Reducing Thicknesses of PbZrₓTi₁₋ₓO₃ Films in Capacitors

A document describes experiments performed to determine effects of reducing the thicknesses of films of lead zirconate titanate (PbZrxTi1-xO3, wherein 0<x<1) used as ferroelectric dielectric layers in some capacitors. The fabrication of specimen capacitors for the experiments involved numerous steps, including spin-coating of PbZrxTi1-xO3-precursor sol-gel solutions onto bottom Pt electrode layers on silicon substrates, heat treatments to covert the sol-gel coats to PbZrxTi1-xO3, and deposition of top Pt electrode layers on the PbZrxTi1-xO3 layers. Various spin rates and solution compositions were used to obtain various PbZrxTi1-xO3- film thicknesses and compositions. Current responses of specimens to applied voltage waveforms were measured to characterize the specimens in terms of capacitance, hysteresis, and polarization. It was concluded that thicknesses of PbZrxTi1-xO3 films could be reduced to between 1,800 and 2,200 A while retaining ferroelectric performance adequate for a proposed development in which nanoelectromechanical switches containing PbZrxTi1-xO3 films would be integrated with complementary metal oxide/semiconductor transistors. One of the sol-gel solutions, characterized by x = 0.45 and a molarity of 0.367, was found to be the most promising for further work to improve performance at thicknesses < 1,800 A.

Posted in: Briefs, Physical Sciences, Capacitors, Transistors, Fabrication, Ferrous metals and alloys, Silicon alloys

Virtual Network Computing Software for DataWall Remote Display

VNC (Virtual Network Computing) is open-source software that allows a user to view and interact with a remote computer (known as the VNC server) from a local computer (known as the VNC viewer/client). VNC is used to display multiple remote desktops on the DataWall. The original VNC software can only project the whole desktop from a server to the DataWall. The VNC server and viewer were modified to project the whole desktop or an application of interest from a server to the DataWall.

Posted in: Briefs, Software, Computer software / hardware, Data exchange, Human machine interface (HMI), Displays

Software Suite for a Large Defense System

A suite of software tools was developed to enable networks composed of many hundreds, thousands, or even millions of commodity computers to protect themselves against a variety of security threats. These tools include Anagram, a content-based anomaly detection (AD) tool; ASSURE, which provides automatic software self-healing; and Aeolos, a distributed intrusion detection and event correlation infrastructure.

Posted in: Briefs, Software, Computer software / hardware, Cyber security, Neural networks

2D Laser Profiling Scanner for Detecting Targets

The Radiometric Sensor Development and Applications Team of the Sensors and Electron Devices Directorate (SEDD) at the U.S. Army Research Laboratory (ARL) has developed a 2D laser profiling scanner system to study its operational characteristics, performance, and effectiveness in detecting targets in the battlefield and homeland security environments. A profiling scanner provides output images that reveal the size, height, and outline or shape of an object. This information can be useful in a wide range of applications, ranging from simple intrusion detection, to monitoring of parts during a manufacturing process for quality control purposes.

Posted in: Articles, Aerospace

New All-Digital RF Technology Simplifies the Radio Environment

The concept of a software or “cognitive” radio has been around for about 20 years, and has progressed to the point where open-source software code is available. A cognitive radio is “smart” in the sense that it is continuously aware of changes in radio frequency (RF) spectrum and can decide which frequency and power choices are best at a particular time.

Posted in: Application Briefs, RF & Microwave Technology, RF & Microwave Electronics

Wireless Sensor Network with Geolocation

Maintaining situational/positional awareness in indoor and urban environments is difficult because buildings, walls, and other obstacles obstruct vision and RF propagation. Propagation channels are typically characterized by direct line-of-sight (DLOS) and non-line-of-sight (NLOS) performance. As more obstruction is added to the propagation channel, the DLOS path amplitude decreases relative to the NLOS path due to multipath and shadow fading. Thus, the DLOS path, which is the key enabling parameter for geolocation, is harder to detect. The challenge is to develop geolocation algorithms that overcome the DLOS obstructions, and integrate the algorithms into a communication network that is easily deployed, low cost, and provides accurate and reliable location information.

