时域实现结构球面阵的最差性能优化稳健宽带波束形成器设计

针对球面阵模态域波束形成器对传声器失配误差敏感的问题,研究了时域实现结构球面阵的最差性能优化稳健宽带波束形成器设计。揭示了波束响应误差上界的保守性是影响现有最差性能优化方法性能的主要原因,进而提出了一种波束响应误差上界更为紧凑的优化设计方法。理论分析表明,与现有最差性能优化方法相比,所提出方法的代价函数更小、且可行解的范围也更大。针对最差性能优化设计方法存在的波束指向上阵列响应随频率变化波动偏大而引起信号失真的问题,还给出了一种减小波束图在指向方向上受信号频率影响的约束方法。仿真分析结果表明:在相同传声器失配误差条件下,所提出的设计方法要优于现有方法,得到的波束图具有更低的旁瓣级。     

Fabrication of Silicon Condenser Microphone Using Porous Silicon aa Sacrificial Layer

A new technology for the fabrication of silicon condenser microphones is presented. The technology is based on the use of porous silicon as sacrificial layer for the acoustic holes and the polyimide diaphragm for the acoustic membrane. The microphone with an open-circuit sensitivity of -107. 8dB and a flatter frequency response between 400Hz and 10kHz has been fabricated with this technology. The microphone can be used for acoustic communication.     

传声器阵列语音增强新方法与仿真实验

结合宽带LCMV语音增强和噪声自适应对消原理,提出了一种基于传声器阵列的多级自适应语音增强方法。在真实声学环境下构建实验模型并对语音信号进行采集,通过MATLAB仿真验证了算法。分析表明,该方法计算复杂度低,对语音信号损伤小,信号SNR提高显著。     

旋转翼无人机低功率激光探测系统

由于现存系统存在误判点较多、信号分割点方差较大的问题,因此,提出一种新的旋转翼无人机低功率激光探测系统,并对其进行深入研究.系统的硬件构成为:音频采集模块、激光探测模块、电源模块、微处理器模块、光学组件模块.其中音频采集模块主要由麦克风阵列、音频同步编解码电路以及信号调理电路构成;激光探测模块由距离激光传感器、二维激光...     

SMA、OMMT对PA6/ABS共混物聚集态结构及性能影响的研究

采用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线衍射(XRD)等手段研究了苯乙烯-马来酸酐共聚物(SMA)、有机蒙脱土(OMMT)对尼龙6(PA6)/丙烯腈-丁二烯-苯乙烯(ABS)共混物体系聚集态结构及性能的影响.结果表明,SMA与OMMT的加入均可提高PA6/ABS共混物体系的强度及模量,但加入OMMT后共混物的韧性有所下降,而PA6/ABS/SMA共混物的韧性随SMA含量的增加呈上升趋势.SMA、OMMT对PA6/ABS共混体系都有细化ABS分散相的作用,随SMA加入量的增加,ABS分散相尺寸逐渐减小,分布趋于均匀;当OMMT加入量在4 phr以内时,对ABS分散相粒径影响不大,超过4 phr后,随着OMMT含量的增加,ABS分散相的尺寸逐渐减小.XRD与TEM的分析结果表明,对PA6/OMMT(100/5)共混物,OMMT主要以剥离形态分布,同时也存在少量OMMT聚集体;PA6/ABS/OMMT共混物中OMMT则基本以剥离形态选择分布在PA6基体相中.     

埋入电容基板技术

概述了埋入电容树脂基板的高频特性和埋入电容树脂基板的制造例,可以获得20PF/mm~2的电容密度。与表面安装部件相比,埋入电容具有优良的电性能和安装占有面积小的优越性。     

噪声环境下信号相位获取的快速算法

提出一种基于快速傅立叶变换(FFT)的算法来计算噪声环境中的有用信号相位,可用于无线通信中双传声器应用系统中的自适应定向。通过理论推导和仿真结果给出有效计算有用信号相位,进而提供有效减小来自目标信号不同方向噪声的方法。与其他一些可用的方法相比,此方法实现简单,可以消除处理单元的附加时延,有效解决传声器适配问题,并可排除目标信号必须严格的在正前方的假设。     

Studies of structures of poly-ε-caprolactam/montmorillonite nanocomposite: Part 2. Tests of annealed specimens

Using the novel version of thermomechanical analysis (TMA) method, a poly-ε-caprolactam (PA6) and its nanocomposite (PNC) containing 1.6 wt.% of montmorillonite (MMT) were examined. Several disc specimens of those as investigated in the first part of this article were then melted, annealed, and sheared at a rate of 0.5 s⁻¹ engendering ca. 140% strain at 240 °C in a rotational rheometer, and next solidified in ambient air. In PNC as in PA6 specimens prepared in the same way, an amorphous isotropic structure in the surface layer up to 0.5 mm thick was identified, with topological regions differing in thermal expansion properties and related a state of order. This finding differs from other tests, which detect a high level of crystallinity. Probably, it is related with small thickness of the tested layer of material and kinetics of solidification in ambient air.An increase in the free volume fraction, V_f^TMA, evaluated as equal to 3ΔαT_g (Δα is the difference in linear thermal expansion coefficients below and above the glass transition temperature T_g) and resulted from melting, annealing, shearing, and next solidification in ambient air was observed. It suggests that these operations introduce into the specimen some amount of gases (e.g., evaporated water absorbed when cooling) what increases thermal expansion over high-temperature transition of the high-temperature topological region. It means that V_f^TMA is a sum of all voids within a specimen tested (not only a real free volume) independently on their origin. Because of this, it is better to term it as micro or nanoporosity.     

基于麦克风阵列的宽带健壮自适应波束形成算法

研究了用于麦克风阵列语音增强的宽带健壮自适应波束形成算法。该算法结合频率聚焦技术和对角加载技术。在此基础上,通过优化最坏情况下的波束性能确定对角加载因子,求得了最优加载因子的近似解析表达式。和相关算法相比,使用最坏情况性能优化的算法具有更好的语音增强性能,由于求得了最优加载因子的解析解,还具有运算量低、容易实现等优点。同时,该解析解揭示了哪些因素可以影响最优加载因子,以及如何影响。计算机仿真验证了该结果的正确性和有效性。