ABSTRACT
The high-resolution and noninvasive imaging of stationary and moving human and its vital signatures through clutter, such as visually opaque obstacles (e.g. walls, doors, ground) has sparked a growing interest in through-the-wall radar imaging (TWRI) and ground-penetrating radar (GPR) in both military and civilian applications, such as homeland security, urban counterterrorism, search and rescue missions, and monitoring of the sick and elderly [1,2]. In many TWRI situations, exterior and/or interior building walls induce shadowing effects, which may result in image degradation, errors in geolocation, or complete masking of targets within the building. All of these effects are attributed to direct and multiple reflections from the scene, as well as amplitude and phase distortions of the electromagnetic waves as they penetrate the medium [3–8]. Furthermore, the effects are exacerbated for multilayered and composite walls [9,10]. In order to aid in mitigating these adverse wall effects and enhance the capability for imaging and classification of targets behind walls, various advanced synthetic aperture radar (SAR) and multiple-input multiple-output (MIMO) radar techniques have been developed over the years to accurately estimate the wall constituent parameters. We note that in addition to TWRI, intrawall imaging is also important in many scenarios. For example, detecting and imaging of metallic reinforcement, or locating embedded water pipes and other construction materials, may assist law enforcement personnel in operational planning of counterterrorism or other hostile situations, firefighters in civilian search and rescue operations, and utility companies in planning and delivering electricity, gas, and water services.
