Multistatic Ka-Band (26.5–40 GHz) Millimeter-Wave 3-D Imaging System

This article presents a multistatic or multiple-input–multiple-output (MIMO) antenna array millimeter-wave imaging system operating in the Ka-band (26.5–40 GHz) frequency range. This imaging system consists of eight 1-D arrays each containing 32 transmitters and 32 receivers for a total of 256 transmitting and 256 receiving antennas, each of which is independently addressable. By scanning the imaging system over a 1-D line path, a dense multistatic imaging aperture can be synthesized and used to generate high-resolution (sub-wavelength) 3-D synthetic aperture radar (SAR) images in the near field of the array. In this work, the design of the imaging system is detailed, including the 1-D linear array layout, the antenna element design, and various other supporting components. The imaging methodology used to create SAR images is detailed as well. The calibration process used to calibrate the imaging system is explained, and some relevant calibration results are shown. Subsequently, several imaging experiments are performed, the results of which demonstrate the capabilities of this multistatic imaging system. These SAR images specifically showcase the effectiveness of multistatic SAR measurements for near-field imaging. In addition, several experiments are performed to showcase the utility of the imaging system for nondestructive testing (NDT) and security inspection purposes.