Showing papers by "Raytheon published in 2002"

On-demand multicast routing protocol in multihop wireless mobile networks

Abstract: An ad hoc network is a dynamically reconfigurable wireless network with no fixed infrastructure or central administration. Each host is mobile and must act as a router. Routing and multicasting protocols in ad hoc networks are faced with the challenge of delivering data to destinations through multihop routes in the presence of node movements and topology changes. This paper presents the On-Demand Multicast Routing Protocol (ODMRP) for wireless mobile and hoc networks. ODMRP is a mesh-based, rather than a conventional tree-based, multicast scheme and uses a forwarding group concept; only a subset of nodes forwards the multicast packets via scoped flooding. It applies on-demand procedures to dynamically build routes and maintain multicast group membership. ODMRP is well suited for ad hoc wireless networks with mobile hosts where bandwidth is limited, topology changes frequently, and power is constrained. We evaluate ODMRP performance with other multicast protocols proposed for ad hoc networks via extensive and detailed simulation.

Building secure software: how to avoid security problems the right way

Abstract: This book defines a wide range of techniques which may be used for use case modeling. Going beyond introductory texts, it gives the bnsinc~-oriented software analyst a variety of advanced approaches which also comply with the UML specification. The book's flexible process ~rarnework is designed to be used on large, complex projects with many developers, while also being adaptible to incremental, iterative delivery scenarios. An example of a bank loan processing system is used throughout the book. The book is divided into five parts: Fundamentals; Project Initiation; two sections on the main topic, called the Advanced Use Case Modeling Framework; and a section on additional topics. The part on Fundamentals discusses the basic concepts of actors and use cases. A thorough breakdown and definition of every conceivable type of actor is presented. The part on Project Initiation presents how to scope a system and how to balance a system using the techniques of domain analysis, interface specification, and architecture definition. Domain analysis should generate what's called a domain object model, which is a starting point for object-oriented analysis. The parts on use case modeling cover a host of topics. One interesting issue discussed is whether or not to describe use cases from a purely external perspective or from an internal perspective as well. As an illustration of how current the book is, the recently popular agile development methods are mentioned throughout the book with regards to how use case modeling may be used with them. A 22-page chapter on creating test cases documents the interrelationship between use cases and test cases. This is a topic Lhat most other books ignore or gloss over. A subsequent chapter discusses organizing use cases in relation to one another using packages and activity diagrams. Change management focussing on expecting change and working within its reality is another timely topic in today's business climate. Two chapters focus specifically on determining the correct level of detail and artifact generation for a particular project. One appendix deals with using use case analysis within the Rational Unified Process (RUP). Two other appendices show all of the use case documentation and the user interface specification for the book's loan processing system example. This is far better than only having it scattered throughout the book. Anyone who is performing use case modeling in the business application domain should seriously consider this book. The variety of topics covered almost ensures that …

Trapping effects in GaN and SiC microwave FETs

Abstract: It is well known that trapping effects can limit the output power performance of microwave field-effect transistors (FETs). This is particularly true for the wide bandgap devices. In this paper we review the various trapping phenomena observed in SiC- and GaN-based FETs that contribute to compromised power performance. For both of these material systems, trapping effects associated with both the surface and with the layers underlying the active channel have been identified. The measurement techniques utilized to identify these traps and some of the steps taken to minimize their effects, such as modified buffer layer designs and surface passivation, are described. Since similar defect-related phenomena were addressed during the development of the GaAs technology, relevant GaAs work is briefly summarized.

Trading computation for bandwidth: reducing communication in distributed control systems using state estimators

Abstract: Describes a new framework for distributed control systems in which estimators are used at each node to estimate the values of the outputs at the other nodes. The estimated values are then used to compute the control algorithms at each node. When the estimated value deviates from the true value by more than a pre-specified tolerance, the actual value is broadcast to the rest of the system; all of the estimators are then updated to the current value. By using the estimated values instead of true value at every node, a significant saving in the required bandwidth is achieved, allowing large-scale distributed control systems to be implemented effectively. The stability, performance, and expected communication frequency of the reduced communication system are analyzed in detail. Simulation and experimental results validating the effectiveness and communication savings of the framework are also presented.

Phased arrays - part 1: theory and architectures

Abstract: An overview of electronically scanned array technology with a brief introduction of the basic theory and array architectures are presented. Implementations, current state-of-the-art, and future trends are briefly reviewed in Part II of this paper.

