Raytheon

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.

Modular learning strategy for signal detection in a nonstationary environment

Abstract: We describe a novel modular learning strategy for the detection of a target signal of interest in a nonstationary environment, which is motivated by the information preservation rule. The strategy makes no assumptions on the environment. It incorporates three functional blocks: (1) time-frequency analysis, (2) feature extraction, and (3) pattern classification, the delineations of which are guided by the information preservation rule. The time-frequency analysis, which is implemented using the Wigner-Ville distribution (WVD), transforms the incoming received signal into a time-frequency image that accounts for the time-varying nature of the received signal's spectral content. This image provides a common input to a pair of channels, one of which is adaptively matched to the interference acting alone, and the other is adaptively matched to the target signal plus interference. Each channel of the receiver consists of a principal components analyzer (for feature extraction) followed by a multilayer perceptron (for feature classification), which are implemented using self-organized and supervised forms of learning in feedforward neural networks, respectively. Experimental results based on real-life radar data are presented to demonstrate the superior performance of the new detection strategy over a conventional detector using constant false-alarm rate (CFAR) processing. The data used in the experiment pertain to an ocean environment, representing radar returns from small ice targets buried in sea clutter; they were collected with an instrument quality coherent radar and properly ground truthed.

Subsurface traveling wave antenna

Abstract: A subsurface traveling wave antenna for generating and receiving primarily surface waves in either the vertical or horizontal position below the surface. The antenna comprises an insulated linear radiating element terminated with a matched load for coupling a portion of the surface wave component. Impedance elements interconnecting portions of the radiating element at periodic intervals along its extent provide speed matching between the phase velocity of the wave propagating down the radiating element and the surface wave component.

Antenna mutual coupling neutralizer

Abstract: A mutual coupling neutralizer for neutralizing adverse mutual coupling between a pair of patch antennas for mobile communication system. The coupling neutralizer includes a first and second capacitor each having a first end and a second end, where the first ends are coupled to a respective patch antenna. The neutralizer further includes a high impedance transmission line connected to the second ends of the capacitors. The transmission line and capacitors are sized and configured to neutralize adverse mutual coupling between the pair of patch antennas over a predetermined frequency band. The neutralization of mutual coupling is achieved by extracting a signal present at one patch antenna and injecting the signal at the other patch antenna at a substantially equal amplitude and opposite in phase.

National land‐cover pattern data

Abstract: Land cover and its spatial patterns are key ingredients in ecological studies that consider large regions and the impacts of human activities. Because land-cover maps show only cover types and their locations, further processing is needed to extract pattern information and to characterize its spatial variability. We are producing a nationally consistent spatial database of six land-cover pattern indices: forest area density, forest connectivity, the U index (a measure of general land-use pressure by humans), land-cover connectivity, land-cover diversity, and landscape pattern types. We use the land-cover maps produced by the Multi-resolution Land Characteristics Consortium for the conterminous United States at 30-m resolution. The goal of this paper is to encourage use of the pattern data as: contextual information and independent variables for studies involving a set of field sites; indicators of landscape conditions for ecological assessments; and dependent variables in biogeographic and socioeconomic models. The new maps will be most useful in studies that require consistent and comparable land-cover pattern measurements over large regions and can be combined with the original land-cover maps and other data. The complete data sets corresponding to abstracts published in the Data Papers section of the journal are published electronically in Ecological Archives at http://esa.sdsc.edu/Archive. (The accession number for each Data Paper is given directly beneath the title.)

Liquid carbon dioxide cleaning using jet edge sonic whistles at low temperature

Abstract: A cleaning system (10) and method utilizing sonic whistle agitation to enhance the soil removal and mass transport capacity of the liquid carbon dioxide (20) at low process temperatures Sonic whistles (61) are within a cleaning chamber (40), and liquid carbon dioxide (20) is forced out of the sonic whistle jets to ultrasonically emulsify and disperse non-miscible liquids or insoluble solids, such as remove low solubility oils and greases, in the liquid carbon dioxide contained in the cleaning chamber Cleaning is accomplished at temperatures between -68 °F and 88 °F, and the temperature of the liquid carbon dioxide is typically below 32 °F