Tech Briefs

Implementing a GPS Waveform Under the SCA

A continuing development effort focuses on implementation of a Global Positioning System (GPS) waveform under the Software Communications Architecture (SCA). [As used within the special technological discipline of the SCA, "waveform" signifies not only a waveform in the commonly understood sense of the word, but also subsystems and components for receiving and transmitting the waveform; subsystems for processing the information conveyed by the waveform; subsystems that perform ancillary communication and control services relevant to the role of the affected software-defined radio (a transmitter, receiver, or transceiver) as a node in a data-communication network; and any or all of the aforesaid information and services.] The intent is to optimize GPS services by providing position and time information as an embedded waveform within a software-defined radio (SDR), rather than using additional GPS chip sets to provide the information. It is further intended that the GPS waveform first will be used to provide position and time information in Joint Tactical Radio System (JTRS) radios. [The JTRS is a family of military SDRs, waveforms, and cryptographic algorithms designed under the SCA.] The JTRS radios are reprogrammable to run a family of special waveforms that utilize carrier frequencies from 2 MHz to 2 GHz — a frequency range that includes the 1.2- and 1.5-GHz GPS frequencies.

Posted in: Briefs, Physical Sciences
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Nanodevices Based on Actin-Filament End-Tracking Motors

In a continuing research project, nanoscale actuators based on actin-filament end- tracking motors have been synthesized and characterized. It is envisioned that such actuators will eventually be utilized, variously, as molecular shuttles in biosensor devices or as nanoscale biomotors for effecting selection or separation of target microorganisms or molecules. In addition, this research is expected to enhance the fundamental understanding of molecular motors, both in vitro and in vivo and lead to modification of previously developed biomolecular machines and nanobiostructures to make them perform new functions. Some nanoscale actuators like those developed in this research may prove useful as components of micro- and nanofluidic systems. By contributing to understanding of how living cells convert chemical energy into mechanical work during actin-based and microtubule-based cell motility in cell crawling and cell mitosis, this research may lead to development of new therapeutic agents for combating invasive and metastatic cancers, gouty arthritis, Wiskott Aldrich syndrome, and those neurodegenerative disorders linked to loss of functional synapses.

Posted in: Briefs, Physical Sciences
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Tethered, Remotely Operated Miniature Submarine

A tethered, remotely operated, armed underwater vehicle has been conceived to satisfy a need for an uninhabited vehicle for Navy missions in which positive identification of targets is needed. Examples of such missions include those involving detection of swimmers and neutralization of mines. Unarmed versions of the vehicle might also be useful in civilian applications involving underwater inspections under hazardous conditions.

Posted in: Briefs, Mechanical Components
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Arcing and Vibration Tests of High-Power Patch Antennas

Electric-breakdown and vibration tests were performed on one-patch and two-patch versions of a prototype of a patch antenna designed to radiate a continuous- wave or pulsed signal in the S band (1.5 to 4 GHz) having a spectral width of 420 MHz and a peak power that could exceed 2 kW. This antenna is being developed for military use in neutralizing unattended improvised explosive devices. The patch antenna configuration was chosen for this development because it offers an efficient, less-bulky alternative to a conventional horn microwave antenna design.

Posted in: Briefs, Physical Sciences
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Antenna Electronically Steered Using MEMS Phase Shifters

An experimental phased-array microwave antenna assembly includes an array of eight patch antenna elements connected to Microelectromechanical System (MEMS) phase shifters, by means of which the directional radiation pattern of the antenna can be controlled electronically. The antenna and the MEMS-based phase shifters were designed for a nominal operating frequency of 17 GHz. In addition, some 35-GHz MEMS phase shifters were designed, built, and tested. This work is part of a continuing effort to develop relatively inexpensive electronically steerable antennas.

Posted in: Briefs, Physical Sciences
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Design Study of a C-Band Crestatron

Total Efficiencies of the designed crestatron and a comparable complex-gain-optimized TWT as functions of frequency were predicted by computational simulation.A design study of a crestatron that would operate in the frequency range from 3 to 6 GHz (which overlaps with the C band) has been performed. The basic crestatron concept was developed during the 1950s. The present interest in crestatrons is spurred by the prospect of realizing compact, efficient, high-power, high-gain microwave transmitters in which crestatrons would be combined with low-noise, solid-state drivers into microwave power modules (MPMs). Such transmitters and MPMs could be attractive for applications in which there are severe constraints on volume and weight.

Posted in: Briefs, Electronics & Computers
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Protection Schemes for Advanced Shipboard Electrical Systems

A research program has made progress toward the development of schemes for protection against faults in next-generation DC zonal shipboard electrical systems (DC SESs) and for configuration management in these systems to enable surviving parts of the systems to continue to distribute electric power to critical loads. Computational simulations of a representative prototype DC SES have shown that these schemes could afford protection at a system level (in contradistinction to a local level), thereby imparting, to the DC SES, an intended capability for self-healing.

Posted in: Briefs, Electronics & Computers, Architecture, Electrical systems, Reliability, Marine vehicles and equipment
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