共查询到20条相似文献,搜索用时 93 毫秒
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Zipparo M.J. Shung K.K. Shrout T.R. 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》1997,44(5):1038-1048
The performance of transducers operating at high frequencies is greatly influenced by the properties of the piezoelectric materials used in their fabrication. Selection of an appropriate material for a transducer is based on many factors, including material properties, transducer area, and operating frequency. The properties of a number of piezoceramic materials have been experimentally determined by measuring the electrical impedance of air-loaded resonators whose thickness corresponds to resonance frequencies from 10 to 100 MHz. Materials measured include commercially available compositions of lead zirconate titanate (PZT) with relatively high dielectric constants and a modified lead titanate (PT) composition with a much lower dielectric constant. In addition, materials which have been designed or modified to result in improved properties at high frequencies are studied. Conclusions concerning the influence of the microstructure and composition on the frequency dependence of the material properties are made from the calculated properties and microstructural analysis of each material. Issues which affect transducer performance are discussed in relation to the properties. For transducers larger than about 1 mm in diameter, the use of a lower dielectric constant material is shown to result in a better electrical match between the transducer and a standard 50 Ω termination. For transducers whose impedance is close to that of the connecting cables and electrical termination, equivalent circuit model simulations show improved performance without the need for electrical matching networks. Measurements of fabricated transducers show close agreement with the simulations, validating the measurements and showing the performance benefits of electrically matched transducers 相似文献
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During the last years, measuring equipment has evolved toward the massive use of digital techniques and devices. The performance of analog-to-digital converters (ADC) and computing devices has constantly improved, and very accurate and flexible instruments can now be realized with bandwidths up to several kilohertz. Unfortunately, the transducers used to adapt the input signals to a suitable ADC input levels have not improved to the same extent so that the metrological characteristics of a DSP-based measuring instrument are mainly determined by the input transducers. Improving the performance of such transducers is thus of the utmost importance. This paper proposes a new voltage-to-voltage transducer, based on a capacitive divider and the Σ-Δ modulation techniques, that features a bandwidth wider than that of the traditional magnetic and capacitive voltage transformers. Specifications are provided on the transducer design, and the results of experimental tests on a lab prototype with primary voltage up to 500 V are reported 相似文献
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Wilhjelm JE Pedersen PC Jacobsen SM 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2001,48(2):511-521
The received electrical echo signal from a pulse-echo system insonifying a planar interface was measured for varying degrees of rms roughness [0 to 0.29 mm (0 to 1.7 λ)], angles of incidence, &thetas;, (-7° to 7°), and ranges to a planar or focused transducer. The effect of varying a is quantified in terms of the energy of the received signal, E(&thetas;), and the normalized spectrum of the received signal. E(&thetas;) is approximately Gaussian when using a planar transducer or a focused transducer with the reflecting interface located at or beyond the focal point. For focused transducers with the interface located closer than the geometrical point of focus, two maxima can sometimes be observed when varying the incident angle. As is generally known, the width of E(&thetas;) is strongly dependent on transducer type, e.g., for a smooth interface, the -3 dB width for a 25.4 mm diameter 5-MHz planar and focused transducer was approximately 0.5° and 4° (at the focal point), respectively. E(0°) as a function of surface roughness, Rq, was nearly linear on a decibel scale, with a slope of -109 dB/(Rq/λ) and -61 dB/(Rq/λ) for planar and focused transducers, respectively. The characteristic nulls present in the normalized spectra of the echo signal at non-normal incidence tend to vanish with increasing Rq when using planar transducers. For focused transducers, the normalized spectra change from relatively flat to monotonically decreasing as Rq increases, and they exhibit reduced amplitude with increased incident angle 相似文献
