Coherent millimeter-wave imaging for security applications

Homeland Security today presents a major field for technology improvement and systems development. For instance body scanners, commonly operated at airports, are basically metal detectors and therefore are not able to detect other potential hazards like ceramics or explosives as well. In this context millimeter-wave (MMW) radar systems are a promising approach, because the radiation does not present a health hazard to people under surveillance and readily passes through many optically opaque materials such as clothing fabrics. For indoor systems we propose to apply active and coherent sensors. Based on the principles of Synthetic Aperture Radar small physical apertures can be used in order to get very good resolved images providing all the image features necessary for localizing relevant objects. In order to get a view of the person from all sides either the person has to be rotated standing on a turntable or a sensor is moved on a circular path around the person. Additionally interferometric principles can be applied firstly in order to obtain a geometrically improved mapping of the reconstructed scene and secondly to reduce ambiguities related to numerical reconstruction.