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.

How Autopilot Requirements Constrain the Aerodynamic Design of Homing Missiles

Abstract: When an aerodynamically controlled missile is used in a homing application, the transfer function of the vehicle becomes part of an overall homing and attitude control feedback loop. Therefore, the missile must be designed so that its aerodynamics meet the constraints required to accomplish homing successfully. For radar homing, these constraints are stringent enough to require an autopilot that controls the aerodynamic transfer function using body instruments and internal feedback loops. Even with an autopilot, there are limits on the aerodynamic moment parameters such as M ? and M ? that must be considered at the very beginning of the missile system design. This paper explores the nature and sources of these limits and presents numerical examples to illustrate what kinds of numbers are required.

Effective protocol for high-rate, long-latency, asymmetric, and bit-error prone data links

Abstract: A system (10) for efficiently and reliably communicating over a high-speed asymmetric communications link. A first mechanism for connecting a first device to a second device via a channel. Includes Transmission Control Protocol/Internet Protocol (TCP/IP) functionality on the first device and the second device for establishing a first TCP/IP link from the second device to the first device. Universal Datagram Protocol (UDP) functionality on the first device and the second device for transferring UDP packets from the first device to the second device.

The Star Formation History of Leo T from Hubble Space Telescope Imaging

Abstract: We present the star formation history (SFH) of the faintest known star-forming galaxy, Leo T, based on deep imaging taken with the Hubble Space Telescope (HST) Wide Field Planetary Camera 2 (WFPC2). The HST/WFPC2 color-magnitude diagram (CMD) of Leo T is exquisitely deep, extending ~2 mag below the oldest main-sequence turnoff, permitting excellent constraints on star formation at all ages. We use a maximum likelihood CMD fitting technique to measure the SFH of Leo T assuming three different sets of stellar evolution models: Padova (solar-scaled metallicity) and BaSTI (both solar-scaled and ?-enhanced metallicities). The resulting SFHs are remarkably consistent at all ages, indicating that our derived SFH is robust to the choice of stellar evolution model. From the lifetime SFH of Leo T, we find that 50% of the total stellar mass formed prior to z ~ 1 (7.6?Gyr?ago). Subsequent to this epoch, the SFH of Leo T is roughly constant until the most recent ~25?Myr, where the SFH shows an abrupt drop. This decrease could be due to a cessation of star formation or stellar initial mass function sampling effects, but we are unable to distinguish between the two scenarios. Overall, our measured SFH is consistent with previously derived SFHs of Leo T. However, the HST-based solution provides improved age resolution and reduced uncertainties at all epochs. The SFH, baryonic gas fraction, and location of Leo T are unlike any of the other recently discovered faint dwarf galaxies in the Local Group, and instead bear strong resemblance to gas-rich dwarf galaxies (irregular or transition), suggesting that gas-rich dwarf galaxies may share common modes of star formation over a large range of stellar mass (~105-109 M ?).

Semiconductor Particle Detectors: A Reassessment of the Fano Factor Situation

Abstract: The problems dealt with concern the production of electron-hole pairs in a semiconductor nuclear radiation sensor. The goal is to develop a semiphenomenological model capable of describing the present experimental situation from the standpoint of yield, variance and bandgap dependence. We proceed on the premise that ?, the average amount of radiation energy consumed per pair, can be accounted for by a sum of three contributions: the intrinsic bandgap (EG), optical phonon losses r(h?R), and the residual kinetic energy (9/5)EG. Both the bandgap and the temperature dependence of pair-creation energies conform to this model and suggest that optical phonon losses remain essentially constant [0.5 ? r(h?R) ? 1.0 eV]. Fano-factor variations are found to reflect the relative weight of phonon losses [? = r(h?R)/EG], but residual energy fluctuations govern the statistical behavior for ?2 ? 0.3; an application to Ge detectors yields good agreement with the best measurements available (F ? 0.13). Finally, it is shown that materials such as Si or CdTe (1.0 ? EG ? 1.5 eV) provide optimized media in terms of the "ultimate" resolution capability.

Semiconductor structures having dual surface via holes

Abstract: A semiconductor structure having an active layer formed over a first surface of a substrate. The semiconductor structure includes an electrode formed over a first surface of the structure. A conductive layer is formed over a second surface of the substrate. A conductor section passes through the semiconductor structure between the electrode and the conductive layer. The conductor section includes two conductive elements, one having a first end connected to the electrode and a second end terminating in the semiconductor structure; and the other conductive element having a first end connected to the conductive layer and a second end connected to the second end of the first conductive element. The second end terminates at, or in, an etch resistant layer disposed in the semiconductor structure between the active layer and the substrate. The method for forming the conductive sections includes etching the second via hole from the second surface of the substrate until the etching reaches an etch resistant layer. The walls of the second via hole and exposed portions of the conductive material covering the walls of the first via hole are covered with an electrically conductive material.