an onsite ionospheric sounder at full ... |
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| Proceedings of the Antenna Applications Symposium (32nd) Held in Monticello, Illinois on 16-18 September 2008. Volume 2 |
20-Dec-2008 |
265 pages |
| Authors:
Daniel Schaubert; J D Wolf; T L Roach; J T Bernhard; D Filipovic; G Potvin; D Fontaine; Y Saito; J-M Rollin; L M Paulsen; M J Buckley; M W Elsallal; J B West; R J Mailloux; S G Santarelli; T M Roberts; D Luu; M Stasiowski; D Schaubert; Z Popovic; MASSACHUSETTS UNIV AMHERST DEPT OF ELECTRICAL AND COMPUTER ENGINEERING
|
| The Proceedings of the 2007 Antenna Applications Symposium is a collection of state-of-the art papers relating to antenna arrays millimeter wave antennas simulation and measurement of antennas integrated antennas and antenna bandwidth and radiation improvements. |
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| Proceedings of the Antenna Applications Symposium (32nd) Held in Monticello, Illinois on 16-18 September 2008. Volume 1 |
20-Dec-2008 |
279 pages |
| Authors:
M W Elsallal; T L Roach; J T Bernhard; D Filipovic; G Potvin; D Fontaine; Y Saito; J-M Rollin; Z Popovic; J D Wolf; L M Paulsen; J B West; R J Mailloux; S G Santarelli; T M Roberts; D Luu; M Stasiowski; D Schaubert; M J Buckley; D H Schaubert; MASSACHUSETTS UNIV AMHERST DEPT OF ELECTRICAL AND COMPUTER ENGINEERING
|
| The Proceedings of the 2008 Antenna Applications Symposium is a collection of state-of-the art papers relating to antenna arrays, millimeter wave antennas, simulation, and measurement of antennas integrated antennas and antenna bandwidth and radiation improvements. |
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| Performance Analysis of an Alternative Link-16/JTIDS Waveform Transmitted Over a Channel with Pulse-Noise Interference |
Dec-2008 |
66 pages |
| Authors:
Ho K Wei; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| The Joint Tactical Information Distribution System (JTIDS) is a hybrid frequency-hopped direct sequence spread spectrum system that utilizes a (31, 15) Reed- Solomon (RS) code and cyclical code-shift keying modulation for the data packets, where each encoded symbol consists of five bits. The primary drawback to JTIDS is the limited data rate. In this thesis, an alternative waveform consistent with the existing JTIDS waveform but with twice the data rate ... |
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| Efficient THZ Source Based on Cascaded Optical Down-Conversion in Orientation-Patterned GaAs Structures |
20-Nov-2008 |
34 pages |
| Authors:
Xiaojun Yu; Walter Hurlbut; Vladimir Kozlov; James Harris; Anjie Lin; Paulina Kuo; Joe Schaar; Martin Fejer; Konstantin Vodopyanov; Candace Lynch; David Bliss; Yun-Shik Lee; STANFORD UNIV CA EDWARD L GINZTON LAB OF PHYSICS
|
| The goal of this DARPA TIFT project was to demonstrate an efficient room temperature source for THz imaging systems based on optical down-conversion in an orientation-patterned GaAs microstructure, incorporated into an optical resonant cavity, and pumped by a compact solid state laser. The main achievements are: (1) quasi-phase-matched (QPM) GaAs microstructures with periodic reversal of crystalline orientation, including orientation-patterned GaAs (OPGaAs), diffusion-bonded GaAs (DB-GaAs) and optically-contacted GaAs (OC-GaAs) suitable for ... |
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| The Comparative Study of the Effects of Extremely Low Frequency Electromagnetic Fields and Infrasound on Water Molecule Dissociation and Generation of Reactive Oxygen Species |
Nov-2008 |
54 pages |
| Authors:
Sinerik Ayrapetyan; UNESCO YEREVAN (ARMENIA) LIFE SCIENCES HIGHER EDUCATIONAL SCHOOL
|
| The project was devoted to the study of the mechanisms of the effect of non-ionizing (extremely low frequency electromagnetic field and infrasound) radiation and gas composition of the medium on water dissociation and hydrogen peroxide (H2O2) formation in water and water solutions. Lack of knowledge of the effect of extremely low frequency electromagnetic field (ELF EMF) and infrasound (IS) on physicochemical properties of water and water solutions (the dominant component ... |
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| Integration of Microwave Plasma Ignition Into a Multi-Fuel Engine |
Oct-2008 |
14 pages |
| Authors:
James Smith; WEST VIRGINIA UNIV MORGANTOWN
|
| The purpose of this effort was to demonstrate the successful integration of a Quarter-Wave Coaxial Cavity Resonator Plasma Igniter into a multi-fuel engine. The grantee successfully accomplished the objective by demonstrating successful engine operation with both gasoline and jet fuel. Microwave frequency stimulation of the highly ionized combustion mixture, and generation of reactive oxygen species can potentially result in more complete combustion, preventing in-cylinder build-up of deposits and achieving improved ... |
