基于嵌套阵列的稀疏表示稳健波束形成方法

针对波束形成中目标方位失配以及噪声加干扰的协方差矩阵非精确重构造成的波束形成方法性能下降的问题,提出一种基于嵌套阵列的稀疏表示稳健波束形成方法。在该方法中,计算嵌套阵的采样协方差矩阵,通过差合作阵处理得到一孔径扩展的虚拟均匀线列阵;基于稀疏表示的方法来估计目标以及干扰的准确方位信息;进一步利用得到的方位信息构造导向矢量,通过最小二乘方法计算干扰信号的精确功率值;最后重构干扰加噪声协方差矩阵,通过波束形成实现干扰抑制。数值仿真表明,所提方法有效提升了干扰加噪声协方差矩阵重构精确度,在不同信噪比和快拍数条件下,输出信噪比都能逼近最优信干噪比,验证了该算法的有效性。     

Adaptive array beamforming for cyclostationary signals

This paper concerns the adaptive array beamforming using signal cyclostationarity. We present recursive algorithms for implementing the self-cohesive restoral (SCORE) approaches which were originally developed by Agee, Schell and Gardner (1990) to perform blind adaptive signal extraction using antenna arrays. Utilizing the theory of matrix factorization in conjunction with a power normalization scheme, we first reformulate the original problems considered by the SCORE approaches as simpler constrained optimization problems. By employing the modular Gram-Schmidt orthogonalization (GSO) structure, adaptive algorithms are then developed for finding the optimal weight vector. It is shown that although the GSO structure used requires a computation load O(N² ) for an adaptive-beamformer with N elements, the computing time required for producing an output data vector is reduced to O(N) due to the pipeline implementation suitable for the GSO process. The convergence property for each of the proposed algorithms is considered. A simple and efficient method is proposed for choosing appropriate initial guesses to initiate the adaptive algorithms. Simulation examples are given to show the effectiveness of the proposed algorithms     

Edge-connected, crossed-electrode array for two-dimensionalprojection and beamforming

A novel geometry for planar structures which allows simpler implementation and construction while trading off higher signal processing costs and possible reduced performance is introduced. A geometry for array construction which uses two sets of orthogonal striped electrodes is discussed. The basic operation principles of the geometry are given. While obtaining N² intersecting points in a two-dimensional structure, only 2N control points are required. Thus, N² active elements are controlled with 2N degrees of freedom, which simplifies both implementation and data handling. This gain in simplicity is traded off against reduced performance when used as a projector and increased signal processing when used in beamforming if the process is carried out in a two-step process. The limitations of the crossed-electrode geometry and discussed, and a theory for operation as a projector and a receiver is presented     

Least-squares regenerative hybrid array for adaptive beamforming

The least-squares method is applied to adaptive beamforming in a regenerative hybrid array that utilizes both the steering vector and reference signal acquired from the array output to preserve the desired signal. It is shown that like the gradient-search-based regenerative hybrid array, the proposed array converges to the steady state of the Applebaum-type array adapted without the desired signal present. The array transient behavior is simulated with weights updated by the QR decomposition algorithm. Results show that the least-squares regenerative hybrid array converges much faster than the original regenerative hybrid array on which it is based. Simulations of the steady-state performance show that the regenerative hybrid array performs better than high-order derivative constraint arrays     

用于声学波束成形的传声器阵列设计与优化

针对目前传声器阵列对于中低频声源(尤其200 Hz以下低频)识别分辨率低的问题,本文提出了一种基于波束成形算法的、对于中低频声源(150～2500 Hz)识别性能较好的传声器阵列.该传声器阵列采用渐开线螺旋臂的形式,多条螺旋臂围绕阵列中心均匀分布.采用田口法对阵列几何参数进行了选取和优化,分析出最佳参数组合和几何参数对...     

Optimum beamforming for pre-FFT OFDM adaptive antenna array

It is well known that orthogonal frequency-division multiplexing (OFDM) is robust to frequency-selective fading in wireless channels due to the exploitation of a guard interval that is inserted at the beginning of each OFDM symbol. However, once delayed signals beyond the guard interval are introduced in a channel with a large delay spread, intersymbol interference causes a severe degradation in the transmission performance. In this paper, we propose a novel pre-fast Fourier transform (FFT) OFDM adaptive antenna array, which requires only one FFT processor at a receiver, for suppressing such delayed signals. We derive the optimum weight set for beamformers based on the maximum signal-to-noise-and-interference power ratio (Max-SNIR) and the minimum mean square error (mmse) criteria, respectively. In addition, we propose a novel mmse-criterion-based commutative optimization scheme, which is more robust to the estimation error of the channel state information. Furthermore, we show the equivalence between the Max-SNIR-criterion-based scheme and the proposed commutative optimization scheme. Computer simulation results show its good performance even in channels where directions of arrival of arriving waves are randomly determined.     

A new nested array for direction-of-arrival estimation

Multidimensional Systems and Signal Processing - In this paper, the problem of direction-of-arrival (DOA) estimation with a new nested array is addressed. It is known that the original two-level...     