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Iula A Bollino G 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2012,59(1):121-127
In this work, numerical simulations and experimental measurements carried out on a high-power ultrasonic motor are presented. The proposed motor is composed of an annular shaped stator and two cone-shaped rotors. The rotors are pressed into contact with the edges of the inner surface of the stator by means of a pre-stress system. A traveling rotating wave is generated in the stator by three pairs of Langevin transducers suitably shifted both in space and time. Each transducer is designed to excite radial nonaxisymmetric modes in the ring. The motor has been effectively clamped to the housing by using two flanges passing through the middle plane of 2 transducers. Finite element analysis was employed to evaluate two different configurations of the motor, both using 6 driving transducers, and to analyze the effect of the flange on the design and on the performance of the transducer. Experimental measurements carried out on a manufactured prototype show that the proposed motor exhibits greatly improved performance in terms of output torque and mechanical power compared with similar previous prototypes which use fewer driving transducers and a different clamping system. The motor weighed 0.67 kg, and had a working frequency of 23.6 kHz, maximum rotational speed of 116 rpm, and static torque of 0.94 Nm. 相似文献
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为了使超声波流量计能够获得最佳的超声波信号,从理论上分析了超声波流量计的换能器系统,在此基础上提出了用收发电压灵敏度参数来表征换能器系统的综合发射和接收性能。采用等效网络理论,计算了超声波压电换能器的发射特性和接收特性,同时给出了收发电压灵敏度的表达式以及在流量计工作频率下换能器的最优设计准则。应用该准则设计并制作了适用于热量表的超声波换能器。实验结果表明:采用该设计理论研制的换能器系统可以使热量表在工作频率上获得最优的超声波信号,同时也证明了采用该理论设计的超声波流量计换能器系统的有效性。 相似文献
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Ultrasonic imaging using a computed point spread function 总被引:1,自引:0,他引:1
Rangarajan R Krishnamurthy CV Balasubramaniam K 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2008,55(2):451-464
An explicit point spread function (PSF) evaluator in the frequency domain is described for an ultrasonic transducer operating in the pulse-echo mode. The PSF evaluator employs the patch element model for transducer field determination and scattered field assessment from a small but finite "point" reflector. The PSF for a planar transducer in a medium has been evaluated in the near and the far field. The computed PSFs were used to deconvolve and restore surface images, obtained experimentally, of a single hole and a five-hole cluster in an Al calibration block. A calibration plot is arrived at for estimating, without the need for deconvolution, the actual diameters of circular reflectors from apparent diameters obtained experimentally for a single-medium imaging configuration. The PSF, when the transducer and the point reflector are in two media separated by a planar interface, was evaluated in the near and far field. The computed PSFs were used to deconvolve and restore subsurface images, obtained experimentally, of flat bottom holes (FBHs) in an Al calibration block. We show that the PSF, in the presence of a planar interface, can be obtained from a single-medium PSF model using an effective single-medium path length concept. The PSFs and modulation transfer functions (MTFs) are evaluated for spherical focused and annular transducers and compared with those for the planar transducer. We identify imaging distances to get better-resolved images when using planar, spherical focused, and annular transducers. 相似文献
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Pablo Marin-Franch Sandy Cochran Katherine Kirk 《Journal of Materials Science: Materials in Electronics》2005,15(11):715-720
