基于傅里叶系数权函数的宽带波束形成算法

提出了一种基于傅里叶级数系数函数权的宽带恒定束宽波束形成方法。该方法首先确定各个子带中心频率处的波束响应图,继而利用傅里叶系数求取公式分别求得各个子带中心频率处对应的权函数。并通过仿真验证了该方法可实现在信号带宽内基阵波束图主瓣宽度保持恒定,与基于Bessel函数的方法相比,具有更高的运算效率。     

宽带波束域频率聚焦自适应波束形成算法

针对传统时延控制波束形成器无法适应宽带信号接收的问题,提出一种宽带波束域频率聚焦自适应波束形成算法。首先,通过时延控制方法在空间预设方位形成多个独立波束,利用傅里叶变换将多波束数据变换到频域,针对每个频点构造聚焦矩阵,通过聚焦变换将宽带信号对齐到同一参考频率;然后,估计子带聚焦后的协方差矩阵,并进行特征分解得到信号子空间;最后,利用基于特征子空间(ESB)的波束形成方法得到权矢量,实现自适应波束形成。仿真结果表明,该算法能够实现对宽带信号的自适应接收,具有良好的抗干扰能力和稳健性。     

基于加权最小二乘的宽带波束形成算法

宽带波束形成技术是阵列信号处理研究的一个重要方向。基阵对信号的响应特性随频率而改变导致通过基阵的宽带信号产生波形畸变。恒定束宽波束形成可以实现在信号带宽内基阵波束图主瓣宽度保持恒定。主要研究基于加权最小二乘的恒定束宽宽带数字波束形成方法及其实现,MATLAB仿真实验表明算法的正确性和有效性。     

宽带波束形成技术的研究

在很多情况下,要求基阵能够不失真地接收宽带信号,因此要求波束形成器的波束图具有与频率无关的特性。深入研究了利用自适应方法设计具有特定频率响应的FIR滤波器用于进行时域宽带波束形成的应用,给出了仿真结果,验证了算法的有效性。采用FPGA或DSP实现带通滤波器是一项成熟的技术,所以通过设计特定频率响应的FIR滤波器来实现宽带波束形成技术在工程上是可实现的。     

基于凸优化的最小旁瓣恒定束宽时域宽带波束形成

 提出了基于凸优化的适用于任意结构基阵的最小旁瓣恒定束宽时域宽带波束形成方法.首先将基阵波束响应表达成一组有限脉冲响应(FIR)滤波器权值的线性函数,然后采用基于恒定束宽限制条件的最小旁瓣优化准则设计FIR滤波器权值.同时对滤波器系数进行范数约束以及对干扰方向设置展宽零陷来提高波束形成器的鲁棒性.将期望波束响应的设计过程与实际波束响应的逼近过程融合在一起进行优化搜索,获得了全局最优解.该波束形成器设计问题被转化成凸优化问题求解,仿真结果验证了所提方法的有效性.     

空间重采样法恒定束宽波束形成器设计

本文视均匀线列阵为连续线阵的均匀离散采样，将宽带方位估计中的空间重采样思想用到恒定束宽波束形成器设计中，并从滤波器设计的观点出发，将阵元权系数等效为空间滤波器的脉冲响应，提出用恢复公式计算不同频率所对应的阵元权系数，从而利用频域波束形成的方法完成恒定束宽波束形成器设计。     

一种子阵级宽带数字波束形成技术

在宽带数字阵列设计中,传统的窄带数字波束形成方法会导致带宽范围内不同频率的信号之间存在指向偏差。文章从宽带数字波束形成的原理分析出发,给出了基于子阵级划分的宽带数字波束形成算法,并通过仿真实验结果验证了子阵级宽带数字波束形成的可行性。     

基于子阵的宽带数字恒定波束形成技术

主要研究了基于子阵的宽带恒定波束形成方法,探讨了子阵带宽、子阵大小和最大波束偏移角三者之间的约束关系,最后给出了在子阵级实现低副瓣宽带波束形成的条件。     

基于空-时子带结构的宽带波束形成

提出一种基于空域嵌套复合阵和时域多率子带相结合的空-时宽带自适应波束形器。子带的实现以通用参数滤波器组为基础。每个子阵的宽带波束处理器采用同一组FIR滤波器来实现,大幅减少了加权数目,同时子阵实现了并行处理,每个子阵工作在最低的采样速率下,进一步降低了处理器的运算量。仿真结果表明,此结构的处理器不仅能实现宽带波束形成,而且还大大降低了波束形成器的数据运算量。     

