Unfolded coprime bistatic MIMO radar for joint DOD and DOA estimation: from viewpoint on aperture augment for sum coarray

Generally, the coprime linear array (CLA) consisting of two interleaved uniform linear subarrays can enlarge the array aperture to attain the better angle estimation performance compared with the uniform linear array (ULA). In this paper, we ulteriorly study the virtual sum coarray of the unfolded coprime (UC) bistatic multiple-input multiple-output (MIMO) radar whose transmitter and receiver array are both unfolded CLA from the viewpoint on the geometry and array aperture. The UC MIMO radar can be exploited to obtain the better joint direction of departure (DOD) and direction of arrival (DOA) estimation performance due to the larger array aperture. Furthermore, we propose an all sum coarray multiple signals classification (ASCA-MUSIC) algorithm for the UC MIMO radar. ASCA-MUSIC can fully exploit all the degrees of freedom (DOFs) in the sum coarray and can obtain the better estimation performance. We also prove that ASCA-MUSIC can avoid the phase ambiguity problem due to the coprime property. In addition, we devise a reduced complexity scheme for ASCA-MUSIC to reduce the high computational complexity and utilize Cramer–Rao Bound (CRB) as a benchmark for the lower bound on the root-mean-square error (RMSE) of unbiased angle estimation. Finally, the numerical simulations verify the effectiveness and superiority of the UC MIMO radar, ASCA-MUSIC and the reduced complexity scheme.     

一种新的分布式小卫星SAR系统抗干扰方法

针对分布式小卫星SAR系统抗干扰时编队构形的限制,研究了优化阵列在超稀疏构形抗干扰中的应用.使用优化阵列确定编队构形中小卫星的相对位置,可以提高方向分辨率,减小达到一定波束形成性能所需要的孔径长度,减小所需小卫星数目,降低硬件开销.分析了卫星位置偏差对抗干扰性能的影响.仿真证明,采用优化阵列构形可以使分布式小卫星SAR系统获得良好抗干扰性能.     

基于原子范数的互质阵列协方差矩阵重构算法

针对互质阵列的虚拟阵列插值过程中协方差项的非均匀加权问题,将互质阵列协方差矩阵重构转换为低秩矩阵填充与原子范数重构,提出基于原子范数的互质阵列协方差矩阵重构算法。该算法先利用广义增广法得到非完备的互质阵列协方差矩阵,并利用截断的均值奇异值门限填充法得到虚拟阵列的协方差矩阵初值,然后对其进行原子范数最小化求解,实现稳健的正定Toeplitz协方差矩阵重构。该算法充分利用互质阵列协方差矩阵信息,有效提高互质阵列DOA估计算法的稳定性,降低计算复杂度。     

优化阵列在寄生式星载SAR系统抗干扰中的应用

针对寄生式星载SAR系统抗干扰时编队构形的限制,研究了优化阵列在超稀疏构形抗干扰中的应用。使用优化阵列确定编队小卫星的相对位置,可以提高方向分辨率,减小达到相同波束形成性能所需要的孔径长度,减小所需小卫星数目,降低硬件开销。仿真证明,优化阵列可以使寄生式星载SAR系统获得良好抗干扰性能。     

多基线InSAR信号处理中优化阵列的应用

多基线干涉合成孔径雷达（Multi-Baseline　interferometric　SAR）是传统单基线InSAR的扩展,能够得到高分辨的高度地形图。但同时传感器的增加使得硬件开销大大增加。本文研究了优化阵列在多基线InSAR信号处理中的应用。在仿真实验中,通过与相同阵元个数的均匀阵列和传统单基线InSAR相比优化阵列显著提高了高度分辨率;同时,若要达到相同分辨率,则阵列优化可大大减少阵元个数,从而减少了硬件开销。     

DOA estimation of mixed coherent and uncorrelated targets exploiting coprime MIMO radar

We propose a new scheme to estimate the directions-of-arrival (DOAs) of mixed coherent and uncorrelated targets exploiting a collocated multiple-input multiple-output (MIMO) radar with transmit/receive coprime arrays. In the proposed scheme, the DOAs of the uncorrelated targets are first estimated using subspace-based methods, whereas those of the coherent targets are resolved using Bayesian compressive sensing. Compared with the previous works, the proposed approach achieves improved DOA estimation accuracy with a flexible coprime array configuration and may resolve more targets than the number of coarray elements. Theoretical analysis and simulation results validate the effectiveness of the proposed technique.     

基于L形嵌套的混合MIMO相控阵雷达阵列设计

混合MIMO相控阵雷达发射端的子阵分割会导致自由度损失,为了解决这一问题,提出了一种基于嵌套阵结构的L形收发阵列设计方法。首先将发射端的混合MIMO相控阵雷达线阵纵向放置,然后接收阵列设计为横向布置的嵌套阵结构,最后通过在虚拟阵列中构造差异阵列,以L形的线阵结构实现了二维混合MIMO相控阵雷达的功能。通过形成虚拟阵元数目扩展,在保留混合MIMO相控阵雷达优势的同时增大了阵列自由度。且本文给出了这种结构下阵列流形的闭合表达式。仿真结果表明,与传统的混合MIMO相控阵雷达相比,这种方法能够提高自由度和波达方向估计精度。