I. Introduction
Non-contact human activity detection and classification technology is important for public safety, counterterrorism, and disaster relief. For military and commercial applications, new research is developing physics-based models for ana-lyzing and imaging targets behind complex wall structures. Through-the-wall imaging uses microwave and millimeter-wave frequencies to image things or people behind walls. At search and rescue locations, through-wall radar life technology for detection is more resistant to light, noise, and climate change and is highly penetrative, precise, and anti-jamming.