| Simulating Future GPS Clock Scenarios with Two Composite Clock Algorithms |
NOV 2010 |
23 pages |
| Authors:
Matthias Suess; Demetrios Matsakis; Charles A. Greeenhall; NAVAL OBSERVATORY WASHINGTON DC
|
 | Using the GPS Toolkit, the GPS constellation is simulated using thirty-one satellites (SV) and a ground network of seventeen monitor stations (MS). At every 15 minute measurement epoch, the monitor stations measure the time signals of all satellites above a parameterized elevation angle. Once a day the satellite clock estimates are uploaded to the satellites. Two composite clock algorithms are applied to estimate the station and satellite clocks. The first ... |
|
| Applications of GPS Provided Time and Frequency |
20 Oct 2010 |
21 pages |
| Authors:
Edward Powers; NAVAL OBSERVATORY WASHINGTON DC
|
|
| Advances in Time and Frequency Transfer From Dual-Frequency GPS Pseudorange and Carrier-Phase Observations |
Dec-2008 |
19 pages |
| Authors:
Paul Collins; Patrizia Tavella; Giancarlo Cerretto; Francois Lahaye; NATURAL RESOURCES CANADA OTTAWA (ONTARIO)
|
| Although carrier-phase observations are thought to drive the accuracy of time and frequency transfer accuracy obtainable using geodetic GPS receivers, there has been evidence of how colored noise on the pseudorange observations reduces the effectiveness of the technique. We present a new parameterization of the GPS pseudorange and carrier-phase observations, called the decoupled-clock model, where a pseudorange bias is estimated for each clock in the system as a white noise ... |
|
| Global Positioning System Timing Criticality Assessment - Preliminary Performance Results |
Dec-2008 |
23 pages |
| Authors:
James Carroll; Kirk Montgomery; JOHN A VOLPE NATIONAL TRANSPORTATION SYSTEMS CENTER CAMBRIDGE MA
|
| Precision timing and time interval (PTTI) capabilities are becoming more commonplace throughout the world. The increasing demand for and use of precise time comes with a potentially increasing risk of over-reliance on a single timing source. In addition, many precise time applications are considered critical, in that service disruption could result in severe consequences. The Global Positioning System (GPS) provides PTTI services that meet or exceed most user requirements, at ... |
|
| Time and Frequency Activities at the NASA Jet Propulsion Laboratory |
01-Nov-2007 |
17 pages |
| Authors:
R L Tjoelker; CALIFORNIA INST OF TECHNOLOGY PASADENA JET PROPULSION LAB
|
| The Jet Propulsion Laboratory, NASA's lead center for frequency and timing, develops and implements state-of-the-art atomic frequency standards, clocks, dielectric resonators, stabilized photonic links, and low-noise test and measurement capabilities in support of demanding applications for spaceflight and the NASA Deep Space Network (DSN). When implemented into the DSN Frequency and Timing Subsystem (FTS), these technologies provide precise and stable phase, frequency, and time references for NASA's deep space communication, ... |
|
| Effects of the Rooftop Environment on GPS Time Transfer |
01 JAN 2007 |
19 pages |
| Authors:
Michael A. Lombardi; Andrew N. Novick; NATIONAL INST OF STANDARDS AND TECHNOLOGY BOULDER CO TIME AND FREQUENCY DIV
|
| We examine the effects of the rooftop environment on GPS time transfer, in particular the effects of multipath reflections from nearby metallic objects. Three different antenna sites on the roof of the NIST laboratories at Boulder, Colorado, were selected, each with different multipath characteristics that we discuss. Simultaneous tests were conducted at each site with the same model of L1 band GPS receiver, but with different types of antennas. Four ... |
|
| Time-Variant Least Squares Harmonic Modeling |
07 SEP 2005 |
5 pages |
| Authors:
Qin Li; Les Atlas; WASHINGTON UNIV SEATTLE DEPT OF ELECTRICAL ENGINEERING
|
