智能天线是第三代移动通信系统中不可或缺的关键技术之一,埃及裂颜蝠超声辐射波束形成结构的研究可为智能天线的改进提供理论依据.文章利用时域有限差分法(FDTD)和基尔霍夫积分等数值方法研究埃及裂颜蝠鼻叶组成部分(凹坑、上叶和下叶)对超声辐射波束的影响.运用扫描和图像处理获得鼻叶的三维数字模型,对其组成部分进行剔除得到各种新的鼻叶模型,并对所有鼻叶模型进行数值计算分析,获得不同鼻叶结构的近场声压幅度分布图、远场辐射波瓣图和方向性的相关性系数.结果表明:凹坑不仅可以对近场声场进行聚焦,也会对远场声场的形成和远场辐射的方向性产生影响;上叶对凹坑附近和前方产生的声压幅度进行轻微的调节,下叶起到聚焦的作用;凹坑、上叶和下叶3个部分的不同组合会对辐射波束的形成产生复杂的影响,而这3个部分全被剔除掉的鼻叶结构对声场的分布产生的影响最大,其相关性系数平均值低于0.85.%Smart antenna is the indispensable key technology of the third generation mobile communication system,and theoretical basis obtained by this work can improve the characterise of smart antenna.The purpose of this study is to explore the effect of different parts(pit,upper leaf and lower leaf)of noseleaf on ultrasonic emission beamforming using finite difference time domain method (FDTD)and Kirchhoff integral.Three dimensional numerical model of noesleaf was built by scanning sample and processing scanned images,and all various models of noesleaf were got by removing different sections separately or together.Then,all models were studied by numerical method. Acoustic near-field pressure magnitude,far-field radiation pattern and directivity correlation coefficient were represented as results.Simulation results show that the pit has a significant impact on increasing magnitudes near the area of pit,and it also can focus the acoustic near field as well as shaping the radiation patterns and hence enhancing the directionality.In terms of the function of upper leaf,it can adjust the amplitudes of the acoustic beam near the pit and front.The lower leaf seems to overall focus the acoustical near field.What's more,interactions between the acousticeffects of the parts were also evident,and different combinations of three parts generate complicated influence on beam-forming. Theaveragedirectivity correlation coefficient of a model which was removed all three parts is lower than 0.85,this phenomenon indicates that this kind of model has the most obvious effect on the distribution of sound field.
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