| UV and Visible Harmonic Generation Through Enhanced Transmission from GaAs-filled Nanocavities |
Oct 2011 |
4 pages |
| Authors:
M A Vincenti; D de Ceglia; V Roppo; M Scalora; ARMY MISSILE RESEARCH DEVELOPMENT AND ENGINEERING CENTER REDSTONE ARSENAL AL
|
 | A theoretical study of harmonic generation from a silver grating having slits filled with GaAs has been conducted. The enhanced transmission regime that guarantees high field localization inside the slits, and the phase-locking mechanism that take place between the pump and its harmonics allows enhanced harmonic generation under conditions of high absorption at visible and UV wavelengths. |
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| Coherent Beam Combining of Fiber Amplifiers in a kW Regime |
21 APR 2011 |
8 pages |
| Authors:
Anthony D. Sanchez; Angel Flores; Thomas M. Shay; Chunte A. Lu; Craig Robin; Benjamin Pulford; Dane W. Hult; Ken B. Rowland; AIR FORCE RESEARCH LAB KIRTLAND AFB NM DIRECTED ENERGY DIRECTORATE
|
| We report kW scale coherent beam combination (CBC) of both conventional silica fiber and photonic crystal fiber (PCF) amplifiers via LOCSET phase locking technology. Single-frequency CBC of 16 100W fiber lasers with 1.4 kW total output power is presented. In addition, kW scale CBC of novel SBS suppressive PCF amplifiers is presented. Three 350W PCF amplifiers arranged in a filled aperture configuration were combined into a single kW level laser ... |
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| Coherent Combining of High-Power Yb Fiber Amplifiers |
20 Apr 2011 |
9 pages |
| Authors:
Charles X Yu; Steven J Augst; Shawn M Redmond; Kris C Goldizen; Daniel V Murphy; Antonio Sanchez; Tso Y Fan; MASSACHUSETTS INST OF TECH LEXINGTON LINCOLN LAB
|
| Commercial 0.5-kW Yb-doped fiber amplifiers have been characterized and been found to be suitable for coherent beam combining. Eight such fiber amplifiers have been coherently combined in a tiled-aperture configuration with 78% combining efficiency. The power-in-the-bucket vertical beam quality of the combined output is 1.25 times diffraction limited at full power. The beam-combining performance is independent of output power. |
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| Phase-Locked Second Harmonic Generation in GaAs Nanocavities |
JUN 2010 |
3 pages |
| Authors:
M. A. Vincenti; D. de Ceglia; M. C. Buncick; M. Scalora; M. J. Bloemer; AEGIS TECHNOLOGIES GROUP HUNTSVILLE AL
|
| We theoretically study light propagation through sub-wavelength apertures on a silver substrate filled with GaAs, in the enhanced transmission regime. We predict enhanced conversion efficiencies even under high absorption conditions. |
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| Phase-Locking and Frustration in an Array of Nonlinear Spin-Torque Nano-Oscillators (Preprint) |
23-Oct-2009 |
11 pages |
| Authors:
Elena Bankowski; Grant Gerhart; Andrei Slavin; Vasil Tiberkevich; OAKLAND UNIV ROCHESTER MI DEPT OF PHYSICS
|
| We demonstrate that high-frequency cooperative dynamics of an array of coupled nonlinear spin-torque nano-oscillators (STNO) can be controlled by introduction of an additional external phase shift BETAc between the microwave current, which couples STNOs, and the total array microwave voltage. When this external phase shift BETAc compensates the intrinsic phase shift BETA0, caused by the STNO nonlinearity, a phase-locking regime with increased output power and vanishing inhomogeneous linewidth broadening is ... |
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| High Average Power Diode Pumped Solid State Lasers: Power Scaling With High Spectral and Spatial Coherence |
30-Mar-2009 |
97 pages |
| Authors:
Robert L Byer; J Wisdom; K Urbanek; S Sinha; A Serpry; T Plettner; Y Lee; P S Kuo; R Gaume; H Bae; R Route; M Digonnet; S Wong; STANFORD UNIV CA
|
| The main program objective was the development of a kilowatt class, cw Nd:YAG diode-laser-pumped solid-state laser (DPSSL) with quantum noise limited amplitude and phase, 24by7 operation capability and the ability to be repaired while in operation. The approach was a master-oscillator power-amplifier (MOPA) laser utilizing a series of zig-zag slab power amplifiers stages. We developed fiber amplifiers at the 200W level to generate power with high optical efficiency that can ... |
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| A Prototype Cesium Clock Ensemble for The Loran-C Radionavigation System |