时域宽带自适应波束形成器设计

针对现有含反馈支路的时域宽带自适应波束形成器运算量大、干扰抑制能力受限的问题,基于广义旁瓣相消结构,引入一条固定系数的全极点反馈支路,设计一种新的时域宽带自适应波束形成器,减少了前向支路所需抽头延迟线个数即自适应权个数,从而降低了运算量,加快了收敛速度。全极点反馈支路以逼近包含干扰频带的带通滤波器为目标进行离线最优化设计,在保证稳定性的同时,增强了波束形成器的干扰抑制能力。仿真结果表明：与现存含反馈支路的时域宽带自适应波束形成器相比,采用相同的自适应算法,设计的波束形成器收敛更快、干扰抑制能力更强;实现相同的 SINR 改善时,新的波束形成器所需运算量远小于现存波束形成器。     

基于均匀同心圆阵列的近场宽带波束形成

该文提出了一种频率不变近场宽带波束形成的方法。该方法将均匀同心圆阵列的输出经傅里叶逆变换转换成相位模式信号,并经过近场矫正和频率补偿网络,可达到频率响应不变的远场阵列响应效果。在此基础上,该文将传统远场窄带波束形成法推广到近场宽带阵列中。仿真结果表明,该文提出的近场宽带阵列响应具有近似频率响应不变的效果,其波束图也接近远场窄带阵列波束图。另外,与其他几种波束形成方法相比,基于该文提出的频率不变近场宽带阵列提升了波束形成性能,且具有较低的计算复杂度。     

Wideband beam and steering using a rectangular array of planar monopoles

This article presents the design of a wideband rectangular array of planar monopoles, which is able to steer its beam and s over a wide frequency band using real-valued weights. These weights can be realized in practice by amplifiers or attenuators leading to a low cost development of a wideband array antenna with beam and steering capability. The weights are determined by applying an inverse discrete Fourier transform to an assumed radiation pattern. This wideband beam and forming concept is verified by full electromagnetic simulations which take into account mutual coupling effects between the array elements.     

Design and Analysis of Broadband Beamspace Adaptive Arrays

A beamspace adaptive planar array for broadband beamforming is proposed based on the frequency invariant beamforming technique. A detailed analysis is provided for both the linear arrays and the planar arrays, where two conditions are imposed: the beams should exhibit a good frequency invariant property and be linearly independent. These two conditions are not independent and there is a tradeoff between them. To improve the interference cancellation capability of the array, we may need to sacrifice the frequency invariant property to some degree for more linearly independent beams. A sufficient condition for the linear independence of the beams is derived with a DFT matrix based design proposed. Simulation results verified our analysis and the proposed method.     

Broadband Frequency Invariant Beamformer

In the broadband signal processing, the array has different relative aperture for the different frequency bins, which results in waveform distortion. Moreover, the greater the bandwidth is, the more serious the distortion becomes. It is valuable to study the Frequency-invariant beam patterns (FIBPs) for receiving broadband signals without distortion. Based on the array dimensions, this paper will summarize some new methods to design a broadband beamformer with an FIBP. There will be two categories: One-dimensional arrays and Multi-dimensional arrays. For one-dimensional array, there are sampling rate method, minimax frequency invariant beamforming, etc. For multi-dimensional array, there are Bessel function method, Bessel function and phase mode method, and so on. Finally, we will discuss the pros and cons of every method.     

Uniform Concentric Circular Arrays With Frequency-Invariant Characteristics—Theory, Design, Adaptive Beamforming and DOA Estimation

This paper proposes a new digital beamformer for uniform concentric circular arrays (UCCAs) having nearly frequency-invariant (FI) characteristics. The basic principle is to transform the received signals to the phase mode and remove the frequency dependency of the individual phase mode through the use of a digital beamforming or compensation network. As a result, the far-field pattern of the array, which is governed by a set of variable beamformer weights, is electronically steerable, and it is approximately invariant over a wider range of frequencies than conventional uniform circular arrays (UCAs). This also makes it possible to design the compensation network and the beamformer weights separately. The design of the compensation network is formulated as a second order cone programming (SOCP) problem and is solved optimally for minimax criterion. By employing the beamspace approach using the outputs of a set of fixed UCCA frequency-invariant beamformers (FIBs), a new beamspace MUSIC algorithm is proposed for estimating the direction-of-arrivals (DOAs) of broadband sources. Since the beampatterns of the UCCA-FIB is approximately invariant with frequency and is governed by a small set of weights, a very efficient adaptive beamformer using the minimum variance beamforming (MVB) approach can be developed. Simulation results using broadband Gaussian and multisinusoidal inputs show that the proposed adaptive UCCA-FIB is numerically better conditioned than the conventional broadband tapped-delay-line-based adaptive beamformers, due to the FI property and significantly fewer numbers of adaptive parameters. Consequently, a higher output signal-to-inference-plus-noise ratio over the conventional tapped-delay-line approach is observed. The usefulness of the proposed UCCA-FIB in broadband DOA estimation is also verified by computer simulation     

