Bistatic 3D SAR for wall parameter extraction in cluttered environments

Through-wall radar is an emergent technology rooted in urban surveillance, a key component being synthetic aperture radar (SAR). Accurate through-wall SAR relies on knowledge of the refractive index and thickness of any obscuring walls. Such information is rarely known beforehand and is subject to change on a sample-by-sample basis. It is therefore necessary to obtain the material properties in conjunction with any SAR measurement. In this letter, a remote data-driven asymmetric bistatic SAR approach is taken by means of matching the range to the direct back face reflection with an explicit geometry-based model. The proposed method relies on an accurate knowledge of the bistatic measurement geometry. Using the bright reflection from the front face of the wall, a method for refining an estimate of the bistatic measurement geometry is proposed. This approach is extended to three-dimensions to improve usability in heavily cluttered environments. This method is empirically validated using three-dimensional SAR measurements of both a wall-only, and a heavily cluttered scene. The method is shown to accurately extract both the refractive index and thickness of a concrete wall, with both measurements in agreement with each other and an independent validation measurement.