Pattern Synthesis of Nonuniformly Spaced Arrays Based on Unit Circle Representation and Taguchi Method

Unit circle representation techniques such as Schelkunoff null placement method have been extensively used to synthesize uniformly spaced linear arrays. In this work, it is attempted to extend the unit circle representation approach to synthesize nonuniformly spaced linear arrays with some desired null directions and minimum achievable sidelobe level. The problem is formulated as an optimization task upon which Taguchi method is employed to solve for the set of element positions. Illustrative examples are included to demonstrate the design effectiveness and flexibility for modern wireless communication system applications.     

一种相干信号自适应波束形成零陷展宽算法

针对传统自适应波束形成器在相干干扰位置出现快速变化时,输出性能下降,甚至干扰抑制失效的问题,提出了一种相干信号自适应波束形成零陷展宽算法。首先,对接收数据协方差矩阵进行解相干处理得到Toeplitz矩阵;其次,对协方差矩阵进行重构和优化;最后,进行零陷展宽和对角加载处理。仿真结果表明：该算法不仅能对相干干扰自适应形成宽零陷,而且可以灵活地控制零陷的深度和宽度;与Mailloux算法相比,在输入信噪比较高的情况下,该算法能得到更低的波束旁瓣电平和更高的输出信干噪比     

Beam pattern design of circular antenna array via efficient biogeography-based optimization

In this paper, an efficient biogeography-based optimization (EBBO) method is proposed to synthesize the circular antenna arrays (CAA) for specific radiation beam pattern properties and null controls. The proposed method achieves the desired beam patterns by jointly optimizing the excitation currents as well as the spaces between the array elements. Three improved components, including chaotic search theory, model learning method and a new random perturbation operator, are introduced into the standard biogeography-based optimization (BBO) to improve the performance of the algorithm. Simulation results show that the maximum sidelobe level obtained by EBBO can be suppressed effectively compared with other algorithms. Moreover, the null controlling performance of EBBO is the best among the algorithms.     

一种多模馈源的设计

介绍了一种X波段多模馈源的设计方法,采用多种的魔T形成和差网络,多模喇叭的波束宽度、零值深度与边沿照射电平结合天线的系统要求确定其结构尺寸,具有零值深、零点漂移小、隔离度高、驻波系数低及耐大功率的特点。     

Minimization in variations of different parameters in different φ planes of a small-size concentric ring array antenna using firefly algorithm

The radiation pattern of a small-size concentric ring array antenna does not remain φ-symmetric, if the array is made with an appreciably lesser number of antenna elements. The sidelobe level, first null beamwidth (FNBW), half-power beamwidth (HPBW), and the null depths of the radiation pattern change significantly in different φ planes. An efficient pattern synthesis method has been developed in this work to reduce the variation of sidelobe level, FNBW, and HPBW of a small-size concentric ring array of isotropic antennas, for different φ cuts. It is done by finding out an optimum set of amplitude distribution of the array elements using firefly algorithm. The sidelobe level and the first null depth of the array are kept below a desired value for all the defined φ cuts. The directivity of the optimized array and the uniform array has been computed. The variation of all these parameters for different φ cuts has been compared to the same array with uniform excitation among the elements.     

毫米波锥面共形相控阵天线的仿真与优化*

以弹载共形相控阵雷达导引头天线为应用背景,在未考虑极化的情况下,首先推导了任意共形天线单元方向图从局部极坐标系到全局极坐标系转换的一种实用方法;然后采用凹槽加载的中心馈电方式设计了毫米波锥面共形微带天线单元,并建立锥面共形相控阵天线模型,推导了锥面共形天线阵列的导向矢量及其方向图函数;最后采用能量迭代法对15 阵元的锥面共形相控阵天线方向图进行了仿真优化,在副瓣电平约束和零点约束两种情况下,分别给出了相应最优加权矢量的求解方法,实现了对方向图波束指向、副瓣电平以及零点的控制。     

零陷加深的自适应波束形成技术研究

在干扰方向和功率稳定的情况下,传统的自适应数字波束形成器能有效抑制干扰、提高信干噪比,但在干扰功率起伏的环境下,自适应数字波束形成器不能持续可靠地抑制干扰。针对这一问题,给出了一种增强信号中的干扰分量,再进行自适应波束形成的处理方法。该方法能根据需要对自适应数字波束形成器的自适应零点的零深进行调整,提高系统的抗干扰性能。理论分析和仿真实验验证了该方法的可行性。     

基于G-S正交化方法的宽零陷方向图综合

在线性阵列天线方向图无约束Gram-Schmidt(G-S)正交化综合方法基础上加入零点导数约束条件实现宽零陷波束图综合.此方法保持了无约束正交化方法中因采用对阵列导向矢量正交化处理而使得计算简便的优点,适合均匀或非均匀直线阵的综合.实验结果表明,此零点约束正交方法能很好实现在零阶、一阶和二阶导数约束条件下线性阵列波束图的综合.     

一种基于遗传算法的唯相位宽零陷波束赋形方法

传统阵列方向图宽零陷形成技术需要对阵元施加复加权或者阵元位置扰动等复杂操作,实际实现比较困难。提出了一种基于遗传算法的唯相位波束赋形方法,针对宽零陷特点,结合均匀线阵方向图数学模型,设计一种适应度函数,优化阵元相位扰动值,最终获得符合要求的宽零陷阵列方向图。仿真结果表明,该方法可以在唯相位条件下形成较深的宽零陷,且零陷较平坦,收敛速度较快,稳健性较好。     

Minimum p-error design of nonuniformly spaced linear array

A design method which minimizes the p-error of a weighted array pattern for nonuniform linear array is studied. The Fletcher-Powell method is used to find the minimum set of sensor locations. With uniform weight and large p, the result has sidelobes of almost equal level. In addition, an array pattern with null(s) at some specified value can be designed with proper choices of weights.     