| An algorithm for harmonic decomposition of time-variant signals is derived from a least squares harmonic (LSH) technique. The estimates of harmonic amplitudes and phases are formulated as the solution of a set of linear equations for minimizing mean square error; the signal frequency is modeled by a linear or quadratic polynomial and obtained via a local search over polynomial coefficients. An initial estimate of signal frequency is necessary to reduce ... |
|
| Ultra-Wideband Analog-to-Digital Conversion Via Signal Expansion |
Sep-2005 |
15 pages |
| Authors:
Brian M Sadler; Sebastian Hoyos; CALIFORNIA UNIV BERKELEY BERKELEY WIRELESS CENTER
|
| We consider analog to digital (A/D) conversion, based on the quantization of coefficients obtained via the projection of a continuous time signal over a set of basis functions. The framework presented here for A/D conversion is motivated by the sampling of an input signal in domains which may lead to significantly less demanding A/D conversion characteristics, i.e., lower sampling rates and lower bit resolution requirements. We show that the proposed ... |
|
| Radar Waveform Design of Undersampled Signals |
01 AUG 2005 |
86 pages |
| Authors:
James Schroeder; Murali Rangaswamy; ADELAIDE UNIV (AUSTRALIA)
|
| A primary goal in radar waveform design is to achieve a prescribed discrete time radar ambiguity function. Radar waveform design to meet a given ambiguity function specification is an important issue under the waveform diversity technology. Much of the development in this area is for continuous time signals. For the discrete time case, the sampling rate becomes an important design issue. On the one hand, too low of a sampling ... |
|
| Navigation System and Method Using Directional Sensor |
27 JAN 2005 |
11 pages |
| Authors:
Benjamin A. Cray; NAVAL UNDERSEA WARFARE CENTER DIV NEWPORT RI
|
| An apparatus for determining a position includes a source which transmits a signal having a source position and a transmission time coded therein. A sensor having a directional beam pattern is positioned at the location of interest. A signal processor steers the directional beam pattern of the sensor in order to determine the direction to the signal source. A sensor processor uses a clock to find a receipt time of ... |
|
| Testing of the Methods of Real-Time MTIE Calculation |
01-Jan-2005 |
8 pages |
| Authors:
Andrzej Dobrogowski; Michal Kasznia; POZNAN UNIV OF TECHNOLOGY (POLAND)
|
| In this paper the experimental tests of the methods enabling real-time quasi-parallel assessment of Maximum Time Interval Error (MTIE) are presented. The idea of real-time quasi-parallel computation of MTIE is introduced first. Then two methods enabling real-time MTIE calculation are described. The results of computation experiments performed using several different data sequences and different computers are included. |
|
| Time and Frequency Activities at the Physikalisch-Technische Bundesanstalt |
01-Dec-2004 |
13 pages |
| Authors:
D Piester; A Bauch; J Becker; T Polewka; PHYSIKALISCH-TECHNISCHE BUNDESANSTALT BRAUNSCHWEIG (GERMANY)
|
| PTB is entrusted to provide legal time for Germany and is serving as the European node for time comparisons among institutes collaborating with the BIPM in the realization of TAI. Recent activities pursued in this context were directed towards an improved knowledge of internal delays of PTB's time comparison equipment. The standard frequency and time signal transmission via DCF77 remains the most important means to disseminate legal time, and we ... |
|
| ITU-R Special Rapporteur Group on the Future of the UTC Time Scale |
SEP 2004 |
7 pages |
| Authors:
Ron Beard; NAVAL RESEARCH LAB WASHINGTON DC
|
| As a result of issues raised by sector members of the ITU-R (international Telecommunication Union - Radiocommunications) and a letter from the Director of the Bureau International des Poids et Mesures (BIPM) to the Secretary General of the ITU, a new question, ITU-R 236/7 (2000) The Future of the UTC Timescale, was generated by ITU-R Study Group 7 (Science Services) Working Party 7A (Standard Frequency and Time Signal Services). The ... |
|
