基于稀疏分解的双基地ISAR一维距离成像方法

摘要

In bistatic Inverse Synthetic Aperture Radar (ISAR) , resolution of one-dimensional range profile is restricted not only by transmission signal bandwidth but also by imaging bistatic angle, which result in the bistatic ISAR range profile resolution far lower than monostatic ISAR with the same transmission signal bandwidth. To resolve the range profile resolution decline problem caused by imaging bistatic angle, a method for range profile creation is presented based on the analysis of sparse characteristic of target baseband echo signal. The sparse decomposition coefficients of target baseband signal in the according redundant basis are used to create the one-dimensional range profile. If the equivalent time-delay cell used for the construction of sparse decomposition redundant basis is shorter, the range profile resolution is higher. Base on this idea, the time-delay cell proportional to half bistatic angle cosine and inverse proportional to transmission signal bandwidth is created. Then the redundant basis is constructed via this time-delay cell. And the extended generalization FOCUSS ( Focal Underde-termined System Solver) algorithm is used to estimate the sparse decomposition coefficients of baseband echo signal. Finally, one-dimensional range profile immune to bistatic-angle-influnence is created by the sparse coefficients. Simulation experiment of space target with ideal scatters validates the algorithm.%双基地ISAR成像中,一维距离像分辨率不仅受发射信号带宽限制,同时还受制于成像双基地角,最终导致双基地ISAR距离像分辨率远低于同等带宽的单基地ISAR.为了解决双基地角造成的一维距离像分辨率下降问题,在研究双基地ISAR目标基带回波稀疏性的基础上,提出了利用目标基带回波信号稀疏分解系数生成一维距离像的方法.构建稀疏分解冗余基的等效延迟时间单元越短,则距离像分辨率越高,基于此思路,首先构造出与半双基地角余弦成正比,且与发射信号带宽成反比的延迟时间单元,然后利用此延迟时间单元构建冗余基,最后基于推广的正则化FOCUSS算法估计基带信号的稀疏表示,得到分辨率不受双基地角影响的目标一维距离像.空间目标理想散射点的仿真实验验证了算法的有效性.