01-Dec-2008 |
15 pages |
| Authors:
Aaron P Dahlen; COAST GUARD WILDWOOD NJ ELECTRONICS ENGINEERING CENTER
|
| This paper presents a prototype real time clock ensemble designed for semi-autonomous operation at unmanned Loran-C radionavigation transmitting stations. This clock is designed to mitigate a doomsday scenario where all space-based timing assets are lost. It is implemented using three free-running commercial cesium oscillators, a traditional measurement system, and an Auxiliary Output Generator (AOG) phase-locked to the weighted mean of the cesium ensemble. A relatively inexpensive rubidium oscillator is used ... |
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| Effects of Pulsed-D.C. Discharge Plasma Actuators in a Separated Low Pressure Turbine Boundary Layer (Postprint) |
01-Jan-2007 |
11 pages |
| Authors:
J D Wall; I C Boxx; R B Rivir; M E Franke; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH
|
| A pulsed DC dielectric barrier discharge plasma actuator is investigated to reattach the simulated separated flow of a highly loaded turbine blade suction surface. Pulse rates of 25, 50, 75, and 100 pulses per second were investigated at a nominal constant pulse power of 8.5 kW for a constant pulse width of 250 ns. The separation of the flat plate boundary layer is induced with an adverse free stream pressure ... |
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| Reattachment of a Separated Boundary Layer on a Flat Plate in a Highly Adverse Pressure Gradient Using a Plasma Actuator (Postprint) |
01-Jun-2006 |
12 pages |
| Authors:
Issac G Boxx; Richard B Rivir; Jeffery M Newcamp; Nathan M Woods; AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH TURBINE ENGINE DIV
|
| An experimental study was performed to examine the phase-dependent response characteristics of a dielectric barrier discharge plasma flow control actuator. The actuator was investigated on a fully separated flat plate boundary layer with an adverse freestream pressure gradient distribution. The actuator was positioned downstream of the boundary layer separation. Phase-locked particle image velocimetry (PIV) was used to obtain two-dimensional velocity field measurements at thirty equally spaced phase-angles along the sinusoidal ... |
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| An Investigation into the Relationship between Ionospheric Scintillation and Loss of Lock in GNSS Receivers |
01 JUN 2006 |
52 pages |
| Authors:
Robert W. Meggs; Cathryn N. Mitchell; Andrew M. Smith; BATH UNIV (UNITED KINGDOM)
|
| Irregularities in the ionospheric electron density can cause a phenomenon known as scintillation, in which the phase and amplitude of transiting radio signals fluctuate rapidly. Scintillation can have an adverse effect on Global Navigation Satellite Systems (GNSS) signals as they pass from a satellite to a receiver, and extreme cases can cause a GNSS receiver to lose lock on the signal. This limits the availability of path-length measurements, and compromises ... |
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| Reattachment of a Separated Boundary Layer on a Flat Plate in a Highly Adverse Pressure Gradient Using a Plasma Actuator(POSTPRINT) |
JUN 2006 |
12 pages |
| Authors:
Isaac G. Boxx; Richard B. Rivir; Jeffrey M. Newcamp; Nathan M. Woods; AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH PROPULSION DIRECTORATE
|
| An experimental study was performed to examine the phase-dependent response characteristics of a dielectric barrier discharge plasma flow control actuator. The actuator was investigated on a fully separated flat plate boundary layer with an adverse freestream pressure gradient distribution. The actuator was positioned downstream of the boundary layer separation. Phase-locked particle image velocimetry (PIV) was used to obtain two-dimensional velocity field measurements at thirty equally spaced phase-angles along the sinusoidal ... |
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| Photonic Arbitrary Waveform Generation Technology |
JUN 2006 |
37 pages |
| Authors:
Jr Delfyett Peter J.; UNIVERSITY OF CENTRAL FLORIDA ORLANDO
|
| Modelocked semiconductor lasers emit short (1 GHz) and can be utilized for a wide variety of applications, but are typically geared towards time domain applications, e.g., optical time division multiplexed optical links, optical sampling, etc. Additionally, the periodic nature of optical pulse generation from modelocked semi conductor diode lasers also makes these devices ideal candidates for the generation of high quality optical frequency combs, or multiple wavelengths, in addition to ... |
