联合多方位角调频率估计的星载SAR三维成像方法

Space-borne SAR Three-dimensional Imaging by Joint Multiple Azimuth Angle Doppler Frequency Rate Estimation

星载合成孔径雷达(Synthetic Aperture Radar, SAR)通过波束的方位向扫描可以实现单次航过的多方位观测。在多方位角观测过程中,卫星弯曲轨道可等效为长3维曲线阵列,从而具备了3维成像能力。由于多方位角观测在高度维采样的稀疏性,无法直接通过3维FFT实现无模糊成像,且目标在不同方位角SAR图像的投影与高程间的传递相对复杂。针对该问题,该文提出了联合多方位角调频率估计的星载SAR3维成像方法。该方法首先给出了不同观测方位角下多普勒调频率误差与目标高程误差间的关系,利用视错位法(Map Drift, MD)估计多普勒调频率误差。然后,联合多方位角高程估计结果提升高程估计精度。最后,利用高程估计结果恢复目标3维几何信息,从而实现3维成像。仿真实验验证了该方法的高程估计精度可达米级。

Using azimuth beam steering,space-borne Synthetic Aperture Radar(SAR)can observe from multiple azimuth angle in single pass.During multiple azimuth angle observation,the satellite orbit is equivalent to long three-dimensional(3-D)curvilinear array,which has the potential for 3-D imaging.Sampling by space-borne multiple azimuth angle SAR is sparse in height dimension,which makes unambiguous 3-D imaging by 3-D fast Fourier transform infeasible.Besides,the complex relationship between the targets’projection in multi-angle SAR images and the height error is difficult to determine.To overcome this limitation,in this paper,we present a 3-D imaging method based on joint multiple azimuth angle Doppler frequency rate estimation.First,a relationship is proposed between the height error and Doppler frequency rate at different azimuth angle.Then,the Doppler frequency modulation rate error is estimated by Map Drift(MD)technique.Next,the height estimation results of different azimuth angle are combined to improve the estimation accuracy.From the estimated height and the target location in the SAR images,3-D geometric information is retrieved and 3-D imaging is achieved.Our simulation experiments validate that the height estimation can achieve an accuracy of few meters with the proposed method.