基于有限元法的声表面波换能器电荷分布的静电解

从麦克斯韦方程和声场波动方程出发，在准静态近似的条件下，建立分析声表面波换能器的有限元方程，计算声表面波换能器表面的静电荷分布，并把有限元计算结果和格林函数法结果进行了比较，为声表面波器件的结构优化和设计提供精确的参数。     

基于COMSOL的声表面波器件仿真

声表面波器件在通信、传感、射频识别等领域有着广泛的应用.以有限元方法为基础,利用有限元软件COMSOL对声表面波器件进行了仿真.从器件的模型建立入手,按由浅入深的顺序对无电极压电基片、压电基片表面沉积叉指换能器、叉指换能器表面溅射薄膜、薄膜上负载液体的4种结构进行了仿真分析.仿真研究表明:叉指换能器的电极效应会产生正、反特征频率,并且两种频率都随着叉指电极的敷金比与高度增加而向低频偏移;薄膜厚度的增加同样会导致器件频率向低频变化;当器件负载液体用于液体密度检测时,可通过器件频率变化对液体密度的灵敏程度来对薄膜厚度进行优化.其研究结果可以为声表面波器件的设计制作提供依据.     

硅酸镓镧单晶材料的声表面波标签研究

声表面波射频识别标签在射频标签领域获得广泛关注,其中对标签基底材料的研究也成了研究热点。文章旨在研究使用硅酸镓镧单晶材料为压电基底的声表面波标签的标签特性。对使用硅酸镓镧单晶材料为压电基底的声表面波标签进行频域和时域分析,并结合有限元分析方法,对标签的特征频率、叉指换能器(Interdigital Transducer, IDT)的反射系数、叉指电极金属化比、金属电极厚度以及标签回波特性进行研究分析,提取了耦合模COM(Coupled-mode)模型参数。分析结果表明了压电效应是声表面波的谐振与反谐振频率存在的根源,验证了脉冲幅度编码方式,并为使用硅酸镓镧材料作为压电基底的声表面波标签的制作提供了仿真实验依据。     

声表面波器件中叉指换能器及外电路引起的附加相移特性

一般的声表面波器件是由与外电路相联接的两个叉指换能器组成，其中所要处理的信号都要经受电 － 声和声 － 电两次转换。又指换能器的结构和外电路的特性对这些转换的效率和相位变化有着密切的联系。本文从声表面波又指换能器交叉场等效电路模型出发，较详细地讨论了声表面波器件中输入、输出又指换能器的设计参数（中心频率和叉指电极对数等）及外电路负载和匹配网络对信号的转换效率和相移（或延迟时间）的影响。本文还针对某些又指换能器的实际例子，给出了详细的计算数据。文中所给出的公式和计算结果，可作为设计声表面波延迟线和振荡器的参考。     

宽通带小矩形系数的声表面波滤波器

一、声表面波滤波器的设计 理论分析指出,叉指换能器的频率响应[H(ω)],可由叉指换能器的脉冲响应H(t)通过付里叶交换求得,而叉指换能器脉冲响应H(t)的包络恰好是叉指换能器叉指指端的轨迹。所以叉指换能器的脉冲响应就是叉指换能器的空间图像。这种一一对应的关系可由图1来说明。由此可知,通过对叉指换能器电极指条位置与重迭长度的设计便能控制叉指换能器的脉冲响应,从而也就控制了叉指换能器的频率响应。 在一般情况下,声表面波滤波器中的二个叉指换能器只有一个是设计成加权的,另一个采用简单的宽带形式。此时滤波器的频率响应只取决…     

Ⅳ型弯张换能器的数字建模

Ⅳ型弯换能器的振动机理比较复杂,它包涵着驱动振子的振动、壳体的振动、水介质振动及它们之间相互耦合而构成的复合振动。本文对其进行了较详细的理论分析,给出了换能器壳体的振动位移分布和谐振频率。并根据干模态讨论了换能器在水中的声辐射特性;再者,结合压电方程及换能器的振速、应力分布给出了换能器在水中的电机声等效电路。理论分析结果与有限元法及实验测量进行比较,符合较好。     

