具有单相单向换能器的水平剪切声表面波压力传感器插入损耗特性

为实现水平剪切声表面波压力传感器低损耗设计,系统研究了均匀叉指换能器(IDT)和单相单向换能器(SPUDT)器件的声波能量损耗性能。在确定最优反射系数的SPUDT结构的基础上,建立3D周期性有限元仿真模型,计算器件表面振动位移和双向输出电压瞬态响应。通过对电压信号进行傅里叶变换获得器件模型的插入损耗,并制备两种不同换能器的声学传感器,测试其频率特性和灵敏度。与均匀IDT相比,基于SPUDT器件插入损耗的仿真和实验结果分别降低了5.2 dB和5.6 dB,SPUDT器件灵敏度约为均匀IDT器件的两倍。结果表明,SPUDT能有效降低SH-SAW压力传感器声波能量的单向损耗,提高检测灵敏度,且构建的3D周期性有限元仿真模型有助于声学传感器的声波损耗分析,实现高精度和小型化的声学测量系统。      

应用于无线传感器的声表面波反射型延迟线的耦合模分析

基于耦合模理论对一种应用于无线传感器的声表面波(SAW)反射型延迟线的性能进行了优化模拟分析。结合混合等效电路模型推导出评价这种器件性能的时域反射系数S_(11)。典型的SAW反射型延迟线包含置于压电基片之上的一个换能器与沿声波传播方向设置的多个反射器。讨论了器件性能的各种结构性影响因素如换能器结构以及反射器类型等,并以此获得优化的器件设计参数。在理论优化分析的基础上,以41°YX LiNbO_3为压电基片,结合铝电极试验制作了采用单向单相换能器(SPUDT)与3个短路栅反射器的440 MHz SAW反射型延迟线器件,并与理论分析结果予以对比与评价分析。     

双凯塞尔加权的声表面波带通滤波器

仅对表面波滤波器一个换能器加权(辛克函数乘凯塞尔窗口,以下简称单加权)可控制整个频响。根据此原理,我们制作了单加权声表面波滤波器。在其基础上,用两换能器都进行幅度加权,中间加一多条耦合器结构(以下简称双加权),制成了中心频率f_0=30—70MHz,相对带宽△f_зdB=(11％—40％)f_0,带内波纹(相邻峰值)△b=±0.2—±0.4dB;旁瓣抑制SS≥42—49dB,矩形系数K_0.01=1.36—1.45的几种规格的带通滤波器。     

声表面波四相单向叉指换能器

四相单向换能器与三相单向换能器及群型单向换能器相比具有最佳的单向性,适宜用来制作宽带低插损声表面波滤波器。四相换能器的等效电路、声辐射导、静态电容以及频率响应等,还给出了简便的四相移相电路,计算了移相电路对频响的影响,从而得到了较完整的四相换能器的设计理论。 用等指长不加权的四相换能器得到了插入损耗小于0.72dB的滤波器,在仪器分度为0.1dB的仪器上观察不到带内波纹。实测频响与理论频响符合良好。     

Implementation of GHz SAW filters using quasi-harmonic interdigital transducers

本文利用准谐频设计方法,在常规光刻工艺水平上,成功地实现了GHz级声表面波(SAW)器件。准谐频叉指换能器(QHIDT)的优点为其指条宽与指间隙可以比一般的单指换能器宽,克服了单指换能器内指间的多次反射,并且又较好地解决了普通谐频叉指换能器基频抑制不好的缺点。本文给出了制作在ST石英基片上,工作频率1128MHz的声表面波滤波器的实验结果。     

利用准谐频叉指换能器实现GHz高频SAW滤波器

本文利用准谐频设计方法,在常规光刻工艺水平上,成功地实现了ＧＨＺ级声表面波（ＳＡＷ）器件,准谐频叉指换能器（ＱＨＩＤＴ）的优点为：其指条宽与指间隙可以比一般的单指换能器宽,克服了单指换能器内指间的多次反射,并且又较好地解决了普通谐频叉指换能器基频抑制不好的缺点,本文给出了制作在ＳＴ石英基片上,工作频率１１２８ＭＨＺ的声表面波滤波器的实验结果。     

双色散声表面波脉冲压缩滤波器的加权修正

本文给出了双色散声表面波脉冲压缩滤波器的一种改进的设计方法.这方法是在利用计算机进行器件性能模拟的基础上,修正指长加权包络,得出简单易行的近似设计公式.按此设计公式设计制作了三种脉冲压缩滤波器,实验结果是主付瓣比最好达到37dB.     