Adaptive Beamforming Using Frequency Invariant Uniform Concentric Circular Arrays

This paper proposes new adaptive beamforming algorithms for a class of uniform concentric circular arrays (UCCAs) having near-frequency invariant characteristics. The basic principle of the UCCA frequency invariant beamformer (FIB) is to transform the received signals to the phase mode representation and remove the frequency dependence of individual phase modes through the use of a digital beamforming or compensation network. As a result, the far field pattern of the array is electronic steerable and is approximately invariant over a wider range of frequencies than the uniform circular arrays (UCAs). The beampattern is governed by a small set of variable beamformer weights. Based on the minimum variance distortionless response (MVDR) and generalized sidelobe canceller (GSC) methods, new recursive adaptive beamforming algorithms for UCCA-FIB are proposed. In addition, robust versions of these adaptive beamforming algorithms for mitigating direction-of-arrival (DOA) and sensor position errors are developed. Simulation results show that the proposed adaptive UCCA-FIBs converge much faster and reach a considerable lower steady-state error than conventional broadband UCCA beamformers without using the compensation network. Since fewer variable multipliers are required in the proposed algorithms, it also leads to lower arithmetic complexity and faster tracking performance than conventional methods.     

一种宽带数字相控阵天线比幅曲线的设计方法

随着宽带数字化技术的发展,如何利用宽带DBF 技术在电子对抗领域中进行精确测角测向一直是研 究的热点。文中论述了一种宽带数字相控阵天线比幅曲线的优化设计方法,从多波束类型的选择出发,分析了和和 交叠电平的选择、空域覆盖和增益覆盖的取舍等问题,并且通过对雷达探测领域和差比幅曲线绘制方法的演化,得 到宽带数字和和比幅曲线的绘制方法,分析了基于正弦空间的多波束比幅曲线、中心频点的频率转移、侦察频点的 频率转移等问题,最终仅用一条标准比幅曲线进行装订即可解决宽带带宽内和扫描空域内的所有和和比幅测角问 题,该设计方法拟制的宽带多波束比幅曲线,可应用于宽带数字相控阵体制的雷达探测或电子对抗领域,在简化比 幅曲线数量、减少比幅曲线存储空间、提升比幅测角测向精度等方面均有明显的优势。     

共享孔径同心圆阵稀疏交错优化布阵方法

同心圆阵列天线具有波束对称、360°方位角扫描、抗干扰能力强等优点，被广泛应用于星载、机载、舰载雷达及飞机声呐等领域。在天线孔径有限的情况下，如何进一步提高同心圆阵的孔径利用率，通过孔径的空分复用，设计出子阵稀疏交错分布的多功能同心圆阵列天线，具有较大的研究价值。利用均匀同心圆阵列天线激励与方向图函数存在二维傅里叶-贝塞尔变换关系，基于二维三次插值和密度加权，提出了一种同心圆阵稀疏交错优化布阵的方法。该方法通过对均匀同心圆阵列天线方向图采样值的频谱能量进行分析，采用三次插值的方法，实现了同心圆天线阵列方向图函数到同心圆阵元激励能量的映射转换；基于密度加权的原理，对排序后归一化阵元激励的奇偶交错选取，使得稀疏交错子阵方向图频谱能量均分匹配，实现了同心圆阵的稀疏交错优化布阵设计。仿真结果表明，该方法得到的交错子阵天线具有峰值旁瓣电平低、主瓣宽度窄且方向图性能近似程度高的优点，有效解决了同心圆阵列天线稀疏交错优化布阵的设计难题，实现了两子阵交错的共享孔径多功能同心圆阵列天线设计。     

一种恒定束宽的宽带自适应波束形成算法

宽带波束形成是相控阵雷达数字信号处理的难点。针对目前宽带波束形成只能满足单一恒定束宽或自适应情况,为兼具两种优势使雷达工作状态更佳,文中基于最小二乘算法提出了一种自适应波束形成方法,该方法通过获得自适应参考波束图,确定波束图恒定范围根据最小二乘算法求取其他频点权值,并进行宽带波束形成。该方法不仅能保证恒定束宽,而且可实现自适应零陷控制。仿真实验证明了算法的有效性。