IV型弯张换能器的数学建模

ＩＶ型弯张换能器的振动机理比较复杂,它包涵着驱动振子的振动、壳体的振动、 水介质振动及它们之间相互耦合而构成的复合振动。本文对其进行了较详细的理论分析,给 出了换能器壳体的振动位移分布和谐振频率。并根据干模态讨论了换能器在水中的声辐射特 性;再者,结合压电方程及换能器的振速、应力分布给出了换能器在水中的电机声等效电路。 理论分析结果与有限元法及实验测量进行了比较,符合较好。     

超磁致伸缩换能器磁力耦合固有特性分析

建立了超磁致伸缩换能器弹性支撑连续体磁力耦合模型,从第一类压磁方程出发,利用简化后得出的轴向压磁方程,建立了超磁致伸缩换能器的磁力耦合波动方程,在静态磁场下对换能器的磁力耦合固有特性进行了理论分析,初步确立了超磁致伸缩换能器的磁力耦合固有频率,并与一般连续体纵向振动固有频率进行了分析比较.     

抑制声表面波器件中三次行程信号的阻抗失配法

本文介绍了抑制声表面波器件中三次行程信号的阻抗失效法的工作原理，分析工纯电阻负载凡对电感并联调谐和串联调谐时表面波叉指换能器的声反射损耗Ｌ１１和声电转换损耗Ｌ１３。的影响，给出了三次行程信号与表面波器件频率响应波纹的关系。     

超磁致伸缩超声换能器结构研究

为了实现大功率、大振幅的超声振动输出,设计了一种新型的超磁致伸缩超声换能器,换能器的形状是一个窗形的结构,用ANSYS软件对设计的超磁致伸缩换能器进行动力学分析,验证了设计方法的有效性。采用ansoft Maxwell软件分别对窗形换能器和棒形换能器进行了磁分析,发现窗形换能器的磁路是一个闭合的磁路,漏磁较少。分别对窗形换能器和棒形换能器的阻抗和振幅进行测量。结果表明,窗形换能器和棒形换能器的谐振频率基本一致,窗形换能器的阻抗比棒形换能器的阻抗要小很多,但是在相同的驱动电压下,窗形换能器的平均振幅大约是棒形换能器平均振幅的1.5倍。窗形换能器的阻抗小、结构紧促、输出振幅大,是未来超磁致伸缩换能器发展的新方向。     

A simple equivalent circuit for interdigital transducers based on the coupled-mode approach

The coupled-mode approach is a powerful tool for analyzing surface acoustic wave (SAW) periodic structures such as reflectors and interdigital transducers. The relations among the terminal quantities at two acoustical ports and one electrical port of an interdigital transducer (IDT) are derived from coupled-mode equations. A simple distributed-parameter equivalent circuit representing the entire IDT is proposed. A few examples of applications of this equivalent circuit to analysis of SAW devices are presented.     

An electroacoustic method for measuring the intensity of high-powermicrowave pulses

A microwave electric field intensity meter for single high-power radiowave pulses is described. A surface acoustic wave (SAW) dielectric acoustic line is used which has nonlinear electroacoustic properties and is comprised of two transducers. The first (nonlinear) transducer is affected by a microwave electric field and provides the SAW excitation due to nonlinear effects. A delayed SAW signal, carrying information about the electric field strength, is received by a linear interdigital transducer     

Fast computation of static capacitance for periodic SAW transducers

An efficient algorithm to compute the static capacitance of periodic SAW (surface acoustic wave) interdigital transducers is proposed. The method is based on a new formulation of the well-known relationship giving the capacitance as a linear combination of the charges induced on an infinite transducer for one-electrode excitation. Besides computational efficiency, an interesting physical interpretation of static capacitance results. The algorithm itself is also tailored to split-finger transducers.     