LB膜在SAW ILRAC及RAC相位修正中的应用

声表面波反射栅脉冲压缩器件(RAC)及直列式反射栅脉冲压缩器件(ILRAC),在脉冲压缩雷达及其他一些系统中用作匹配滤波,是一种重要的模拟信号处理器件。声表面波在器件基片上的各处速度的轻微差别将会影响器件的性能。器件中的金属膜结构(叉指换能器;金属栅条,点阵等)会改变表面波速度,因而镀膜,光刻等工艺的误差将对器件的参数产生影响,最终表现为对于到达输出换能器的声表面波的相位导致误差,降低脉冲压缩输出的主副瓣比。     

锗酸铋声表面波沟槽栅脉冲压缩滤波器

声表面波沟槽栅脉冲压缩滤波器(RAC器件)是一种优良的色散延迟线.它利用声表面波在沟槽栅阵上的反射,形成色散时延,具有时延长、带宽大、寄生信号小、可以内加权、脉冲压缩性能好等特点.制作在锗酸铋材料上的RAC器件除这些特点外,由于声表面波速度比一般材料约低一倍,因而更适于制作小体积、大时延     

基于ANSYS提取单相单向换能器耦合模参数

基于有限元理论,给出了基于ANSYS提取单相单向换能器（Single Phase Unidirectional Transducers,SPUDT）耦合模参数的方法。首先,结合声表面波在压电介质中的传播原理,给出了压电有限元分析方程和对应的ANSYS分析步骤。然后针对SPUDT结构,给出了周期性近似分析的理论模型,利用耦合场分析对其进行模态分析和谐响应分析,最后结合两者的结果来计算SPUDT的耦合模参数。本文给出基底材料为压电晶体128°YX-LiNbO₃和YZ-LiNbO₃,电极材料为铝的三种不同SPUDT的计算结果,理论结果与Hashimoto和Hartmann文献报道的结果相吻合,并且和实验测试的结果基本一致。从而给出了提取SPUDT耦合模参数的一种通用、有效的方法。     

聚苯硫醚材料复合棒型换能器

本文选择了高聚物中杨氏模量较大、损耗较小的聚苯硫醚作为复合棒型换能器的前盖板。计算了聚苯硫醚棒中的纵波传播速度,研究了基于聚苯硫醚材料的复合棒型换能器的等效电路设计方法。利用有限元方法计算了换能器谐振频率、轴向应变分布、平均耗散功率等性能参数。对本文研制的前盖板为聚苯硫醚、后盖板为钢(1#)和前后盖板均为聚苯硫醚(2#)的两个换能器进行了测试。结果表明,理论计算的谐振频率与实验测试相吻合;两个换能器的振幅均与所施加的电压成正比,且1#换能器的振幅电压比更大;两个换能器的耗散功率与外加电压平方成正比,在应变较大处耗散功率较高,导致局部升温明显,测得两个换能器温度最高处均位于应变最大位置处。1#换能器的前后振幅比为26,与同频率的金属组件换能器相比,若后盖板为尺寸相同的钢材,前盖板采用聚苯硫醚材料能够显著提高换能器的前后振幅比,且带宽也较大。      

Optimization of ultrasonic transducers

The so-called KLM-model for ultrasonic transducers is employed to optimize transducer design. Some new performance characteristics are defined which change monotonically with design parameters. These characteristics are based on the area of the envelope of the echo waveform produced by the transducer and of the corresponding amplitude spectrum. The efficiency of the transducer is defined by the round trip energy factor. The performance characteristics are used in a composite performance measure, which is then employed as a criterion in the optimization procedure. Two transducers are investigated: for medical imaging purposes and for spectral analysis of clinical echograms. The influence of electrical matching, backing impedance, matching layer impedance, bond line thickness and series induction on the optimized transducers is investigated.     

A novel ultrasonic clutch using near-field acoustic levitation

This paper investigates design, fabrication and drive of an ultrasonic clutch with two transducers. For the two transducers, one serving as a driving element of the clutch is connected to a driving shaft via a coupling, and the other serving as a slave element of the clutch is connected to a slave shaft via another coupling. The principle of ultrasonic levitation is first expressed. Then, a series-resonant inverter is used to generate AC voltages at input terminals of each transducer, and a speed measuring system with optic sensors is used to find the relationship between rotational speed of the slave shaft and applied voltage of each transducer. Moreover, contact surfaces of the two transducers are coupled by the frictional force when both the two transducers are not energized, and separated using the ultrasonic levitation when at least one of the two transducers is energized at high voltages at resonance.     

