【作者】 张燕；

【导师】 张云华；

【作者基本信息】 中国科学院研究生院（空间科学与应用研究中心） ， 计算机应用技术， 2010， 博士

【摘要】 自1973年L. E. Brennan等人首次提出了空时二维自适应处理(Space-Time Adaptive Processing, STAP)的概念后,随着大规模集成电路、计算机技术和数字信号处理技术的飞速发展,STAP技术已经越来越广泛地应用于地面运动目标指示(Ground Moving Target Indication, GMTI)雷达中,众多的专家学者在STAP理论和应用领域开展了大量的研究工作。但是由于技术保密的原因,在公开发表的文献中,很少涉及STAP算法在实际动目标检测应用中的细节问题,基于STAP算法的GMTI雷达的完整仿真系统并不多见。星载稀疏孔径雷达GMTI系统能够提供超长基线和极大有效孔径,优越性显而易见。但是星载STAP技术相对不成熟,在实现和应用问题上仍面临诸多挑战。尤其是,星载超稀疏阵空间欠采样会引发稀疏栅瓣(均匀阵)或高旁瓣(非均匀阵)和盲区问题,严重恶化STAP的性能。另外,从STAP思想出现之时起,计算量就是一个困扰阻碍其发展和应用的最主要问题之一。本文以STAP算法为轴线,围绕上述问题展开工作并试图提出有效的解决办法。本文的主要工作总结如下:论文首先系统地讨论了STAP算法的基本思想,研究了STAP处理器的原理,结构和性能。简要比较了几种常见的GMTI算法。仿真和比较的结果显示了STAP算法的优异性能。通过引入了人为干扰、杂波子空间泄露、载机偏航和非线性天线等实际因素,详细分析了这些实际因素对STAP检测性能的影响,讨论了实际因素存在时杂噪比(CNR)的Iceberg效应。在介绍STAP算法基本思想基础上,论文基于均匀直线阵列(ULA),建立了基于STAP算法的GMTI雷达动目标检测的完整仿真系统。分别给出了系统的杂波模型,噪声模型和信号模型,讨论了对角加载技术,给出了回波模拟和信号处理的完整流程,详尽讨论了STAP技术在实际应用中的细节。实验结果证明了该系统的有效性。论文随后研究了提高STAP算法的性能和降低计算量的问题。讨论了降维STAP算法的原理和应用。本文从降维算法的逆问题出发,讨论如何在提高性能的同时而不增加系统维数。论文提出了基于APES方法的STAP算法。将APES方法用于STAP实际仿真系统的两个方面。首先,我们应用APES方法来得到角度-多普勒域的杂波特性。其次,我们将APES方法用于普通STAP算法的后处理,提出STAP+APES算法。实验结果证明了该算法在有效提高性能的同时避免了大计算量的增加。论文的最后一部分工作研究了星载稀疏孔径雷达STAP算法盲区问题的成因和解决该问题的众方法。在分析了广义DPCA条件、破坏阵列周期性、多波形/多载频算法对STAP算法性能的影响的基础上,提出了将最优不可约阵(OIAs)和多载频结合来解决盲区问题的方法。实验结果表明,本算法可极大减少盲区数目。因为破坏了阵列的周期性,盲区凹陷的展宽相对多载频算法也有所改善,因此STAP的检测性能也得到明显改善。更多还原

【Abstract】 Up to now since Brennan proposed the concept of space-time adaptive processing (STAP) in 1973, numerous scientists, researchers and engineers have done a lot of works on STAP theory and its practical applications and significant progresses have been made as the rapid development of large scale integrated circuit technology, computer and digital signal processing technique. Nowadays, STAP has proven to be one of the best techniques capable of detecting weak moving targets in strong clutter environment and has been widely applied in ground moving target indication (GMTI) radar.However, because of the technical secrecy reason, the STAP details in real applications have seldom been introduced and discussed in published literatures, as well as complete GMTI simulation systems based on STAP algorithm. Spaceborne distributed GMTI radar can provide very large baseline and the minimum detectable velocity (MDV) for STAP algorithm can be much lower. Up to now the spaceborne STAP technology is relatively not mature and there are many challenges in its realization and applications. The performance of STAP is heavily deteriorated due to the undersampling in spatial frequency domain, so large grating-lobes and sidelobes are induced. On another hand, huge computation load is the major fact to prevent the development and application of STAP in real situations ever since the idea was proposed.The dissertation concentrates the study on STAP algorithms in view of the above problems and tries to find effective methods to solve them. The major work of the dissertation can be summarized as follows.Firstly, we discuss the basic idea of STAP algorithm and the principle, structure and performance of STAP processor. Common GMTI algorithms are compared with each other. Simulations show the outstanding performance of STAP algorithm. The impacts of several practical factors on the detection performance of STAP, e.g. jams, clutter subspace leakage (channel mismatch, dispersion, internal clutter motion(ICM)), yaw and nonlinear antenna array, are analyzed as well as the iceberg effect are discussed when these practical factors exist.Based on the principle of STAP algorithm, a GMTI simulation system is established for the uniform linear array (ULA) system. The clutter model, noise model and signal model of the simulation system are built, diagonal loading technique is discussed, as well as echo signal simulation and signal processing flowchart. Simulations are presented to show the effectiveness of the method and the reliability of the system.Then, we conduct study on the improvement and computational complexity reduction of STAP algorithm and the dimension-reduced STAP algorithm is discussed. Starting from the inverse problem of dimension-reduction, how to improve the performance without increasing the system dimension is discussed. We propose a STAP algorithm combined with APES technique to improve the performance of ordinary STAP algorithm. We apply APES method to two aspects of the STAP simulation system. First, we obtain the clutter characteristics by using APES approach. Then, APES approach is combined to STAP algorithm to improve the results of STAP algorithm. Simulations show that by applying APES the GMTI detection performance can be improved without increasing the number of antennas and pulses, at the same time no high computational complexity is involved.Finally, we study the reason why the blind-zone problem of STAP altorithm is introduced by spaceborne sparse array radar and applicable methods for solving the problem. On the analyzing basis of the general DPCA condition, nonuniform linear array with periodic structure destroyed and waveform diversity/frequency diversity techniques, we proposed a new STAP algorithm incoperating the idea of Minimum Redundancy Arrays (MARs) and Optimally Irreducible Arrays (OIAs), to solve the blind zone problem for space-based distributed aperture radars. Simulations show that the proposed aglrorithm can greatly reduce the number of blind zones and achieve better detection performance than that of waveform diversity algorithm with less widening of the notch of the SINR curve.更多还原