Security-related active imaging of dielectric objects attached to human bodies

In the last years, several approaches for the detection of concealed threats at the body of a person have been developed using millimetre-waves. The utilisation of millimetre-waves allows for the detection of both metallic and non-metallic objects. Setups using active illumination mainly exploit coherence between transmitted and received signal to perform beamforming or processing along a synthetic aperture. When dielectric objects should be detected, the assumptions done in these processing steps are often no longer given. The same applies for objects that are placed in front of a reflecting background like the human skin. The effects that can occur for these conditions are discussed in this paper.