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| Large-Bandwidth Phase-Locked Measurements for High-Speed Flow Experiments with Controlled Disturbance Inputs |
JUL 2005 |
25 pages |
| Authors:
Ndaona Chokani; DUKE UNIV DURHAM NC OFFICE OF SPONSORED PROGRAMS
|
| The purpose of the present work is to develop an experimental apparatus that will enable us to accurately detect, and then measure, the phase-locked interactions that occur in high-speed flows. In particular, we examine the structure of the shockwave/boundary layer interaction induced by an unswept compression ramp flow in the Supersonic Low Disturbance Wind Tunnel at the NASA Langley Research Center. SLDT has a unique capability for generating a very ... |
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| Spatial Modulation in the Underwater Acoustic Channel |
20 DEC 2004 |
21 pages |
| Authors:
Daniel Kilfoyle; Lee Freitag; SCIENCE APPLICATIONS INTERNATIONAL CORPFALMOUTH MA
|
| Multiple-input multiple-output (MIMO) communication channels are an active area of research for terrestrial wireless applications. The natural bandwidth limitations of the underwater acoustic channel (UAC) combined with the potential for a rich spatial propagation structure suggest the ocean may be another useful application area for MIMO techniques. An underwater acoustic communications experiment was conducted in the waters surrounding Elba, Italy, using spatially modulated signals. Two frequency regimes (9.5-14.5 kHz and ... |
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| A Paper Clock Model for the Cesium Clock Ensemble of TL |
SEP 2004 |
12 pages |
| Authors:
Shinn Y. Lin; Hsin M. Peng; NATIONAL STANDARD TIME AND FREQUENCY LAB TAOYUAN (TAIWAN)
|
| A paper clock model based on limited numbers of atomic clocks and a typical time interval counter was developed. The aim of this work is to use a small ensemble of cesium clocks and a traditional measurement system to generate a time scale keeping both short-term and long-term accuracy. We removed each clock's drift, then weighted the residual fluctuations. The weight function is set to be proportional to the inverse ... |
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| Tera-Op Reliable Intelligently Adaptive Processing System (TRIPS) |
APR 2004 |
29 pages |
| Authors:
Stephen W. Keckler; Doug Berger; Michael Dahlin; Lizy John; Calvin Lin; Kathryn McKinley; Tom Keller; Kevin Nowka; TEXAS UNIV AT AUSTIN DEPT OF COMPUTER SCIENCES
|
| The TRIPS project proposes and evaluates technology for scalable and adaptive computer systems. The TRIPS processor and on-chip memory architectures are designed to handle both the increasing wire delays and power constraints of near-future integrated circuit fabrication technology. Combined with the new TRIPS compiler, the results of detailed architectural models show that the TRIPS system can achieve performance improvements by up to an order of magnitude over that of conventional ... |
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| Experimental Dynamics of Stressed, Strongly Correlated Magnetized Plasmas |
24 JUN 2002 |
10 pages |
| Authors:
T. B. Mitchell; J. J. Bollinger; W. M. Itano; D. H. Dubin; NATIONAL INST OF STANDARDS AND TECHNOLOGY BOULDER CO TIME AND FREQUENCY DIV
|
| We study the control of the rotation of a laser-cooled ion crystal in a Penning trap by a rotating electric field perturbation. We show that application of a small torque produces sudden angular jumps or slips' of the crystal orientation spaced by intervals when the crystal is phase- locked or stuck' relative to the rotating perturbation. The distribution of angular slips is described by a power law, where the power-law ... |
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| Pulsed RF Signal Diagnostic System for Cyro-Amplified Research |
31 MAR 2002 |
7 pages |
| Authors:
John Rodgers; MARYLAND UNIV COLLEGE PARK INST FOR RESEARCH IN ELECTRONICS AND APPLIED PHYSICS
|
| The diagnostic equipment purchased under this DURIP grant directly supported University of Maryland basic research under the DoD MURI on Innovative Vacuum Electronics (AFOSR subcontract 99RA073403). Specifically, we studied advanced gyro-amplifiers and phase-locked oscillators operating at harmonics of the electron cyclotron frequency. Recently, a Ka-band harmonic inverted gyrotwystron (phigtron) was studied for which 720 kW of peak power, with a bandwidth of 0.7%, saturated gain of 30 dB and efficiency ... |