Experimental performance of adaptive beamforming in a sonarenvironment with a towed array and moving interfering sources

The performances of adaptive array algorithms are known to suffer from a strong degradation in scenarios with moving interfering sources. In this article, basic adaptive beamforming techniques are compared using shallow sea sonar data recorded in a towed horizontal array environment with moving interfering sources originated from shipping noise. Our experimental results show the relationship between the practical performances of adaptive and conventional beamforming techniques compared in terms of output SINR or a related measure given by the noncompensated postbeamforming interference power. These results demonstrate noticeable performance improvements that can be achieved using several robust algorithms relative to traditional adaptive beamforming schemes     

基于人工神经网络的时间调制阵列谐波波束形成

针对时间调制阵列(time-modulated array, TMA)提出了一种基于人工神经网络(artificial neural network, ANN)的谐波波束形成技术.该技术通过一个由编码器和解码器串联组成的ANN实现时序信息的优化,其中,编码器以目标角度的方向图约束值作为输入,通过在线训练输出对应的激励值;而解码器经过预训练可以实时输出辐射方向图.然后利用训练完成优化后的激励可以获得不同阵元的开关导通持续时间和起始时刻. 8元/16元不同指向TMA谐波波束形成算例仿真结果表明,所提方法可以有效抑制副瓣电平(sidelobe level, SLL),快速精确控制方向图,在目标角度实现高方向性波束形成,同时该方法具有耗时短、鲁棒性好和易调节的特点,有望应用于快速目标搜索和跟踪.     

A compact digital beamforming SMILE array for mobile communications

A compact spatial multiplexing of local elements (SMILE) scheme smart antenna array with adaptive beamforming is presented. Low-noise amplifiers are implemented as switching elements to maintain a low system noise figure and allow fast switching. The switching scheme effectively reduces N RF channels to one, reducing the amount of costly RF hardware by a factor of N. The sampling rate must be higher than the signal bandwidth based on the Nyquist criterion to ensure proper restoration of the original signal. Measured data for destination of arrival estimation, beamforming, and digital data recovery demonstrate the capability and benefits of digital beamforming with this architecture.     

Fast adaptive blind beamforming algorithm for antenna array in CDMA systems

In this paper, the maximum signal-to-interference-plus-noise ratio (MSINR) beamforming problem in antenna-array CDMA systems is considered. In this paper, a modified MSINR criterion presented in a previous paper is interpreted as an unconstrained scalar cost function. By applying recursive least squares (RLS) to minimize the cost function, a novel blind adaptive beamforming algorithm to estimate the beamforming vector, which optimally combines the desired signal contributions from different antenna elements while suppressing noise and interference, is derived. Neither the knowledge of the channel conditions (fading coefficients, signature sequences and timing of interferers, statistics of other noises, etc.) nor training sequence is required. Compared with previously published adaptive beamforming algorithms based on the stochastic-gradient method, it has faster convergence and better tracking capability in the time-varying environment. Simulation results in various signal environments are presented to show the performance of the proposed algorithm.     

分布式嵌套阵列及其DOA估计

提出了一种分布式嵌套阵列天线结构,由两个相互独立的四级嵌套子阵构成。两个子阵间存在一个基线长度,且满足一定条件。对该阵列天线接收到的信号进行高阶累积量和Khatri-Rao积运算可以得到三个完全相同的均匀直线阵列天线结构。针对新得到的阵列天线结构,使用基于空间平滑技术的双尺度酉旋转不变子空间( ESPRIT)波达方向( DOA)估计算法对信号进行DOA估计。该方法可以有效地提高阵列天线的自由度,进而达到提高估计精度的目地。仿真结果证明了基于所提出阵列天线结构的DOA估计方法的有效性。     

Robust adaptive array beamforming for cyclostationary signals undercycle frequency error

This paper deals with the problem of robust adaptive array beamforming for cyclostationary signals. By exploiting the signal cyclostationarity, the SCORE algorithms presented by Agee, Schell and Gardner (1990) have been shown to be effective in performing adaptive beamforming without requiring the direction vector of the desired signal. However, these algorithms suffer from severe performance degradation even if there is a small mismatch in the cycle frequency of the desired signal. In this paper, we first evaluate the performance of the SCORE algorithms in the presence of cycle frequency error (CFE). An analytical formula is derived to show the behavior of the performance degradation due to CFE. Based on the theoretical result, we then develop an efficient method in conjunction with the SCORE algorithms to achieve robust adaptive beamforming against the CFE. Several simulation examples for confirming the theoretical analysis and showing the effectiveness of the proposed method are also presented     

大型线阵自适应数字波束形成超低副瓣技术

自适应数字波束形成技术是现代阵列天线系统必须采用的关键技术。为了对付强有源干扰,现代相控阵雷达都必须具有自适应的干扰抑制能力。除了对抗有源干扰外,大部分雷达还要求具有强杂波背景下检测目标的能力,这就需要雷达天线具有低或超低副瓣电平。本文针对大型线阵,结合数字波束形成,讨论了在保证自适应干扰置零的前提下,如何控制自适应波束的副瓣电平,从而实现阵列系统的超低副瓣性能。     