Posted in: Articles, RF & Microwave Technology, RF & Microwave Electronics

Active Thermal Management for Cooler Body Armor

The military places greater demands on its equipment — electronic and otherwise — than any other market segment. It is also true that it places its greatest thermal demands on the men and women who serve in the armed forces. In cold environments, body armor acts as thermally protective clothing to keep a soldier warm, but in hot climates where removing body armor to cool the human is not practical or advisable, another solution is required.

Posted in: Articles, Aerospace

Heterogeneous System-on-a-Chip for Self-Powered Wireless Sensor Networks

A new dimension of system architecture design is emerging where hundreds to thousands of ultralight (

Posted in: Briefs, Electronics & Computers, Architecture, Integrated circuits, Remote sensing, Sensors and actuators, Wireless communication systems

Sensing for Controls and Propulsion Health Management in Turbine Engines

Advances in engine performance and reliability require sensor components that operate reliably under extreme engine operating conditions (e.g., takeoff, max thrust) and in harsh environments (e.g., high temperature and radiation). The design of advanced controls and Propulsion Health Man agement (PHM) also depend on the use of components with increased susceptibility to atmospheric radiation. Current and future engine operating temperature environments that provide major challenges in sensor design for control and propulsion health management are being explored.

Posted in: Briefs, Mechanical Components, Sensors and actuators, Diagnostics, Gas turbines, Durability, Reliability

Tightly Coupled INS, GPS, and Imaging Sensors for Precision Geolocation

To address the issue of poor georegistration performance for small unmanned aerial vehicles (UAVs), navigation and target-location accuracy improvements achievable by tightly integrating an image-based feature-tracking algorithm with Global Positioning System (GPS) and a consumer-grade inertial navigation system (INS) sensor are being investigated. The image-aiding algorithms add to the solution across a wide variety of terrain types, thus allowing for additional estimates of camera position and orientation in the dynamic adjustment.

Posted in: Briefs, Physical Sciences, Mathematical models, Imaging, Navigation and guidance systems, Unmanned aerial vehicles

Fabricating Biologically Inspired Artificial Haircell Sensors

As electronics packaging and equipment have decreased in size and weight, so have the potential dimensions of unmanned aircraft. Specifically, a classification of micro air vehicles (MAVs) has emerged that limits the scale of the aircraft to approximately 6" (15 cm). A project is underway aimed at developing artificial haircell flow sensors following biological inspiration of insect flow sensors, and demonstrate the potential of these sensors for controlling the flight of MAVs.

Posted in: Briefs, Manufacturing & Prototyping, Downsizing, Sensors and actuators, Biological sciences, Unmanned aerial vehicles

Polypeptide-Based Molecular Electronics

Polypeptide supramolecules that will self assemble from solution and will form molecular wires that exploit quantum mechanical transport mechanisms can enable the formation of molecular devices such as transistors, diodes, and sensors. The peptides were designed and then arranged on substrates using self-assembly, Dip-PEN nanolithography, and e-beam assisted lithography. The peptides were characterized using atomic force microscopy (AFM) and the electrical properties of the self-assembled interconnects are characterized as well. These peptides can be nanoengineered/nanoassembled individual building blocks at the molecular level to form conducting channels towards realization of molecular MOSFETs/CMOS device technology.

Posted in: Briefs, Electronics & Computers, Sensors and actuators, Transistors, Additive manufacturing, Forming, Materials properties, Semiconductors

Photon-Counting Chirped Amplitude Modulation Ladar

This work is a follow-on to an effort to develop a method using Geiger-mode avalanche photodiode (GM-APD) photon-counting detectors in the U.S. Army Research Laboratory’s chirped amplitude modulation (AM) ladar receiver to yield sensitivities approaching the shot noise limit. Such sensitivities represent about four orders of magnitude improvement over the sensitivities of the currently used unity-gain, optoelectronic mixing (OEM) metal-semiconductor-metal (MSM) detectors. A variant of the chirped AM ladar has been experimentally assembled and tested, and new single photon-counting detector products were evaluated in terms of their benefits to the chirped AM ladar.

