On the transient electrical response of a piezoelectric transducer due to shock-loaded stress

The methods of transform calculus are made use of in finding the electrical response in a piezoelectric transducer due to shock-loaded stress. The response is found to be transient in character to a first order of approximation.The author is deeply indebted to Dr. D. K. Sinha for his constant guidance in preparing this paper. He also thanks the referee for his comments and suggestions for improving the paper.     

压电式传感器频率响应特性的展宽

从理论上探讨了压电式压力传感器频率响应特性的展宽原理。并利用BBD器件设计了FIR校正系统。证实了设计原理的正确性。     

Vibration attenuation by means of piezoelectric transducer shunted to synthetic negative capacitance

This paper deals with vibration attenuation by use of piezo-actuators connected to a Negative Capacitance circuit, generally formed by a synthetic impedance based on operational amplifiers.The goal of this paper is to investigate the means to improve vibration attenuation performances and to avoid instability applying proper choices of the values of the electric elements composing the Negative Capacitance. This is accomplished using an analytic-numerical approach, which furthermore affords a full understanding of this technique. The paper also illustrates the mentioned instability problems at low-frequency and provides indications on how to avoid them. The results this way obtained are finally validated through experimental tests.     

Pulsed mode of operation of a piezoelectric transducer with a correcting RL circuit

The pulsed mode of operation of a water-loaded piezoelectric plate is considered. Parallel or series RL circuits are connected to the plate, while the latter is excited by a voltage source with internal resistance R _i . The exciting pulse is preset in the form of a half-period of sinusoidal voltage with frequency equal to the antiresonance frequency of the plate. The optimal (from the point of view of obtaining the minimum duration of the emitted pulse) values of the parameters characterizing each of the emitting systems are calculated. Comparative estimates of the durations and amplitudes of emitted pulses are presented for all cases of using the RL circuits under study.     

Optimization of the performance of the sandwich piezoelectric ultrasonic transducer

The resonance and antiresonance frequency, the effective electromechanical coupling coefficient, and the mechanical quality factor of a sandwich piezoelectric ultrasonic transducer are studied and optimized. The effect of the thickness of thick piezoelectric element electrodes on the transducer performance is analyzed. The effect of the length and position of the piezoelectric elements in the transducer is also studied. It is shown that, although using thick electrodes is beneficial for releasing heat produced by the piezoelectric elements, the effective electromechanical coupling coefficient and the mechanical quality factor are reduced. The length and the position of the piezoelectric elements affect the performances of the transducer. Increasing the length of the piezoelectric elements decreases the mechanical quality factor, but the effective electromechanical coupling coefficient increases. When the length reaches a certain value, the effective electromechanical coupling coefficient reaches a maximum value. When the piezoelectric elements are located at the geometrical center or the displacement node, the effective electromechanical coupling coefficient and the mechanical quality factor are maximized.     

Application of piezoelectric transient response in transducer acoustic power measurement

To explore a more convenient method for measuring the focused ultrasound power,a piezoelectric ceramic plate was used to receive ultrasonic signal directly.Due to an acoustic force acts on the surface of piezoelectric ceramic plate,the piezoelectric response was obtained by means of electromechanical analogy,which was composed of voltage response caused by forced vibration and high frequency attenuation response caused by natural vibration.The conversion relationship between output signal of piezoelectric ceramic plate and acoustic power of transducer was analyzed.The envelope of output piezoelectric signal was extracted in twice,and a voltage amplitude curve with sinusoidal distribution that could describe the changes of acoustic power was obtained.Under different drive voltage of transducer,the maximum peak voltage of envelope curve was found respectively.Their squared values were made a linear fitting with acoustic power measured by acoustic power meter,and then the proportional coefficient of theoretical relational expression was calibrated.The experimental results are in good agreement with the theory.The relative error between calibrated theoretical acoustic power and that measured by acoustic power meter was less than 8.7%.The paper can provide a guideline for measuring acoustic power of transducer by using piezoelectric signal.     

压电瞬态响应在换能器声功率测量中的应用

探索一种简便的聚焦超声功率测量方法,利用压电陶瓷片直接接收超声信号,通过机电类比得到压电瞬态响应由压电片在声波作用力下引起受迫振动产生的电压响应与固有振动产生的高频衰减响应叠加而成,分析输出压电信号与换能器声功率之间的换算关系。对输出压电信号进行二次包络提取,获得表征声功率变化的电压幅度曲线,分别找出不同换能器驱动电压下包络曲线的最大峰值电压,将其平方值与声功率计所测声功率进行线性拟合,并对理论关系式中的比例系数进行标定。实验结果所得线性拟合度较高,且标定后所得声功率与声功率计所测值相对误差低于8.7%,证明了通过压电瞬态响应测量换能器声功率具有可行性。     

Optimization of the transfer function of an acoustooptic cell with an apodized piezoelectric transducer

It is shown that an apodized piezoelectric transducer can significantly reduce the side lobe level of the acoustooptic cell transfer function. Series and symmetric connections of the transducer sections and measures to suppress the effect of spurious elements arising in the electric circuit are proposed. In particular, the effect of spurious capacitances and inductances on the frequency response of the transducer is studied. It is shown that they violate the optimal condition for the suppression of the transfer function side lobes, especially at high frequencies. It is shown by calculations that the effect of spurious elements can be eliminated by the insertion of additional capacitors at 80 and 150 MHz.     

On mechanical response of a non-uniform piezoelectric transducer under the influence of a body-force

The mechanical response of a non-uniform piezoelectric transducer when there is a body force acting on it has been evaluated using the methods of transform calculus.The author is grateful to Dr. D. K. Sinha of Jadavpur University for his kind help in the preparation of this note.     