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| Propagating Potential Disturbances in Turbomachinery |
02 MAR 2002 |
34 pages |
| Authors:
Eric J. Jumper; NOTRE DAME UNIV IN DEPT OF AEROSPACE AND MECHANICAL ENGINEERING
|
| This report documents the work performed at Notre Dame on attempting to acquire a clean set of phase-locked unsteady velocity data and concomitant unsteady pressure response for upstream-propagating potential disturbances interacting with a sharp-trailing-edged cascade vane in compressible, subsonic flow. The report documents the importance of the work and classifies the types of potential-disturbance interactions that can occur in a turbine engine. A case is made for the importance of ... |
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| A New Synchronized Miniature Rubidium Oscillator with an Auto-Adaptive Disciplining Filter |
01-Nov-2001 |
8 pages |
| Authors:
Pascal Rochat; Bernard Leuenberger; TEMEX TIME NEUCHATEL (SWITZERLAND)
|
| A new rubidium line (SRO) integrating timing functions and time interval measurements was developed using an auto-adaptive disciplining algorithm. This led to an ultra-stable time & frequency machine usable for many applications such as: synchronization of telecommunications systems (SDH, SONET, CDMA), military communications, navigation, and instrumentation. The frequency and phase-time correction is calculated from an internal phase-time error signal measured within 1 ns resolution issued from an internal PPS signal ... |
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| Performance Enhancement of Gas-Turbine Combustor by Active Control of Fuel Injection and Mixing Process - Theory and Practice |
JUN 2001 |
10 pages |
| Authors:
Christian O. Pascherelt; Ephraim Gutmark; Bruno Schuermans; CINCINNATI UNIV OH DEPT OF AEROSPACE ENGINEERING AND ENGINEERING MECHANICS
|
| Unstable thermoacoustic modes were investigated and controlled in an experimental low-emission swirl stabilized combustor, in which the acoustic boundary conditions were modified to obtain combustion instability. Axisymmetric and helical unstable modes wore identified for fully premixed combustion These unstable modes were associated with flow instabilities related to the recirculation region on the combustor axis and shear layer in- stabilities at the sudden expansion (dump plane). The combustion structure associated with ... |
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| Ultrashort Pulse, Monolithic Modelocked Lasers for WDM Systems |
MAY 2001 |
29 pages |
| Authors:
P. D. Dapkus; UNIVERSITY OF SOUTHERN CALIFORNIA LOS ANGELES DEPT OF ELECTRICAL ENGINEERINGAND ELECTROPHYSICS
|
| A program of research to investigate the use of modelocked lasers as sources for WDM systems is reported. The objective of the program was to demonstrate modelocked lasers with ultrashort pulse widths that contain as many as 16 phase locked longitudinal modes. Analysis was carried to understand the role of self phase modulation on the spectral range of modes that could be phase locked in such a device. The results ... |
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| High-Speed All-Optical Switching in Semiconductor Microcavities via Coherent Control of Excitons |
APR 2001 |
30 pages |
| Authors:
Theodore B. Norris; MICHIGAN UNIV ANN ARBOR
|
| We have carried out an extensive series of experiments on coherent control of semiconductor quantum microcavities. In these experiments, a phase- locked femtosecond optical pulse pair is used to excite the lower normal mode (cavity polariton), thereby controlling the reflection of a signal pulse tuned to the upper normal mode. Such a controlled reflection may be used as an all- optical switch with picosecond switching time. We have demonstrated that ... |
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| High-Frequency Properties of Two-Dimensional Josephson-Junction Arrays |
DEC 2000 |
25 pages |
| Authors:
Christopher J. Lobb; MARYLAND UNIV COLLEGE PARK
|
| This research is designed to evaluate the potential of two- dimensional Josephson-junction arrays as high-Q, tunable, EHF sources of electromagnetic radiation. To achieve usable amounts of power, the oscillations of many junctions must be in phase with each other. To assure coherent oscillations, we must understand how the oscillations of single Josephson junctions are affected by the electromagnetic environment of the other junctions in the array, as well as the ... |
