Microwave Imaging of Concealed Objects With Linear Antenna Array and Optical Tracking of the Target for High-Performance Security Screening Systems

This article describes a prototype of microwave personal screening system, which uses the motion of the target to obtain synthetic aperture. A linear multiple-input and multiple-output (MIMO) antenna array, developed for this purpose, consists of 16 transmit and four receive vertically distributed antennas and uses a stepped frequency modulated signal in the range from 12 to 18 GHz. Position of the target relative to the antenna array is obtained by a depth sensor. The processes of designing the antenna array, aligning the antennas individually, calibrating antenna-feeder paths in the signal channels, and finding the transformation between the reference frames of the depth sensor and the antenna array are given. A method of calculating the radar image by the back projection method with the application of the fast Fourier transform is described in detail. The results of experiments with moving objects and hidden items are presented with their radar images.