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| Quantification of Rock Damage from Small Explosions and its Effect on Shear-Wave Generation: Phase I - Homogeneous Crystalline Rock |
30-Sep-2008 |
11 pages |
| Authors:
Jessie L Bonner; Randolph J Martin; Mark Leidig; Peter Boyd; James F Lewkowicz; Dorothy Richter; Robert Garfield; Jeffrey A Reid; WESTON GEOPHYSICAL LEXINGTON MA
|
| We are currently conducting a one-year feasibility study to determine the most efficient way to characterize the damage from an explosive source and to identity the source(s) of shear wave generation. We hope to quantify crack nucleation and growth (Ashby and Sammis, 1990) as an S-wave generation mechanism in the far-field (Sammis, 2002) and to map the cone of damage (Patton et. al. 2005; Stevens et. al. 2003) above a ... |
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| Permalloy Film Array Spin Dynamics and High Performance Integrated Microwave Devices |
25-Sep-2008 |
8 pages |
| Authors:
Pingshan Wang; CLEMSON UNIV SC OFFICE OF SPONSORED PROGRAM
|
| Major contributions of this project include (1) the highest permalloy (Py) array FMR frequency reported so far without DC magnetic bias field, and (2) an ultra-sensitive method for ferromagnetic material characterization. Shape-induced high frequency properties of patterned submicron Py arrays are obtained. Py films are sputtered and patterned on gold (Au) transmission lines. Chromium (Cr) is used as adhesion layers for Au and Py deposition. Each Py bar in the ... |
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| Terahertz Plasmon-Induced Conductance Effects in Semiconductor Heterostructures |
05-Sep-2008 |
27 pages |
| Authors:
Robert E Peale; UNIVERSITY OF CENTRAL FLORIDA ORLANDO
|
| Experimental investigation of the coupling of free space radiation to surface plasmons by silver or Pd2Si gratings was performed for different grating profiles at CO2 laser wavelengths. Comparison of the results with the theory of Hessel and Liner 1965 and of Wheeler, Arakawa, and Ritchie 1976 suggests that the former gives the more accurate description in the long-wave IR. For that theory, the comparison gives an empirical non-linear relation between ... |
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| Aircraft Free-Space MIMO Wireless Communications (Preprint) |
01-Sep-2008 |
13 pages |
| Authors:
Michael Gans; John Matyjas; Michael Medley; Stephen Reichhart; Jared Feldman; AIR FORCE RESEARCH LAB ROME NY INFORMATION DIRECTORATE
|
| In Airborne Networks, because of the high mobility, a communications link is typically available for only a short period of time. Thus it is desirable to communicate at as high a data rate as possible to complete one's information transfer in the available time. High data rate suggests the use of MIMO communications, multiplexing many messages over the link by using multiple antennas at each end of the link. However, ... |
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| A Plasma-Assisted Megawatt Class Microwave Source With an Output of 1KJ Per Pulse |
01-Sep-2008 |
9 pages |
| Authors:
Yuval Carmel; MARYLAND UNIV COLLEGE PARK INST FOR RESEARCH IN ELECTRONICS AND APPLIED PHYSICS
|
| The Air Force requires lightweight, compact sources of high-power high-frequency radiation for numerous applications in communications, radar, ECM, and directed-energy weapons (DEW). This effort will be a satellite effort under the "Microwave Power Research Initiative (MiPRI)" program that addresses important research issues that impact directly on both the high-power microwave (HPM) and microwave vacuum electronics (MVE) R&D thrusts within the DOD. The goal of the proposed basic research is to ... |
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| Detection of Frequency Hopped Signals Timing Information Using the Temporal Correlation Function |
01-Sep-2008 |
99 pages |
| Authors:
Yuan-Pin Cheng; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| This work extends earlier work derived by Overdyk and investigates the use of wavelet transform and image processing tools to estimate hopping times occurring in frequency hopping schemes. The detection algorithm identifies frequency hopping time locations found in FH schemes from the information provided by the two-dimensional short-term signal temporal correlation function. Hopping time locations are shown to be provided by identifying TGF phase discontinuities. The detection scheme has three ... |
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| Performance Analysis of a Link-16/JTIDS Compatible Waveform Transmitted Over a Channel with Pulse-Noise Interference |
01-Sep-2008 |
110 pages |
| Authors:
Dimitrios Lekkakos; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| The Joint Tactical Information Distribution System (JTIDS) is a hybrid frequency-hoped, direct sequence spread spectrum system that utilizes a (31, 15) Reed-Solomon (RS) code and cyclical code-shift keying (CCSK) modulation for the data packets, where each encoded symbol consists of five bits. In this thesis, an alternative waveform consistent with the existing JTIDS channel waveform is analyzed. The system to be considered uses (31, 15) RS encoding as the original ... |
