自旋目标逆合成孔径激光雷达成像算法

Inverse Synthetic Aperture Ladar Imaging Algorithm for Spinning Targets

受激光调制技术的限制及大气湍流的影响,逆合成孔径激光雷达对自旋目标成像的过程中存在方位多普勒模糊和回波不相干的问题.同时,在成像中相邻回波脉冲间目标转角较大,回波相关性很差,现有的一些相位误差补偿算法难以补偿上述相位误差,传统方位相干积累法无法获取聚焦良好的二维图像.本文利用回波包络信息进行成像,建立了自旋目标逆合成孔径激光雷达成像的空间几何模型,分析了回波信号的特征,提出了一种基于广义Radon变换的自旋目标逆合成孔径激光雷达成像算法.首先采用自相关法在距离-慢时间域对距离压缩后的包络求取目标的自旋角速度,之后对距离-慢时间域的包络作广义Radon变换,实现对包络的非相干积累,并获得自旋目标的二维高分辨图像.由于没有利用回波相位信息,因此避免了相位误差的影响.仿真结果表明:传统距离-多普勒算法无法成像,而提出的方法在低信噪比、多普勒模糊和回波不相干条件下仍能够获得聚焦良好的图像.

Due to the limitation of the laser modulation technique and the interference of the atmospheric turbulence,inverse synthetic aperture ladar （ISAL） has the problems of azimuth Doppler ambiguity and echo noncoherence when imaging a spinning target.Meanwhile,the large relative rotation angle of the spinning target results in a poor correlation between adjacent echoes that makes the present phase error compensation methods fail to work.Hence,the traditional coherent integration algorithms are incapable to obtain a well-focused 2-D image.In order to solve these problems,the envelope of the echo is considered for imaging.The ISAL imaging geometry of a spinning target is established,and the characteristic of the echo is analyzed.An ISAL imaging algorithm based on the generalized radon transform （GRT） is proposed for spinning targets.Firstly,the spinning velocity of the target is estimated by autocorrelation with the rangecompressed envelope in the range-slow-time domain.Then,noncoherent integration with the range-compressed envelope is realized by using the GRT,and hence the 2-D image of the spinning target with high resolution is obtained.Since the phase is not used in imaging,the phase errors are avoided.Simulation results show that,the traditional range-Doppler algorithm fails to work,while the proposed algorithm successfully obtained a well-focused ISAL image in the case of low signal-to-noise ratio,Doppler ambiguity,and echo noncoherence.