Review of Concealed Object Detections using RF Imaging over UWB Regime for Security Applications

In the realm of contemporary communication, navigation, and remote sensing, the microwave spectrum stands as a pivotal natural asset. Spanning an extensive heritage of over a century, the method of utilizing electromagnetic principles for imaging has intrigued the intellectual pursuits of researchers and engineers alike. As the frontiers of science and technology advanced, solutions for imaging within the lower echelons of the microwave spectrum gradually came to light. The advent of airborne Synthetic Aperture Radars (SAR) marked pioneering steps in this trajectory. Endowed with unparalleled capabilities in terrestrial observation and reconnaissance, these SAR technologies started a new interest among researchers to expand SAR imaging further, encompassing different frequencies and a diverse array of applications. In a striking testament to progress, the last two decades have witnessed a cascade of breakthroughs and transformative innovations, revitalizing microwave technologies for the sole purpose of personnel security screening. Employing microwave signals, endowed with the unique capability to safely permeate clothing, concealed threats such as explosives and firearms can be unveiled without causing any concerns to personal health or inducing unwanted aftereffects. This document presents a brief journey in the advancements in Microwave Imaging (MI) technology for security imaging applications using Ultra-Wideband (UWB) devices.