Review of millimeter-wave and terahertz near-field synthetic aperture radar imaging technology

This paper comprehensively reviews the development of millimeter-wave (MMW) and terahertz (THz) near-field imaging technologies, with an emphasis on the state of synthetic aperture radar (SAR)-based imaging technologies. Near-field imaging technologies are categorized into passive and active imaging modes, among which active imaging is favored because of its strong signal-to-noise ratio and three-dimensional (3D) reconstruction capabilities. This paper discusses SAR-based active imaging systems with various antenna array structures, including planar SISO (Single-Input Single-Output)-SAR, cylindrical SISO-SAR, planar MIMO (Multiple-Input Multiple-Output)-SAR and cylindrical MIMO-SAR. Specifically, the paper emphasizes the advancements in SISO-SAR and MIMO-SAR technologies, highlighting the advantages of MIMO-SAR in improving imaging speed and reducing costs. Finally, the paper provides a summary and outlook on SAR-based MMW and THz near-field imaging technologies.