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.

Microelectromechanical micro-relay with liquid metal contacts

Abstract: A MEM relay (110') includes an actuator, a shorting bar (52) disposed on the actuator, a contact substrate, and a plurality of liquid metal contacts (126, 128) are disposed on the contact substrate such that the plurality of liquid metal contacts are placed in electrical communication when the MEM relay is in a closed state Further, the MEM relay includes a heater (129, 129') disposed on said contact substrate wherein said heater is in thermal communication with the plurality of liquid metal contacts The contact substrate can additionally include a plurality of wettable metal contacts (125, 127) disposed on the contact substrate wherein each of the plurality of wettable metal contacts is proximate to each of the plurality of liquid metal contacts (126, 128) and each of the wettable metal contact is in electrical communication with each of the plurality of liquid metal contacts

MIMO radar: Snake oil or good idea?

Abstract: MIMO communication is theoretically superior to conventional comm. under certain conditions, and MIMO comm. also appears to be practical and cost effective in the real world for some applications. It is natural to suppose that the same is true for MIMO radar, but the situation is not so clear. Researchers claim many advantages of MIMO radar relative to phased array radars (e.g., better detection performance, better angular resolution, better angular measurement accuracy, improved robustness against RFI & ECM & multipath, etc.). We will evaluate such assertions from a system engineering viewpoint. In particular, there are serious tradeoffs of MIMO vs. phased array radars relative to cost, system complexity and risk, considering numerous real world effects that are not included in most theoretical analyses. Moreover, in many cases one can achieve essentially the same radar system improvement with phased array radars using simpler less expensive and less risky algorithms. We evaluate roughly a dozen asserted advantages of MIMO radar relative to phased arrays.

AlGaN/GaN high electron mobility transistors on Si(111) substrates

Abstract: AlGaN/GaN high electron mobility transistors (HEMTs) on silicon substrates have for the first time been realized using organometallic vapor phase epitaxy (OMVPE) Using 1 /spl Omega/-cm p-Si(111), these devices exhibited static output characteristics with low output conductance and isolation approaching 80 V Under microwave rf operation, the substrate charge becomes capacitively coupled and parasitically loads these devices thereby limiting their performance As a result, typical 03 /spl mu/m gate length devices show a 25 GHz cutoff frequency, with near unity f/sub max//f/sub T/ ratio and 055 W/mm output power A small-signal equivalent circuit incorporating elements representing the parasitic substrate loading accurately models the measured S-parameters Removal of the conductive substrate is one way to effectively eliminate this parasitic loading Through backside processing, freestanding 04-mm HEMT membranes with no thermal management were demonstrated and exhibited a significant improvement in their f/sub max//f/sub T/ ratio up to 25 at the cost of lower f/sub T/ and f/sub max/ along with an almost four-fold reduction of I/sub dss/

Dual-polarization, omni-directional antenna system

Abstract: An antenna system comprising a vertical monopole antenna coupled to a first feed on a ground plane conductor and a dipole antenna comprising a plurality of horizontal dipole antenna elements coupled to a corresponding plurality of feeds on the ground plane conductor, the plurality of dipole antenna elements being disposed about the first feed. The vertical monopole antenna comprises a plurality of monopole antenna elements, the plurality of monopole antenna elements and the plurality of dipole antenna elements being alternately radially disposed about the first feed. With such arrangement, the plurality of vertical monopole elements produce a vertically polarized beam having a predetermined (such as omni-directional) radiation pattern about the first feed, and the plurality of horizontal dipole antenna elements produce a horizontally polarized beam having a predetermined (such as omni-directional) beam pattern about the first feed; that is, the antennas are provided with substantially coincident phase centers. The monopole antenna elements do not substantially adversely affect (i.e. shadow) the omni-directional beam pattern produced by dipole antenna elements, and the dipole antenna elements do not substantially adversely affect the omni-directional beam pattern produced by the monopole antenna elements. Thus, the vertically polarized antenna elements may be disposed in close proximity to the horizontally polarized antenna elements, with no substantial degradation of the omni-directional beam patterns of either antenna, thereby allowing the total size of the antenna system to be reduced.

Polarization diverse antenna for portable communication devices

Abstract: A communications card having an antenna assembly providing polarization diversity for use with a portable computer is provided. The antenna assembly comprises two folded antennas, which may be dipoles or slot radiators, that are disposed orthogonally to one another to provide polarization diversity. Signals are carried to and from the antenna by microstrip feed lines. The microstrip lines are placed off center along each antenna slot to establish an acceptable impedance match for the antenna. The feed lines are coupled to the communications card by way of coaxial cables. The antenna assembly is coupled with the communications card in a hinged arrangement thus allowing for spatial redirection of the antenna, if desired.