双传声器指向性噪声消除在手机中的应用

介绍了一种手机中使用的指向性双传声器噪声消除系统.系统采用两个灵敏度一致性较好的全指向性传声器,形成锥形指向性拾音波束,只接收120.范围以内的信号,大大减少拾音波束之外的噪声干扰;紧接着使用单通道语音增强算法,可进一步衰减采集到信号中的背景噪声.实验结果表明,该系统在保持了较小的语音失真的前提下,对于各种类型的背景噪...     

低副瓣气象雷达天线增益测量及误差分析

简述了低副瓣S波段8.54 m气象雷达天线的基本特性,提出利用方向图积分法计算天线方向性增益,扣除方向图有限积分区域引起的增益损失、漏失损失、交叉极化损失、失配损失和馈源网络插入损耗,从而确定天线增益的方法。给出了各种增益损失因子的计算公式,分析了方向图积分法测量天线增益误差,其均方根误差≤"0.224 dB。最后给出了S波段8.54 m气象雷达天线增益的实测结果,测量结果同理论结果吻合很好。     

医用线列阵声场计算方法

用指向性函数分别描述了医用线列阵单频波和宽带波声场。讨论了应用电子聚焦处理、幅度加权变迹处理和孔径变迹处理的方法来改善波束特性；论述了在实际中应用较多的宽带波声场的计算。通过分析表明，宽带波持续时间愈长，宽带波声场就愈接近于单频波声场。     

Spatial and Temporal Variations of the Indoor Wireless EHF Channel

This paper reports line-of-sight propagation measurements performed at 37.2GHz between two terminals in an empty room in order to investigate the spatialand temporal fadings in terms of antenna directivity and human motion,respectively. The empirical data base consists of recordings of CW envelopefading waveforms with a fixed transmitter and either moving or stationaryreceiver. The reported results include amplitude fading distributions,propagation loss gradients, level crossing rates and fade durationsstatistics. These results can be used in the modeling, design reliableoperation of local multi-point communication systems.     

阵列天线的切比雪夫方向图综合

阵列天线是指由多个离散的辐射元,按一定规律排列组成的天线系统.其具有高增益,强方向性,主瓣可控等特性.文中研究了利用切比雪夫法对阵列天线输入不同参数:馈源单元数N,馈源间距d,副瓣电平SLL,得出参数改变对阵列天线方向图的综合影响,通过工程示例论证出切比雪夫法用于方向图综合的优缺点.为切比雪夫法用于天线方向图综合比较提供了一种有效的参考方法.     

High Performance Piezoelectric Microspeakers and Thin Speaker Array System

This paper reports on an improved piezoelectric microspeaker with a high sound pressure level of 90 dB, a total harmonic distortion of less than 15%, and coherence higher than 0.9. The fabricated Pb(Zr,Ti)O₃ (PZT) microspeakers have a thickness of only 1 mm including the speaker frame and an active area of 18 mm×20 mm. To achieve higher sound pressure and lower distortion, the PZT piezoelectric microspeaker has a well‐designed speaker frame and a piezoelectric diaphragm consisting of a tilted PZT membrane and silicone buffer layer. From the simulation and measurement results, we confirmed that the silicon buffer layer can lower the first resonant frequency, which enhances the microspeaker's sound pressure at a low frequency range and can also reduce useless distortion generated by the harmonics. The fabricated PZT piezoelectric microspeakers are implemented on a multichannel speaker array system for personal acoustical space generation. The output sound pressure at a 30 cm distance away from the center of the speaker line array is 15 dB higher than the sound pressure at the neighboring region 30 degrees from the vertical axis.     

Configurations Optimizing the Directivity of Planar Arrays

The role of the geometrical configuration of isotropic elements in a planar array is investigated with a view to achieve maximum directivity. Distinctions are made between normal and superdirective regions. It is further shown that the configurations leading to optimum directivities may depend on aperture diameter in a manner somewhat analogous to phase transitions in solid state physics. The effect of losses is estimated and it is shown that, particularly for superconductive materials, they do not affect much the achievable gain.     

声波测井相控线阵辐射器幅度加权的实验研究

在声波测井工程中使用相控线阵声波辐射器可以使声波向着接收探头一侧辐射,从而提高声波测井的信噪比和探测距离.对相控线阵进行幅度加权可以改变其辐射主瓣的角宽,这种技术在声波测井中有良好的应用前景.推导了幅度加权条件下相控线阵声波辐射器的指向性函数,研究了利用幅度加权方法增加和减小相控线阵辐射主瓣的方法并用实验测量结果进行了校验,二者取得了良好的一致性.研究表明,当相控线阵阵元幅度由阵的中心向两边对称单调增加时,阵的辐射主瓣角会变窄,反之变宽.     

复射线理论应用于天线一体化设计

分析自由空间天线辐射特性的方法已十分成熟,如口径场积分法、平面波谱积分法等,它们大都是行之有效的,但要求对天线及天线罩进行一体化分析时,现有的经典方法往往不能迅速而准确地给出解答,如果用复射线理论这一新方法则可以对某些问题圆满地给出结果.根据复射线理论,利用复源点远场具有的高斯波束特性,无论是在远区或是近轴区域内,复源点场和高斯函数有很接近的相同分布,理论上论证了对于具有高斯波束分布的口径场可以用复源点场来近似模拟.     

Analysis and design of enhanced directivity microstrip antenna at terahertz frequency by using electromagnetic bandgap material

In this paper, an electromagnetic bandgap (EBG) material in the range of 0.5–0.8 THz has been simulated with Arlon AR 600 (ε=6.0) as host material and air‐cylinders as the foreign embedded material. The effective dielectric permittivity of this material has been analyzed at the frequency range of 0.590–0.620 THz. The reduced effective dielectric permittivity substrate of thickness 50 µm has been used to design the microstrip antenna at 600 GHz with a novel approach. This proposed antenna shows an enhanced directivity of 15.1 dBi at 600 GHz frequency. To compare the analysis, the operating frequency has been scaled down by a factor of 100 and various results have been compared by using two different commercially available simulators CST Microwave Studio based on the finite integral technique and Ansoft HFSS based on the finite element method. Copyright © 2010 John Wiley & Sons, Ltd.