单双叉指换能器的一种新算法

声表面波叉指换能器的分析是换能器分析中的重要方面。对此方面的分析已有单双叉指换能器具有激发二次谐波的作用，但过去所用的方法往往过于繁锁。本文针对单双叉指换能器，从叉指表面电荷分布函数出发，得到该结构的一种新的数学解析模型。该模型能清晰地描述单双叉指结构的二次谐波响应，及叉指的邻近效应对其频响的作用。基于该模型对叉指的频响理论分析的结论与过去的结论及实验结果较为吻合。这一模型对于综合叉指的二阶效应进行单双叉指的设计具有一定的意义     

抽指加权叉指换能器PSPICE仿真

为了能够采用EDA工具设计含高性能声表面波器件的电子系统,研究了直接应用PSPICE仿真抽指加权叉指换能器的仿真方法.它根据抽指加权叉指换能器抽指位置,结合抽指后的相邻指条特点,推导了不同抽指方式下指对等效电路模型,并与其余指对等效电路进行声学端级联、电端并联得到抽指加权叉指换能器总的等效电路模型,仿真结果与实测结果基本相近.     

叉指对数对阶梯形叉指换能器的频响特性研究

阶梯形叉指换能器具有频响性能好,设计简单等特点,为了能在实际应用中对阶梯形叉指换能器进行灵活设计,首次采用改进的δ函数模型对阶梯型叉指换能器进行建模,并通过Matlab软件进行仿真分析,研究了叉指对数对阶梯形叉指换能器频响特性的影响。分析结果表明,阶梯形结构在叉指换能器中所占比例越大,叉指换能器的主峰曲线越好,旁瓣抑制程度也越好。该研究结果对高性能声表面波器件的设计研究具有很强的实用意义。     

声表面波薄膜叉指换能器静态电容的计算

本文提出薄膜叉指换能器叉指边界上的电位分布和电荷分布的解析函数模型。用该模型计算声表面波薄膜叉指换能器的静态电容在金属化比α取[1/16,13/16]时,其误差只有千分之几。     

用电路模型分析非周期声表面波叉指换能器

本文给出一种电路模型方法,用于计算非周期又指换能器,如抽指加权和色散换能器的静电电荷分布。知道这一电荷分布就可计算出电端导纳参数。此方法中,换能器内的每一电极和间隔被分为若干小的电极,从而组成等周期阵列。每一小电极在电路中表示为一个节点。换能器的电位和电荷分布分别由节点电压及每个节点所具有的电荷给定。由电路模型得到的公式化可以用来分析长阵列非周期换能器而没有计算机内存的限制。     

用二维格林函数分析静态电荷分布

叉指换能器精确的频率响应是由它的表面电荷分布所决定的，所以，计算换能器的表面电荷受到越来越多的关注。文章推导了二维格林函数的表达式，使用二维格林函数计算了叉指换能器的静态电荷分布，最后指出为什么在表面波设计中对于切趾加权换能器的理论设计总与实验有差别，需要辅以大量的实验来修正指条的加权系数的原因。     

叉指换能器新的等效电路模型及其PSPICE仿真

声表面波器件PSPICE仿真是包含声表面波器件电子系统设计的难点,文章提出了适于PSPICE仿真的叉指换能器新等效电路模型,它应用LC网络等效Mason等效电路模型的复阻抗,由Y导纳矩阵推导计算声表面波器件的二阶效应频率特性,根据电路理论综合出与Y矩阵得到的声表面波器件二阶特性相同的等效电路,并与主信号叉指换能器等效电路模型叠加,PSPICE仿真结果与实验结果在中心频率处插入损耗和带宽相符.     

基于遗传算法的抽指加权叉指换能器进化设计

提出了极性抽指加权叉指换能器设计的新方法,克服了传统设计方法的繁杂性。将极性抽指加权叉指换能器作为染色体,通过独特的（-1,1）的二值编码,以目标频率响应曲线和待进化的叉指换能器频率响应曲线在考虑的频率范围内的1601个采样点的误差值为进化目标,对种群中的染色体进行选择、交叉和变异等遗传操作,自动进化出符合目标要求的极性抽指加权叉指换能器极性加权状况。进化实验结果表明,应用本文提出的进化方法设计出的极性抽指加权叉指换能器的频响曲线与目标频响曲线基本重合,达到设计要求,进化设计方法效率高,实用性强。     

96 MHz锥形叉指宽带声表面波滤波器

介绍声表面波锥形叉指换能器的基本原理,采用折线电极锥形叉指换能器制作的TD-SCDMA制式用96MHz宽带滤波器,1dB带宽4.8MHz,15dB抑制小于6.4MHz,插入衰耗约12dB,封装为SMD(13.3mm×6.5mm)。     

电容加权叉指换能器进化设计

为简化电容加权叉指换能器的设计过程,提出了一种新的设计方法,他将电容加权叉指换能器各指对的两加权电容差值为进化对象,目标频率响应特性和待进化的电容加权叉指换能器的频率响应特性在考虑频率范围内1601个频率点处最大差值的最小值为进化目标,通过排序选择、交叉和变异等遗传操作自动进化出符合任意给定性能要求的电容加权叉指换能器。进化实验结果表明,进化设计得到的电容加权叉指换能器频率响应几乎与任意给定的频率响应特性重叠,进化设计方法正确、高效、实用性强。     

A quasi-field equivalent circuit of an interdigital transducer of surface acoustic waves

A new equivalent circuit of a surface-acoustic-wave (SAW) interdigital transducer (IDT) is proposed. A method using this circuit for calculation of the device’s gain-frequency characteristic and impedance is described. The fingers of the transducer can be arbitrarily shaped and positioned. The electrode current is obtained via the rigorous calculation of the SAW-related charge in the piezoelectric substrate and of the charge induced by the former charge in the transducer electrodes. The method allows design of SAW devices with an arbitrary complex finger structure and a multilayer substrate.     