| Global Positioning System Constellation Clock Performance |
SEP 2004 |
13 pages |
| Authors:
Jay Oaks; Ken Senior; Marie M. Largay; Wilson G. Reid; Hugh Warren; NAVAL RESEARCH LAB WASHINGTON DC
|
| The Naval Research Laboratory (NRL) conducts comprehensive analyses of the Global Positioning System (GPS) atomic frequency standards under the sponsorship of the GPS Joint Program Office (JPO) and in cooperation with the 2nd Space Operations Squadron (2SOPS) at the Master Control Station (MCS) in Colorado Springs, Colorado. The purpose of the analyses is to determine the performance of the timing signals originating with the atomic frequency standards carried aboard the ... |
|
| Measurement of Anisotropic Elastic Constitutive Properties at High Temperatures |
30 DEC 2003 |
116 pages |
| Authors:
Michael L. Peterson; MAINE UNIV AT ORONO
|
| The ability of a single acoustic element to produce a compact time domain signal from a multi-mode solid cylindrical waveguide using a time- reversal mirror (TRM) is considered. Two single element longitudinal contact transducers were used to excite and receive multiple longitudinal modes in a fused quartz waveguide in a TRM experiment. The TRM is demonstrated to be effective with the limited information from a single longitudinal transducer. Experimental results ... |
|
| A New Approach to Blind Channel Identification for OFDM Systems |
SEP 2003 |
28 pages |
| Authors:
Mounir Ghogho; LEEDS UNIV (UNITED KINGDOM) DEPT OF ELECTRICAL AND ELECTRONIC ENGINEERING
|
| Orthogonal frequency division multiplexing (OFDM) is, with substantial progress in digital signal processing, becoming an important part of the telecommunications arena. The most appealing feature of OFDM is the simplicity of the receiver design due to the efficiency with which OFDM can cope with the effects of frequency-selective multipath channels. Here, we address the problem of channel estimation for OFDM systems. Exploiting receive antenna diversity, a second-order statistics-based (SOS) blind ... |
|
| Satellite Time Transfer Past and Present |
01-Dec-2002 |
13 pages |
| Authors:
Jay Oaks; James A Buisson; NAVAL RESEARCH LAB WASHINGTON DC
|
| An overview of past accomplishments is presented that shows the development of satellite time transfer techniques and capabilities that are used today. The development is traced from the concepts and early demonstrations using a single satellite to the global coverage now provided by a constellation of satellites. Predictions of future technology are compared with what has been accomplished over the last 25 years. Co-operative experiments performed jointly by colleagues of ... |
|
| The Role of Biothogonal Partners in Sampling Theory for Non Bandlimited Signals: A Review |
2002 |
5 pages |
| Authors:
Bojan Vrcelj; P. P. Vaidyanathan; CALIFORNIA INST OF TECH PASADENA DEPT OF ELECTRICAL ENGINEERING
|
| It is well known that a broad class of non bandlimited signals can be reconstructed from uniformly spaced samples by relating the problem to the inversion of a digital filter. This simple idea has given rise to many applications, some of them quite sophisticated. This includes spline interpolation, fractionally spaced equalization (FSE) of noisy channels and more recently, rational FSEs. On the theoretical front, it has given rise to the ... |
|
| Active Control of Combustor Processes |
JUN 2001 |
16 pages |
| Authors:
B. T. Zinn; M. G. Allen; A. Glezer; J. I. Jagods; Y. Neumeier; GEORGIA INST OF TECH ATLANTA
|
| This paper describes results of several studies of sensors, actuators and control systems for active control of combustor processes. First, the paper discusses the performance of an adaptive active control system (ACS) for controlling detrimental combustion instabilities. This ACS consists of an observer that determines the time dependent characteristics of the instability in real time, a adaptive controller and a fueled a injector actuator. During control, the controller sends a ... |
|
