Advanced portal-based multistatic millimeter-wave radar imaging for person security screening

Millimeter-wave radar portal scanners are the most prevalent nearfield imaging passenger security systems. This paper presents an improved radar configuration that avoids dihedral artifacts, offers increased resolution, enhances depth information, allows for material characterization, and increases the overall percentage of well-imaged body regions, relative to currently-employed mm-wave systems. The improved system can produce accurate geometric reconstructions of the human body torso and body-borne metallic and non-metallic objects concealed under clothing with size as small as 1 cm. For this purpose, a multistatic Synthetic Radar Aperture (SAR) imaging system working in the 56-63 GHz frequency band, and a novel elliptic/parabolic reflector antenna design capable of providing wide illumination in azimuth and a very narrow beam in elevation is used. Narrow illumination enables independent processing of 2-dimensional contours of the human body, which can be mechanically translated and then stacked for a full 3D reconstruction. Fast and accurate SAR imaging techniques have been developed to recover the reflectivity of these stacked slices from the acquired scattered field. A first prototype of the mm-wave portal is presented in this contribution, together with an application example which clearly shows the system capability for detecting small objects placed on a manikin torso.