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Institution

Raytheon

CompanyWaltham, Massachusetts, United States
About: Raytheon is a company organization based out in Waltham, Massachusetts, United States. It is known for research contribution in the topics: Signal & Antenna (radio). The organization has 15290 authors who have published 18973 publications receiving 300052 citations.
Topics: Signal, Antenna (radio), Radar, Turbine, Amplifier


Papers
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Journal ArticleDOI
Y. Ayasli1, R. Mozzi, J.L. Vorhaus, L.D. Reynolds, R.A. Pucel 
TL;DR: In this paper, a monolithic GaAs traveling-wave amplifier with 9dB gain and + 1-dB gain flatness in the 1-13 GHz frequency range is described, which is realized in monolithic form on a 0.1mm GaAs substrate with 50-Omega input and output lines.
Abstract: This paper describes a monolithic GaAs traveling-wave amplifier with 9-dB gain and +-1-dB gain flatness in the 1-13-GHz frequency range. The circuit is realized in monolithic form on a 0.1-mm GaAs substrate with 50-Omega input and output lines. In this approach GaAs FET's periodically load input and output microstrip lines and provide the coupling between them with proper phase through their transconductance. Experimental results and the circuit details of such a structure are discussed. Initial results of a noise analysis and predictions on the noise performance are also given.

212 citations

Journal ArticleDOI
TL;DR: In this paper, the authors present a new three-dimensional electron gun and collector design tool, which targets problem classes including gridded-guns, sheet-beam guns, multibeam devices, and anisotropic collectors.
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.

211 citations

Journal ArticleDOI
TL;DR: In this article, an ultraviolet color-magnitude diagram (CMD) spanning the hot horizontal branch (HB), blue straggler, and white dwarf populations of the globular cluster NGC 2808 was presented.
Abstract: We present an ultraviolet color-magnitude diagram (CMD) spanning the hot horizontal branch (HB), blue straggler, and white dwarf populations of the globular cluster NGC 2808. These data, obtained with the Space Telescope Imaging Spectrograph (STIS), demonstrate that NGC 2808 harbors a significant population of hot subluminous HB stars, an anomaly only previously reported for the globular cluster omega Cen. Our theoretical modeling indicates that the location of these subluminous stars in the CMD, as well as the high temperature gap along the HB of NGC 2808, can be explained if these stars underwent a late helium-core flash while descending the white dwarf cooling curve. We show that the convective zone produced by such a late helium flash will penetrate into the hydrogen envelope, thereby mixing hydrogen into the hot helium-burning interior, where it is rapidly consumed. This phenomenon is analogous to the "born again" scenario for producing hydrogen-deficient stars following a late helium-shell flash. The flash mixing of the envelope greatly enhances the envelope helium and carbon abundances that, in turn, leads to a discontinuous increase in the HB effective temperatures. We argue that the hot HB gap is associated with this theoretically predicted dichotomy in the HB properties. Moreover, the changes in the emergent spectral energy distribution caused by these abundance changes are primarily responsible for explaining the hot subluminous HB stars. Although further evidence is needed to confirm that a late helium-core flash can account for the subluminous HB stars and the hot HB gap, we demonstrate that an understanding of these stars requires the use of appropriate theoretical models for their evolution, atmospheres, and spectra.

211 citations

Proceedings ArticleDOI
T. Ko1
15 Oct 2008
TL;DR: This paper reviews developments and general strategies of stages involved in video surveillance, and analyzes the feasibility and challenges for combining motion analysis, behavior analysis, and standoff biometrics for identification of known suspects, anomaly detection, and behavior understanding.
Abstract: Surveillance cameras are inexpensive and everywhere these days but the manpower required to monitor and analyze them is expensive. Consequently the videos from these cameras are usually monitored sparingly or not at all; they are often used merely as archive, to refer back to once an incident is known to have taken place. Surveillance cameras can be a far more useful tool if instead of passively recording footage, they can be used to detect events requiring attention as they happen, and take action in real time. This is the goal of automated visual surveillance: to obtain a description of what is happening in a monitored area, and then to take appropriate action based on that interpretation. Video surveillance for humans is one of the most active research topics in computer vision. It has a wide spectrum of promising homeland security applications. Video management and interpretation systems have become quite capable in recent years. This paper looks into how hardware and software can be put together to solve surveillance problems in an age of increased concern with public safety and security. In general, the framework of a video surveillance system includes the following stages: modeling of environments, detection of motion, classification of moving objects, tracking, behavior understanding and description, and fusion of information from multiple cameras. Despite recent progress in computer vision and other related areas, there are still major technical challenges to be overcome before reliable automated video surveillance can be realized. This paper reviews developments and general strategies of stages involved in video surveillance, and analyzes the feasibility and challenges for combining motion analysis, behavior analysis, and standoff biometrics for identification of known suspects, anomaly detection, and behavior understanding.

211 citations

Journal ArticleDOI
TL;DR: In this article, the authors present analytical results for a square law detector and a Swerling case 1 fluctuating target, supplemented by simulation results for non-fluctuating target and envelope and logarithmic detector laws.
Abstract: Curves are presented showing the additional constant false-alarm rate (CFAR) loss which results when a "greatest of" logic is imple mented between the leading and lagging sets of reference cells. Thee analytical results for a square law detector and a Swerling case 1 fluctuating target are supplemented by simulation results for a nonfluctuating target, and envelope and logarithmic detector laws.

211 citations


Authors

Showing all 15293 results

NameH-indexPapersCitations
Peter J. Kahrilas10958646064
Edward J. Wollack104732102070
Duong Nguyen9867447332
Miroslav Krstic9595542886
Steven L. Suib8986234189
Gabriel M. Rebeiz8780632443
Charles W. Engelbracht8321028137
Paul A. Grayburn7739726880
Eric J. Huang7220122172
Thomas F. Eck7215032965
David M. Margolis7022717314
David W. T. Griffith6528814232
Gerhard Klimeck6568518447
Nickolay A. Krotkov6321911250
Olaf Stüve6329014268
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Performance
Metrics
No. of papers from the Institution in previous years
YearPapers
20232
20228
2021265
2020655
2019579
2018457