March 11, 2011

DARPA developing microscale radio transmitters and another program for light weight optics

1. Most military RF transmitters today use large, fixed-voltage power converters to supply conditioned power to the semiconductor power amplifier, DARPA officials explain. This is barrier to higher levels of microsystem integration. DARPA is developing a radio transmitter that generates radio signals efficiently through the DC power supply of the transmitter. They want the new RF transmitter integrated as a monolithic integrated circuit or system-in-package module that relies on a monolithic microwave integrated circuit (MMIC) power amplifier that is integrated with a dynamic-voltage power supply and control circuit.

The Microscale Power Conversion program seeks to develop power electronics technology for efficient, very fast supply modulation with high power handling capabilities to make practical use of new RF power amplifier designs. The program seeks to develop a compact, power-efficient RF transmitter by inventing dynamic power conditioning circuits and closely integrating them with RF MMIC power amplifiers and necessary control circuits.

The electrical supply chain from the AC power source to power amplifier supply typically functions as three lumped stages, DARPA officials explain: converting AC power to high-voltage DC power; converting high-voltage DC power to an intermediate DC voltage; and, finally, conditioning the resulting power to remove ripple and make subtle adjustments. In the final stage, the drain bias is either on or off at a set value.

DARPA is focusing the MPC program on the final stage of this process by seeking to develop an efficient high-speed power supply modulator to convert input DC voltage rapidly to any DC supply voltage. For this the key enabling technology will be a fast, low-loss gallium nitride power switch.

DARPA scientists want to focus the MPC program first on designing high-speed, low-loss packaged field-effect transistor (FET) power switches, and then on the co-designing and prototyping the RF transmitter and supply modulator.

2. DARPA has a new program to create new ways to manufacture lenses to greatly reduce their size and weight. This would have a major impact on a variety of military systems such as laser target designators, night vision gear and laser-based communications systems.
The Manufacturable Gradient Index Optics (M-GRIN) program takes advantage of recent advances in how lenses are designed and manufactured. It will use advanced modeling techniques to quickly develop and test new types of lenses from a range of materials, such as polymers, for better performance across the spectrum.

One advantage of the new manufacturing technologies is that optics can now be shaped to fit a system, rather than making the system conform to the optics, which results in reduced size, weight and assembly costs. She noted that the capability allows the manufacture of a few custom lenses at any time during a high-volume production run without increasing unit cost.

M-GRIN will allow developers to rapidly design, prototype and test new systems throughout the development process. Additionally, DARPA officials noted that the tools developed for the new optics process with push research of GRIN lens design and fabrication methods into new areas.

The program’s first phase began in September 2010 and will conduct its preliminary design reviews in the next month on two challenge areas: wide field-of-view solar concentrators and lightweight night vision goggles. This first phase emphasizes technology development and seeks to expand the range of GRIN lens materials and to extend commercial design tools to accommodate M-Grin lenses, DARPA officials said. Future work will emphasize manufacturability, with the goal of reaching low rate initial production by September 2013, they said.

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