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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
TL;DR: In this article, the noise figure of a general linear amplifier is derived using the condition of linearity and the requirement that the commutator brackets of the pertinent operators are conserved in the amplification.
Abstract: The classical definition of noise figure, based on signal-to-noise ratio, is adapted to the case when quantum noise is predominant. The noise figure is normalized to "uncertainty noise." General quantum mechanical equations for linear amplifiers are set up using the condition of linearity and the requirement that the commutator brackets of the pertinent operators are conserved in the amplification. These equations include as special cases the maser, the parametric amplifier, and the parametric up-converter. Using these equations the noise figure of a general amplifier is derived. The minimum value of this noise figure is equal to 2. The significance of the result with regard to a simultaneous phase and amplitude measurement is explored.

288 citations

Journal ArticleDOI
TL;DR: In this article, an approach is evaluated for the estimation of soil moisture at high resolution using satellite microwave and optical/infrared (IR) data, which can be applied to data acquired by the Visible/Infrared Imager Radiometer Sensor Suite (VIIRS) and a Conical Scanning Microwave Imager/Sounder (CMIS), planned for launch in the 2009-2010 time frame under the National Polar-Orbiting Operational Environmental Satellite System (NPOESS).
Abstract: An approach is evaluated for the estimation of soil moisture at high resolution using satellite microwave and optical/infrared (IR) data. This approach can be applied to data acquired by the Visible/Infrared Imager Radiometer Sensor Suite (VIIRS) and a Conical Scanning Microwave Imager/Sounder (CMIS), planned for launch in the 2009–2010 time frame under the National Polar-Orbiting Operational Environmental Satellite System (NPOESS). The approach for soil moisture estimation involves two steps. In the first step, a passive microwave remote sensing technique is employed to estimate soil moisture at low resolution (∼25 km). This involves use of a simplified radiative transfer model to invert dual-polarized microwave brightness temperature. In the second step, the microwave-derived low-resolution soil moisture is linked to the scene optical/IR parameters, such as Normalized Difference Vegetation Index (NDVI), surface albedo, and Land Surface Temperature (LST). The linking is based on the ‘Universal Triangle’ ...

286 citations

Journal ArticleDOI
TL;DR: It is established that Alice can remain covert with a transmit power that does not decrease with $n$ even when Willie employs an optimal detector.
Abstract: Recent work has established that when transmitter Alice wishes to communicate reliably to recipient Bob without detection by warden Willie, with additive white Gaussian noise (AWGN) channels between all parties, communication is limited to $\mathcal {O}(\sqrt {n})$ bits in $n$ channel uses. However, this assumes that Willie has an accurate statistical characterization of the channel. When Willie has uncertainty about such and his receiver is limited to a threshold test on the received power, Alice can transmit covertly with a power that does not decrease with $n$ , thus conveying $\mathcal {O}(n)$ bits covertly and reliably in $n$ uses of an AWGN channel. Here, we consider covert communication of $\mathcal {O}(n)$ bits in $n$ channel uses while generalizing the environment and removing any restrictions on Willie’s receiver. We assume that an uninformed “jammer” is present to help Alice, and we consider AWGN and block fading channels. In some scenarios, Willie’s optimal detector is a threshold test on the received power. When the channel between the jammer and Willie has multiple fading blocks per codeword, a threshold test on the received power is not optimal. However, we establish that Alice can remain covert with a transmit power that does not decrease with $n$ even when Willie employs an optimal detector.

277 citations

Patent
29 Dec 1980
TL;DR: In this article, an AWTSS is made up of an improved synthetic aperture radar for generating radar maps with various degrees of resolution required for navigation of an aircraft and detection of ground targets in the presence of electronic countermeasures and clutter.
Abstract: An AWTSS is shown to be made up of an improved synthetic aperture radar (SAR) for generating radar maps with various degrees of resolution required for navigation of an aircraft and detection of ground targets in the presence of electronic countermeasures and clutter. The SAR consists, in effect, of four frequency-agile radars sharing quadrants of a single array antenna mounted within a radome on a "four axis" gimbal with a sidelobe cancelling subarray mounted at the phase center of each quadrant. Motion sensors are also mounted on the single array antenna to provide signals for compensating for vibration and stored compensating signals are used to compensate for radome-induced errors. In addition, a signal processor is shown which is selectively operable to generate radar maps of any one of a number of desired degrees of resolution, such processor being adapted to operate in the presence of clutter or jamming signals.

276 citations

Journal ArticleDOI
24 Aug 2011-JAMA
TL;DR: There was no significant difference in the rate of MACEs observed in patients receiving anti-IL-12/IL-23 antibodies or anti-TNF-α treatments in adults, and this study may have been underpowered to identify a significant difference.
Abstract: Context Ustekinumab and briakinumab, monoclonal antibodies to the shared p40 subunit of interleukin (IL)-12 and IL-23, have shown efficacy in treating chronic plaque psoriasis (CPP). Preliminary reports of major adverse cardiovascular events (MACEs) in psoriasis patients receiving anti–IL-12/23 agents have prompted concern. Objective To evaluate a possible association between biologic therapies for CPP and MACEs via meta-analysis. Data Sources Randomized controlled trials (RCTs) of anti–IL-12/23 (ustekinumab and briakinumab) agents and anti–tumor necrosis factor α (TNF-α) agents (adalimumab, etanercept, and infliximab) used in treating CPP were reviewed using the Cochrane Central Register of Controlled Trials, ClinicalTrials.gov, and Ovid MEDLINE from database inception to May 2011. The results of registered nonpublished completed studies were procured through abstract publications or poster presentations. Study Selection Randomized, placebo-controlled, double-blind, monotherapy studies (with safety outcome data for MACE) of IL-12/23 antibodies and anti–TNF-α agents in adults. Studies of psoriatic arthritis were excluded. Data Extraction Two investigators independently searched data while 6 investigators reviewed the abstracted data. Results A total of 22 RCTs comprising 10 183 patients met the predefined inclusion criteria. The primary outcome measure was MACE, a composite end point of myocardial infarction, cerebrovascular accident, or cardiovascular death during the placebo-controlled phase of treatment in patients receiving at least 1 dose of study agent or placebo. Absolute risk differences were used as an effect measure. There was no evidence of statistical heterogeneity across the studies using the I 2 statistic (I 2 = 0), allowing for combination of trial results using the Mantel-Haenszel fixed-effects method. During the placebo-controlled phases of the anti–IL-12/23 studies, 10 of 3179 patients receiving anti–IL-12/23 therapies experienced MACEs compared with zero events in 1474 patients receiving placebo (Mantel-Haenszel risk difference, 0.012 events/person-year; 95% confidence interval [CI], −0.001 to 0.026; P =.12). In the anti–TNF-α trials, only 1 of 3858 patients receiving anti–TNF-α agents experienced a MACE compared with 1 of 1812 patients receiving placebo (Mantel-Haenszel risk difference, −0.0005 events/person-year; 95% CI, −0.010 to 0.009; P = .94). Conclusions Compared with placebo, there was no significant difference in the rate of MACEs observed in patients receiving anti–IL-12/IL-23 antibodies or anti–TNF-α treatments. This study may have been underpowered to identify a significant difference.

275 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