A 2D adaptive beamforming method in sparse array

This study presents an Accelerated Proximal Gradient singular value thresholding based Linearly Constrained Singular Canceler (APG-LCSC) algorithm to improve the performance of two-dimensional (2D) adaptive beamforming in sparse array. Firstly, a signal model is established based on Matrix Completion (MC), which can be proved to meet Null Space Property (NSP). Subsequently, left and right singular value vector of the received signal matrix is achieved via MC, and then a linearly constrained singular canceler is obtained by employing the singular value vector. The proposed algorithm decreases the required number of antennas, lowers the computational complexity and has a robust performance. Computer simulations demonstrate that the proposed APG-LCSC algorithm can acquire high accuracy of 2D beamforming in sparse array.     

一种小尺寸极化阵列及其高精度定位波束形成

提出一种偶极子天线单元构成的极化敏感阵列用于全球卫星导航信号的接收,经过阵列信号波束形成后,在抗干扰的同时保留卫星导航信号中载波相位测量值的准确性,可用于基于载波相位测量的高精度差分定位。与传统的圆极化天线阵列相比,该阵列具有阵元构造简单、尺寸小的特点。通过建立极化阵列接收信号模型,分析了天线极化和波束形成算法对卫星导航信号相位的影响,给出了相适应的相位中心稳定的数字波束形成算法。仿真验证了分析的正确性和算法的有效性。     

基于自适应拟牛顿法的CDMA天线阵列波束形成

针对于CDMA系统自适应天线阵列,提出了一种新的盲自适应MSINR(Maximum Signal-to-Interference plus noise ratio)波束形成算法.首先,将MSINR准则转化为一种新的无约束损失函数,并且从理论上分析该损失函数的性质.然后,应用自适应拟牛顿方法得到在线迭代波束形成算法.该算法无需训练序,而是利用CDMA信号自身的结构特点,结合空间处理提高了系统性能.最后,给出了仿真结果,表明算法具有较快的收敛速度和良好的动态跟踪能力.     

一种基于泛函波束成形的传声器阵列优化方法

本文基于泛函波束成形算法,提出了一种可以用于二三维声源识别的传声器阵列结构优化方法和相应的优化阵列形式.本文的渐开线螺旋臂阵列设计包含4个主要几何参数:传声器数目、阵列孔径、螺旋臂的数目和基圆的大小.通过基于改进的遗传算法的优化,得出两种优化阵列:优化渐开线螺旋阵列和优化随机阵列,目的是减小波束模式的主瓣宽度以提高传声器阵列的分辨率性能.本文的优化过程包括对最优几何参数组合的寻找和对传声器坐标直接优化两个部分,优化关注点在于中低频声源识别的分辨率性能,在对比研究中发现,上述两种优化阵列在二三维声源识别方面都表现出较好的性能.     

Worst-case performance optimization for robust power control in downlink beamforming

In this paper,¹ we examine the problem of robust power control in a downlink beamforming environment under uncertain channel state information (CSI). We suggest that the method of power control using the lower bounds of signal-to-interference-and-noise ratio (SINR) is too pessimistic and will require significantly higher power in transmission than is necessary in practice. Here, a new robust downlink power control solution based on worst-case performance optimization is developed. Our approach employs the explicit modeling of uncertainties in the downlink channel correlation (DCC) matrices and optimizes the amount of transmission power while guaranteeing the worst-case performance to satisfy the quality of service (QoS) constraints for all users. This optimization problem is non-convex and intractable. In order to arrive at an optimal solution to the problem, we propose an iterative algorithm to find the optimum power allocation and worst-case uncertainty matrices. The iterative algorithm is based on the efficient solving of the worst-case uncertainty matrices once the transmission power is given. This can be done by finding the solutions for two cases: (a) when the uncertainty on the DCC matrices is small, for which a closed-form optimum solution can be obtained and (b) when the uncertainty is substantial, for which the intractable problem is transformed into a convex optimization problem readily solvable by an interior point method. Simulation results show that the proposed robust downlink power control using the approach of worst-case performance optimization converges in a few iterations and reduces the transmission power effectively under imperfect knowledge of the channel condition.     

Directional power-based admission control for WCDMA systems using beamforming antenna array systems

A directional power-based admission control (AC) scheme is proposed for base stations deploying beamforming antenna arrays. The proposed AC algorithm is a natural extension of the conventional power based AC scheme for cells using standard sector antennas. The directional scheme takes the load per beam/direction into account in the AC decision, so the cell load is controlled in accordance with the spatial filtering gain provided by using beamforming antenna arrays. The scheme is tested by means of Monte Carlo simulations in a multicell wideband code division multiple access (WCDMA) network, where users with different bit rates are present. The obtained results demonstrate that the directional power based AC scheme allows a higher traffic load in cells using beamforming antenna arrays without jeopardizing the stability of the network. Application of a four element antenna array is found to provide a capacity gain of a factor 2.7 for a network with many low bit rate users, while the gain is reduced to a factor 2.3 for traffic scenarios with a mixture of high and low bit rate users.