Posted in: Briefs, Photonics, Measurements, Radar, Semiconductor devices, Product development, Military vehicles and equipment

Measurement of Transient Heat Flux and Surface Temperature Using Embedded Temperature Sensors

A report describes approximate solutions for surface temperature and heat flux for two embedded temperature sensors. The solutions were verified and the range of validity was established using several methods including comparisons with an exact analytical solution for a linear problem and a numerical calculation for a non-linear problem.

Posted in: Briefs, Physical Sciences, Mathematical models, Sensors and actuators, Thermal testing

Considerations of Aeroacoustics in Turbojet-Engine Testing

A study of the aeroacoustics of a turbojet-engine test cell has been performed as one step in the development of a computational aeroacoustics capability (CAA) that could provide guidance for the design and operation of such cells. Ground testing of turbojet engines in test cells necessarily involves very high acoustic amplitudes, often severe enough to cause damage to test-cell equipment and to engines under test. Heretofore, the acoustic responses of test cells containing energetic jets have been poorly understood and generally unpredictable. The CAA capability is intended to enable prediction of deleterious acoustic events, making it possible to design test cells and choose operating conditions to prevent damage and thereby avoid the costly interruption of test schedules.

Posted in: Briefs, Physical Sciences, Acoustics, Turbojet engines, Performance tests, Aerodynamics

Imaging and Spectral Measurements of Explosions

A document describes experiments performed to investigate rates of delivery of energy onto targets from different explosive formulations. The experiments were designed to measure relative positions of blast fireballs and leading shock fronts; determine whether different explosive formulations exhibit unique spectral signatures; determine temperatures of gases and solids near fireball surfaces; and measure rates of heating as functions of time. In the experiments, unconfined explosions were observed using time-resolved laser shadowgraphy, spectrometry integrated over the first 50 ms following initiation, time-resolved three-wavelength pyrometry, and time-resolved heat-flux measurements.

Posted in: Briefs, Physical Sciences, Measurements, Imaging, Fire, Impact tests, Thermal testing

Satellite Phone

The 9555 satellite phone from Iridium Satellite LLC (Bethesda, MD) is compact and features an intuitive user interface, speakerphone, Short Messaging Service and e-mail capabilities, an upgraded mini-USB data port, and an internally stowed antenna. The phone is designed to withstand rugged, remote, and industrial environments, and is shock- and water-resistant. It utilizes Iridium’s commercial satellite global communications network for operation in any location or condition where cellular, radio, or landline services are not available.

Features include an illuminated, weather-resistant keypad; a 21-language menu; programmable international codes for automatic dialing; standby time up to 30 hours; and talk time to four hours.

For Free Info Click Here.

Posted in: Products

Signal Translator

Luxul Wireless (Lindon, UT) has released the Shock- WAV™ frequency-translating amplifier (FTA) for use in secure military, defense, and homeland security applications. The FTA converts signals generated by commercial off-the-shelf 5.x wireless LAN technologies to the secured 4.4 to 4.94 GHz government band, and transmits that signal over long distances. The bi-directional FTA enables any 802.11a wireless LAN radio to operate in the government band.

The FTA is available with a 500-mW output power option and a 2-W output power option. The 500-mW version achieves throughput speeds in excess of 15 Mbps at distances over 20 miles; the 2-W version is being tested at distances to 40 miles.

For Free Info Click Here.

Posted in: Products

Messaging Communications Bus

Real-Time Innovations (Sunnyvale, CA) offers RTI Data Distribution Service, Safety-Critical Edition, a smallfootprint version of real-time messaging middleware to meet safety certification standards such as DO-178B. It is designed for communication within and between avionics systems and unmanned aircraft system (UAS) ground control stations. It provides a message bus for integrating distributed components of avionics systems such as control systems, sensors, actuators, and displays. It allows individual subsystems to be added or upgraded without impacting existing software.

The Safety-Critical Edition supports the standard DDS interoperability protocol and the Real- Time Publish-Subscribe Protocol (RTPS). Applications developed using the middleware can seamlessly communicate with other systems developed using RTPS-compliant DDS middleware. This allows military UASs to be integrated with net-centric combat systems.

For Free Info Click Here.