Analysis and measurement of transducer end radiation in SAW filterson strongly coupling substrates

The authors present the analysis of spurious responses generated at the ends of surface-acoustic-wave interdigital transducers (IDTs). Utilizing the method of moments, the analysis is based on a Green's function concept and a spectral-domain representation. The influence of end fingers as well as the influence of a grounded metal back plane on the charge distribution was simulated. Three effects are shown: the first is the charge accumulation of grounded guard fingers located close to the IDT end, resulting in unwanted end radiation: the second is acoustic end reflections in split-finger IDTs, occurring at the transition from the periodic finger structure to the free substrate; and the third is the finger charge induced by the metallic ground plane when the transducer is driven unbalanced to ground. Computer simulations based on the proposed method agree well with measurements     

多叉指Rayleigh波器件的建模及特性研究

针对目前改变Rayleigh波器件中波的传播方向和强度较复杂的问题,提出了一种多叉指Rayleigh波器件结构和三维建模方案。该三维建模方案用有限元分析法去逼近实际器件的压电基片和叉指换能器等真实器件结构和尺寸。选取压电基片材料为128°YX-LiNbO_3、叉指换能器为Al电极,分别对叉指换能器数目为4、6、8的多叉指Rayleigh波器件进行三维模型实验,验证了该器件的可行性。实验结果表明,多叉指Rayleigh波器件可以在不同角度激发Rayleigh波,该波只有x、y方向的质点位移分量,且质点的最大位移主要集中在器件表面的中心位置。此外,器件的模态频率和质点最大位移随着叉指换能器数目的增加而增大,由此产生的Rayleigh波强度和器件的混合性能也会增强。     

Unidirectional transducer for lamb-wave delay lines

A new type of unidirectional transducer is proposed and demonstrated. This transducer consists of three electrode groups, one on the bottom surface. The others are interdigital electrode groups 60° out of phase and on the top surface. Better than 20 dB of directionally was obtained for the zeroth symmetrical mode of a Lamb wave.     

基于声表面波油包水微液滴分裂研究

提出了声表面波(SAW)实现油包水微液滴的分裂方法,并在128°YX-LiNbO3基片上研制了分裂油包水微液滴的微器件。在压电基片上采用微电子工艺制作叉指换能器,其激发的SAW部分作用于油包水微液滴,瞬间降低电信号幅度,油相内水微液滴在惯性力作用下发生分裂,油相微液滴由于较大的表面张力发生形变而不分裂。以石蜡油包裹蓝色水相微液滴为研究对象,进行了油包水微液滴分裂实验和理论分析,结果表明,当电信号从功率为12.3dBm瞬间关断时,可实现油相内水微液滴分裂。     

A surface acoustic wave filter for color TV receiver VIF

A surface acoustic wave filter for color TV-VIF with a low insertion loss and high selectivity was developed using modified normal type interdigital transducers. Single-crystalline LiNbO3was used as the substrate and the electrodes were formed by photolithographic technique. The ripples in the passband were suppressed by means of a step-type transducer and the sidelobes in the out-of-band were decreased by eliminating some finger elements of the transducer. Filter chip was so small that it could be packaged in a TO-5 type can.     

Shear-wave transducer using ferroelectric medium with distributed polarisation

A new type of transducer has been obtained for exciting only tangential displacement of a wave using an interdigital transducer. The device utilises a ferroelectric medium with a distributed polarisation caused by interdigital electrodes. An exciting interdigital electrode is located at the optimum position with respect to the polarisation pattern. Experimental results obtained with one such transducer are presented.     

基于声表面波技术数字微流体微混合器研究

报道了在128°旋转Y切割X传播方向LiNbO3基片上研制了数字微流体微混合器.它由压电基片上叉指换能器和反射栅组成,当由功率放大器放大后的射频电信号加到叉指换能器时,它激发的声表面波经微流体后转化为径向表面波驱动微流体,使其与同一路径上的另一微流体合并,在反射栅反射回的声表面波共同作用下,加速微流体内分子扩散运动,提高了微流体混合效率.采用1 μL的水和1 μL红墨水以及1 μL的红墨水和1 μL甘油各自进行混合实验,结果表明:在声表面波作用下,微混合器能快速混合微流体.为片上实验室提供了廉价、易集成的微混合单元,具有潜在的应用价值.     

Frequency response of an interdigital transducer for excitation of surface elastic waves

Excitation of elastic waves in a piezoelectric solid by an interdigital transducer, in terms of a simplified model, has been analyzed using Lamb's integral solution. The transducer generates three types of disturbances propagating at the velocities of irrotational, equivoluminal, and Rayleigh waves. While the amplitudes of the former two waves diminish as the three-half power of the distance from the transducer, that of the latter does not decay with distance on the surface. Dependence of particle displacement of the waves on electric fields, number of electrodes, electrode width, and wave numbers has been derived. It has been shown that a conventional interdigital transducer, in which all the electrode widths and all the spacings are respectively equal among themselves, can respond to fundamental and odd harmonic excitations, but not to the even harmonics. Means to improve the insertion loss and the bandwidth of the transducer are discussed. A flat overall frequency response can be synthesized by parallel operation of two or more transducers, the fundamental frequencies of which are properly staggered.