Distant detection of hidden objects with a THz imaging radar

Detection of concealed threats at large distances is a key issue in public security. The paper describes a 0.8-THz radar that is capable to indicate hidden objects at a distance of more than 20 meter with a spatial resolution of less than 1 cm. The radar scans the scene with a narrow terahertz beam and uses heterodyne receiver with a hot-electron bolometer mixer. With integration time of 0.3 sec the receiver distinguishes a temperature difference of 2 K at the 20 m distance.