Posted in: Products

Submersible Pressure Sensors

The AST4520 media-isolated, submersible pressure sensor from American Sensor Technologies (Mt. Olive, NJ) features a flush diaphragm steel cage design with stainless steel construction for level monitoring of turbulent tanks with viscous media. It is approved to UL/cUL913 Class 1, Division 1 IS, Groups C and D with an approved barrier. The steel cage design allows for proper flow of media while keeping the sensor at the bottom of the tank or well. It also features an engraved 316L housing and Kynar PVDF cable.

Units operate at temperature ranges of -40 to 185°F and offer pressure ranges from 0-5 to 0-15 PSIG. All units come standard with EMI/RFI protection of 100V/meter and a 4-20mA output.

For Free Info Click Here.

Posted in: Products, Sensors

Avionics Bus Box

Ballard Technology (Everett, WA) offers the Avionics BusBox 2000 Series, a DO-160 box designed for rugged environments. The embedded computer has built-in interfaces for standard peripherals and various avionics databases. Using application-specific software, the box also is expandable. Con - ductively cooled, it is suitable for rugged applications such as serving and recording data, converting protocols, and providing federated control.

The box features a user-programmable PowerPC processor that controls the standard (serial, Ethernet, and USB) and avionics databus (MIL-STD-1553, ARINC 429/708717) interfaces. Programs are developed on a host computer and uploaded to the box, where they can be saved in non-volatile Flash memory. Applications can then boot from the Flash memory and run without host intervention.

For Free Info Click Here.

Posted in: Products, Aviation

Aerospace Engine Components

Sandvik Coromant (Fairlawn, NJ) has released an Aerospace Engine Solutions Package that contains five standard products to support the aerospace engine industry. The GC1115 is a PVD-coated grade for high-temperature alloys that offers wear resistance; the CoroCut angled inserts are a grooving system that uses 24 standard articles in grade GC1115 to provide access to complex features in disc, shaft, and casing manufacturing; and the SL70 modular serration lock and oval blade coupling combines with Coromant Capto to provide accessibility and stability. The carbide solutions come equipped with high-pressure coolant nozzles and are available for CoroCut, ceramic RCGX, and carbide RCMT.

The other two products are the CoroMill Plura conical ball nose end mills, which are 12 standard articles with radii and taper options for the 5-axis machining of titanium blisk and impeller turbo parts; and the CoroMill 316 solid carbide with exchangeable head coupling that has diameter and radii options for features such as scallop milling on discs, casings, and shafts.

For Free Info Click Here.

Posted in: Products

Thermal Wind Tunnel

OMEGA Engineering (Stamford, CT) offers the WT-2000 thermal wind tunnel in a portable, benchtop design. Made of clear polycarbonate and PVC, it is designed to provide uniform and repeatable airflow up to 1000 fpm. The control box allows for open-loop, full-scale operation of individual fans, groups of two fans, or all fans at once. The large test chamber with a hinged access door and access panel allows for comparison testing or different size heat sinks and circuit boards. The unit is CE compliant.

For Free Info Click Here.

Posted in: Products

Robotic Platform

The Chaos™ robotic platform from Auton - omous Solutions (Logan, UT) is designed to remotely access hazardous areas previously accessible only by foot, reducing risk to personnel. The robot is able to navigate over rough, steep, and loose terrain with four independent drive tracks that can continuously change orientation a full 360 degrees. It can alter its pitch, roll, and yaw to navigate surfaces too uneven for other tracked platforms.

The robot features a high payload capacity and an available manipulator arm with a 50-pound capacity at full reach of 72". Its low base weight allows it to be lifted out of a vehicle and deployed by two people. As a JAUS-compatible platform, the robot allows addition of a variety of sensors and other robotic payloads.

For Free Info Click Here.

Posted in: Products

Air-Cooled Enclosures

Carlo Gavazzi Computing Solutions (Brockton, MA) has introduced the 715 Series of recirculating, air-cooled, rugged ATR enclosures for protection of commercial off-the-shelf convection-cooled cards de ployed in caustic environments. The enclosures withstand extremes in temperature, vibration, humidity, and contaminants. The cooling system uses a recirculating fan on the inside to transfer circuit card heat energy to the conducting walls. The walls are engineered thermal cores that provide heat transfer to the exterior surfaces of the system. The enclosures feature a brazed aluminum frame construction and are available with scalable power options for a variety of airborne and vehicle applications.

