近场波束形成算法及其应用研究

【作者】 杨冬；

【导师】 李立萍；

【作者基本信息】 电子科技大学 ， 信号与信息处理（专业学位）， 2012， 硕士

【摘要】 阵列信号处理系统广泛地应用于声纳、航天和雷达等领域,它包括两个核心技术：信源参数估计和波束形成。现有的阵列处理系统大多都是建立在远场假设的条件下,但是阵列的远场平面波模型只有在目标处于阵列远场区时才是合理的。当目标处于阵列近场区时,远场的平面波模型不再成立。如果继续采用远场的假设进行信号处理,势必带来处理效果的下降甚至失效。本文以近场球面波模型为基础进行近场阵列信号处理相关研究,重点分析和研究了以下几个方面的内容：(1)研究了近场阵列信号处理模型,首先以阵列球面波模型为基础,推导了近场阵列响应矩阵,并与远场阵列响应矩阵进行了对比。其次,研究了近场自适应波束形成算法,以LMS算法为例进行实验仿真,实现了对同一方向上不同距离的两个信号的分离。(2)研究了近场窄带波束形成算法,包括近场常规波束形成算法(加权延时求和)和近场约束最优化波束形成算法。其中,针对相控阵波束形成系统控制复杂、成本高的缺陷,提出了一种简便的基于幅度加权的近场波束形成算法；研究了窄带条件下的阵列近场空间能量分布问题,推导了阵列近场范围内任意点处的功率密度分布函数。(3)研究了近场宽带恒定束宽波束形成算法,主要包括基于远-近场转换和虚拟变换的近场宽带波束形成算法,提出了一种基于窗函数法的近场二维恒定束宽波束形成算法。(4)研究了近场宽带源定位问题,分析了目前常见近场宽带源定位算法的优缺点,提出了一种基于子空间夹角理论的近场宽带信号定位算法,避免了信源位置预估、宽带聚焦等处理过程。本文对近场模型下的波束形成和宽带源定位问题进行了分析和研究,通过计算和仿真实验得出一些具有指导意义的结论,为近场阵列信号处理研究提供一定的参考。更多还原

【Abstract】 Array signal processing system is popularly applied in sonar, spaceflight, radar and so on. And it basically covers two key technologies:source parameter estimation and beamforming. The existing array processing system mostly is based on the assumption of the far-field conditions, but the plane wave model is applicable only when the target is in the far field of the array. The far-field hypothesis model is not appropriate when the target is in the near field. If the far-field assumption is still adopted when processing the near-field array signal, it will bring the processing result down even failure. This paper mainly studies the near-field array signal processing algorithms based on the sphere wave model, and the several aspects of content are as follows:(1) The near-field array signal processing model is studied;first of all, this paper deduces the near-field array response matrix based on the array sphere wave model, and makes a comparison between the far-field array response matrix and the near-field one. Second, it adopts the LMS algorithm for an example in the near-field adaptive beamforming algorithm simulation, and realizes the separation of two signals at the same direction but different distances.(2) The near-field narrowband beamforming problem is studied; for the narrowband beamforming, this paper’s study mainly includes the near-field conventional beamforming algorithm (delay and sum beamforming) and constraint optimization beamforming algorithm. For phased array beamforming system has the defect of complicated control and high cost, this paper puts forward a simple near-field beamforming algorithm based on the weighted amplitude theory; under the narrowband condition, this paper also investigates the near-field space energy distribution problem, and deduces the power density distribution at any point of the near-field range for an array.(3) The near-field broadband constant beam width beamforming problem is studied; this paper mainly studies the near-field constant beamwidth beamforming algorithm including the far-near field conversion and virtual transformation broadband constant beamwidth beamforming algorithm, and proposes a window function method to design the near-field2-D constant beamwidth beam.(4) Finally, this paper studies the broadband source localization method. First, it analyzes the advantages and disadvantages of the existing common near-field source localization methods, and then proposes a new near-field broadband source localization algorithm based on the theory of subspace included angle. The new algorithm can avoid the source location prediction and broadband focusing processing.In this article, the near-field beamforming and wideband source localization problems are analyzed and studied based on the sphere wave model.Through the calculation and simulation, some instructional conclusions and references are drawn for the near-field array signal processing.更多还原