A new set of linear constraints for broad-band time domain element space processors

A new set of linear constraints for designing broad-band time domain element space antenna array processors is presented. The set of linear constraints is used to ensure that a desired look-direction response of the processor over a frequency band of interest can be closely approximated. The design technique is posed in such a way that three types of presteering can be handled: no presteering, coarse presteering, and exact presteering. The elimination of presteering time delays or the possibility to use coarse presteering is an attractive feature in a digital implementation of antenna array processors. The relationship that the new processor has to other broad-band processors is also established. Furthermore, the approach enables various types of errors and mismatches between signal model and actual scenario to be incorporated in the problem formulation.     

Robust presteering derivative constraints for broadband antennaarrays

The weights of an optimum presteered broadband (PB) antenna array processor are often obtained by solving a linearly constrained minimum variance (LCMV) problem. The objective function is the mean output power (variance), and the constraint space is a set of linear equations that ensure a constant gain in a specified direction known as the look direction. The LCMV optimization results in a set of weights that attenuate all signals except for the look direction signal. However, it is well known that array calibration errors can degrade the performance of the processor with only look direction constraints. For instance, a slight mismatch between the direction of arrival (DOA) of the desired signal and the calibrated look direction of the processor will cause the optimization process to interpret the signal as interference, causing signal attenuation. To alleviate the directional mismatch problem, the spatial power response of the PB processor in the vicinity of the look direction can be widened by imposing additional constraints known as the derivative constraints on the processor weights. While derivative constraints are effective against directional mismatches, we demonstrate that they are no longer robust when there are additional calibration errors like positional errors in the sensors or quantizational errors in the presteered front end of the broadband processor. The main contribution of this paper is the derivation of a new set of constraints referred to as presteering derivative constraints, which are able to maintain processor robustness despite multiple errors including directional mismatches, positional errors, and quantization errors. It is also demonstrated that the presteering derivative constraints are sufficient conditions for derivative constraints, and hence, the spatial power response of the optimized broadband processor is also maximally flat in the vicinity of the look direction     

基于波形优化和天线位置选择的MIMO雷达波束扫描算法研究

为实现集中式多输入多输出(MIMO)雷达波束扫描,本文在峰值平均功率比(PAPR)、能量以及布尔(天线位置选择)约束下,基于min-max波束图匹配准则,首次提出MIMO雷达天线位置和多组探测波形(一组波形对应一个独立的波束图)的联合优方法。由于非凸PAPR约束、布尔约束以及min-max目标函数的非凸非光滑性导致了优化问题成为典型的大规模NP-难问题。为求解该NP-难优化问题,该文首先利用Lawson算法将min-max问题转化为迭代加权最小二乘(ILS)问题,然后根据上界函数最小化(MM)准则简化ILS优化问题,最后用交替方向乘子法(ADMM)求解简化后的上界优化问题。数值仿真结果检验了所提算法的有效性。      

基于改进麻雀搜索算法的稀布线阵综合方法

针对阵列天线中阵列孔径、阵元数目、阵元间距等多约束的稀布线阵综合问题,文中提出了一种基于改 进麻雀搜索算法的稀布阵列综合优化方法。给出了改进麻雀搜索算法的流程,并在确定阵列孔径、阵元数目和最小阵 元间距的约束条件下,采用Tent 混沌映射进行天线阵元位置的初始化,提高算法的搜索性和收敛性,实现了抑制天线 峰值旁瓣电平(PSLL)的稀布线阵综合仿真。仿真结果表明,所提出的方法相比于其它文献中的优化方法,能够得到更 低的峰值旁瓣电平,稳健性好,效率高。在仿真结果的基础上,引入实际天线进行组阵分析,验证了该方法的可行性。     