In recent years, single crystal materials with better piezoelectric properties than the existing ceramics have become available. These new materials will potentially provide improved performance in ultrasonic applications such as NDT, sonar and biomedical diagnosis. In order to select the best material and optimize transducer design, comparison must be carried out. However, due to material and transducer fabrication costs, initial comparisons can be based on simulation. In this paper, a comparison is reported between transducers based on the single crystal lead magnesium niobate-lead titanate (PMN-32% PT) and the ceramic lead zirconate titanate (PZT-5H). Material performance is assessed both for single materials and piezoelectric-polymer composite configurations by defining the relevant piezoelectric parameters. Furthermore, the effect of such parameters on the performance of different ultrasonic transducers is illustrated. Practical limitations are also discussed. We conclude that the new single crystal material will be capable of outperforming the present widely used ceramic for almost all practical applications. 相似文献
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Pablo Marin-Franch Sandy Cochran Katherine Kirk 《Journal of Materials Science: Materials in Electronics》2004,15(11):715-720
In recent years, single crystal materials with better piezoelectric properties than the existing ceramics have become available. These new materials will potentially provide improved performance in ultrasonic applications such as NDT, sonar and biomedical diagnosis. In order to select the best material and optimize transducer design, comparison must be carried out. However, due to material and transducer fabrication costs, initial comparisons can be based on simulation. In this paper, a comparison is reported between transducers based on the single crystal lead magnesium niobate-lead titanate (PMN-32% PT) and the ceramic lead zirconate titanate (PZT-5H). Material performance is assessed both for single materials and piezoelectric-polymer composite configurations by defining the relevant piezoelectric parameters. Furthermore, the effect of such parameters on the performance of different ultrasonic transducers is illustrated. Practical limitations are also discussed. We conclude that the new single crystal material will be capable of outperforming the present widely used ceramic for almost all practical applications. 相似文献
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Qian Zhang Lewin P.A. Bloomfield P.E. 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》1997,44(5):1148-1156
To improve the pulse-echo sensitivity of a piezopolymer transducer while preserving its broad bandwidth property, several multilayer transducer design approaches have been suggested. This paper presents formulae derived to describe three types of multilayer transducers: a folded multilayer-, Barker-coded, multilayer-, and switchable Barker-coded multilayer transducer. The pulse-echo responses of the multilayer transducers under various excitation signals were calculated and compared with those achievable with an equivalent PZT transducer. Also, the influence of a tissue layer on the transducer responses was examined. The simulation results indicated that the switchable Barker coded transducer design outperforms all other transducer designs analyzed with respect to the axial resolution and overall sensitivity in the medical imaging frequency range. To verify the simulation results, several prototypes of multilayer Barker coded transducers were fabricated and tested in water. A good agreement between the experimental results and the corresponding computer predictions was achieved 相似文献
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匹配层对超声换能器的性能起着至关重要的作用,寻找合适的匹配层材料是换能器设计中的关键步骤。提出了一种基于环氧树脂-氧化铝复合材料的匹配层材料。首先,测试了不同配比的环氧树脂-氧化铝复合材料的声学性能,对比了其声学特性,并确定了材料的最佳配比。其次,研制了相应的换能器,分析该匹配层对换能器性能的影响,通过脉冲-回波方法测试了其性能参数。最后,基于四分之一波长匹配层原理对匹配层的厚度进行了优化。结果显示,环氧树脂中加入质量分数为 60%的氧化铝粉末的匹配层对换能器的改善效果最佳,该方案减小了换能器接收回波的拖尾,接收回波的幅值提高至 1 136 mV(+104%),-6 dB带宽达到 49.679%(+107%)。结果表明,氧化铝-环氧树脂混合材料可以提升换能器的声学性能,是较为理想的匹配层材料,在高频超声换能器的设计与应用中具有很好的应用前景。 相似文献
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新型弛豫铁电单晶材料铌铟酸铅-铌镁酸铅-钛酸铅晶体(Pb(In1/2Nb1/2) O3-Pb(Mg1/3Nb2/3) O3-PbTiO3, PIMNT)的压电系数是陶瓷材料的 6 倍以上,应变量高出压电陶瓷 10 倍以上,具有较高的机电耦合系数,压电性能优于传统 PZT 材料。文章将单晶材料应用于带空气腔的弯曲圆盘换能器中,利用 ANSYS 仿真软件优化换能器结构,确定换能器尺寸,设计制作 PIMNT 压电单晶换能器和PZT4压电陶瓷换能器,并进行了水池实验。换能器实测结果与仿真结果保持一致,单晶换能器的谐振频率为 2.85 kHz,最大发送电压响应为 136.3 dB。结果表明,相比于同尺寸的陶瓷换能器,将 PIMNT 压电单晶应用于弯曲圆盘换能器可降低谐振频率,提高发送电压响应,提升换能器的工作性能,为进一步改善单晶换能器综合性能提供参考。 相似文献
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Kramer SM McBride SL Mair HD Hutchins DA 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》1988,35(2):253-263
