Detection of Concealed Individuals Based on Their Vital Signs by Using a See-Through-Wall Imaging System With a Self-Injection-Locked Radar

This paper presents a self-injection-locked (SIL) radar with ranging and tracking capabilities to see through walls for discovering hidden people. Characterized by low complexity and high sensitivity, the proposed SIL radar merges the frequency-modulated continuous-wave and sum-difference pattern detection approaches to determine the distance and azimuth from the radar to each individual in a scene behind a wooden partition wall. An individual can be distinguished from a stationary object by using dynamic spectral subtraction to extract human motions or vital signs. Additionally, two or more individuals can be distinguished from each other by decomposing the Doppler signal into contributions of individuals in a polar domain. Consequently, a see-through-wall imaging system is constructed with the proposed SIL radar to position different individuals concealed behind a wall.