A vacuum packaged surface micromachined resonant accelerometer

Abstract: This paper describes the operation of a vacuum packaged resonant accelerometer subjected to static and dynamic acceleration testing. The device response is in broad agreement with a new analytical model of its behavior under an applied time-varying acceleration. Measurements include tests of the scale factor of the sensor and the dependence of the output sideband power and the noise floor of the double-ended tuning fork oscillators as a function of the applied acceleration frequency. The resolution of resonant accelerometers is shown to degrade 20 dB/decade beyond a certain characteristic acceleration corner frequency. A prototype device was fabricated at Sandia National Laboratories and exhibits a noise floor of 40 /spl mu/g//spl radic/(Hz) for an input acceleration frequency of 300 Hz.

Next-generation wireless communications concepts and technologies

Abstract: Next-generation wireless (NextG) involves the concept that the next generation of wireless communications will be a major move toward ubiquitous wireless communications systems and seamless high-quality wireless services. This article presents the concepts and technologies involved, including possible innovations in architectures, spectrum allocation, and utilization, in radio communications, networks, and services and applications. These include dynamic and adaptive systems and technologies that provide a new paradigm for spectrum assignment and management, smart resource management, dynamic and fast adaptive multilayer approaches, smart radio, and adaptive networking. Technologies involving adaptive and highly efficient modulation, coding, multiple access, media access, network organization, and networking that can provide ultraconnectivity at high data rates with effective QoS for Next Gare are also described.

Optomechanical uncooled infrared imaging system: design, microfabrication, and performance

Abstract: This paper presents the design, fabrication and performance of an uncooled micro-optomechanical infrared (IR) imaging system consisting of a focal-plane array (FPA) containing bi-material cantilever pixels made of silicon nitride (SiNx) and gold (Au), which serve as infrared absorbers and thermomechanical transducers. Based on wave optics, a visible optical readout system is designed to simultaneously measure the deflections of all the cantilever beams in the FPA and project the visible deflection map onto a visible charge-coupled device (CCD) imager. The IR imaging results suggest that the detection resolution of current design is 3-5 K, whereas noise analysis indicates the current resolution to be around 1 K. The noise analysis also shows that the theoretical noise-equivalent temperature difference (NETD) of the system can be below 3 mK.

Detection of a large-scale mass redistribution in the terrestrial system since 1998.

Abstract: Earth9s dynamic oblateness (J2) had been undergoing a decrease, according to space geodetic observations over the past 25 years, until around 1998, when it switched quite suddenly to an increasing trend that has continued to the present. The secular decrease in J2 resulted primarily from the postglacial rebound in the mantle. The present increase, whose geophysical cause(s) are uncertain, thus signifies a large change in global mass distribution with a J2 effect that considerably overshadows that of mantle rebound.

Assessing satellite-derived start-of-season measures in the conterminous USA

Abstract: National Oceanic and Atmospheric Administration (NOAA)-series satellites, carrying advanced very high-resolution radiometer (AVHRR) sensors, have allowed moderate resolution (1 km) measurements of the normalized difference vegetation index (NDVI) to be collected from the Earth's land surfaces for over 20 years. Across the conterminous USA, a readily accessible and decade-long data set is now available to study many aspects of vegetation activity in this region. One feature, the onset of deciduous plant growth at the start of the spring season (SOS) is of special interest, as it appears to be crucial for accurate computation of several important biospheric processes, and a sensitive measure of the impacts of global change. In this study, satellite-derived SOS dates produced by the delayed moving average (DMA) and seasonal midpoint NDVI (SMN) methods, and modelled surface phenology (spring indices, SI) were compared at widespread deciduous forest and mixed woodland sites during 1990-93 and 1995-99, and these three measures were also matched to native species bud-break data collected at the Harvard Forest (Massachusetts) over the same time period. The results show that both SOS methods are doing a modestly accurate job of tracking the general pattern of surface phenology, but highlight the temporal limitations of biweekly satellite data. Specifically, at deciduous forest sites: (1) SMN SOS dates are close in time to SI first bloom dates (average bias of +0.74 days), whereas DMA SOS dates are considerably earlier (average bias of -41.24 days) and also systematically earlier in late spring than in early spring; (2) SMN SOS tracks overall yearly trends in deciduous forests somewhat better than DMA SOS, but with larger average error (MAEs 8.64 days and 7.37 days respectively); and (3) error in both SOS techniques varies considerably by year.

The MICHELLE three-dimensional electron gun and collector modeling tool: theory and design

Abstract: The development of a new three-dimensional electron gun and collector design tool is reported. This new simulation code has been designed to address the shortcomings of current beam optics simulation and modeling tools used for vacuum electron devices, ion sources, and charged-particle transport. The design tool specifically targets problem classes including gridded-guns, sheet-beam guns, multibeam devices, and anisotropic collectors, with a focus on improved physics models. The code includes both structured and unstructured grid systems for meshing flexibility. A new method for accurate particle tracking through the mesh is discussed. In the area of particle emission, new models for thermionic beam representation are included that support primary emission and secondary emission. Also discussed are new methods for temperature-limited and space-charge-limited (Child's law) emission, including the Longo-Vaughn formulation. A new secondary emission model is presented that captures true secondaries and the full range rediffused electrons. A description of the MICHELLE code is presented.

