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

Abstract 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.