The transient pressure fields of ideal planar ultrasonic transducers may be described in terms of plane and edge wave contributions. Based on this concept, a technique is developed which allows characterization of wideband unfocused transducers by a single measurement close to the transducer face. This method is examined experimentally for both polyvinylidene difluoride and commercial PZT transducers. Also investigated is the effective radiated frequency of these devices. 相似文献
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This paper presents a microfluidic mixer that uses acoustic stirring created by ultrasonic waves. The ultrasound is introduced into the channel by integrated piezoelectric transducers. The transducers are made of a zinc oxide thin film, which is deposited on the bottom surface of a quartz substrate. The poly(dimethylsiloxane) channel is aligned to the transducers on the top surface of the substrate. The transducers are designed for operation around 450 MHz. The main mechanism of the mixing is the acoustic stirring of the fluid perpendicular to the flow direction. The radiation pressure that is generated by the transducer causes the stirring inside the microfluidic channel. The performance of the mixer is characterized by mixing phenolphthalein solution and sodium hydroxide dissolved in ethyl alcohol. Flow rates on the order of 1-100 microL/min are used. The transducers are driven by 1.2 V(rms) sinusoidal voltages at 450 MHz. 相似文献
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回顾了超声键合用换能器的发展状况,特别是在我国的研究状况。对超声键合用换能器的研究方法进行了总结,例如等效网络法、直接解振动与波动方程法、有限元法。不少单位已经编制了等效网络法的计算程序,可以迅速准确地得到细长和简单换能器结构的频率特性和导纳曲线;利用有限元软件可以计算复杂结构的换能器特性,是当今设计仿真的有效工具。论文结合当前微电子、集成芯片对超声键合的大量需求,展望了超声键合换能器的发展前景。除高频换能器和小体积的换能器需要进一步研究外,性能更加稳定和优良的换能器依然是研究的热点。 相似文献
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Frijlink ME Goertz DE de Jong N van der Steen AF 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2008,55(10):2154-2163
Mechanically scanned transducers are currently used for tissue harmonic imaging (THI) and nonlinear microbubble imaging at high frequencies. The pulse inversion (PI) technique is widely used for suppressing the fundamental signal, but its effectiveness is reduced by relative tissue/ transducer motion. In this paper, we investigate multipulse inversion (MPI) sequences that achieve a significant improvement on the fundamental suppression for mechanically scanned single-element transducers. MPI was subsequently applied on simulated and measured RF-data and relative fundamental suppression was compared with the 2-pulse PI technique. Simulations showed, for example, an increased fundamental suppression of 6 and 10 dB for MPI-sequences that combined 3 and 7 pulses, respectively, for a rotating intravascular ultrasound transducer with an interpulse angle of 0.15deg. Initial application of MPI sequences on RF-data from in vivo acquisitions resulted in similar fundamental suppression levels. The investigated MPI technique will help to reduce relative tissue/transducer motion effects and might lead to improved sensitivity and spatial resolution in nonlinear tissue imaging and improved microbubble detection in contrast imaging for mechanically scanned transducers. 相似文献
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Huang C Marmarelis VZ Zhou Q Shung KK 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2005,52(3):469-479
Inversion layer ultrasonic transducers have been investigated recently as an interesting approach in wideband transducer design. In this paper we present an analytical model of multilayer ultrasonic transducers with an inversion layer. Our analysis of the wave propagation problem of an inversion layer transducer includes a functional decomposition of the electrical input impedance. It becomes clear from this decomposition that an inversion layer transducer can be modeled as three elements in series connection, i.e., a clamped capacitance, a classical motional impedance, and a coupled motional impedance. The first two elements make up the classical model of a single element transducer. The coupled motional impedance describes the coupled interaction between the regular and the inverted piezoelectric sublayers, and thus reflects the effect of an inversion layer. We present examples which show that inversion layer transducers are advantageous in achieving such useful features as dual-frequency operation mode as used in harmonic imaging or broadband performance desired in most ultrasonic applications. 相似文献