Phased arrays-part II: implementations, applications, and future trends

Abstract: In part I of this paper, we presented the basic architectures and theory for passive and active phased arrays. Here, we review array implementation, state-of-the-art applications, and identify future trends in phased-array technology.

A comprehensive model of the quiet‐time, near‐Earth magnetic field: phase 3

Abstract: SUMMARY The near-Earth magnetic field is caused by sources in the Earth’s core, ionosphere, magnetosphere, lithosphere and from coupling currents between the ionosphere and the magnetosphere, and between hemispheres. Traditionally, the main field (low degree internal field) and magnetospheric field have been modelled simultaneously, with fields from other sources being modelled separately. Such a scheme, however, can introduce spurious features, especially when the spatial and temporal scales of the fields overlap. A new model, designated CM3 (Comprehensive Model: phase 3), is the third in a series of efforts to coestimate fields from all of these sources. This model has been derived from quiet-time Magsat and POGO satellite and observatory hourly means measurements for the period 1960‐1985. It represents a significant advance in the treatment of the aforementioned field sources over previous attempts, and includes an accounting for main field influences on the magnetosphere, main field and solar activity influences on the ionosphere, seasonal influences on the coupling currents, a priori characterization of the influence of the ionosphere and the magnetosphere on Earth-induced fields, and an explicit parametrization and estimation of the lithospheric field. The result is a model that describes well the 591 432 data with 16 594 parameters, implying a data-to-parameter ratio of 36, which is larger than several popular field models.

Radar detection method and apparatus

Abstract: A radar detection process includes computing a derivative of an FFT output signal to detect an object within a specified detection zone. In one embodiment, a zero crossing in the second derivative of the FFT output signal indicates the presence of an object. The range of the object is determined as a function of the frequency at which the zero crossing occurs. Also described is a detection table containing indicators of the presence or absence of an object within a respective radar beam and processing cycle. At least two such indicators are combined in order to detect the presence of an object within the detection zone.

Staying alive: a docking station for autonomous robot recharging

Abstract: Autonomous mobile robots are constrained in their long-term functionality due to a limited on-board power supply. Typically, rechargeable batteries are utilized that may only provide a few hours of peak usage before recharging is necessary. Recharging requires a robot to be taken offline, and attached to a battery charger via human intervention. This is unacceptable in environments where long-term autonomous capabilities are necessary. We present a method to provide long-term autonomy by implementing autonomous recharging. A recharging station design is presented, consisting of a stationary docking station and a docking mechanism mounted to a Pioneer 2DX robot. The docking station and robot docking mechanism are designed to work together, providing a mechanical and electrical connection between the charging system and the robot. Algorithms are implemented to monitor the battery voltage and control the docking procedure, as well as account for any errors that may occur. Initial experiments that demonstrate the validity of the approach and design are presented.

Magmatic activity beneath the quiescent Three Sisters volcanic center, central Oregon Cascade Range, USA

Abstract: [1] Images from satellite interferometric synthetic aperture radar (InSAR) reveal uplift of a broad ∼10 km by 20 km area in the Three Sisters volcanic center of the central Oregon Cascade Range, ∼130 km south of Mt. St. Helens. The last eruption in the volcanic center occurred ∼1500 years ago. Multiple satellite images from 1992 through 2000 indicate that most if not all of ∼100 mm of observed uplift occurred between September 1998 and October 2000. Geochemical (water chemistry) anomalies, first noted during 1990, coincide with the area of uplift and suggest the existence of a crustal magma reservoir prior to the uplift. We interpret the uplift as inflation caused by an ongoing episode of magma intrusion at a depth of ∼6.5 km.

Automotive side object detection sensor blockage detection system and related techniques

Abstract: A system is provided for detecting blockage of an automotive side object detection system (“SODS”) The system includes a blockage detection processor, which is operative to determine whether an RF leakage signal level sensed between transmit and receive antennas of the system substantially match one or more of a plurality of pattern recognition information curves If it is determined that the leakage signal level substantially matches one or more of a plurality of pattern recognition information curves, a blocked condition of the SODS is declared, as may be caused by mud, salt, ice, etc The blockage detection processor is further operative to determine whether the leakage signal exceeds a predetermined blockage threshold level If the leakage exceeds the predetermined blockage threshold level, a blocked condition of the SODS is also declared

System and method for reading license plates

Abstract: A method for reading a license plate disposed on a vehicle includes determining whether a license plate image is required, automatically processing the license plate image in response to determining that the license plate image is required, providing at least one verified image, and determining whether to manually read the license plate image by matching the license plate image with the at least one verified image.

