Machine Design

Radar goes digital

A novel digital crystal-video receiver (DCVR) from researchers at the Georgia Tech Research Institute could make radar equipment more reliable and cheaper to build.

GTRI researcher Mike Willis displays the digital crystal-video receiver. The device converts analog radar-warning receivers to digital, providing more stable in-air detection of enemy ground radar, at a lower cost.

The patented DCVR is a key part of a radar-warning receiver that alerts military aircraft crew to enemy ground-radar activity. In it, digital circuitry performs the logarithmic transfer function, a task formerly allotted to problematic and temperature-sensitive analog chips. The logarithmic transfer function coordinates the input and output of a radar-warning receiver's signal-processing system. Performing the logarithmic transfer function digitally boosts circuit stability and eliminates time-consuming calibration say researchers. The approach could also slash the cost of a radar-warning receiver by a factor of between five and 10.

The DCVR is comprised of an analog-to-digital converter and a programmable logic component. Together, they transform most received analog signals to digital. Earlier crystal-video receiver architectures detected RF signals instantly without intermediate processing. Such analog "direct-conversion" receivers often needed multiple receivers to detect radar signals over a range of frequencies.

By contrast, the DCVR readily detects RF signals through a wide range of frequencies using modern broadband receiver techniques. "Video" in this context means that the receiver demodulates received radar signals into video waveforms. The DCVR produces a digital equivalent of the video waveforms with a logarithmic function applied to them for simpler processing.

DCVRs will first serve in radar-warning receivers on numerous U.S. military aircraft, though the discovery could work on any radio receiver needing a logarithmic transfer function. Production versions of the device are about two years out, says the group.


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