| Control Circuitry for High Speed Video Camera Operation |
28 APR 2000 |
20 pages |
| Authors:
John R. Raposa; Daniel P. Thivierge; DEPARTMENT OF THE NAVY WASHINGTON DC
|
| A device for controlling a video camera in underwater high speed photography in a first aspect includes a plurality of spaced break screen or sense coil members, a projectile for launch through the series of break screen or sense coil members, a video camera operated to video at a predetermined timing upon release of the projectile, and a source of illumination to aid in the video photography. A trigger device ... |
|
| Time and Frequency Activities at the CSIRO National Measurement Laboratory, Sydney, Australia |
Dec-1999 |
9 pages |
| Authors:
Peter T Fisk; R B Warrington; Malcolm A Lawn; Michael J Wouters; COMMONWEALTH SCIENTIFIC AND INDUSTRIAL RESEARCH ORGANIZATION LINDFIELD (AUSTRALIA)
|
| The current activities of the Time and Frequency Section of the CSIRO National Measurement Laboratory are outlined. In addition to the usual responsibilities of a national timing laboratory, these activities include: * Development of a trapped ion microwave frequency standard, * Development of reliable, low cost GPS common-view time transfer systems, * Two-way satellite time transfer |
|
| Testing the Effects of M-Code on GPS Timing Receivers |
Dec-1999 |
8 pages |
| Authors:
J Brad; I Galysh; D Koch; J White; G Landis; NAVAL RESEARCH LAB WASHINGTON DC
|
| The Naval Research Laboratory has measured the effects of several modulation schemes proposed for use as the new Global Positioning System (GPS) M-Code on the operation of existing GPS timing receivers. Three candidate codes were tested at varying power levels to quantify the effects of the new signal added to a traditional GPS signal generated by a 10-channel GPS signal simulator. The M-Codes were generated in hardware to make representative ... |
|
| Time and Frequency Activities at IEN |
Dec-1999 |
12 pages |
| Authors:
F Cordara; G Brida; A Godone; F Levi; L Lorini ;M Mascarello; S Micalizio; V Pettiti; P Tavella; G Vizio; INSTITUTO ELETTROTECNICO NAZIONALE GALILEO FERRARIS TORINO (ITALY)
|
| The Time and Frequency Department of the Istituto Elettrotecnico Nazionale (IEN), as national laboratory for time and frequency metrology in Italy, is charged of the realization and dissemination of the national time and frequency standards and the development of new frequency standards and synchronization techniques. The present status of these activities and their future developments are reported in the paper. |
|
| Recent Results with Transatlantic GeTT Campaign |
Dec-1999 |
10 pages |
| Authors:
R Dach; T Schildknecht; T Springer; G Dudle; L Prost; BERN UNIV (SWITZERLAND) ASTRONOMICAL INST
|
| A dedicated time and frequency transfer experiment over the Atlantic by GPS Carrier Phase (GPS CP) has now been running for more than one year. For this experiment a geodetic time-transfer terminal (GeTT) was installed at the PTB and another at the USNO. The data are processed in the framework of a small network of IGS stations, most of which are driven by H-masers. Frequent comparisons between GPS CP and ... |
|
| Analysis Noise, Short-Baseline Time Transfer, and a Long-Baseline GPS Carrier-Phase Frequency Scale |
Dec-1999 |
15 pages |
| Authors:
Lee A Breakiron; Ken Senior; Demetrios N Matsakis; NAVAL OBSERVATORY WASHINGTON DC
|
| The calibrated carrier-phase GPS technique promises time transfer between remote sites with 5-minute precision approaching 20 ps. Uncalibrated time transfers between many sites are routinely made available by the Earth Orientation Department of the U.S. Naval Observatory (USNO). Although important technical issues involving long-term accuracy and calibration are still being resolved, it is possible to generate sample time and frequency scales so as to anticipate the full power of the ... |
|
| Frequency Transfer Using GPS Codes and Phases: Short- and Long-Term Stability |
Dec-1999 |
10 pages |
| Authors:
