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.

Vacuum package fabrication of integrated circuit components

Abstract: A method for manufacturing integrated circuit device lids includes creating a lid cavity on the surface of a lid wafer, forming a sealing surface on the lid wafer that surrounds the lid cavity, and forming a trench on the lid wafer between the lid cavity and the sealing surface. The resulting structure uptakes excess sealing surface material and prevents such material from entering the lid cavity.

Exact finite-dimensional nonlinear filters

Abstract: A new nonlinear filter is derived for continuous-time processes with discrete-time measurements. The filter is exact, and it can be implemented in real time with a computational complexity that is comparable to the Kalman filter. This new filter includes both the Kalman filter and the discrete-time version of the Benes filter as special cases. Moreover, the new theory can handle a large class of nonlinear estimation problems that cannot be solved using the Kalman or discrete-time Benes filters. A simple approximation technique is suggested for practical applications in which the dynamics do not satisfy the required conditions exactly. This approximation is analogous to the so-called "extended Kalman filter" [10], and it represents a generalization of the standard linearization method.

Eruptions arising from tidally controlled periodic openings of rifts on Enceladus

Abstract: The Cassini flyby of 14 July 2005 revealed plumes of water vapour and ice associated with the 'tiger stripe' features on the surface of Saturn's icy moon Enceladus. Since then the challenge has been to explain the nature of the plumes and the forces driving them. Two papers this week offer an explanation that accounts for both the plume characteristics and the presence of hot spots without the need to assume the existence of near-surface liquid water, a requirement of some previous models. Nimmo et al. identify tidally driven lateral fault motions near the tiger stripes as the most likely drivers of heat and vapour production. And Hurford et al. show that as Enceladus orbits Saturn, the parent planet's tides make the satellite's ice flex. This may cause the tiger stripes to open and close periodically, exposing volatile gases and allowing them to be released. Plumes of gas have been seen near the south polar region of Enceladus, a small icy satellite of Saturn, and observations revealed large rifts in the crust, informally called ‘tiger stripes’. Hurford et al. report that during each orbit, every portion of each tiger stripe rift spends about half the time in tension, which allows the rift to open, exposing volatiles, and allowing eruptions: plume activity is expected to vary periodically. In 2005, plumes were detected near the south polar region of Enceladus1, a small icy satellite of Saturn. Observations of the south pole revealed large rifts in the crust, informally called ‘tiger stripes’, which exhibit higher temperatures than the surrounding terrain and are probably sources of the observed eruptions2. Models of the ultimate interior source for the eruptions are under consideration1,3,4,5. Other models of an expanding plume6 require eruptions from discrete sources, as well as less voluminous eruptions from a more extended source, to match the observations. No physical mechanism that matches the observations has been identified to control these eruptions. Here we report a mechanism in which temporal variations in tidal stress open and close the tiger-stripe rifts, governing the timing of eruptions. During each orbit, every portion of each tiger stripe rift spends about half the time in tension, which allows the rift to open, exposing volatiles, and allowing eruptions. In a complementary process, periodic shear stress along the rifts also generates heat along their lengths7,8,9, which has the capacity to enhance eruptions. Plume activity is expected to vary periodically, affecting the injection of material into Saturn’s E ring10 and its formation, evolution and structure. Moreover, the stresses controlling eruptions imply that Enceladus’ icy shell behaves as a thin elastic layer, perhaps only a few tens of kilometres thick.

Optimum pulse amplitude modulation--I: Transmitter-receiver design and bounds from information theory

Abstract: Intersymbol interference and additive noise are two common sources of distortion in data transmission systems. For pulse amplitude modulation (PAM) communication links, the combination of transmitter waveform and linear receiver that minimizes the mean-squared error arising from these sources is determined. An extension to include the effects of timing jitter is performed in a companion paper. Performance characteristics of the optimal PAM systems, showing the mean-squared error versus the signal-to-noise ratio, are determined explicitly for several examples. These characteristics are compared both with those of certain suboptimal systems and with the optimal performance theoretically attainable (OPTA), derived by combining Shannon's concepts of the capacity of a channel and the rate distortion function of a source. The optimal PAM systems are seen to perform very close to the OPTA for low signal-to-noise ratios. For high signal-to-noise ratios, however, the mean-squared error of optimal PAM systems decreases as the reciprocal of the signal-to-noise ratio, but the OPTA decreases more rapidly, except for band-limited channels. The performance of PAM systems can be improved at high signal-to-noise ratios by coding techniques. One such technique, called Shannon-Cantor coding, is discussed briefly.

Experiments Involving a Microwave Beam to Power and Position a Helicopter

Abstract: This paper describes two different experiments involving a microwavebeam and a helicopter. The first experiment utilized a CW microwavebeam to supply a small helicopter with all of the power that it neededfor its propulsion. The second experiment utilized an unmodulated CW microwave beam for supplying a position reference to the helicopterer with respect to roll, pitch, yaw, and horizontal translation. Thesecond experiment also involved the construction of a fully articulatedhelicopter and a complete control system carried on board theli-helicopter. The paper also attempts to relate the small scale experimentsand the present state of component technology to practical, full scalemicrowave-powered helicopter systems that can operate at altitudesof up to 50 000 feet.