基于扩展方位NLCS的斜视TOPSAR成像算法

A Squint TOPSAR Imaging Algorithm Based on Extend Azimuth Non-linear Chirp Scaling

斜视TOPSAR(Terrain Observation by Progressive scans SAR)成像模式中,场景内各点目标多普勒中心频率的差异导致方位向信号欠采样并加剧频谱的耦合。针对TOPSAR的回波特点,该文提出一种新的TOPSAR全孔径成像算法:首先引入高阶视向速度补偿消除回波信号的频域模糊;接着用非线性变标法对方位空变性进行补偿;最后用2维线性变标算法校正高阶视向速度补偿产生的几何形变问题。与传统算法相比,该文算法可在扩展较少数据量的情况下避免插值运算,提高成像效率。仿真结果证明了算法的正确性和有效性。

In the squint Terrain Observation by Progressive scabs （TOPSAR） mode, the different azimuth scatters have different Doppler center frequencies, which causes azimuth under-sampling problem and increase the coupling between range and azimuth. Considering at the characteristics of squint TOPSAR echo, this article proposes a new full aperture imaging algorithm： first, the azimuth signal aliasing is removed by introducing the nonlinear walk correction; second, the nonlinear chirp scaling algorithm for azimuth focusing is applied to compensating the Doppler modulation rate; finally, the image geometric distortion is eliminated by 2-D chirp scaling operation. Compared with the traditional algorithm, the proposed algorithm avoids the interpolation under the case of extending a small amount of data, hence the calculation needed is less. The simulation results prove the effectiveness of the algorithm.