P Defraigne; C Bruyninx; ROYAL OBSERVATORY BRUSSELS (BELGIUM)
|
| GPS codes and carrier phases measured by multi-channel geodetic receivers can be used for accurate frequency transfer applications when using geodetic data analysis methods. At the Royal Observatory of Belgium, previous on-site studies have shown the sensibility of the frequency transfer to the temperature variations around the hardware (GPS receiver, cable, and antenna). Now, some parts of the old set up have been improved: the GPS receiver was moved to ... |
|
| Time and Frequecy Activities at ROA |
Dec-1999 |
8 pages |
| Authors:
J Palacio; F J Galindo; R Boloix; REAL OBSERVATORIO DE LA ARMADA (SPAIN)
|
| The Real Instituto y Observatorio de la Armada (ROA) was founded in 1758 to increase the knowledge of the Spanish Navy's midshipmen in astronomy matters. Since then, the Observatory has been the astronomical center of the Spanish Navy and it is the oldest Spanish observatory. Jorge Juan, the Spanish Navy Officer, who founded the Observatory, participated in the expedition to Peru to measure the length of one degree of arc ... |
|
| Update on Time and Frequency Activities at NIST |
Dec-1999 |
10 pages |
| Authors:
T E Parker; D B Sullivan; NATIONAL INST OF STANDARDS AND TECHNOLOGY BOULDER CO TIME AND FREQUENCY DIV
|
| The mission and organization of the Time and Frequency Division of the National Institute of Standards and Technology (NIST) are reviewed and a discussion is presented of recent activities. Among the major recent milestones have been the development of cold-atom frequency standards, including the construction of a new cesium-fountain frequency standard and the design of a standard for operation on the International Space Station. In addition, the use of GPS ... |
|
| 1999 GPS Time Transfer Performance |
Dec-1999 |
12 pages |
| Authors:
Michael Rivers; Steven H Osborne; SPACE OPERATIONS SQUADRON ( 2ND) SCHRIEVER AFB CO
|
| In the 1990s, the number of military and civilian government agencies who have become dependent on GPS for accurate timing and navigation has consistently increased. The GPS Operational Control Segment (OCS), using information provided by the United States Naval Observatory (USNO), maintains the GPS timing signal well within specifications. This paper summarizes the 1999 performance of One-Way (Direct-Access) GPS time transfer for authorized users. Data from previous years will also ... |
|
| Precise Time-Transfer Experiment Using Two-Way Carrier-Phase Method Planned for ETS-VIII Satellite |
Dec-1999 |
8 pages |
| Authors:
Michito Imae; Mizuhiko Hosokawa; Yukio Takahashi; Hitoshi Kiuchi; Yasuhiro Takahashi; Hiroyuki Noda; Naokazu Hamamoto; COMMUNICATIONS RESEARCH LAB TOKYO (JAPAN)
|
| A precise time and frequency transfer between the satellite-onboard atomic clocks and the ground reference clocks has been planned for the Engineering Test Satellite-VIII (ETS-VIII) under the collaboration between the Communications Research Laboratory (CRL) and the National Space Development Agency (NASDA). We will show the plan and the status report of this experiment. ETS-VIII is a Japanese Geostationary Satellite, which will be launched in 2002. It has missions for mobile ... |
|
| Recent and Pending Improvements at the U.S. Naval Observatory |
Dec-1999 |
10 pages |
| Authors:
Demetrios M Matsakis; NAVAL OBSERVATORY WASHINGTON DC TIME SERVICE DIV
|
| The U.S. Naval Observatory (USNO) Time Service Department has recently made many operational improvements to its clock ensemble, measurement systems, computer systems, timescale algorithms, and time-transfer systems. |
|
| Independent Control of One of Normally Interdependent Light Transmission Characteristics of Optical Fiber |
11 MAY 1999 |
|
| Authors:
Robert M. Payton; DEPARTMENT OF THE NAVY WASHINGTON DC
|
