Concurrent adaptive beamforming for standard hexagonal array based on dual norm‐constraint correntropy in the presence of alpha stable noise

This article presents dual norm‐constraint correntropy beamforming methods for standard hexagonal array (SHA) to mitigate the effects of alpha stable noise and maintain the sparsity of filter coefficients. Both goals are achieved simultaneously through the use of norm regularization constraint and the novel convex combination technique. Firstly, we construct constrained optimization equations considered the constraints present in the constrained least‐mean‐square (CLMS) algorithm by incorporating the maximum correntropy criterion (MCC). In addition, in order to decrease the number of active elements for limited power supply array system, we introduce an L1‐norm equation to the list of constraints of the adaptive filter that forces the coefficients with small magnitudes to zero. Then, we utilize the convexity and stability of L2‐norm to devise the constrained maximum correntropy gradient L2‐norm (CMCG‐L2) for further reducing the misadjustment caused by alpha noise and improving the directivity performance of the adaptive beamformer. A novel convex combination scheme is also reported to satisfy the conflicting requirements between the sparsity and mean‐square‐error. Our simulation results demonstrate the superiority of the proposed methods over other previously developed beamforming techniques.     

Design of robust nearfield wideband beamformers with optimum subband constraints

Design of nearfield wideband beamformers robust against microphone mismatches is of great interest in practical applications. The state-of-the-art design approach is based on the fullband processing. In this paper, the over-constraint problem suffered by the fullband design approach is studied, which typically leads to the undesired signal distortion with low-pass filtered characteristics. To combat the over-constraint problem, a new design approach for robust nearfield wideband beamformers with optimum subband constraints is proposed. The performance of the proposed design approach is evaluated and compared with the fullband design counterpart via design examples.     

Signal enhancement techniques for through-the-earth communication based on multiple references and beamforming

Through-the-Earth Communication (TEC) is very vulnerable to electromagnetic interference (EMI) and the conventional signal enhancement techniques employing local primary and remote reference antennas are unfeasible for downlink signal reception due to the limited space and complicated terrain on the receiving sites. In this paper, a novel magnetic field sensing system for downlink reception, in which multiple reference sensors are deployed locally and orthogonally with the primary receiving sensor, is introduced and the signal model is constructed from a perspective of array reception. A modified minimum variance distortionless response (MVDR) beamformer is designed by exploiting the TEC operating conditions for suppressing the EMIs and enhancing the signal. Real tests with power line harmonic interferences (PLHIs) from household wiring in laboratory and an additional wideband jamming demonstrated a great reduction of the EMIs and thus reliable downlink signal reception could be obtained.     

A Six-Beam-Switched Array Antenna for 5.2 GHz High-Speed Wireless Local Area Networks

A six-beam-switched array antenna witha flat profile was designed for the application of high-speed wirelesslocal-area networks in the range of 5–6 GHz. This six-beam-switchedarrayantenna is composed of an analog beamformer and a microstrip-slot array. Thebeamformer, including single-pole double-throw switches, quadrature couplers,and power splitters, was implemented on a single substrate, while the arraywas designed with three pairs of microstrip slots for the ease of integrationwith the beamformer as a low-profile two-layer structure. The circuitsimulator and the full-wave numerical electromagnetic simulator were employedfor circuit and antenna design to generate six spatially oriented antennabeams. Measurement of the six-beam-switched antenna was also conductedand showed the accurate generation of six switchable antenna beams.     

单指向水听器以及双圈十元阵的实验研究

从单指向水听器的定义出发,分析其在水下波束形成中的应用,并利用单指向水听器构建了双圈十元阵这一特殊的基阵模型,以此阵为基础在消声水池进行了实验研究,验证了单指向水听器应用于水下波束形成时的有效性和实用性。从理论、仿真和实测数据处理等各方面都证实单指向性水听器及其应用于基阵波束设计的可行性和优异性能。     

Mathematical model of bessel beamformer with automatic gain control for smart antenna array system in Rayleigh fading channel

This paper analyzes the mathematical model of a Bessel beamformer with automatic gain control (AGC) in a multipath scenario using a digital modulation technique and makes comparison with the one without AGC. The Bessel beamformer with AGC is designated here as the modified Bessel beamformer. The desired useful and interfering signals operate with the same carrier frequency and Doppler shifts but in different directions. Based on simulation results, this modified Bessel beamformer is shown to provide an optimum solution and to accommodate more users in real‐time base stations of mobile communication system when implemented on smart antenna array systems. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

MIMO雷达稳健的自适应失配滤波器设计算法

针对发射导向矢量存在未知误差的问题,提出了一种MIMO雷达稳健的自适应失配滤波器(Robust Adaptive Mismatched Filter,RAMiF)设计算法.该算法在稳健的接收波束形成算法的基础上,对其输出做稳健的失配滤波处理,以一定的主瓣电平损失为代价换取更低的旁瓣电平,从而提高系统对发射导向矢量误差的稳健性.仿真结果表明该滤波器在信噪比较高的情况下对发射导向矢量误差具有自适应的稳健性.     

一种小样本下的方向图副瓣控制算法

为解决常规方向图控制算法中的方向图副瓣较高、样本量较小时方向图起伏较大的问题,提出了一种小样本下的方向图副瓣控制算法。该算法在最小方差无失真响应（MVDR）波束形成器中,将输出方向图的低副瓣控制和降低样本处理数量的方法相结合,通过对MVDR波束形成器的最优权矢量附加Dolph-Chebyshev锥化权和把阵列权矢量约束于噪声子空间,得到的方向图在小样本情况下干扰置零的同时,解决了副瓣电平过高和方向图不稳定的问题,减小了快变干扰的影响。计算机仿真实验证实了所提算法的有效性。     

基于子空间的稳健自适应波束形成方法

波束形成器在声纳平台轻微震动或干扰移动的情况下出现零陷致使其工作性能下降,为此提出一种基于子空间的具有自动扩宽干扰抑制零陷的稳健波束形成方法,利用子空间投影和数据协方差矩阵非对角元加载来形成波束形成器的权向量,使波束形成器具有子空间波束形成器对系统误差的稳健性,同时可自动地在干扰方位形成展宽的干扰抑制零陷,从而使波束形成器有效地抑制干扰而稳健地工作.实验仿真的结果验证了该方法的正确性和有效性.     

一种自适应收缩因子的循环平稳波束形成器

针对常用循环平稳波束形成器收敛速度慢的问题,提出一种基于自适应收缩因子形式的对角加载方法的稳健循环平稳波束形成器.首先采用收缩因子对采样协方差矩阵进行修正然后得到估计的阵列协方差矩阵,通过求解真实协方差矩阵与估计协方差矩阵之间均方误差最小的最优问题,进而求出收缩因子的大小.最后利用循环自适应波束形成(cyclic adaptive beamforming,CAB)算法求取阵列权值.仿真过程中,用所提算法与传统的循环平稳波束形成算法在低功率干扰和高功率干扰两种条件下作对比,表明该算法在收敛速度方面具有较好的性能,并且在低采样快拍数目情况下所提算法的输出SINR也相对较高.