Tech Briefs

Software-Defined Radios for Urban and Indoor Navigation

Software-defined radios (SDRs) are being developed to provide positioning and communication (POSCOMM) services inside buildings and tunnels, under tree canopies, and in other environments in which local radio- communication systems are accessible but Global Positioning System (GPS) signals are not present or are degraded. These SDRs could be especially helpful for teams of first responders (e.g., firefighters), and military personnel operating in urban settings. These SDRs are capable of navigating by use of GPS signals and can switch over to time-of-arrival (TOA) pseudolite navigation when GPS signals become unavailable, provided that signals from suitably placed TOA pseudolite transmitter nodes are available.

Posted in: Briefs, Electronics & Computers
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Conjugated Polymers Having High Charge-Carrier Mobilities

A three-year research project encompassed multiple studies of (1) polymer semiconductors that exhibit relatively high electric-charge- carrier mobilities and (2) applications of these polymers in electronic (including optoelectronic and nanoelectronic) devices. Although these polymers are of broad importance to all polymer semiconductor devices — including light-emitting diodes, photovoltaic cells, photodetectors, and electrophotographic imaging devices — the focus in this project was largely upon the use of these polymers in thin-film transistors, organic light-emitting diodes, and related light-emitting transistors.

Posted in: Briefs, Electronics & Computers
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Incorporating Functional Fillers into Silicone Elastomer Systems

Silicones can be developed into fluids, gels, adhesives, elastomers, and resins designed with unique properties that make them ideal for specific application uses in the defense and aerospace industries. Silicones are most widely known for their ability to maintain elastomeric properties in extreme conditions, but an additional benefit of these materials is the ability to incorporate large amounts of fillers that can impart properties such as electrical and thermal conductivity, and radar-absorbing characteristics. Silicone materials appear in a wide variety of material compositions, and this broad range of material compositions makes silicone a viable option to endless numbers of optic applications.

Posted in: Briefs, Materials, Optics, Composite materials, Elastomers, Materials properties, Silicon alloys
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Gold-Based Nanoparticle Liquids for Electronic Applications

Electrically conductive, solventless nanoparticle liquids, consisting of gold nanoparticles chemically functionalized with large organic molecular groups, have been investigated for potential utility in electronic and electrical applications. These and other solventless nanoparticle liquids, including electrically nonconductive ones, have been topics of recent research directed toward understanding and exploiting their unusual properties. The most obvious unusual property is that a collection of nanoparticles of this type can flow in a liquid-like fashion, notwithstanding the absence of free solvent molecules. By modifying the attractive and repulsive forces between the nanoparticles through modifications of the surface chemistry of the organic ligands, the properties of the resulting nanoparticle liquids can be tailored for specific applications.

Posted in: Briefs, Materials
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Dimensional Stabilization of Composite Space Structures

A research project has yielded progress on several fronts toward the goal of minimizing thermal and aging distortions of composite-material (specifically, polymer- matrix/graphite-fiber) outer-space structures that are required to retain precise dimensions and shapes. The achievements of this project are also applicable to terrestrial composite-material structures to the extent to which various environmental effects can be properly taken into account. Examples include effects of expansion caused by absorption of atmospheric moisture (similar to effects of purely thermal expansion) and effects of outgassing of volatile constituents of polymers (effects of out-gassing are more pronounced in the outer-space vacuum).

Posted in: Briefs, Materials
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Adaptive Deblurring of Noisy Images

An algorithm for adaptive deblurring of images has been designed to be less adversely affected by image noise than are prior deblurring algorithms. The need for this or another noise-tolerant deblurring algorithm arises as follows: For a typical imaging instrument, in which the blurring function (also known as the point-spread function) approximates a Gaussian function in the spatial-frequency domain, a simplistic spatial-frequency-domain deblurring function equal to the inverse of the blurring function magnifies the noise at high spatial frequencies. In the present adaptive deblurring algorithm, the spatial-frequency-domain deblurring function is the product of (1) the inverse of spatial-frequency-domain blurring function and (2) a smoothing or low-pass filter function denoted variously as a power window or a P-deblurring filter function (wherein "P" signifies "power"). The term "adaptive" in the name of the algorithm characterizes the process for choosing the parameters of the power window.

Posted in: Briefs, Physical Sciences
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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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