Effects of External PIM Sources on Antenna PIM Measurements

Antenna Passive Intermodulation (PIM) level measurement results are rarely credited to be due to external signal receiving characteristics of the antennas or serious effects from external PIM sources, such as the anechoic chamber absorber and antenna tower. This paper presents an antenna PIM model for a reflected PIM measurement method. Based on the findings of null point generation and the behavior of the third order PIM values obtained by theoretical predictions and experimental results, we concluded that the results of the antenna PIM level test were influenced by the external PIM sources generated by the anechoic chamber absorber and the path differences of PIM signals coming into the antenna.     

发射DBF预置零点波束控制技术

在介绍均匀线阵发射数字波束形成技术的基础上,对预置零点的控制问题进行了研究,将发射波束的零点控制描述为一个约束优化问题,并利用Lagrange乘子法得到了发射波束的最优权值.仿真结果表明,文中给出的方法对预置零点的发射波束控制是非常有效的.     

自适应天线方向图干扰零陷加宽方法研究

在自适应天线阵抗干扰的一些应用环境中，往往需要自适应天线方向图在对准干扰的位置形成宽的零陷从而增强算法的稳定性。本文从统计模型的角度出发，导出一种对干扰零陷加宽的自适应波束形成方法，该方法能在由于数据失配引起的干扰位置扰动的情况下有效地抑制干扰，大大增强了算法的稳定性，并且方法简单、所增的运算量很小。计算机仿真结果也证明了该方法的有效性。     

分析线性反馈网络的新方法

本文应用回路阻抗矩阵的行列式和广义余因式导出一种分析线性反馈网络的新方法,深入系统地研究了网络函数,灵敏度、回归差、零回归差及其矩阵等,得到了规律性很强适合机辅分析的一系列公式。此法不局限于研究平面网络,特别适用于RLCM和流控电压源组成的受电压源激励的网络。     

旁瓣电平软约束下干扰功率搜索的波束形成

实际中,期望信号或干扰的先验方向信息往往不能精确已知(即存在阵列流形误差),当信噪比超过一定门限时,线性约束自适应波束形成器对阵列流形误差有高敏感性从而导致输出信干噪比下降。为解决上述问题,该文提出一种旁瓣电平软约束条件下搜索人工干扰功率值的波束形成方法。在粗估干扰来波方向的基础上,约束旁瓣最大峰值起伏在一定范围内,采用子空间投影和加宽干扰零陷区的技术提高波束形成器的鲁棒性,通过粗、精两种模式的搜索获得干扰零陷区的注入功率值估计,具有良好的干扰抑制效果和对阵列流形误差不敏感的特性。计算机仿真验证了方法的有效性和鲁棒性。     

基于内点法的动目标检测滤波器组设计

雷达系统常采用基于快速傅里叶变换的方法实现动目标检测(MTD)滤波器组,其关键是通过加窗降低滤波器副瓣,但普遍存在加窗的结果使滤波器零点产生偏移,不能保证非零速滤波器在零频形成真正零点。文中基于窗函数的理想频率响应构造了简化的目标函数,以零频形成零点为约束实现滤波器峰值旁瓣电平比最大化,采用内点法求解该问题,并推导了窗函数系数的显式表达式。同时,引入了扰动因子,以保证迭代过程的收敛性。仿真表明MTD滤波器组满足地杂波抑制的需求,且峰值旁瓣电平为-41 dB。该方法为MTD应用提供了一种新思路。     

分类模式挖掘在属性预测中的应用

数据挖据是一种处理海量数据的技术。分类挖掘是数据挖掘的重要方法。决策树算法能有效在训练数据集上建立数据属性和类别的映射。利用决策树算法建立目标数据库分类器,对数据对象的缺失属性预测。针对分类预测模型对单个目标多个预测类别的现象,提出一种单个目标预测结果的综合分析算法,处理结果得到单个目标的预测类别及其可信度。分类结果可用于空缺或错误字段补全或校正。     

基于Golay互补序列空时编码的MIMO雷达波形设计

针对多输入多输出(MIMO)雷达正交波形设计中数值优化方法所得波形脉冲压缩旁瓣较高的问题,该文提出一种基于Golay互补序列空时编码的设计方法。该方法利用Golay互补序列的互补性,并通过对序列构成的脉冲串进行扩展的空时编码,减小了波形的自相关旁瓣和互相关,从而降低了脉冲压缩波形的旁瓣;然后,为解决多普勒频移导致波形检测性能下降的问题,利用零空间向量加权法对脉冲压缩后波形进行多普勒补偿,显著提高了其目标检测能力。仿真结果验证了该文方法的有效性。     

Adaptive null steering beamformer implementation for flexible broad null control

An implementation of adaptive null steering beamformer for flexible broad null control, based on constrained recursive updating of array response zeros and spatial FIR filters, is presented. The design allows the beamformer to form broad nulls and control their widths readily. The new method is of great advantage for sensor array in which the number of array elements is very large compared with the number of interferences the array is designed to suppress. The new beamformer is useful and effective in the environment where both stationary and moving interference signals exist since it can steer both sharp and controlled broad nulls in the appropriate directions. When compared with the conventional LMS covariance matrix taper (CMT) based broad null synthesis method, the proposed beamformer has a faster convergence rate; and compared with the QR-RLS CMT based broad null synthesis method, the proposed method has a lower complexity.     

Null steering employing polynomials and restricted coefficients

Several novel formulations of analytic null steering algorithms for linear arrays are described. Two of them, the β-technique and the positive coefficient model, allow for placing an arbitrary number of nulls in arbitrary directions, while maintaining main-beam and sidelobe level control