A unified approach to the design of robust narrow-band antennaarray processors

A unified approach to the design of robust narrowband antenna array processors is presented. The approach is based on the idea of minimizing the weighted mean-square-deviation between the desired response and the response of the processor over variations in parameters. Three specific examples of robust design are considered: robustness against directional mismatch, robustness against array geometry errors, and robustness against channel phase errors. Initially, a general quadratic constraint on the weights is developed. However, it is then shown that the quadratic constraint can be replaced by linear constraints or at most linear constraints plus norm constraint. These latter constraints are no more complex than those required for designs which do not incorporate robustness features explicitly. Numerical results show that the proposed approach appears to offer a unified treatment for directly designing narrowband processors which are robust against various types of errors and mismatches between signal model and actual scenario     

基于框架理论的最小阵元数稀疏阵综合算法研究

随着越来越高的角度分辨率要求与进一步降低的天线成本,大规模阵列越来越普及。在重量、体积和成本有限时,要获得大孔径天线得到较高的角度分辨率,且尽量减少天线阵元数目,可采用最小阵元稀疏阵设计方法。本文基于框架理论,提出了一种新的最小阵元数的稀疏阵综合方法。该方法将稀疏阵设计问题转化为压缩感知问题模型,然后利用次优反馈的零空间追踪硬阈值算法求解。该方法可同时综合阵元位置与阵元权重来匹配给定的阵列方向图,并可有效降低阵元数。仿真实验证明了算法的正确性和有效性     

一种稀布矩形平面阵的多约束优化方法

针对矩形孔径平面稀布阵的多约束优化问题(包括阵元数、阵列孔径和最小阵元间距约束), 提出了一种基于矩阵映射的差分进化算法.该方法把差分进化算法的优化变量与阵元位置坐标按照特定的关系进行矩阵映射, 使含有多约束的阵元分布优化问题转换为仅含差分进化算法优化变量上、下限约束的优化问题, 从根本上避免了进化过程中的不可行解.通过抑制阵列峰值副瓣电平进行仿真实验, 结果显示了该算法的高效性和稳健性, 且能获得比现有方法更好的优化结果.     

Design of coherently radiating structures in a linear array geometry using genetic algorithms

The design problem of coherently radiating structures in a linear array geometry is dealt with. The key idea is to accept the unavoidable presence of the mutual coupling between antenna elements but force it to be coherent by including additional passive elements in between the active ones. This design of coherently radiating structures considers the optimization of the spacing between antenna elements by using the well-known method of genetic algorithms. Simulation results for coherently radiating structures with uniform and non-uniform separation are provided. A comparative analysis of the performance of different coherently radiating structures is achieved in order to set new design philosophies in antenna arrays.     

任务驱动的自组织蜂群柔性阵列波束赋形算法研究

根据无人机蜂群构型自组织调整位置和权向量能够实现波束指向特定方向的任务需求，该文提出了一种新颖的任务驱动的自组织蜂群柔性阵列波束赋形算法。首先，建立以无人机蜂群距离为约束、以无人机机载天线坐标位置及权向量为优化变量的波束赋形数学模型。接着，应用Lawson准则简化目标函数，将天线坐标位置及权向量的两类变量优化问题简化为天线坐标位置的单类变量优化，解决了波束赋形模型优化变量耦合带来的求解难题。同时，引入辅助变量，进行约束和复杂目标函数的分离，并通过交替方向乘子法进行求解，降低了包含约束的高度非线性优化问题的求解难度。此外，该文将上述算法扩展至目标方向不精确的应用场景。仿真结果表明，该方法可有效降低波束赋形峰值旁边电平。      

Wide-band smart antenna design using vector space projection methods

We use vector space projection (VSP) methods to design wide-band adaptive and self-healing arrays. Rectangular arrays are assumed but the VSP algorithm can be applied to any configuration. In the VSP method, we formulate a set of design constraints and then iteratively improve on a trial solution by operations known as "alternating projections". When all of the constraint sets are convex and the intersection of these sets is not the empty set, we can meet the design specifications in a finite dimensional setting. In our simulations, we show that reasonable design constraints are readily met. We demonstrate that VSP is useful for broad-band self-healing, i.e., the reconfiguration of the array when some broad-band elements fail to operate. Finally we compare our results with a known design procedure for broadband antenna arrays.     