 | A method and apparatus for controlling polarization, as one of a pair of interdependent light characteristics of an optical fiber, in response to a time dependent signal without the introduction of any significant variation in phase delay. A pair of transducers compress the optical fiber at spaced locations. When phase of energization of a first transducer in response to the time dependent signal is 180 deg out of phase with ... |
|
| 1998 GPS Time Transfer Performance |
Dec-1998 |
11 pages |
| Authors:
Stacy Jo Huser; Steven T Hutsell; SPACE OPERATIONS SQUADRON ( 2ND) SCHRIEVER AFB CO
|
| Every year more and more government and civilian agencies rely on GPS for accurate timing and navigation. The GPS Operational Control Segment, using information provided by the United States Naval Observatory, maintains the GPS timing signal well within specifications. This paper summarizes 1998 GPS Time Transfer performance for authorized users and relates the results to the mechanics of the GPS time steering algorithm. Data from previous years will also be ... |
|
| IRIG Serial Time Code Format |
MAY 1998 |
51 pages |
| Authors:
RANGE COMMANDERS COUNCIL WHITE SANDS MISSILE RANGE NM
|
| The 1995 version of this document defined the characteristics of the serial time code formats A, B, D, E, G, and H. This 1998 edition of the IRIG serial Time Code Formats incorporates Manchester modulation for codes so designated. This standard should be adhered to by all U.S. Government ranges and facilities where serial time codes are generated for correlation of data with time. |
|
| Method and Apparatus for Non-Invasive Detection and Analysis of Turbulent Flow in a Patient's Blood Vessels. |
17 MAR 1998 |
|
| Authors:
Norman L. Owsley; DEPARTMENT OF THE NAVY WASHINGTON DC
|
| A method and apparatus for the diagnosis of pathological turbulent arterial blood flow in a patient includes energy wave detectors for sensing at a plurality of spaced positions on the patient forces generated by turbulent arterial blood flow. The detectors generate a plurality of space time signals that are arranged in a vectorized data structure. A processor converts the vectorized data structures into an output that indicates the form of ... |
|
| An Evaluation of Frequency Domain Ensemble Averging to Improve Aircraft Stability Derivative Estimation |
MAR 1998 |
184 pages |
| Authors:
Lawrence M. Hoffman; AIR FORCE INST OF TECH WRIGHT-PATTERSONAFB OH SCHOOL OF ENGINEERING
|
| This research evaluated a process to improve aircraft stability derivative estimation results. The Have Derivatives process used overlap ensemble averaging in the frequency domain to minimize noise on the original time domain signals. The process estimated average complex frequency response functions that were then transformed back into the time domain as a set of discrete pulse responses with far less noise than the original signals. These clean signals were used ... |
|
| Analysis of Ocean Wave Fields Using the Harmonic Phase Tracking Parameter Estimation Technique |
SEP 97 |
427 pages |
| Authors:
P. A. Palo; NAVAL FACILITIES ENGINEERING SERVICE CENTER PORT HUENEME CA
|
| A uniquely new time series analysis technique called 'Harmonic Phase Tracking' (HPT) was developed and used to examine the spatial and temporal evolutionary characteristics of a hurricane wave field. The fundamental motivation was to investigate whether ocean waves were random, or if they instead self-organize into a finite number of locally stationary discrete sinusoids. Instead of the uniformly-spaced set of component frequencies inherent with the commonly-used Fourier Series (FFT) representation ... |
|
| Demodulation Processes in Auditory Perception |
01 JUN 97 |
8 pages |
| Authors:
Lawrence Feth; OHIO STATE UNIV COLUMBUS DEPT OF SPEECH AND HEARING SCIENCE
|
| The long range goal of this project was the understanding of human auditory processing of information conveyed by complex, time varying signals such as speech, music or important environmental sounds. Our work was guided by the assumption that human auditory communication is a 'modulation - demodulation' process. That is, we assume that sound sources produce a complex stream of sound pressure waves with information encoded as variations (modulations) of the ... |