Track association and track fusion with nondeterministic target dynamics

Abstract: Representative track fusion algorithms and track association metrics are quantitatively compared using a simple linear-Gaussian-Poisson model, under various degrees of nondeterministicity of the target dynamics, i.e., process noises, and of the initial condition uncertainty. Track fusion algorithms are compared using an analytical method, while track association metrics are evaluated by Monte Carlo simulations.

Evaluation of Biases of Satellite Rainfall Estimation Algorithms over the Continental United States

Abstract: A bias-adjusted radar rainfall product is created and used for evaluation of two satellite rainfall estimation algorithms. Three years of collocated rainfall estimates from radar, rain gauges, a microwave satellite algorithm, and a multispectral (visible through near-infrared) algorithm were collected over the continental United States from July 1998 through July 2001. The radar and gauge data are compared to determine the locations and times at which the rainfall occurrences estimated by these two sensors are in sufficient agreement for the data to be used for validation. This procedure serves as quality control for both sensors and determines the locations at which the radar has difficulty detecting rainfall and should not be used in a validation dataset. For the data remaining after quality control, the gauge data are used for multiplicative adjustment of the radar estimates to remove the radar bias with respect to the gauges. These bias-adjusted estimates are compared with the satellite rainfall estimates to observe the evolution of the satellite biases over the 3-yr period. The multispectral algorithm was under development throughout the 3-yr period, and improvement is evident. The microwave algorithm overestimates rainfall in the summer months, underestimates in the winter months, and has an east-to-west bias gradient, all of which are consistent with physical explanations and previous findings. The multispectral algorithm bias depends highly on diurnal sampling; there is much greater overestimation for the daytime overpasses. These results are applicable primarily to the eastern half of the United States, because few data in the western half remain after quality control.

Mems-tuned high power, high efficiency, wide bandwidth power amplifier

Abstract: A circuit for matching the impedance of an output load to an active device includes a transformer including a first winding having a terminal for coupling to the output of the active device and a second winding electromagnetically coupled to the first winding, and a plurality of taps, each of the plurality of taps having a first end coupled to a position on the second winding corresponding to a ratio of the second winding to first winding differing from other ones of the plurality of taps, and a second end. The matching circuit further includes a plurality of MEMS switches each having a control input for receiving a corresponding control signal, a first terminal coupled to the second end of a corresponding one of the plurality of taps, and a switched output selectively coupled to a matching junction in response to the corresponding control signal.

NPOESS VIIRS sensor design overview

Abstract: A new era in remote sensing will begin with the launch of the National Polar-orbiting Operational Environment Satellite Systems (NPOESS) Preparatory Project (NPP) spacecraft in 2005, and the multiple operational NPOESS launches in sun-synchronous orbital planes (nominally 13:30, 17:30, or 21:30 local equatorial crossing times) starting in 2008. Users of polar-orbiting environmental satellite data will see a profound improvement in the radiometric quality, spectral coverage, and spatial resolution of routinely available visible and infrared data relative to current operational civilian and military polar-orbiting systems. The improved data will be provided by the NPOESS Visible Infrared Imaging Radiometer Suite (VIIRS). VIIRS will provide Environmental Data Records (EDRs) to meet civilian and national defense operational requirements, including day and night cloud imagery, sea surface temperatures (SST), and ocean color. EDRs will be produced by ground processing of raw data records (RDRS) from the VIIRS sensor. VIIRS will replace three currently operating sensors: the Defense Meteorological Satellite Program (DMSP) Operational Line- scanning System (OLS), the NOAA Polar-orbiting Operational Environmental Satellite (POES) Advanced Very High Resolution Radiometer (AVHRR), and the NASA Earth Observing System (EOS Terra and Aqua) MODerate-resolution Imaging Spectroradiometer (MODIS). This paper describes the VIIRS all-reflective 22-band single-sensor design. VIIRS provides low noise (driven by ocean color for the reflective visible and near-IR spectral bands and by SST for the emissive mid and long-wave IR spectral), excellent calibration and stability (driven by aerosol, cloud, and SST), broad spectral coverage, and fine spatial resolution driven by the imagery EDR. In addition to improved radiometric, spectral, and spatial performance, VIIRS features DMSP OLS-like near- constant resolution, global twice-daily coverage in each orbit plane, and direct heritage to proven design innovations from the successful Sea-viewing Wide Field-of- view Sensor (SeaWiFS) and Earth Observing System (Terra) MODIS.

Transmit/receive modules

Abstract: This paper begins with a discussion of the microwave functions performed by transmit/receive (T/R) modules for phased-array antenna applications. The paper then addresses performance and cost aspects of semiconductor, packaging, and assembly technologies associated with T/R modules.