Tomlinson-Harashima Precoding for Broadcast Channels with Uncertainty

We consider the design of Tomlinson-Harashima (TH) precoders for broadcast channels in the presence of channel uncertainty. For systems in which uplink-downlink reciprocity is used to obtain a channel estimate at the transmitter, we present a robust design based on a statistical model for the channel uncertainty. We provide a convex formulation of the design problem subject to two types of power constraints: a set of constraints on the power transmitted from each antenna and a total power constraint. For the case of the total power constraint, we present a closed-form solution for the robust TH precoder that incurs essentially the same computational cost as the corresponding designs that assume perfect channel knowledge. For systems in which the receivers feed back quantized channel state information to the transmitter, we present a robust design based on a bounded model for the channel uncertainty. We provide a convex formulation for the TH precoder that maximizes the performance under the worst-case channel uncertainty subject to both types of power constraints. We also present a conservative robust design for this type of channel uncertainty that has reduced computational complexity for the case of power constraints on individual antennas and leads to a closed-form solution for the total power constraint case. Simulation studies verify our analytical results and show that the robust TH precoders can significantly reduce the rather high sensitivity of broadcast transmissions to errors in channel state information.     

一种减小相控阵天线球面近场测量截断误差的方法

在相控阵天线球面近场测量中,有限扫描面和相控阵天线波束扫描将会引起较大的截断误差.为了解决这一问题,提出利用基于遗传算法参数优化的余弦窗函数对近场数据进行加权处理的方法来有效减小截断误差.以半波振子组成的矩形平面阵作为待测天线,对相控阵天线球面近场测量进行了计算机模拟.模拟结果表明,通过对近场数据进行加余弦窗的处理并用遗传算法对参数进行优化能够大大减小相控阵天线波束扫描时的有限扫描面截断误差,从而证实了文中所提出方法的正确性和有效性.     

Efficient implementation of robust adaptive beamforming based on worst-case performance optimisation

Traditional adaptive beamforming methods undergo serious performance degradation when a mismatch between the presumed and the actual array responses to the desired source occurs. Such a mismatch can be caused by desired look direction errors, distortion of antenna shape, scattering due to multipath, signal fading as well as other errors. This mismatch entails robust design of the adaptive beamforming methods. Here, the robust minimum variance distortionless response (MVDR) beamforming based on worst-case (WC) performance optimisation is efficiently implemented using a novel ad hoc adaptive technique. A new efficient implementation of the robust MVDR beamformer with a single WC constraint is developed. Additionally, the WC optimisation formulation is generalised to include multiple WC constraints which engender a robust linearly constrained minimum variance (LCMV) beamformer with multiple-beam WC (MBWC) constraints. Moreover, the developed LCMV beamformer with MBWC constraints is converted to a system of nonlinear equations and is efficiently solved using a Newton-like method. The first proposed implementation requires low computational complexity compared with the existing techniques. Furthermore, the weight vectors of the two developed adaptive beamformers are iteratively updated using iterative gradient minimisation algorithms which eliminate the estimation of the sample matrix inversion. Several scenarios including angle-of-incidence mismatch and multipath scattering with small and large angular spreads are simulated to study the robustness of the developed algorithms.     

智能天线阵列误差校正算法的实验验证

阵列误差的校正是智能天线技术实用化的关键所在。对各种阵列误差进行了深入分析并建立了数学模型。阵列误差可以用一个误差矩阵来表征,通过对误差矩阵的估计,能够恢复理想的阵列流型。实验结果表明,这种阵列误差校正方法能够有效减小各阵元通道之间的差异,改善了系统的性能。     

天线单元存在幅相不一致性时的波束零点合成技术

波束零点对阵列幅相不一致非常敏感,这一点往往降低了利用零点技术抗干扰的性能.为了改善波束零点在实际系统中对干扰的抑制效果,本文通过对理想约束模型进行预畸变处理,大大的降低了天线单元幅相不一致性对波束零点的影响.对该方法的进一步推广,天线单元存在方向性误差和天线单元有缺失情况下的零点合成问题也得到了解决.本文中的仿真结果和实际数据处理结果都进一步证明了该方法的有效性.     

