Through-wall imaging: Historical perspective and future directions

Through-wall imaging approaches are highly desirable for a range of applications including police, fire and rescue, first responder, and military applications. The ultimate desire of such systems is to provide detailed information in areas that cannot be seen through conventional measures. Borrowing from successes in geological and medical imaging environments, researchers have attempted to apply radio frequency (RF) and other sensing modes to penetrate wall materials and optimally estimate the content and structure of rooms and buildings. There are many propagation differences that provide unique challenges that must be addressed to make through-wall penetration sensors operationally viable. This paper outlines the historical context of early research and provides new directions for future research in the exciting interplay between electromagnetic propagation, signal processing, and knowledge-based reasoning algorithms.