Microwave Imaging in Security — Two Decades of Innovation

The microwave spectrum is one of the most valuable natural resource used nowadays in communication, navigation, and remote sensing. With over a century of heritage, imaging with electromagnetics had been puzzling researchers and engineers alike. When science and technology advanced enough, early imaging solutions at the lower end of the microwave spectrum were revealed. Airborne synthetic aperture radars (SAR), and later spaceborne SAR, were first to evolve. With their unprecedented capabilities in earth observation and reconnaissance, researchers became even more eager to extend SAR imaging to higher frequencies and for different applications. The last two decades have remarkably delivered breakthroughs and innovations to re-invent microwave technologies for personnel security screening purposes. Microwave signals can safely penetrate clothing and reveal concealed threats, e.g., explosives and firearms, without imposing any health risks or side effects. This paper presents a historical overview of this evolution and highlights the latest advances in security microwave imaging.