Phased arrays in communication system based on Taguchi‐neural networks

Phased antenna array design is one of the most important electromagnetic optimization problems. This research combined the Taguchi method and artificial intelligence methods, used them as the prediction tool in designing parameters for the communication system, and then constructed a set of the optimal parameter analysis flow and steps. In this paper, we present an application of artificial neural networks in the electromagnetic domain. We particularly look at the multilayer perceptron network, which has been the most used of artificial neural networks architectures both in the electromagnetic domain and in the Taguchi optimization technique and describes the Taguchi method to optimize the excitations elements of the linear array to produce a radiation pattern with minimum side lobe level and null placement control. This paper investigates how the implementation of the signal processing in hardware affects the performance of the adaptive array antenna. The investigation is confined to uplink or receive antenna array only. Results of a prototype of antenna array with feeding values designed using the proposed techniques are also presented. Copyright © 2013 John Wiley & Sons, Ltd.     

LabVIEW与MATLAB混合编程在数字天线阵列测试中的应用

数字天线阵列由于其众多的优点使其在军事和民用领域都得到了广泛的应用。但是阵列系统的多天线单元和多收发通道必然带来阵列系统的误差,这些误差会影响系统的性能,所以必须对其进行校正。在虚拟仪器系统开发平台——LabVIEW上编制具有友好人机交互界面的数据采集和监视VI(虚拟仪器);利用MATLAB强大的数据处理能力进行数据分析。并通过LabVIEW调用MAT-LAB Script节点和COM组件法进行LabVIEW与MATLAB的混合编程,实现了阵列天线测试过程中的通道监视、数据采集和验证,最终完成了数字天线阵列的测试工作。     

Linear antenna array pattern synthesis with prescribed broad nulls

A technique of synthesizing an antenna array pattern with prescribed broad nulls is presented. The array pattern synthesis problem is formulated as a least-square null constrained optimization problem. Numerical techniques based on the matrix factorization method are developed for reducing the computational complexity of determining the optimal weight vector. Subsequently, a set of eigenvector constraints are used to approximate the effect of the quadratic constraint. Numerical results are presented to illustrate the performance achievable     

基于特征空间的极化敏感阵列滤波分析

为了提高极化敏感阵列的滤波性能,提出将基于特征空间的滤波方法和多线性约束最小方差波束形成准则联合应用到极化敏感阵列滤波中。首先给出了系统模型,然后介绍了基于特征空间的滤波方法,并进一步分别讨论了存在导数约束和零点约束的条件下不同的滤波方法,在此基础上对比分析了不同条件下的滤波性能。计算机仿真结果表明,文中方法具有比传统极化敏感阵列滤波更高的输出信干噪比,具有对阵列指向误差不敏感的特性,而且可以灵活地选择保存或不保存约束,同时也优于传统标量阵列的滤波性能。     

Constraints for maximally flat optimum broadband antenna arrays

Frequency response shaping for the direct form pre-steered broadband (PB) antenna array processor is often achieved by imposing look direction constraints on the weights of the processor. This results in a linearly constrained optimization problem. To ensure a maximally flat spatial response of a specified order in the look direction of the PB processor, additional constraints known as derivative constraints can be further imposed on the weights. In general, derivative constraints corresponding to necessary and sufficient (NS) conditions for a maximally flat spatial power response can result in a quadratic equality constrained optimization problem. We transform the quadratic NS derivative constraints to parameterized linear forms. These parameterized linear forms allow the global optimum of the quadratic equality constrained optimization problem to be obtained easily. They also provide a general framework for deriving new sets of derivative constraints which correspond only to sufficient conditions for a maximally flat spatial power response. These sufficient derivative constraints are useful for real-time processing because of their reduced computational requirements and because they ran deliver performance comparable to the NS derivative constraints