For Free Info Click Here.

Posted in: Products

Aerospace Seals

Trelleborg Sealing Solutions (Fort Wayne, IN) has introduced Turcon® Varilip® PDR industrial seals for the aerospace industry. They are designed for high-speed rotating applications, and are constructed from one or multiple PTFE-based sealing elements, which are mechanically retained in a precision-machined metal body. The metal body provides a static seal against the housing, preventing thermal cycling. The Turcon sealing element provides positive dynamic sealing on the shaft at high rotary speeds.

The seals reduce temperature generation, permit higher peripheral speeds, and lower power consumption. The seals offer a choice of standard parts in various corrosion-resistant materials and lip geometries.

For Free Info Click Here.

Posted in: Products

Weapon and Armor System Power in Future Combat Vehicles

Future combat vehicles will require unconventional weapons and armor systems such as electromagnetic (EM) or electrothermal chemical (ETC) guns, electromagnetic (EM) armor, and directed- energy weapons (DEWs). To meet these requirements, a hybrid electric power system has been identified as the best alternative to support the demand for propulsion, continuous auxiliary power demand, and pulsed power demand for weapons and armor.

Although the development of these weapons and armor technologies is progressing at a fast rate and can be demonstrated at a smaller scale today, the power supply needed in the vehicles to support these systems presents a great challenge to technology developers and vehicle integrators.

In a 20-ton combat hybrid vehicle platform, power supply will mainly consist of two sources of energy: a prime power source driving an AC generator such as a heat engine, and an energy storage system consisting of advanced batteries, ultra capacitors, and flywheels, or a combination of these three devices. Currently and in the near term, the prime power will be either a diesel engine or a turbine, and in the far term, fuel cells may become viable options.

The power supply has to meet the demands of mobility, lethality, and survivability. The demand for electric power becomes even more challenging during silent watch, when the power draw must be provided solely from energy storage for extended periods of times (4 to 8 hours). Power supply must be delivered in two forms: continuous and pulsed. For a vehicle weighing about 20 tons, the continuous power ranges from 400 to 500 kW, which is supplied from the main prime mover, supplemented by 25-30 kW-hr of energy from a storage system. Pulsed power, however, depends on the loads and repetition rate.

Since electric power is used for continuous loads such as mobility, and also for pulsed loads such as electric weapons, it would make sense to have one common power and energy management system onboard the vehicle to distribute electric power to various users according to a defined precedence. Thus, a Combat Hybrid Power System (CHPS) program was introduced to evaluate such a power management and distribution system.

Enabling Technologies

The CHPS program was initiated by the Defense Advanced Research Projects Agency (DARPA) and continued by the U.S. Army RDECOM – TARDEC (Tank Automotive Research, Development and Engineering Center). The major goal was to design, develop, and test a 15-ton notional hybrid electric combat vehicle, incorporating all the power demand onboard a vehicle system, and assess the feasibility of simultaneous power distribution to propulsion.

In the course of designing the components for the 15-ton combat vehicle, some critical and enabling technologies were identified. They included high-temperature power electronics, high-energy-density and high-power-density batteries (namely Li-Ion batteries), and high-torque-density traction motors. To the extent possible, all the components and auxiliary systems had to be integrated within the space available in a 15-ton combat vehicle. Two technical challenges appeared: the amount of power needed for all the loads, and the size and weight of the components. A first estimation revealed that using state-of-the-art technologies would require at least twice the space available within a combat vehicle.

The most aggressive goals were set for the power electronics, the motor and generator inverters and rectifier, and the DC-DC converters, and also for the thermal management. Another aggressive metric was set for the Pulse Forming Network (PFN), which had to be reduced by more than half of its current size in order to install it in the vehicle. Improvement in both the power converters and the PFN hinged on the maturation of wide bandgap (WBG) materials such as SiC. This material provides the capability to build converters that operate at high temperature, high frequency (50-100 kHz), and higher efficiency.

Vehicle Mobility

In a combat vehicle, there are three main users of continuous power: mobility, thermal management, and silent watch. Power is supplied to most of the mobility and thermal loads from the prime mover (the engine), whereas the silent watch is solely supplied from the energy storage (a battery bank), which is also recharged from the engine driven generator. For optimum performance, the power is split between engine and battery for either best fuel efficiency or burst power, according to the specified vehicle duty cycle.

