Exploring Near-Field SAR with mmWave Pulsed Coherent Radar

Abstract: This thesis explores the option to apply Synthetic Aperture Radar (SAR) techniques to image near-field targets utilizing mmWave pulsed coherent radar (PCR). The recent development of mmWave radars has broadened the scope for SAR, but there are few concrete examples explaining and demonstrating the fundamental SAR algorithms from a PCR perspective. This thesis aims to address this gap by investigating the imaging capabilities of near-field SAR, where the curvature of the incoming waves has to be considered. The focus is on a comparative analysis of two distinct imaging approaches: frequency-based image formation and time-based image formation. The two approaches are compared using elementary algorithms in each category: Doppler Beam Sharpening and Global Backprojection. The comparison involves explaining the theory and approximations of each algorithm, discussing the shortcomings, and examining the expected effects when applying them in near-field applications. These effects are later exemplified through simulations. Finally, the algorithms are applied to measurements made using the Acconeer A121 PCR system, showcasing the remarkable potential of basic SAR techniques in rendering intricate images of near-field targets. By making these investigations, we endeavor to contribute to the academic understanding and practical utilization of near-field SAR with PCR systems.