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.

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.

Using immersive game-based virtual reality to teach fire-safety skills to children

Abstract: Virtual reality (VR) has been used both to simulate situations that are too dangerous to practice in real life and as a tool to help children learn. This study was conducted as part of a larger more comprehensive long-term research project which aims to combine the two techniques and demonstrate a novel application of the result, using immersive VR to help children learn about fire hazards and practice escape techniques. In the current study, a CAVE was used to immerse participants in a fire scene. To improve the children’s motivation for learning over prior VR fire-safety training methods, game-like interface interaction techniques were used and students were encouraged to explore the virtual world. Rather than being passive viewers, as in prior related studies, the children were given full control to navigate through the virtual environment and to interact with virtual objects using a game pad and a 6DOF wand. Students identified home fire hazards with a partner and then practiced escaping from a simulated fire in the virtual environment. To test for improved motivation, a user study was completed. Results indicate that students were more engaged by the new game-like learning environment and that they reported that they found the experience fun and intriguing. Their enhanced enthusiasm for what is relatively standard fire-safety information demonstrates the promise of using game-based virtual environments for vital but otherwise tedious fire-safety skills training for children.

Motion Compensation for Synthetic Aperture Radar

Abstract: A generalized motion compensation approach applicable to all SAR modes, i.e., strip mapping (side-looking or squint), spotlight (or telescope) mapping, and Doppler beam sharpened mapping (DBS), is described. The basic concept is the formation for unit vector ? and the slaving of the real illuminating antenna and the processed synthetic antenna to this unit vector. The amount of motion compensation which is required is developed in terms of transfer curves for the main motion reduction paths, i.e., translational, rotational (lever arm), and real antenna stabilization. The transfer curves are obtained by dividing the expected motion spectrum by the required sensitivity spectrum. The most critical motion reduction path for typical parameters is shown to be the translational path. The lever arm and real antenna stabilization paths are less critical, but must also be implemented.

Digital interpolation beamforming for low-pass and bandpass signals

Abstract: Digital time-domain beamforming requires that samples of the sensor signals be available at a sufficient rate to realize accurate time delays for beam steering. For many applications, this input rate, which may be significantly higher than the Nyquist rate required for waveform reconstruction, places stringent requirements on A/D converter hardware and transmission cable bandwidth. Recently, a technique referred to as digital interpolation beamfonning was introduced which greatly relaxes the sampling requirement and provides substantial hardware savings through more flexible design options. In this approach, the sensor channels need only be sampled at a rate which satisfies aliasing requirements. The vernier beam-delay increments are then synthesized using digital interpolation which can be implemented at the beamformer input or output to minimize digital processing complexity. Previously, this concept was presented for the case of "low-pass" signals. This paper extends this work by examining the relationship between interpolation and beamforming for the important class of "bandpass" signals. Specifically, sampling methods are discussed whereby the original waveform can be reconstructed from samples taken at a rate consistent with the bandwidth of the bandpass signal. Beamformer implementations are presented which utilize these bandwidth-sampling techniques in conjunction with interpolation and which compute beam output points at the generally low rate dictated by the signal bandwidth. The interpolation beamformer achieves time-delay quantization (beam-steering accuracy) independent of both the input and output sampling rates. This approach generally requires less hardware than conventional procedures. Interpolation falter characteristics dictated by the bandwidth-sampling procedure are described and efficient methods of implementation employing nonrecursive digital bandpass and low-pass filters are presented.

Ferrite phase shifter and phase array radar system

Abstract: A phase shifter comprises a substrate, a ground plane formed on a first surface of the substrate, a support structure positioned on a second surface of the substrate opposite the first surface, three parallel, non-co-planar microstrip lines supported by the support structure above the second surface of the substrate, a ferrite element supported by the support structure between the second surface of the substrate and the three non-co-planar microstrip lines, and means for applying a magnetic field to the ferrite element.