Military vehicles must have the capacity to operate anywhere in the world, under extreme environmental conditions, from the frigid temperatures of the Arctic, to the intense heat of the deserts, and from hard rocky and paved roads, to hilly and soft soil. They must withstand the vibration, shock, and violent twisting experienced during crosscountry travel over rough terrain, and they must be able to operate for long periods of time with very little or no maintenance. However, there are additional requirements that are changing the whole philosophy of vehicle design. Future vehicles must be lighter, faster, and more deployable, but at the same time, more lethal and more survivable.

For a 20-ton vehicle, the power required to meet the acceleration, top speed, and gradeability requirements at 10 kph is about 400-500 kW. In a hybrid electric vehicle, the engine provides most of that power. The engine is normally programmed to operate within the band of optimum efficiency on its fuel map. Boost power for transient operation is supplemented by the stored energy from the battery pack. Thus, for propulsion, a relatively small energy storage system would be sufficient.

Requirements such as acceleration, top vehicle speed, steering at large radii, and cross-country speed depend on the available horsepower from the prime mover and the energy storage device (batteries) getting to the sprockets or wheels when needed for the various vehicle mobility conditions. For all vehicles, the power is transmitted from the prime mover to the wheels or sprockets according to a specific architecture, series, or parallel, depending on the application and duty cycle of the vehicle.

Thermal Management

In the current fleet, in addition to the power demand to operate the vehicle, 10 to 15% of the generated power from the prime mover is needed for the cooling system. For a hydraulic drive using hydrokinetic or hydromechanical transmission, all of the mobility requirements are manageable. For a hybrid electric system, the situation is more complex. The cooling system of a hybrid electric vehicle with the currently available technologies can conceivably be four to six times the size of its mechanical counterpart. Consequently, high-operating-temperature components must be developed to reduce the current hybrid electric cooling requirements.

Silent Watch

The power demand for silent watch is difficult to establish because the requirements are not well defined. However, using high-energy-density batteries such as Li-Ion, it is conceivable to have 25-30 kW-hr of energy onboard the vehicle. This amount of energy storage can support silent watch missions for a duration of two hours if the power requirements do not exceed 10 kW. The amount of energy supply must exceed the amount of energy demand by 50% to account for the system efficiency, degradation at temperature extremes, and cycle life.

High-voltage pulse power is required to power the ETC/ETI, the ETC gun, and the EMA envisioned for future hybrid electric vehicles. Intermediate energy storage for these pulse power loads is achieved through the use of high-energy-density thin-film capacitors, currently utilizing Biaxial-Oriented Polypropylene (BOPP) as the dielectric film. The total amount of energy storage required varies based on such factors as simply achieving ETI or full–blown temperature compensation (ETC), the type of propellant used, the specific armor design, the threats to be countered, and the desired safety factor. This results in intermediate energy storage from tens to hundreds of kilojoules.

The basic building block for these high-voltage pulse power systems is an extremely high-power-density (~4.5 kW/l) 150-kW pulse charger. Depending on factors such as the total amount of intermediate energy storage required, the number of rounds per minute the system is required to fire, and the required rate of recharge for the EMA, additional chargers can be added.

Directed Energy Weapons

The most likely DEW to be integrated into a vehicle platform is the Solid State Heat Capacity Laser (SSHCL), which will be integrated onto a hybrid electric ground combat vehicle in order to provide forward air defense against unmanned aerial vehicles (UAVs), helicopters, and other low-flying craft, as well as area-wide active protection against incoming threats including mortars and missiles. The system will generate a 100-kW laser output at ~10% electrical efficiency, meaning the hybrid electric vehicle will need to provide 1 MW for short durations (several seconds).

Although the power management and distribution to both types of loads is feasible within the hybrid architecture, the integration burden is extremely challenging in a 20-ton vehicle, and depends to a great extent on the pulsed load specifications. Currently, it is difficult to envision a hybrid electric combat vehicle without the development and maturation of the emerging technologies in power semiconductors and energy storage. However, in the last ten years, these technologies have progressed by more than one order of magnitude.