|
| Report From the ITU-R Working Party 7A on Time Signals and Frequency Standard Emissions |
Dec-1996 |
8 pages |
| Authors:
Gerrit de Jong; NMI VAN SWINDEN LABORATORIUM DELFT (NETHERLANDS)
|
| The Working Party 7A (WP-7A) on Time Signals and Frequency Standard Missions is one of the four Working Parties of Study Group 7 Science Services (SG 7) of the Radiocommunication Sector of the International Telecommunication Union (ITU-R). The subjects which are addressed in the WP-7A meetings on the basis of input documents as answers to questions are: (worldwide) Standard frequency and time (T&F) dissemination from terrestrial transmitters and from satellites, ... |
|
| Real-Time 3-D Ultrasonic Diagnostic Imager for Battlefield Application |
OCT 96 |
102 pages |
| Authors:
Timothy White; Anthony M. Nicoli; Kenneth Erikson; LORAL INFRARED AND IMAGING SYSTEMS INC LEXINGTON MA
|
| This program seeks to apply a solid state, staring, ultrasonic hybrid array to demonstrate the first real-time, portable, C-scan diagnostic ultrasound medical imaging system with three-dimensional (3-D) capability for battlefield and trauma care. The objective of Phase II of the BUDI program is to demonstrate a prototype ultrasonic imager capable of high quality ultrasound imagery suitable for 3D reconstruction. Phase II is a two year effort. This report covers the ... |
|
| Time Domain Version of the Uniform Geometrical Theory of Diffraction |
FEB 96 |
165 pages |
| Authors:
P. R. Rousseau; P. H. Pathak; OHIO STATE UNIV COLUMBUS ELECTROSCIENCE LAB
|
| A time domain (TD) version of the uniform geometrical theory of diffraction which is referred to as the TD-UTD is developed to analyze the transient electromagnetic scattering from perfectly conducting objects that are large in terms of pulse width. In particular, the scattering from a perfectly conducting arbitrary curved wedge and an arbitrary smooth convex surface are treated in detail. These TD-UTD solutions are obtained in the form of relatively ... |
|
| Frequencies Used with Satellites. Part 1 |
FEB 96 |
8 pages |
| Authors:
Chen Daoming; NATIONAL AIR INTELLIGENCE CENTER WRIGHT-PATTERSON AFB OH
|
| The International Telecommunication Union has designated operating frequencies for satellites. They are scattered in Article 8 of the Radio Regulations, where it is inconvenient to look them up. In light of this, the author has compiled this material from the Radio Regulations which were revised at the 1992 World Administrative Radio Conference and from the European Space Bureau's 'Satellite Frequencies' data, and has classified it according to satellite services. However, ... |
|
| Arbitrary Waveform Generator. |
31 OCT 1995 |
|
| Authors:
Maurice J. Griffin; Glenn S. Sugawara; DEPARTMENT OF THE NAVY WASHINGTON DC
|
| This report describes a system for storing an arbitrary waveform on non-volatile random access memory (NVRAM) device and generating an analog signal using the NVRAM device. A central processing unit is used to synthesize an arbitrary waveform and create a digital representation of the waveform and transfer the digital representation to a microprocessor which, in turn, writes the digital data into an NVRAM device which has been mapped into a ... |
|
| Multidimensional Signal Coding in the Visual System |
17 SEP 95 |
125 pages |
| Authors:
Gershon Buchsbaum; PENNSYLVANIA UNIV PHILADELPHIA OFFICE OF RESEARCH ADMINISTRATION
|
| Natural images contain spatiotemporal information comprised of motion and other time varying details such as flicker. Motion in the retinal image includes object motion in the visual scene, observer motion, and eye motion. Image motion presents a significant problem for efficient coding and representation of images in the visual system. The visual system must code and interpret the visual scene while accounting for objects moving at velocities which may exceed ... |
|