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| 220-320 GHz Harmonic Mixer for a Full Band Sweep Vector Network Analyzer |
29 SEP 2000 |
4 pages |
| Authors:
Francois Mattiocco; Matthew Carter; Bernard Lazareff; DOMAINE UNIV SAINT MARTIN D'HERES (FRANCE) INST OF RADIO ASTRONOMIE MILLIMETRIQUE
|
| This paper presents the design and characterization of a fixed tuned 220 - 320 GHz harmonic mixer employing commercial Schottky beam lead diodes in an antiparallel configuration. A diplexer provides distinct ports and matching for the subharmonic LO (26-40GHz) and the IF (20 MHz). The conversion loss was measured using a Gunn + tripler or quadrupler source calibrated with an absolute bolometer. We have built a 220 - 320 GHz ... |
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| Nonlinear Optics and Nonlinear Dynamics in Semiconductor Lasers Subject to External Optical Injection |
31 JUL 2000 |
124 pages |
| Authors:
Thomas B. Simpson; JAYCOR SAN DIEGO CA
|
| This Phase II SBIR effort investigates novel output characteristics of semiconductor lasers that can be induced by external optical injection. Specific interest is in characteristics relevant to the control of microwave and millimeter-wave electronics through enhanced modulation characteristics, characterization of vertical cavity surface emitting laser (VCSEL) arrays, and analysis of chaotic dynamics that can be induced by optical injection. Under external optical injection, all semiconductor ... |
|
| Noninvasive Intracranial Volume and Pressure Measurements Using Ultrasound |
MAR 2000 |
44 pages |
| Authors:
Alan R. Hargens; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION MOFFETT FIELD CA AMES RESEARCHCENTER
|
| Prevention of secondary brain injuries following head trauma can be accomplished most easily when intracranial pressure (ICP) is monitored. However, current measurement techniques are invasive and thus not practical in the combat environment. The Pulsed Phase Lock Loop (PPLL) device, which was developed and patented by collaborators Dr. Yost and Dr. Cantrell, uses a unique, noninvasive ultrasonic phase comparison method to measure slight changes in cranial volume ... |
|
| Spatial-Phase-Locked Electron-Beam Lithography |
30 DEC 1999 |
16 pages |
| Authors:
Henry I. Smith; MASSACHUSETTS INST OF TECH CAMBRIDGE RESEARCH LAB OF ELECTRONICS
|
| Spatial-phase-locked electron-beam lithography (SPLEBL) is a novel approach to achieving very high pattern-placement accuracy, and precision, in electron beam lithography. The accuracy achieved by SPLEBL is essential in order to enable the continuation of next-generation lithography techniques to below 20-nm feature sizes. |
|
| Silicon-on-Sapphire |
06 AUG 1999 |
37 pages |
| Authors:
Paul DE LA Houssaye; Isaac Lagnado; SPACE AND NAVAL WARFARE SYSTEMS COMMANDSAN DIEGO CA
|
| In this presentation, the major issues, which confronted the formation of very thin layers of silicon (30-100 nm) on sapphire substrates for application to sub 100-nm device technology, will be reviewed. The focus of the investigation was, and still is, to achieve a structure in which the modern CMOS technology, the mainstay technology and workhorse of the electronic revolution, can be affordably implemented. In this context, ... |
|
| The Response of a Mixing Layer Formed Between Parallel Streams in a Concomitant Excitation at Two Frequencies |
AUG 1999 |
44 pages |
| Authors:
Ming DE Zhou; I. Wygnanski; ARIZONA UNIV TUCSON DEPT OF AEROSPACE AND MECHANICAL ENGINEERING
|
| Simultaneous excitation of a turbulent mixing layer by two frequencies, a fundamental and a subharmonic, was investigated experimentally. Plane perturbations were introduced to the flow at its origin by a small oscillating flap. The results describe two experiments that differ only in the amplitudes of the imposed perturbations and both are compared to the data acquired while the mixing layer was forced at a ... |
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| The Case of the Missing Pitch Templates: How Harmonic Templates Emerge in the Early Auditory System |
1999 |
25 pages |
| Authors:
Shihab Shamma; David Klein; MARYLAND UNIV COLLEGE PARK INST FOR SYSTEMS RESEARCH
|
