Tech Briefs

Liquid-Crystal-Based Optical Phased Array for Steering Lasers

A paper describes the basic design and concepts of tunable liquid-crystal polarization gratings with a nematic liquid crystal (LC) optical phase plate, with a large, continuous in- plane gradient that is variable, and its application to a beam steering device with high efficiency.

Posted in: Briefs, Physical Sciences, Calibration, Lasers, Waveguides

Channel Modeling for a Wireless Transmission System

A wireless transmission system provides high-quality video transmission over severely impaired wireless links between nodes that are connected within airborne networks. The target bit rate for the proposed video communication can be in the range between 24 Kbps and 384 Kbps with relatively high visual quality. However, the system may operate at extreme low bit rates down to 10 Kbps and at high bit rates up to 1.5 Mbps. To accommodate the large range of the data rate for heterogeneous wireless links and devices, the H.264 SVC standard for video coding and decoding was adopted.

Posted in: Briefs, Information Technology, Mathematical models, Cryptography, Imaging, Wireless communication systems

Power for Micro Autonomous Systems

The Micro Autonomous Systems and Technology (MAST) Collaborative Technology Alliance (CTA) has been initiated to spur basic research in small autonomous robots, particularly in four main areas: Microsystem Mechanics, Autonomous Processing, Micro electronics, and Integration. In order to focus its efforts, the Army proposed multiple scenario missions of increasing difficulty to work towards: small unit building search (flat, straight walls, no wind, etc.), a small unit cave search (potential for wind gusts, no regular surfaces to use as reference points), and perimeter defense (longer required mission time, and range and potentially harsh environments). The size ranges considered were defined as “palm-size” and below, where no lower limit was specified.

Posted in: Briefs, Physical Sciences, Microelectricmechanical device, Robotics

Low-Power Circuit for an Electromagnetic Warning System Sensor

Low-power sensors are important to the Army for monitoring infrastructure of the lifecycle of an operation. Isotope batteries can power and operate compact, low-power sensors for decades. A lowpower circuit has been developed to generate a repetitive radio frequency (RF) impulse, which will be used to indicate that a sensor has detected a target. This sensor circuit has been modeled and built to evaluate several isotope batteries in preparation. A parametric study of components in the circuit has been performed to minimize power consumption as a function of repetition rate and pulse width of the light-emitting diode indicator or RF impulse output.

Posted in: Briefs, Electronics & Computers, Batteries, Integrated circuits, Radio equipment, Sensors and actuators, Test equipment and instrumentation

Effects of Differing Carbon Nanotube Field-Effect Transistor Architectures

Understanding the differing methods and materials that can be used for producing carbon nanotube (CNT)- based electronic components means an informed use of materials and architectures can unleash the potential of carbon nanotube field-effect transistors (CNTFETs) for a wide array of future electronic applications.

Posted in: Briefs, Electronics & Computers, Architecture, Electronic equipment, Transistors, Nanomaterials

Silicon Carbide Junction Field-Effect Transistor Devices for Scalable Solid-State Circuit Breakers

Power electronic converters functioning as components in high-power systems, such as those of hybrid military ground vehicles, require fast fault isolation, and in most cases, benefit additionally from bidirectional fault isolation. To prevent converter damage or failure, fault current interrupt speeds in the hundreds of microseconds to few millisecond range are necessary. Presently used mechanical contactors do not provide adequate actuation speeds, and suffer severe degradation during repeated fault isolation. Instead, it is desired to use a large array of semiconductor devices having a collectively low conduction loss to provide large current-handling capability and fast transition speed for current interruption.

Posted in: Briefs, Electronics & Computers, Power electronics, Transistors, Semiconductors

Indoor Navigation for Unmanned Aerial Vehicles

This research proposed the use of inexpensive, lightweight range sensors for indoor unmanned aerial vehicle (UAV) navigation. Two potential range sensors were tested for suitability and error characteristics. The SHARP infrared range sensors provide a narrow beam and a higher resolution distance measurement, at the expense of de creased range (approximately 150–180 cm maximum). The MaxBotix® EX1™ ultrasonic range sensors had a longer range (up to 6.45 m) and a wider beam.

Posted in: Briefs, Physical Sciences, Navigation and guidance systems, Sensors and actuators, Flight tests, Unmanned aerial vehicles