|
| Atmospheric Effects on Signal Propagation in Adverse Environmental Conditions: A Validation of the Advanced Refractive Effects Prediction System |
01-Sep-2008 |
93 pages |
| Authors:
Erin E O'Marr; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| Signal propagation measurements from an 802.16 wireless communications network link were analyzed and compared with respect to effects-based model outputs influenced by atmosphere conditions. Atmospheric data collected included in situ ground measurements, radiosonde upper air observations, and numerical weather model data. Extrapolated vertical atmospheric profiles, based on boundary layer constant flux theory and using the in situ ground measurements, were compared to the radiosonde upper air observations and high resolution ... |
|
| Comparison of Linear and Nonlinear Processing with Acoustic Vector Sensors |
01-Sep-2008 |
92 pages |
| Authors:
Skevos T Psaras; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| Towed arrays of vector sensors are currently being employed in a variety of naval applications. The use of acoustic vector sensors, which measure the acoustic pressure and three orthogonal axes of associated particle motion, are of interest because of the signal gain and additional directionality achievable. The majority of analysis performed on vector sensor arrays has involved the advantages of conventional (linear) standard cardioid beamform processing. In this work, we ... |
|
| Millimeter Wave Modulators Using Quantum Dots |
Sep-2008 |
13 pages |
| Authors:
Dennis W Prather; DELAWARE UNIV NEWARK DEPT OF ELECTRICAL AND COMPUTER ENGINEERING
|
| In this effort electro-optic modulators for millimeter wave sensing and imaging were developed and demonstrated via design, fabrication, and experimental characterization of multi layer quantum dot structures for enhanced electro-optic interaction. Millimeter waves carry small amounts of energy inspiring us to maximize the electro-optic (EO) effect in the developed sensor material. Traditional bulk materials do not have high enough EO coefficients for this application so the goal is to custom ... |
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| Reliable Adaptive Modulation and Interference Mitigation for Mobile Radio Slow Frequency Hopping Channels |
29-Aug-2008 |
14 pages |
| Authors:
MING LEI; Alexandra Duel-Hallen; Hans Hallen; NORTH CAROLINA STATE UNIV AT RALEIGH OFFICE OF CONTRACTS AND GRANTS
|
| The Long Range Fading Prediction algorithm for Slow Frequency Hopping (SFH) systems is proposed and demonstrated to enable combined Adaptive Modulation and adaptive Frequency Diversity to mitigate the effects of fading and partial-band interference. Significant performance gains are demonstrated relative to non-adaptive methods in realistic mobile radio SFH channels where the total bandwidth does not exceed approximately 15 times the coherence bandwidth. |
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| Performance of Improved Channel Allocation for Multicarrier CDMA with Adaptive Frequency Hopping and Multiuser Detection |
29-Aug-2008 |
7 pages |
| Authors:
Alexandra Duel-Hallen; Tao Jia; NORTH CAROLINA STATE UNIV AT RALEIGH OFFICE OF CONTRACTS AND GRANTS
|
| Subchannel allocation for the reverse link of multicarrier code-division multiplex-access (MC-CDMA) system with adaptive frequency hopping (AFH) is investigated. An efficient allocation method that can be employed with the matched filter (MF) receiver as well as with multiuser detectors (MUDs) by exploiting the appropriate signal to interference and noise ratio (SINR) analysis is described. It is demonstrated that combined improved subcarrier allocation and the linear decorrelating detector (LDD) are very ... |
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| Improved Channel Allocation for Multicarrier CDMA with Adaptive Frequency Hopping and Multiuser Detection |
29-Aug-2008 |
27 pages |
| Authors:
Alexandra Duel-Hallen; Tao Jia; NORTH CAROLINA STATE UNIV AT RALEIGH OFFICE OF CONTRACTS AND GRANTS
|
| Multicarrier code-division multiple access (MC-CDMA) system with adaptive frequency hopping (AFH) has attracted attention of researchers due to its excellent spectral efficiency. A suboptimal water-filling (WF) channel allocation algorithm was previously proposed for the reverse link of this system. To overcome the limitations of the WF algorithm in the presence of fading-induced near-far problem, a new allocation algorithm is proposed and demonstrated to improve performance when the conventional matched filter ... |
|
| Miniature High Density Scandate Cathodes for Linear Beam Devices |
14-Jul-2008 |
|
| Authors:
Arthur Carpenter; Bernard K Vancil; Ivor Brodie; E BEAM INC BEAVERTON OR
|
