A coded radar reflector for remote identification of personnel and vehicles

A nonradiating radar reflector transponder (radar reflector) that can be modulated with a unique digital code is described. This code can be detected in the output of a radar sensor and used to remotely identify the bearer of the transponder. When used in a security surveillance system, badge-carrying personnel moving through halls and passageways can be identified as they pass radar monitoring stations. Vehicles fitted with a modulated radar reflector mounted behind the windshield or as part of the license plate can also be detected by suitable sensors. The key to this surveillance concept is the reflector modulator circuit that incorporates a small, low-powered digital circuit to modulate a radar reflector with digitally encoded information. This modulation pattern can be detected by a radar sensor to uniquely identify each unit. Generic system designs for these two application scenarios are described together with coded reflector designs, coding schemes, and signal processing algorithms. Example data from concept feasibility demonstrations are presented.