This article was written by Gus Khalil, Eugene Danielson, Edward Barshaw, and Michael Chait of the U.S. Army TARDEC in Warren, MI. For more information, click here.

Posted in: Articles, Aerospace, Electric power, Hybrid electric vehicles, Military vehicles and equipment

Detecting Improvised Explosive Devices in Urban Areas

Improvised explosive devices (IEDs) are rudimentary bombs that generally consist of commonly found non-military materials. Although common IED threats include roadside bombs, suicide bombers are another emerging problem in the IED arena. Suicide bombers carrying personal-borne IEDs (PBIEDs) are extremely hard to detect or stop. Because no IED emplacement is necessary, a suicide bomber can quickly strap on an IEDladen vest and move to the kill zone. Placed in the proper urban environment, this weapon is capable of inflicting serious structural damage and killing hundreds of people in mere seconds.

Research has been done to detect magnetic materials used in IEDs in urban environments using a wireless sensor network. Using the magnetic detectors in the wireless sensor nodes, magnetic behaviors and patterns are analyzed to differentiate a person carrying an IED and a person possessing magnetic material like jewelry or keychains. Using wireless sensor nodes instead of standard metal detectors enables the detectors to remain hidden to outside observers. The small nodes easily blend into the indigenous environmental settings to provide stealth.

All IEDs require a power source to initiate the weapon. Most initiators are battery- operated electrical devices, but there are other means of initiation. Spring-loaded initiators require no electrical power to function. The IED initiator detonates the weapon and begins the bombing sequence. Common initiators are blasting caps and fuse igniters. Electrical initiators can be triggered in various ways, including a button, radio frequency, and optical. The IED switch arms the weapon after the initiator sequence begins. The switch could be an arming switch, fuse, or both for redundancy. Once the IED is armed, the internal circuit is complete and detonation occurs shortly thereafter.

One of the first solutions to detect IEDs was to detect the frequency spectrum used by the IED initiator devices. By correctly analyzing the frequency spectrum used by the remote triggers, troops successfully jammed the frequencies and prevented IEDs from being triggered. Electromagnetic pulse jamming also destroyed IED circuitry.

Unmanned Aerial Vehicles (UAVs) use mounted cameras to take pictures of probable IED areas and then come back for more images. The Buckeye camera mounted on a UAV uses an electro-optical sensor capable of producing threedimensional images. Using imagery software or the human eye, the pictures are analyzed against pictures from the same area, but taken at a different time. Scrutinizing the images to the nearest pixel, experts can determine if suspicious IED activity has occurred in a region.

Magnetic Wireless Sensor Networks

A wireless sensor network (WSN) is formed from a series of wireless network nodes or motes, generally in an ad-hoc configuration. Each node contains a small processor to handle sensing duties. Nodes are able to relay information using a predetermined routing protocol such as ZigBee. Due to the wireless constraints, each WSN node needs a self-contained power source such as batteries.

A standard WSN uses the nodes for their physical sensing capabilities in conjunction with a base station, which receives information from the nodes and passes it to another source to process the data. Since the base station receives input from the WSN nodes, it has higher power requirements and must always coordinate data delivery out of the network. Each node contains sensing capabilities appropriate for the network application and needs. Nodes cannot process or analyze the information, but can forward information to either another node or the base station.

The mesh-networking feature of the motes allows them to communicate with each mote in the network. Additional motes can be added to the network or motes can be removed from the network seamlessly. The magnetic detection capability within the motes uses a twoaxis magnetic field sensor to detect electronic voltage perturbations around the sensor. The passive infrared sensors detect dynamic changes in the thermal radiation environment within immediate vicinity of the sensor. The mote also contains a dormant microphone to detect acoustic changes within its environment. Each mote contains four magnetic and passive infrared sensors placed within a cubicle housing to provide nearly 360-degree coverage.

Placing a WSN by entry and exit points of urban buildings provides a stealthy means of detecting IED materials. The accuracy of the mote detectors allows observers to distinguish normal routines from suspicious IED activities. The WSN can be set up to alert security officials of possible IED activity, and used in conjunction with standard surveillance methods to provide a more complete and accurate depiction of actual activities taking place in real time.