| Periodicity pitch is the most salient and important of all pitch percepts. Psycho acoustical models of this percept have long postulated the existence of internalized harmonic templates against which incoming resolved spectra can be compared, and pitch determined according to the best matching templates (Goldstein, 1973a). However, it has been a mystery where and how such harmonic templates can come about. Here we present a biologically plausible model for how ... |
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| Studies of Nonlinear Optical Wave Mixing and Phase Conjugation with Partially Coherent Waves |
26 OCT 1998 |
42 pages |
| Authors:
Pochi Yeh; CALIFORNIA UNIV SANTA BARBARA DEPT OF ELECTRICAL AND COMPUTER ENGINEERING
|
| The main objective of this research was the theoretical and experimental investigation of the physics of self-pumped and mutually-pumped phase conjugators and the development of novel applications. In addition, the scope of the research was expanded to include the effect of partial coherence (finite coherence length) on nonlinear wave mixing and phase conjugation in photorefractive media. Specifically, the effect of finite mutual coherence on ... |
|
| Global Positioning System (GPS) Receiver Design For Multipaths Mitigation |
AUG 1998 |
274 pages |
| Authors:
El-Sayed Abdel-Salam Gadallah; AIR FORCE INST OF TECH WRIGHT-PATTERSONAFB OH
|
| Multipath effects are a source of error degrading the accuracy of DGPS signal processing. The statistical models of multipath are determined by user location and, in addition are time varying. There is no unified statistical model for the multipath signal. Therefore the solution of the multipath problem using statistical models is difficult. This research introduces a new estimator that can detect the presence of multipath, can ... |
|
| A Novel Precision Voltage Reference Using a Micromechanical Resonator |
JUN 1998 |
133 pages |
| Authors:
George N. Schwartz; MASSACHUSETTS INST OF TECH CAMBRIDGE CHARLES STARK DRAPER LAB DIV
|
| This thesis describes the analysis and design of a precision voltage reference (PVR) based upon a micromechanical resonator. The precision voltage reference consists of two closed loop controllers and a nonlinear resonator. The oscillator loop maintains oscillations in the resonator. The phase locked loop is a frequency control loop that locks the resonator frequency to an external frequency. The micromechanical device consists of a pair of resonators that are electrostatically ... |
|
| Laser Doppler Velocimetry in the Space-Shuttle Main Engine High-Pressure Fuel Turbopump |
MAR 98 |
171 pages |
| Authors:
James D. Southward; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| Modifications were made to the Naval Postgraduate School cold-flow turbine test rig to enable integration of a two-component laser-doppler velocimetry (LDV) system. The test turbine was the Space-Shuttle Main Engine, High-Pressure Fuel Turbopump, Alternate-Turbopump Development Model, manufactured by Pratt & Whitney. Flow field measurements were obtained, using a the LDV system, in the first-stage rotor end-wall region of the test turbine, at three axial locations and at three depths from ... |
|
| Noninvasive Intracranial Volume and Pressure Measurements Using Ultrasound |
MAR 1998 |
24 pages |
| Authors:
Alan R. Hargens; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION MOFFETT FIELD CA AMES RESEARCHCENTER
|
| Prevention of secondary brain injuries following head trauma can be accomplished most easily when intracranial pressure (ICP) is monitored. However, current measurement techniques are invasive and thus not practical in the combat environment. The Pulsed Phase Lock Loop (PPLL) device, which was developed and patented by consultants Dr. Yost and Dr. Cantrell, uses a unique, noninvasive ultrasonic phase comparison method to measure slight changes in cranial volume which occur with ... |
|
| High-Frequency Properties of Two-Dimensional Josephson-Junction Arrays |
FEB 1998 |
8 pages |
| Authors:
Christopher J. Lobb; MARYLAND UNIV COLLEGE PARK
|
| Niobium Josephson junction arrays show great promise as compact, low dissipation, efficient sources of electromagnetic radiation at frequencies from below 100 GHz to as high as 1 THz. Current small resistively shunted arrays (containing 100 phase locked junctions) are tunable over a broad range and produce power which is within a factor of 3 the theoretical maximum. Unshunted arrays have also been made which are not tunable, but produce very ... |
|
| Design Considerations for Low Phase Jitter Clock Generators |
