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.

Microwave stepped-index luneberg lenses

Abstract: Since materials with a continuous variation of index of refraction were unavailable for the construction of spherical Luneberg lenses, an investigation was made of stepped-index lenses in which the desired continuous variation of index with radius was approximated by a number of constant-index spherical shells. Experimental data on two-dimensional, TE_{10} mode, stepped-index Luneberg lenses indicated that 10 shells were sufficient for 18-inch diameter lenses for use at X band. Expanded polystyrene materials, developed with dielectric constants ranging from 1.1 to 2.0 in increments of 0.1, were used to construct 10-step, 18-inch diameter, spherical Luneberg lenses. Performance data for these lenses are given at wavelengths of 3.2, 1.8, and 0.8 centimeters.

A detailed study of the radio-FIR correlation in NGC 6946 with Herschel-PACS/SPIRE from KINGFISH

Abstract: We derive the distribution of the synchrotron spectral index across NGC 6946 and investigate the correlation between the radio continuum (synchrotron) and far-infrared (FIR) emission using the KINGFISH Herschel-PACS and SPIRE data. The radio-FIR correlation is studied as a function of star formation rate, magnetic field strength, radiation field strength, and the total gas surface density. The synchrotron emission follows both star-forming regions and the so-called magnetic arms present in the inter-arm regions. The synchrotron spectral index is steepest along the magnetic arms (α_n ~ 1), while it is flat in places of giant Hii regions and in the center of the galaxy (α_n ~ 0.6−0.7). The map of α_n provides observational evidence for aging and energy loss of cosmic ray electrons (CREs) propagating in the disk of the galaxy. Variations in the synchrotron-FIR correlation across the galaxy are shown to be a function of both star formation and magnetic field strength. We find that the synchrotron emission correlates better with cold rather than with warm dust emission, when the diffuse interstellar radiation field is the main heating source of dust. The synchrotron-FIR correlation suggests a coupling between the magnetic field and the gas density. NGC 6946 shows a power-law behavior between the total (turbulent) magnetic field strength B and the star formation rate surface density Σ_(SFR) with an index of 0.14 (0.16) ± 0.01. This indicates an efficient production of the turbulent magnetic field with the increasing gas turbulence expected in actively star forming regions. Moreover, it is suggested that the B-Σ_(SFR) power law index is similar for the turbulent and the total fields in normal galaxies. On the other hand, for galaxies interacting with the cluster environment this index is steeper for turbulent magnetic fields than it is for the total magnetic fields. The scale-by-scale analysis of the synchrotron-FIR correlation indicates that the ISM affects the propagation of old/diffused CREs, resulting in a diffusion coefficient of D_0 = 4.6 × 10^(28) cm^2 s^(-1) for 2.2 GeV CREs.

Array antenna having multiple independently steered beams

Abstract: An array antenna system for forming multiple independently steered beams is described. The antenna system includes series or parallel feed circuits and phase shifters which are not disclosed directly in the signal path between the feed circuits and antenna elements included in the array antenna system.

High frequency resonant gate drive for a power MOSFET

Abstract: An efficient power MOSFET resonant gate drive circuit having a large coupled inductor between and in series with two switching transistors. The inductor prevents cross-conduction from the power bus through the drive transistors as may be caused by simultaneous turn-on due either to switching delays or single-event-upset-radiation from energetic cosmic rays. In either case, the inductor presents a high impedance for current that tries to flow through both transistors simultaneously. A center tap on the inductor is connected to the gate of the power MOSFET. An equivalent inductance resonates with the equivalent capacitance of the gate of the power MOSFET providing fast turn-on of the power MOSFET. During turn-off of the power MOSFET, one drive transistor is switched-off and the other drive transistor is switched-on. The voltage generated by the coupled inductor exceeds the magnitude of the input voltage causing a diode within the off-transistor to turn-on and return energy back to the power source, thereby further increasing the circuit efficiency.

Gas turbine engine with axial movable fan variable area nozzle

Abstract: A turbofan engine includes a fan variable area nozzle includes having a first fan nacelle section and a second fan nacelle section movably mounted relative the first fan nacelle section. The second fan nacelle section axially slides aftward relative to the fixed first fan nacelle section to change the effective area of the fan nozzle exit area.