WSN Deployment

In IED detection, the network looks for patterns of activity that appear suspicious and raises alerts when a certain level of confidence has been achieved in the prediction. Ferrous materials compose a large number of IEDs, making magnetic sensors a logical choice for detecting IEDs. However, magnetic sensors alone may not be sufficient in confirming IED presence because the network may be susceptible to false positives (the network falsely detecting IEDs) or false negatives (failure of the network to detect IED). Using a combination of different sensor modalities could mitigate both possibilities.

The urban environment presents many challenges. Large crowds provide many variables unbeknownst to the planning process. For example, the presence of a metal shopping cart in a grocery store is a common occurrence; thus, another reason to use metallic sensors in conjunction with other detection characteristics. Another issue is the emplacement of the wireless sensor nodes. Although relatively small, they must be carefully placed to avoid accidental detection.

To find the optimum deployment scenario, various tests were conducted using the motes, 18" orange safety cones to elevate the motes from the ground, and steel buckets and staples to simulate metallic IED material. The initial setup kept the metal bucket in a fixed position and the mote was walked along a straight-line path over the bucket. The spacing was too great and the motes had trouble detecting magnetic material unless extremely close to the mote.

To test if large amounts of metal at a specified distance would give the same magnetic reading as smaller amounts of metal at a closer distance, a keychain was placed 6" from the mote. The keychain gave readings just as strong as a bucket placed 3' away from the mote.

Another test used a basic rectangular configuration of motes placed at fivemeter intervals. A steel bucket was traversed through various paths around the motes. These various paths often produced dead spots. The mote was then placed 1.5' away from a wall. Metal was placed at varying heights of the wall to determine how high the metal could be detected by the sensor mote. Results showed that a 2.5' height was the maximum distance that still provided consistent results.

In another test, two motes represented an entrance or doorway to an urban building. The motes were placed at 2' intervals. This interval was later increased to 4, 8, and 12'. A subject carrying a metal bucket traversed the network. Final tests were conducted with two and three subjects traversing the network with differing amounts of metal. The 2 and 4' configurations were tested as a means of providing network redundancy and avoiding blind spots inside the mote area. The motes were able to detect strong magnetic signals from the bucket and provided many data points for detection by the mote software.

The mote intervals were then expanded to 8 and 12'. The 8' configuration still provided reliable and consistent results. The 12' configuration showed some readings, but was not consistently able to detect metal from 6' away. So, an 8' interval between motes was optimal for the six-mote network, providing redundancy of motes while avoiding blind spots within the network (see figure).

Overall, a wireless sensor network using only magnetic detection is not a complete solution for the IED problem. The strengths of a WSN include low power requirements, adaptability, and relative ease of use. For controlling entrances to buildings such as shopping malls, places of worship, or office buildings, a cost-effective WSN implementation would be possible. It would require a configuration that leaves no holes in detection and provides redundancy to prevent network failure.

This article was written by Lieutenant Matthew P. H. O’Hara of the United States Navy. For more information on the Navy’s IED detection technologies, click here.

Posted in: Articles, Aerospace, Security systems, Sensors and actuators, Defense industry, Personnel, Magnetic materials, Hazards and emergency management

Evaluation of Four Methods of Reconfiguring an FPGA

A study was performed to evaluate the relative merits of four methods of reconfiguring a field-programmable gate array (FPGA) in response to detection of a faulty configurable logic block (CLB). As used here, “reconfiguration” signifies replacing the faulty CLB by disconnecting it and connecting, in its stead, a previously unused CLB. This study was a major part of an effort to develop a circuit-reconfiguration system (CRS) that could utilize any of the four methods to implement fault tolerance in the FPGA.

Posted in: Briefs, Electronics & Computers, Failure analysis, Architecture, Integrated circuits

Asynchronous Architectures for Large-Integer Processors

New architectures have been developed for cryptographic hardware that offer high throughput, algorithm flexibility, radiation hardness, and low power. The asynchronous (clockless) architecture combines a dedicated large-integer processor (LIP), a field programmable gate array (FPGA), and a simple processor. The asynchronous LIP can perform public-key encryption using large keys at a fraction of the runtime energy consumption of synchronous (clocked) systems. The system is made of quasi-independent components that can be commercialized as stand-alone or in different configurations.

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