Amplitude-frequency response of an acoustooptic deflector with an apodized surface piezoelectric transducer

For a deflector with a surface multielement transducer having a variable length of acoustooptic interaction, amplitude-frequency responses taken at different angles of incidence of light on an ultrasonic column excited by the transducer are analyzed theoretically and experimentally.     

Equivalent circuit of the non-uniform piezoelectric transducer

An equivalent circuit of the piezoelectric transducer with the step-by-step non-uniformity of piezoelectric properties is obtained by means of solving an inhomogenous wave equation by the method of Green's functions. Synthesis assumes that the transducer is governed by pure thickness vibrations. It is shown that the circuit is valid also for the transducer with piezoelectric properties continually varying from point to point. As an example of applying the equivalent circuit the maximum efficiency of electroacoustical transformation for a non-resonant transducer has been defined.     

A method for measuring the electromechanical coupling factor of piezoelectric materials by means of transient response

Transient response of thickness mode piezoelectric plates is theoretically analyzed using a transmission line type equivalent circuit. From the analysis, a method for measuring the electromechanical coupling factor is proposed called the “Transient Response Method”. Experiments showed good agreement with the theory. The feature of this transient response method depends upon the fact that the electromechanical coupling factor of the thickness mode can be measured, when samples have a smaller ratio of diameter to thickness than the usual ratio required in the resonance-antiresonance method.     

Optimization of the parameters of an acoustic delay line by applying a rear acoustic load to a piezoelectric transducer

The operation of a microwave piezoelectric transducer whose piezoelectric element is connected through a number of intermediate layers with two acoustic loads is investigated. One of the loads is the medium in which the transducer excites elastic waves, and the other (the rear load) serves for the formation of the transducer’s characteristics. On the basis of the previous numerical analysis of the transfer coefficients for the direct and inverse transformations, the frequency dependences of the transformation efficiency and the standing-wave ratios in the transmission line (the direct transformation) and in the sound duct (the inverse transformation) are calculated. The theoretical curves that illustrate the effect of the rear load on the characteristics of a specific multilayer transducer operating in the decimetric wave range with a matching LC circuit are discussed.     

Study of the sandwiched piezoelectric ultrasonic torsional transducer

The sandwiched piezoelectric ultrasonic torsional transducer was studied. The transducer consists of front and back metal cylinders, and coaxially segmented, tangentially polarized, piezoelectric ceramic tubes. The torsional vibration of the tangentially polarized piezoelectric ceramic slender tube was studied first and its electromechanical equivalent circuit was derived. Based on the network theory and the electromechanical equivalent circuit, the torsional vibration of the piezoelectric ceramic cylinder, formed by stacking a number of identical short piezoelectric ceramic rings, was analysed and the electromechanical equivalent circuit of the piezoelectric ceramic stack in torsional vibration was developed. Finally, the sandwiched ultrasonic torsional transducer was studied and resonance frequency equations were derived which can be used to design and calculate the torsional transducers for different applications.     

用锁相环电路跟踪压电换能器并联谐振频率区

本在介绍用PLL（Phase-Locked Loop锁相环）电路进行频率跟踪的原理和实质的基础上,给出一种够跟踪压电换能器并联频率fP区间的具体电路,并通过实验研究了匹配电感和负载等对电路跟踪性能的影响,结果表明,这个电路具有很好的频跟踪和功率自动调节性能。     

Mechanical response in a composite free piezoelectric transducer with a time-decaying polarization gradient

This article aims at finding the mechanical response of a composite free piezoelectric transducer with a time decaying polarization gradient when it is subjected to an electric voltage input.The author is grateful to Dr. D. K. Sinha for his immense help and active guidance.     

Vibration characteristics of a piezoelectric open-shell transducer

This paper deals with the vibration characteristics of a piezoelectric open-shell transducer which was made by dividing a cylindrical piezoelectric transducer longitudinally into two segments. Two-dimensional governing equations were derived by using the cylindrical membrane theory. Applying mechanical and electrical boundary conditions yielded a characteristic equation for the resonance frequencies of the piezoelectric open-shell transducer. The fundamental frequency and the electromechanical coupling factor were calculated and compared with the results of the finite element analysis and experiment. The fundamental mode shape obtained theoretically was compared with the result of the finite element analysis. The theoretical analysis was verified to provide the vibration characteristics of an open-shell transducer.     

Estimation of frequency characteristics of the Tonpilz piezoelectric transducer with a bending piezoelectric disk

A Tonpilz piezoelectric transducer which has a bending piezoelectric disk on the radiation surface for widening the frequency band to improve sonar detection performance in shallow water has been proposed. Variance of transmitting voltage response of this transducer depend on the phase difference between signals which applies to the ring-stack and the bending-disk piezoelectric resonators. Thus, an estimation of an optimal phase difference, which can be applied for obtaining the maximum value of transmitting voltage response, is important factor to assemble sonar array with sonar transducers. In this paper, we applied three methods to estimate transmitting voltage response at an arbitrary phase difference from a few measurements, and the estimation errors of those methods affected by internal impedances of power sources and/or noise are investigated to select the best method. The effectiveness of the best method was verified by water-pool experiments.     

Measurement of the directional pattern of a piezoelectric transducer by the half-cylinder reference block

The possibility of measuring the directional pattern of a contact piezoelectric transducer with the use of a CO-3 reference block by measuring the field reflected from the concave cylindrical block surface is substantiated. The advantages of such measurements over those using the CO-2 reference block are demonstrated. Numerical and model results of calculating the directional patterns are presented.     

Broadening the bandwidth of piezoelectric transducers by means of transmission lines

The transfer functions of a transducer at emission and reception of ultrasonic waves are recalled and then verified. In order to broaden its bandwidth, an original method based on transmission lines properties is described.