1998 |
153 pages |
| Authors:
Philip S. Stetson; MICHIGAN UNIV ANN ARBOR DEPT OF ELECTRICAL ENGINEERING AND COMPUTER SCIENCE
|
| This work explores the generation and propagation of phase jitter within the microprocessor clock generator. Introducing the fundamentals of phase-lock circuits, and clock generators in particular, Chapter II overviews the necessary background information required for a more in-depth analysis. Chapter III examines the concept of phase jitter, discussing its origin, its effects on a synchronous circuit, and an analytical method for calculating phase jitter. The chapter concludes by introducing a ... |
|
| Pressure-Sensitive Paint Measurement Technique Development for Turbomachinery Application |
DEC 1997 |
96 pages |
| Authors:
Kevin J. Quinn; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| Pressure-sensitive paint measurement on a transonic compressor rotor required the prior development of phase-locked cumulative imaging using a disk- rotor driven by a high-speed Hamilton-Standard turbine as a developmental test- bed. The turbine was installed in a protective housing in the Gas Dynamics Laboratory and connected to an 8000 cu ft, 300 psi air supply. An hydraulic pump provided bearing lubrication. A once per revolution trigger signal was produced from ... |
|
| High Speed Multiwavelength Opto-Electronic Sources, Modulators and Detector Arrays |
OCT 97 |
25 pages |
| Authors:
Peter J. Delfyett; UNIVERSITY OF CENTRAL FLORIDA ORLANDO DIV OF SPONSORED RESEARCH
|
| In this effort, novel techniques based on semiconductor traveling wave optical amplifiers were demonstrated. These devices provide potential solutions to the challenges in wavelength-division multiplexing - time-division multiplexing (WDM-TDM) networks and millimeter wave communication systems. The semiconductor traveling wave optical amplifier provides a self-stabilized source of multiple optical wavelengths for WDM and low phase noise millimeter-wave and terahertz signals for wireless telecommunications and TDM. A single-stripe semiconductor traveling wave amplifier ... |
|
| Blind Separation of Auditory Event-Related Brain Responses into Independent Components |
SEP 1997 |
8 pages |
| Authors:
Scott Makeig; Tzyy-Ping Jung; Anothny J. Bell; Dara Ghahremandi; Terrence J. Sejnowski; NAVAL HEALTH RESEARCH CENTER SAN DIEGO CA
|
| Average event-related potential (ERP) data recorded from the human scalp reveal electro-encephalo- graphic EEG) activity that is reliable time-locked and phase-locked to experimental events. We report here the application of a method based on information theory that decomposes one or more ERPs recorded at multiple scalp sensors into a sum of components with fixed scalp distributions and sparsely activated, maximally independent time courses. Independent component analysis (ICA) decomposes ERP data ... |
|
| Stochastic Motion in Many Degrees of Freedom |
11 JUN 97 |
4 pages |
| Authors:
Allan J. Lichtenberg; CALIFORNIA UNIV BERKELEY DEPT OF ELECTRICAL ENGINEERING AND COMPUTER SCIENCE
|
| In the first year of the research under the AASERT Grant we have developed a more rigorous approach to studying the synchronization of coupled digital oscillators, the bifurcations in the system, and the transition to chaotic dynamics. We have developed a mapping for a general class of coupled digital oscillators, which we call coupled phase graph (CPG) dynamical systems; coupled digital phase locked loops (DPLL's) is a special case of ... |
|
| Underwater Acoustic Communication Over Doppler Spread Channels |
JUN 97 |
|
| Authors:
Trym H. Eggen; MASSACHUSETTS INST OF TECH CAMBRIDGE
|
 | This work is concerned with coherent communication by means of acoustic signals over underwater communication channels. The estimated scattering functions of real data show that underwater communication channels cannot be captured by a single, simple channel model. This thesis considers mainly a subset of underwater communication channels where the Doppler spread is more severe than the delay spread. An appropriate representation of the linear time variant channel is introduced, and ... |
|
| GPS Attitude Determination |
19 FEB 97 |
6 pages |
| Authors:
P. Axelrad; COLORADO UNIV AT BOULDER
|
