基于SSA算法的无人机载穿墙SAR空变运动误差补偿方法

Small rotorcraft Unmanned Aerial Vehicles (UAVs), owing to their compact size, lightweight nature, and excellent maneuverability, are often used as platforms for Synthetic Aperture Radar (SAR) systems. These UAVs exhibit great potential in complex environment detection at low altitudes. However, the operation of small rotorcraft UAVs involves sharp, random motion errors during flight at low altitudes. Additionally, the limited payload capacity of these vehicles further limits their capacity to carry high-precision positioning equipment. The abovementioned motion errors observed during the operation of UAVs become a key factor that affects the imaging accuracy in UAV-mounted through-the-wall SAR imaging. To address this drawback, a conventional error compensation algorithm based on the Stage by Stage Approaching (SSA) algorithm has been proposed. This approach is based on the bunching SAR imaging mechanism, assuming that the phase error of all the pixels in the scene is the same; this approach is not applicable under the condition of a bandwidth beam. Therefore, this paper presents a wide-beam motion error compensation method for through-the-wall SAR imaging based on the SSA algorithm. The method employs the Back Projection (BP) algorithm to model the motion errors of the radar echo of the rotorcraft UAVs. Using the image entropy evaluation criterion of SAR, the SSA optimization algorithm was applied in this study to estimate the phase errors of the antenna phase center for each pixel in the imaging scene. Subsequently, the BP algorithm was used to perform high-precision phase compensation for each pixel, thereby addressing the spatial variations of motion errors in the wide-beam through-the-wall SAR system. The results of the simulation and experimental data processing reveal that the proposed algorithm can accurately compensate for spatially varying motion errors in wide-beam scenarios. It enables good focusing of multiple targets in the scene and effectively resolves the problem of spatially varying motion errors in wide-beam through-the-wall SAR imaging.