Effects of package parasitics on the performance of SAW filters

Effects of package parasitics on the performance of SAW filters were evaluated. A quasi-static approach based on the finite difference method (FDM) in conjunction with the current simulation method (CSM) was used to extract lumped element parameter values of common interconnections that are found in typical SAW packages. The influence of bond wire connections and package leads on the performance of common interdigital transducers (IDTs) was evaluated     

Suppression of bulk-wave responses in SAW devices using thedifference of power flow angles

If spurious bulk-waves are radiated from the launching interdigital transducers (IDT's) in surface acoustic wave (SAW) devices, it is possible to reduce bulk-wave responses by steering the beams out of the receiving IDT by use of the difference of power flow angles (PFA's) between SAWs and bulk-waves. The spurious bulk wave suppression scheme is clarified. A new crystal cut with excellently suppressed bulk-wave responses using this scheme is located for quartz     

Optimization of broadband withdrawal weighted interdigital transducers for high selective SAW filters

The problem under discussion is the design of highly selective broadband surface acoustic wave (SAW) interdigital transducers (IDT) with uniform electrodes. In most SAW filters, such transducers are used with apodized IDTs or instead of them. The proposed optimization algorithms are intended for improvement of IDT selectivity by means of a withdrawal weighting (WW) technique. Unlike the familiar methods of WW transducer optimization, these algorithms choose the best IDT structure on the basis of how well it meets the specifications, not in the time but in frequency domain directly. This approach is more effective for broadband WW transducers. A number of SAW filters have been designed using the described algorithms. Their experimental characteristics follow: bandwidths of 0.5 to 15%, stopband rejection of 40 to 50 dB, 3 dB/40 dB shape factors of 1.07 to 1.3.     

Rigorous treatment of leaky SAWs and new equivalent circuitrepresentation for interdigital transducers

Leaky surface acoustic wave (SAW) interdigital transducers (LDTs) formed on 36° YX-LiTaO₃ and 41° and 64° YX-LiNbO ₃ are theoretically analyzed, and a new equivalent circuit representation is proposed. The influence of the attenuation constant due to leakage as well as conductance caused by bulk wave radiation are taken into account. A new treatment based on an integral equation approach provides all circuit parameters. Fundamental experiments show fairly good agreement between theoretical and experimental results, confirming that this treatment provides very accurate tools for designing leaky-SAW devices     

A fast Green's function method for the analysis of IDT's for acousto-optical devices

Surface acoustic wave (SAW) interdigital transducers are key components in X-Y LiNbO₃ acousto-optical (A-O) devices. SAW interdigital transducers (IDT's) on this substrate exhibit a high spurious resonance that may reduce the A-O efficiency. In this paper we present a detailed analysis of X-Y LiNbO₃ IDT's based on a fast Green's function method (GFM). In order to correctly evaluate the spurious effects on IDT's performance, we also considered bulk terms of the Green's function. When the GFM is applied to IDT's with general topology and over a wide frequency range, the required computation time can reach quickly unacceptable values for long IDT structures. We developed a new model order reduction technique based on the singular value decomposition (SVD) for the fast generation of the IDT's frequency response. Numerical results for different configurations of X-Y LiNbO ₃ IDT's are in good agreement with measured data and a correct interpretation of the spurious resonance is reported. It is pointed out that bulk wave excitation may be a serious limitation in the design of efficient, wide band IDT's for A-O devices     

Surface acoustic wave characteristics and electromechanical coupling coefficient of lead zirconate titanate thin films

Lead zirconate titanate (PZT) thin films were created on ST-X quartz using radio frequency magnetron sputtering deposition. PZT films deposited on quartz are used as a new piezoelectric substrate for surface acoustic wave (SAW) devices. Microelectromechanical technique was used to fabricate interdigital transducers on the surface of the substrate to be used as a SAW delay line device. The results show that the PZT film was successfully deposited on ST-X quartz, and that the PZT film on ST-X quartz can enhance the electromechanical coupling coefficients of SAW.