Matched Environment Processing System (MEPS) for Overland Target Height Finding

Conventional AEW systems, such as the AWACS, need improved means for determining target altitude at long ranges over land and sea without relying on IFF. The AWACS can operate in an electronic-scan-in-elevation (Elscan) mode, but it provides a crude estimate of target height and has difficulty resolving low-flying targets due to multiple signal reflections, or multipath, from the ground. One solution is to take advantage of the multipath by estimating from the measured waveform the time difference in signal coming directly from the target and from multipath. Target height can then be geometrically computed if range is known. Unfortunately, this time-difference-of-arrival approach has yet to be successful for rough terrains. We propose a Matched Field Processing approach for use with a variety of terrains. This approach uses a wave-propagation predictor interfaced to a database of digital elevation and wavelength independent texture information to predict a signal waveform based on direct and multipath returns from a target at various hypothetical altitudes. Target height may be computed by minimizing the least-mean-squared difference between the measured signal and predicted waveforms. Finally, the sensitivity of this approach to parameters like target range, terrain roughness, and elevation data resolution will be studied.