| This report summarizes the progress for the first quarter of FY'96-97 by the Colorado Center for Astrodynamics Research (CCAR) on the application of GPS based attitude determination techniques to near-Earth spacecraft. Two areas are addressed - application of an open architecture receiver for spaceborne attitude determination and coarse spacecraft attitude determination based on GPS signal to noise ratios. We have started work with the GEC Plessey GPSBuilder 2 receiver and ... |
|
| Research on Self-Generated Stochastic Motion |
06 DEC 96 |
9 pages |
| Authors:
A. J. Lichtenberg; CALIFORNIA UNIV BERKELEY ELECTRONICS RESEARCH LAB
|
| The purpose of the research under this contract was to study the processes by which stochastic motion is self-generated in deterministic systems, and the consequences of the resulting stochasticity. We consider representative problems, each of which incorporates one or more of the main underlying physical phenomena. Phenomena that we have studied under this contract include diffusion through stochastic webs, diffusion along resonances in more than two degrees of freedom (Arnold ... |
|
| Optical Frequency Counting and Synthesis |
NOV 96 |
17 pages |
| Authors:
Ngai C. Wong; MASSACHUSETTS INST OF TECH CAMBRIDGE RESEARCH LAB OF ELECTRONICS
|
| A novel method of optical frequency counting and synthesis has been proposed based on a parallel network of optical parametric oscillators. The scheme utilizes the generation of precise frequency ratios by nonlinear optical techniques to phase lock a calibration optical frequency to the primary frequency standard at 9.2 CHz. By operating entirely in the visible to near IR regions and taking advantage of advances in nonlinear crystals, detectors and modulators ... |
|
| Intense Microwave Pulses IV. SPIE'S 1996 Conference on Millimeter and Microwave Engineering |
AUG 96 |
339 pages |
| Authors:
Pearson; SPIE-THE INTERNATIONAL SOCIETY FOR OPTICAL ENGINEERING BELLINGHAM WA
|
| The primary purpose of this conference was to present and critically assess current research on the generation and transmission of intense microwave pulses. The phenomenon of pulse shortening in high-power microwave sources received special attention. Effects were calculated for asymmetric loading of a magnetron cavity on the resonant frequency and quality factor of various cavity modes. Numerical simulations of magnetron phase locking were also presented. In gyrotron research, experiments on ... |
|
| Advanced Quantum Well Optoelectronics for Optically Controlled Phased- Array Systems |
APR 96 |
50 pages |
| Authors:
Kam Y. Lau; CALIFORNIA UNIV BERKELEY ELECTRONICS RESEARCH LAB
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| During the course of this effort, the researcher successfully completed experimental and theoretical investigations of three techniques used to transmit narrowband millimeter (mm-wave) analog signals over optical fiber: (1) narrowband mm-wave optical transmitters based on resonant modulation of monolithic semiconductor lasers; (2) feedforward optical modulation; and (3) a passively mode locked laser operating in an optoelectronics phase locked loop. |
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| A New Electronic Viscometer Based on Rayleigh Wave Mechanics |
APR 1996 |
10 pages |
| Authors:
James J. Kauzlarich; Robert A. Ross; D. S. Abdallah; VIRGINIA UNIV CHARLOTTESVILLE
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| The operation of a new viscometer is shown to be based on Rayleigh wave mechanics, where a thin walled tube of 5 mm diameter is immersed to a fixed depth of 60 mm in a fluid and is caused to undergo axial vibrations due to a vibrating piezoelectric plate which supports the tube. The motion of the tube is damped by the fluid, and the piezoelectric crystal feedback circuit gives ... |
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| Unsteady Pressure Distributions around Compressor Vanes in an Unsteady, Transonic Cascade. |
DEC 1995 |
279 pages |
| Authors:
Michael K. Fabian; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH
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| Unsteady surface pressure measurements were made at various chord locations on the turning vanes in an unsteady, compressible- flow, linear cascade. The turning vanes were made from production stator vanes from the fan stage of a Garrett F1O9 engine. The cascade unsteady forcing was produced by von Karman shedding from a row of circular-cylinder rods positioned at either 80% chord upstream of the turning vanes (forward forced) or at 80% ... |
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Reports by Keyword(s)
PHASE LOCKED SYSTEMS