 | The work was an investigation of recent promising results by workers in China on scandate impregnated cathodes. The improvement in dispenser cathode performance due to additions of small quantities of scandium oxide has been known since at least the 1980s. But workers in China have produced breakthrough performance with verified current loadings to 100 A/cm2. These results have not been fully reproduced or understood by cathode researchers in this country. ... |
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| Performance Analysis of an Alternative to Trellis Coded Modulation for Waveforms Transmitted over a Channel with Pulse-Noise Interference |
01-Jun-2008 |
59 pages |
| Authors:
Monteiro; Mario R Marques; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| The performance of a communication system having almost the same spectral efficiency as a trellis coded modulation (TCM) system with r = 2/3 convolutional encoding and 8-ary phase-shift keying (8-PSK) modulation is investigated. TCM is a common solution to the problem of adding forward error correction (FEC) coding without an attendant increase in channel bandwidth. The primary drawback to TCM is that the achievable coding gain is limited by the ... |
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| Terrestrial Communication Between Wireless Sensor Networks Using Beam-Forming and Space Division Multiple Access |
01-Jun-2008 |
117 pages |
| Authors:
Chris E Taylor; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| In this thesis, methods for forming a communications link of Wireless Sensor Networks (WSN) by enabling each WSN to act as a smart antenna are presented. Each WSN is simulated as a set of randomly placed sensor nodes within a planar area. The proposed method involves a searching WSN, a receiving WSN and a link budget for establishing the link. The searching WSN has the task of transmitting a search ... |
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| Novel High Frequency Signatures for Classification/Identification |
01-Jun-2008 |
|
| Authors:
Philip L Marston; WASHINGTON STATE UNIV PULLMAN DEPT OF PHYSICS
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| The emphasis of the research summarized here concerns the production of enhancements in the scattering of high frequency sound by various penetrable cylinders. Examples of such cylinders in water include solid polymer (plastic) cylinders having flat or curved ends, plastic cylindrical shells containing a liquid having a low speed of sound, and a solid fiberglass cylinder. In some cases the cylinders were encased in stainless steel or fiberglass. In most ... |
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| Embedded RF Photonic Crystals as Routing and Processing Devices in Naval Aperstructures |
16-May-2008 |
16 pages |
| Authors:
Dennis W Prather; DELAWARE UNIV NEWARK
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| The ability to rapidly detect and process radio frequency (RF) signals is of extreme importance in the modern warfare environment. As the use of the electromagnetic spectrum continues to expand, the technical requirements necessary to maintain such a critical ability becomes very challenging; additional requirements such as miniaturization of the system, reduction in power consumption and the miniaturization of signatures places even more stringent requirements on an already pressing problem. ... |
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| Accurate Representation of Attenuation in Large-Signal Helix TWT Simulation Codes |
Apr-2008 |
3 pages |
| Authors:
Baruch Levush; David Chernin; Antonsen; Thomas M Jr; Demos Dialetis; NAVAL RESEARCH LAB WASHINGTON DC
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| This paper reports on the results of a comparison study of the CHRISTINE one-dimensional helix traveling wave tube (TWT) simulation code with the small signal theory of a beam interacting with a slow wave supported by a sheath helix in the presence of loss to determine whether attenuation is treated with sufficient accuracy by the ad hoc model used in the CHRISTINE code. The study was motivated in part by ... |
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| Energy Losses in Simulated Relativistic Michigan A6 Magnetron with Shaped Cathode |
Apr-2008 |
2 pages |
| Authors:
Peter Mardahl; AIR FORCE RESEARCH LAB KIRTLAND AFB NM DIRECTED ENERGY DIRECTORATE
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| Recently there has been much research interest in improving magnetron performance by employing various priming techniques, such as shaped cathodes and nonuniform magnetic fields. These priming techniques have been successfully applied to reduce magnetron noise and improve mode-locking and efficiency. Inserting a shaped cathode into the simulated Michigan magnetron yields a maximum efficiency (the radiofrequency (RF) output power for a cycle divided by the current times voltage input for that ... |
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Radiofrequency Wave Propagation
