Design of robust differential microphone arrays with the Jacobi–Anger expansion

Due to their small size, differential microphone arrays (DMAs) are very attractive. Moreover, they have been effective in combating noise and reverberation. Recently, a new class of DMAs of different orders have been developed with the MacLaurin’s series and the frequency-independent patterns. However, the MacLaurin’s series does not approximate well the exponential function, which appears in the general definition of the beampattern, when the intersensor spacing is not small enough. To circumvent this problem, we propose in this paper to approximate the exponential function with the Jacobi–Anger expansion. Based on this approximation and the frequency-independent Chebyshev patterns, we derive first-, second-, and third-order DMAs. Furthermore, in order to improve the robustness of DMAs against white noise amplification, we propose to use more microphones combined with minimum-norm filters. It is also shown that the Jacobi–Anger expansion is optimal from a mean-squared error perspective. Simulations are carried out to evaluate the performance of the proposed DMAs.     

Analysis and simulation of QSP beamformer

The real Direction Of Arrival (DOA) varies with time in mobile communication system. In such situation, the performance of conventional beamformers will be degraded obviously. Quantum Signal Processing (QSP) beamformer is insensitive to DOA errors, thus it can achieve stable output performance in such circumstance. This letter verified the effectiveness and feasibility of the QSP beamformer by simulation results.     

Directional neighbor discovery in mmWave wireless networks

The directional neighbor discovery problem, i.e., spatial rendezvous, is a fundamental problem in millimeter wave (mmWave) wireless networks, where directional transmissions are used to overcome the high attenuation. The challenge is how to let the transmitter and the receiver beams meet in space under deafness caused by directional transmission and reception, where no control channel, prior information, and coordination are available. In this paper, we present a Hunting-based Directional Neighbor Discovery (HDND) scheme for ad hoc mmWave networks, where a node follows a unique sequence to determine its transmission or reception mode, and continuously rotates its directional beam to scan the neighborhood for other mmWave nodes. Through a rigorous analysis, we derive the conditions for ensured neighbor discovery, as well as a bound for the worst-case discovery time and the impact of sidelobes. We validate the analysis with extensive simulations and demonstrate the superior performance of the proposed scheme over several baseline schemes.     

分布式目标下行波束形成

研究了智能天线在下行链路的应用。利用上行链路接收数据,建立分布式目标信道模型。估计移动用户的发射角、扩展角度和发射功率以及下行信道相关矩阵,确定下行链路的波束形成方法。即对频分复用（FDD）系统进行上行相关矩阵变换,构建下行信道协方差矩阵,利用最大合并比准则获得下行链路权值。计算机仿真证实了这种方法的有效性。     

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。     

基于波束形成的多类型多声源定位研究

为实现空压机多噪声源的准确定位,仿真对比了多种近场球面波多声源定位算法。基于时域波束形成,研究了相同声源平面、不同声源频率、不同声源纵向距离、不同声源强度下多声源定位以及声源频率、声源纵向距离和声源强度多因素联合的多声源定位仿真方法,模拟了更接近实际的噪声源类型。基于频域波束形成,仿真研究了1400 Hz,2400 Hz,3400 Hz,4400 Hz的多声源。分别利用互功率谱波束形成和除自谱的互功率谱波束形成,仿真研究了相干声源和不相干声源。开发了阵列声成像测试平台,运用频域波束形成和功率谱波束形成对空压机进行了定位试验研究。结果表明,1400 Hz下空压机的主要噪声源是气缸盖、空气滤清器和曲轴附近的机体,这可为空压机减振降噪改进设计提供依据。     

TDD MISO系统中波束成形的性能分析

文中首先指出在时分双工多输入单输出系统中,发送机和接收机的信道状态信息存在时延,而该时延会影响波束成形的性能增益。随后,通过推导接收机误比特率的闭合表达式,说明时延会损害接收机的性能。最后,用数值仿真验证了所做的性能分析的正确性。     

一种低快拍情况下稳健的波束形成算法

针对低快拍情况下自适应波束形成器输出方向图存在主峰偏移,副瓣电平较高的问题,该文提出一种低快拍情况下稳健的波束形成算法。算法通过对线性约束最小方差(LCMV)波束形成器的输入信号协方差矩阵进行指数修正,改善了采用协方差矩阵求逆（SMI）算法的LCMV波束形成器输入信号协方差矩阵小特征值在低快拍情况下的发散程度,从而可在减小主峰偏移的同时,有效地解决副瓣电平较高的问题;最后通过分析波束形成器输出信干噪比(SINR)随修正指数变化的情况,给出算法修正指数的取值范围。计算机仿真结果验证了该算法的有效性和优越性。      

模拟退火算法在波束图设计中的应用

摘要本文提出了基于模拟退火算法的波束设计方法。模拟退火算法模拟了固体缓慢退火从而获得最低内能的物理过程，是一种简单而有效的随机性全局优化算法。为证明该设计方法的可行性和有效性，给出了15元平面阵的设计实例以及仿真结果。结果表明，使用该方法设计的波束与常规方法相比，获得了更低的旁瓣级。     

基于相关域的二维自适应波束形成算法

 该文针对使用最小方差无失真响应算法进行2维波束形成时需要大量采样数据和庞大计算复杂度这一问题,提出一种基于相关域的2维自适应波束形成算法。通过将高维权向量分解成两个低维权向量的Kronecker积形式,使用双迭代算法利用相关域信息求解出两个低维权向量,从而降低了估计采样相关矩阵所需的采样数据和计算量。实验仿真表明,所提算法具有良好的收敛性能,在采样数较小的情况下,能够更好地抑制干扰信号。