Military aircraft depend on analog technology to detect enemy ground radar. Analog circuits can hold a multitude of continuous values across any given range. But this continuous-scale analog implementation can be difficult to calibrate and maintain in radar warning receivers. So, scientists at the Georgia Tech Research Institute have turned to the digital domain, which doesn't need calibration and is more robust.
Their digital crystal video receiver (DCVR) is part of the radar warning receiver (RWR) system, which detects ground-radar activity (see the figure). Comprising an analog-to-digital converter (ADC) and a programmable logic component, it takes charge of the logarithmic transfer function that coordinates the input and output of the RWR'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 GTRI researcher Michael Willis. "By moving the logarithmic transfer function into the digital signal-processing domain, we've improved the stability of the circuit."
The digital version of the technology also is much less expensive to manufacture. Willis expects the shift from analog to digital to reduce RWR production costs by a factor of five to 10, making its costs nearly insignificant compared to the rest of the system.
Furthermore, previous crystal video receiver architectures detected RF signals immediately without intermediate processing, but they needed multiple receivers to detect radar signals over a range of frequencies. Instead, the DCVR can detect RF signals through a range of frequencies using up-to-date broadband receiver techniques.
GTRI and the U.S. government have patented the technology. Willis expects the design process and transition from implementation to production to take two years.