This document explores the principles and applications of Synthetic Aperture Radar (SAR) imaging, with a focus on Backprojection (BP) algorithms for microwave data imaging. It starts by introducing SAR technology, its historical development, and fundamental imaging mechanisms. Key differences between SAR and conventional radar systems are highlighted, emphasizing SAR's advantages in achieving high-resolution imaging through pulse compression and Doppler frequency shifts.The document then delves into signal processing techniques, including Linear Frequency Modulation (LFM) signals, range compression, and Doppler phase compensation. The BP algorithm is discussed in depth, covering echo signal modeling, range migration correction, and coherent accumulation. Simulation results demonstrate the BP algorithm's capability to reconstruct detailed images, illustrating the impact of interpolation coefficients on image quality.Additionally, alternative SAR algorithms like DBS, RD, and CS are compared, showcasing their strengths and limitations in various scenarios. The study concludes by emphasizing the BP algorithm's importance in SAR imaging and its potential for future technological advancements.This research, conducted by Fudan University, provides valuable insights into microwave data imaging and signal processing in SAR systems, paving the way for more efficient imaging techniques.