| Apparatus and Method for Producing Three-Dimensional Images. |
28 FEB 1995 |
|
| Authors:
Kenneth K. Knaell; Glen R. Heidbreder; DEPARTMENT OF THE NAVY WASHINGTON DC
|
| An apparatus and method is capable of acquiring useful three-dimensional radar images from an aircraft which travels in a curvilinear path to generate only a sparsely filled synthetic array. A motion measurement unit outputs position measurements as the aircraft travels in the curvilinear path. The system includes a motion compensation and timing unit and a wave transmitter which outputs chirped radar signals. An antenna coupled to the wave generator sends ... |
|
| Observation of X-Ray Generation in a Proof-of-Principle Laser Synchrotron Source Experiment |
15 FEB 95 |
13 pages |
| Authors:
A. Ting; R. Fischer; A. Fisher; J. Krall; E. Esarey; NAVAL RESEARCH LAB WASHINGTON DC
|
| A Laser Synchrotron Source (LSS) was proposed to generate short- pulsed, tunable x-rays by Thomson scattering of laser photons from a relativistic electron beam. A proof-of-principle (p.o.p) experiment on this LSS configuration is performed. An intense laser pulse (Lambda sub 0 = 1.053 micrometers) is Thomson backscattered from a focussed relativistic electron beam. Time integrated x-ray signals from a photocathode/electron multiplier, at an electron beam energy of 650 keV and ... |
|
| The Global Positioning System: Assessing National Policies |
95 |
|
| Authors:
Scott Pace; Gerald Frost; Irving Lachow; David Frelinger; Donna Fossum; RAND CORP SANTA MONICA CA
|
| The Global Positioning System (GPS) is a U.S. military space system operated by the U.S. Air Force. The space segment of GPS consists of a constellation of 24 satellites that broadcast precise time signals. When the satellites are in view of a suitable GPS receiver, these signals aid position- location, navigation, and precision timing. GPS was developed by the U.S. Department of Defense and deployed over two decades at a ... |
|
| Wavefront Simulator for Evaluating RF Communication Array Signal Processors. |
16 AUG 1994 |
|
| Authors:
Steven B. Minarik; DEPARTMENT OF THE NAVY WASHINGTON DC
|
| A wavefront simulator that emulates plane wave propagation from multiple transmitting antennas is used to evaluate, in both a static and a dynamic manner, an array processor used in RF communications to determine the location of transmitting antennas and possibly to perform beamforming for cancelling the energy of an interfering transmitter. The wavefront simulator generates time delay signals, giving the appearance of being emitted from different transmitters or sources, mid ... |
|
| Analysis of the Effects of Surface Pitting and Wear on the Vibrations of a Gear Transmission System |
JUL 94 |
10 pages |
| Authors:
F. K. Choy; V. Polyshchuk; J. J. Zakrajsek; R. F. Handschuh; D. P. Townsend; NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CEN TER
|
| A comprehensive procedure to simulate and analyze the vibrations in a gear transmission system with surface pitting, wear, and partial tooth fracture of the gear teeth is presented. An analytical model was developed where the effects of surface pitting and wear of the gear tooth were simulated by phase and magnitude changes in the gear mesh stiffness. Changes in the gear mesh stiffness were incorporated into each gear-shaft model during ... |
|
| Global Time Transformations |
JUL 94 |
68 pages |
| Authors:
Jon B. Valente; Robert J. Vaeth; ROME LAB GRIFFISS AFB NY
|
| This report on global time transformations comes from an in-house research effort in the area of distributed-parallel computing. The distributed- parallel computing environments are multiple clock systems interconnected by communications networks. The global time transformation maps the data from these different systems into a common (i.e., global) clock for an analysis. The derivation of the global time transformation is given. The primary components of the global time transformation are the ... |
|
Reports by Keyword(s)
TIME SIGNALS