A novel ultrasonic clutch using near-field acoustic levitation

This paper investigates design, fabrication and drive of an ultrasonic clutch with two transducers. For the two transducers, one serving as a driving element of the clutch is connected to a driving shaft via a coupling, and the other serving as a slave element of the clutch is connected to a slave shaft via another coupling. The principle of ultrasonic levitation is first expressed. Then, a series-resonant inverter is used to generate AC voltages at input terminals of each transducer, and a speed measuring system with optic sensors is used to find the relationship between rotational speed of the slave shaft and applied voltage of each transducer. Moreover, contact surfaces of the two transducers are coupled by the frictional force when both the two transducers are not energized, and separated using the ultrasonic levitation when at least one of the two transducers is energized at high voltages at resonance.     

Modeling of functionally graded piezoelectric ultrasonic transducers

The application of functionally graded material (FGM) concept to piezoelectric transducers allows the design of composite transducers without interfaces, due to the continuous change of property values. Thus, large improvements can be achieved, as reduction of stress concentration, increasing of bonding strength, and bandwidth. This work proposes to design and to model FGM piezoelectric transducers and to compare their performance with non-FGM ones. Analytical and finite element (FE) modeling of FGM piezoelectric transducers radiating a plane pressure wave in fluid medium are developed and their results are compared. The ANSYS software is used for the FE modeling. The analytical model is based on FGM-equivalent acoustic transmission-line model, which is implemented using MATLAB software. Two cases are considered: (i) the transducer emits a pressure wave in water and it is composed of a graded piezoceramic disk, and backing and matching layers made of homogeneous materials; (ii) the transducer has no backing and matching layer; in this case, no external load is simulated. Time and frequency pressure responses are obtained through a transient analysis. The material properties are graded along thickness direction. Linear and exponential gradation functions are implemented to illustrate the influence of gradation on the transducer pressure response, electrical impedance, and resonance frequencies.     

Piezoelectric transducer design via multiobjective optimization

The design of piezoelectric transducers is usually based on single-objective optimization only. In most practical applications of piezoelectric transducers, however, there exist multiple design objectives that often are contradictory to each other by their very nature. It is impossible to find a solution at which each objective function gets its optimal value simultaneously. Our design approach is to first find a set of Pareto-optimal solutions, which can be considered to be best compromises among multiple design objectives. Among these Pareto-optimal solutions, the designer can then select the one solution which he considers to be the best one. In this paper we investigate the optimal design of a Langevin transducer. The design problem is formulated mathematically as a constrained multiobjective optimization problem. The maximum vibration amplitude and the minimum electrical input power are considered as optimization objectives. Design variables involve continuous variables (dimensions of the transducer) and discrete variables (the number of piezoelectric rings and material types). In order to formulate the optimization problem, the behavior of piezoelectric transducers is modeled using the transfer matrix method based on analytical models. Multiobjective evolutionary algorithms are applied in the optimization process and a set of Pareto-optimal designs is calculated. The optimized results are analyzed and the preferred design is determined.     

正交偶极声波测井换能器有限元分析*

三叠片型换能器是正交偶极声波测井仪器的重要组成部分。换能器的性能直接影响声波测井数据的质量。本文在前人工作基础上,针对三叠片型声波测井发射换能器长度方向的一阶弯曲振动工作模式,利用有限元方法,模拟了换能器结构尺寸和边界条件变化对换能器性能的影响。结果显示,结构尺寸和边界条件对换能器的谐振频率和电导值均有不同程度的影响。参考数值模拟结果,选取合适的结构尺寸参数和边界固定方式,可以调整和选择正交偶极声波测井仪器发射换能器工作频率和最大发射效率。本文研究结果对三叠片型换能器的优化设计有较好的指导意义。     

水声换能器研究新进展

文章综述了几种典型结构水声换能器近些年的新发展,包括:弯张换能器、圆柱面辐射型换能器、纵向换能器等等,主要介绍这些结构类型水声换能器的设计新思想和多方面优化改进的新成果。     

Miniature piezoelectric conical transducer: fabrication, evaluation and application

This paper reports a new type miniature-conical transducer for acoustic emission measurements. The transducer follows the basic idea and structure of a conventional NBS conical transducer, but is much compact in size and easier to use. The improvements are made possible by introducing an excimer laser micromachining method for fabricating smaller PZT conical elements, which play a key role in the transducer. Conical PZT elements with contact size less then 300 microm are laser-machined and the miniature-conical transducers are constructed. Standard quantitative acoustic emission testing is performed on a plate using the fabricated transducers and good results are observed. The transducers can be very useful in many applications involving quantitative measurements of transient elastic waves.