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.

Radiance and Jacobian Intercomparison of Radiative Transfer Models Applied to HIRS and AMSU Channels

Abstract: The goals of this study are the evaluation of current fast radiative transfer models (RTMs) and line-by-line (LBL) models. The intercomparison focuses on the modeling of 11 representative sounding channels routinely used at numerical weather prediction centers: seven HIRS (High-resolution Infrared Sounder) and four AMSU (Advanced Microwave Sounding Unit) channels. Interest in this topic was evidenced by the participation of 24 scientists from 16 institutions. An ensemble of 42 diverse atmospheres was used and results compiled for 19 infrared models and 10 microwave models, including several LBL RTMs. For the first time, not only radiances, but also Jacobians (of temperature, water vapor, and ozone) were compared to various LBL models for many channels. In the infrared, LBL models typically agree to within 0.05-0.15 K (standard deviation) in terms of top-of-the-atmosphere brightness temperature (BT). Individual differences up to 0.5 K still exist, systematic in some channels, and linked to the type of atmosphere in others. The best fast models emulate LBL BTs to within 0.25 K, but no model achieves this desirable level of success for all channels. The ozone modeling is particularly challenging. In the microwave, fast models generally do quite well against the LBL model to which they were tuned. However significant differences were noted among LBL models. Extending the intercomparison to the Jacobians proved very useful in detecting subtle and more obvious modeling errors. In addition, total and single gas optical depths were calculated, which provided additional insight on the nature of differences. Recommendations for future intercomparisons are suggested.

W-band GaN power amplifier MMICs

Abstract: An advanced high power, high frequency GaN semiconductor process has made possible the design and fabrication of W-band power amplifier MMICs with unprecedented performance. The key enabling semiconductor technology is a 150 nm T-gate GaN HEMT with an output power exceeding 300mW and a peak PAE (power added efficiency) of 37%. With this process, W-band power amplifier MMICs have been designed and fabricated that demonstrate output powers of 1.7 watts, power added efficiencies greater than 20%, and small signal gains of 21 dB. In addition, the compactness of these MMIC designs have allowed for MMIC power densities (MMIC output power relative to MMIC area) exceeding 1/2 watt/mm2.

Opportunistic Cooperation in Cognitive Femtocell Networks

Abstract: We investigate opportunistic cooperation between unlicensed secondary users and legacy primary users in a cognitive radio network. Specifically, we consider a model of a cognitive network where a secondary user can cooperatively transmit with the primary user in order to improve the latter's effective transmission rate. In return, the secondary user gets more opportunities for transmitting its own data when the primary user is idle. This kind of interaction between the primary and secondary users is different from the traditional dynamic spectrum access model in which the secondary users try to avoid interfering with the primary users while seeking transmission opportunities on vacant primary channels. In our model, the secondary users need to balance the desire to cooperate more (to create more transmission opportunities) with the need for maintaining sufficient energy levels for their own transmissions. Such a model is applicable in the emerging area of cognitive femtocell networks. We formulate the problem of maximizing the secondary user throughput subject to a time average power constraint under these settings. This is a constrained Markov Decision Problem and conventional solution techniques based on dynamic programming require either extensive knowledge of the system dynamics or learning based approaches that suffer from large convergence times. However, using the technique of Lyapunov optimization, we design a novel greedy and online control algorithm that overcomes these challenges and is provably optimal.

Biological warfare agent sensor system employing ruthenium-terminated oligonucleotides complementary to target live agent DNA sequences

Abstract: A sensor system and method are provided that are capable of the real-time detection of target live microorganisms, such as biological warfare agents. The sensor system includes a highly-sensitive, highly-selective sensor cell that comprises a single-stranded oligonucleic acid sequence that is complementary to a portion of the DNA of a target live microorganism, the oligonucleic acid having been modified with the covalent attachment of electron donor and acceptor moieties. In the presence of the targeted microorganism, hybridization occurs between the modified oligonucleic acid and the microorganism's DNA, such that the electron conductance between the electron transfer moieties greatly increases, thereby providing a means of detecting the presence of the target live microorganism. Aside from the sensor cell, the sensor system also includes an inlet port in the sensor cell wall by which to introduce a sample from the fluid environment into the sensor cell; a cell wall disrupter to release the nucleic acid of the fluid sample into the sensor cell; an electron transfer rate measuring system to gauge the electron transfer rate between the electron transfer moieties of the modified oligonucleic acid; a power source; a microcontroller to analyze the measured electron transfer rate for evidence of hybridization; and a communication system for relaying information regarding the presence or absence of the target live microorganism to the user of the sensor system. It is contemplated that the sensor system, exclusive of a battery and pump pack, will be only slightly larger than a pack of cigarettes and light enough to be comfortably worn and carried by personnel.