Heterodyne Correlation Random Noise Radar for Through Wall and Building Interior Imaging

Recent terrorist activities and law-enforcement situations involving hostage situations underscore the need for effective through-the-wall surveillance (TWS). Current building interior imaging systems are based on short-pulse waveforms, which are easily recognizable by the intelligent adversary who may employ countermeasures to confound detection. We propose a coherent continuous-wave ultrawideband random noise radar architecture based on heterodyne correlation and adaptive software radar techniques for covertly imaging obscured targets and interfaces. The proposed approach has the following two advantages over competing systems: (i) random noise waveform possesses an ideal ambiguity function with separately controlled down-range and cross-range resolutions, providing unambiguous high resolution imaging at any distance; and (ii) random noise waveform is inherently low-probability-of-intercept (LPI), low-probability-of-detection (LPD), and anti-jam. Thus, it is an ideal candidate sensor for covert imaging of obscured regions in hostile environments. The coherency in the system can be exploited to field a fully-polarimetric system that can exploit polarization features in target recognition. Moving personnel can be detected using Doppler processing. Simulation and experiments not only show detection of human activity and human tracking behind walls with excellent multipath and clutter rejection, but also differences between specific activity types. Mutual information approach exploits waveform diversity features to image building interiors.