多旋翼无人机载SAR的视线运动误差修正与补偿

多旋翼无人机体积小、重量轻、成本低，但由于飞行航迹极不稳定，成像信号处理难度很大。基于惯导数据实时调整脉冲重复频率(PRF)可预先补偿航向位移误差，但是，其残余误差在高波段合成孔径雷达(SAR)斜视成像时不能忽略。为此，利用位移实测值与理想值间的差异提取残余航向位移误差，修正了斜视成像几何下的视线运动误差，改进了传统的1阶、2阶视线误差补偿因子，并基于成对回波理论分析了旋翼无人机正弦位移误差的幅度和频率容限。仿真和实测数据验证了所提方法在大斜视成像时可减小视线运动误差约一个数量级，显著提高多旋翼无人机载SAR成像的性能。 

Modification and Compensation of the Line-of-Sight Motion Error for Multirotor UAV SAR

The multirotor Unmanned Aerial Vehicle (UAV) has the advantages of small size, light weight, and low cost. However, imaging signal processing is complicated due to the extremely unstable flight path. Real-time adjustment of pulse repetition frequency based on inertial navigation data can compensate for the along-track displacement error in advance, but the residual error cannot be ignored for highly squinted high-band Synthetic Aperture Radar (SAR). Therefore, the residual along-track displacement error is extracted based on the difference between the measured displacement value and the ideal one, and then the Line-of-Sight (LOS) motion error of the squint imaging geometry is modified. The traditional first-order and second-order LOS error compensation factors are improved, and the tolerance of the amplitude and frequency of the sinusoidal displacement error of a multirotor UAV is analyzed based on paired echo theory. Simulation and flight experiments verify that the proposed method can reduce the LOS motion error by an order of magnitude in large squint imaging and significantly improve the imaging performance of the squinted SAR of a multirotor UAV.