Tech Briefs

Analysis of Clustering Tools for Moving Target Indication

Current and future forces operating in urban environments need the capability to detect slow-moving personnel inside buildings. To accomplish this, a time-domain approach was developed that uses a low-frequency, ultra-wideband (UWB) radar with a transmit pulse capable of penetrating through the wall. The UWB corresponds to a high-range resolution that gives the capability to better locate the moving target (MT). Previously, the effectiveness of a time-domain, moving target indication (MTI) approach was demonstrated for detecting moving personnel inside wood and cinderblock structures, moving personnel walking in nonlinear trajectories, and multiple moving personnel walking in linear trajectories.

Posted in: Briefs, Electronics & Computers, Mathematical models, Imaging, Radar, Military vehicles and equipment

Considering Software Protection for Embedded Systems

Given the current trend of reprogrammable embedded devices within the Department of Defense and industry, attention needs to be refocused on the benefits or measurability of software protection applied to this domain. Modern reconfigurable embedded systems consider circuits as software and the tamper methods applicable to physical circuits as new threats to a broadened definition of software.

Posted in: Briefs, Information Technology, Cryptography, Cyber security, Embedded software, Integrated circuits, Risk assessments

Field-Programmable Gate Array-Based Software-Defined Radio

There are existing wideband communications systems that were built using field-programmable gate array (FPGA)-based software-defined radio (SDR) designs. Despite the inherent advantages of these systems, some are functionally restricted by limited output bandwidth.

Posted in: Briefs, Electronics & Computers, Integrated circuits, Radio equipment, Wireless communication systems

FPGA-Based System for Tracking Digital Information Transmitted Via Peer-to-Peer Protocols

Peer-to-peer (P2P) networking has changed the way users search for, send, and receive digital information over the Internet. Instead of relying on interactions with centralized servers to upload and download digital content, users now share content directly with other users. While peer-to-peer networking provides new and powerful applications for the legitimate distribution of digital information, it is also being used for many illicit purposes as well.

Posted in: Briefs, Information Technology, Cloud computing, Cyber security, Integrated circuits, Data management

Simulation Concept Exploits Tools for Computing Hybrids

The Simulation Concept – How to Exploit Tools for Computing Hybrids (SCHETCH) project is exploring the design modeling and simulation (M&S) process for developing advanced computing technology for future intelligent systems. The goal is to integrate new alternative computing concepts with existing silicon-based computing technology in hybrid computing architectures. A main premise behind this project is that, for an alternative-computing concept to move from the laboratory to a technology ready for the field, the proper M&S process must be in place. Adaptation and integration of commercially available software provides an opportunity to take advantage of existing functionality without investing time into developing new tools for new concepts. It was decided to focus on hardware concepts rather than software implementations, initially looking at three concepts: nanomechanical quantum computing, membrane computing, and deoxyribonucleic acid (DNA) computing.

Posted in: Briefs, Electronics & Computers, Computer simulation, Architecture, Computer software / hardware, Product development

Asymmetric Core Computing for High-Performance Applications

High-performance computing (HPC) users have traditionally relied upon two things to supply them with processing power: speed of the central processing units (CPUs) and the scalability of the system. There are problems with this approach. Physical limitations are curtailing clock speed increases in general-purpose CPUs, the von Neumann load-execute-store approach does not map well to every computational problem, and systems of thousands of processors might be very inefficient, depending upon processor interconnection limitations.

Posted in: Briefs, Electronics & Computers, Architecture, Computer software / hardware, Integrated circuits

Novel Wavelength Standards in the Near Infrared

The goal of this work was to develop a new class of portable optical frequency references based on sub-Doppler spectroscopy inside gas-filled, hollow-core photonic bandgap (PBG) optical fiber. The change in line width with core size, and narrower transitions inside a new “kagome” structured optical fiber, were demonstrated. A simplified and more compact method for observing saturated absorption spectroscopy in half-sealed photonic bandgap fibers, called the “reflected pump technique,” was realized. Two systems, each consisting of a narrow-line fiber laser locked to the P(13) transition in acetylene, were constructed. By comparing those two systems, it was possible to obtain stability data on the fiber-filled references.

A mode-locked Cr:forsterite laser was developed and stabilized to a GPS-disciplined Rb clock with which to characterize the gas-filled, hollow-fiber optical frequency references. It was found that these lasers offer noisier “f0” beats than Ti:sapphire lasers, but a method was found to dramatically reduce the f0 beat width. A study was initiated into the source of the noise and the exact explanation for the narrowing. In the meantime, absolute frequency measurements of the fiber laser locked to the hollow fiber references are in progress.

A generally useful technique was developed for splicing the photonic bandgap fibers to solid-core fibers using an arc fusion splicer, which makes PBG fibers easier to use in the laboratory. Toward making a completely sealed photonic bandgap fiber cell, PBG was spliced to solid-core fibers inside a vacuum system using a CO2 laser. Efforts to reproduce this in an acetylene vapor proved unsuccessful, most likely due to the thermal properties of acetylene.

This work was done by Kristan L. Corwin of Kansas State University for the Air Force Research Laboratory. For more information, download the Technical Support Package (free white paper) at under the Photonics category. AFRL-0132

Posted in: Briefs, Photonics, Fiber optics, Lasers, Spectroscopy