Atlanta, Ga., 13 March 2007. Researchers at the Georgia Tech Research Institute (GTRI) have patented a discovery that could increase reliability and reduce cost in equipment that helps protect U.S. military aircraft from attack.

The patent covers a device called a digital crystal video receiver (DCVR), part of the radar warning receiver (RWR) system that alerts an aircraft crew to enemy ground-radar activity.

GTRI researchers Michael J. Willis and Michael L. McGuire, working with Air Force scientist Charlie W. Clark, have patented a way to use digital circuitry to perform many functions formerly allotted to more-problematic analog chips.

Specifically, the researchers have moved a critical operation -- the logarithmic transfer function -- from the analog to the digital domain. The logarithmic transfer function coordinates the input and output of a radar warning receiver's signal-processing system.

"Electronic analog technologies have a number of error sources and limitations when subjected to the extended temperature range that our military requires," says Willis, a principal research engineer with GTRI's Electronic Systems Laboratory (ELSYS). "By moving the logarithmic transfer function into the digital signal-processing domain, we've improved the stability of the circuit."

Analog circuits, traditionally used to detect real-world phenomena such as sound or temperature, hold a multitude of continuous values across any given range. By contrast, digital circuits process information in discrete steps governed by the binary code that computers use.

In radar warning receivers, Willis explains, the continuous-scale analog implementation has been difficult to calibrate and maintain. By contrast, the digital domain needs no calibration and is more robust.

The new digital crystal video receiver is comprised of an
analog-to-digital converter and a programmable logic component. Together, they're able to transfer most received analog signals to the more-reliable digital domain.

The recent patent, shared by GTRI and the U.S. government, is significant because it protects the technology. Still, Willis says, the patent is another step in an ongoing process leading to field deployment.