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Ultrasonics, Ferroelectrics, and Frequency Control, IEEE Transactions on

Issue 12 • Date Dec. 2004

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Displaying Results 1 - 21 of 21
  • [Front cover]

    Page(s): i - ii
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  • [Inside front cover]

    Page(s): iii
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  • [Inside back cover]

    Page(s): iv
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  • Table of contents

    Page(s): v - vi
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  • Information for contributors

    Page(s): 1575 - 1579
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  • A multimedia example

    Page(s): 1580
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  • Call for papers

    Page(s): 1581
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  • Extended irreversible thermodynamics modeling for self-heating and dissipation in piezoelectric ceramics

    Page(s): 1582 - 1592
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (341 KB) |  | HTML iconHTML  

    Self-heating or dissipation of piezoelectric ceramic elements is observed to be severe under dynamic operations even in the linear range. A nonequilibrium thermodynamic model is developed to delineate the coupled irreversible mechanical, electric, and thermal processes, which jointly contribute to dissipation. Specifically, additional nonequilibrium state variables, also known as thermodynamic fluxes, are brought in to describe each of these processes. The characteristic relaxation of these processes is modeled. The nonnegative rate of entropy production is found to be in quadratic form of thermodynamics fluxes. The energy balance equation, which governs the transformation between different energy forms, is obtained in the framework of extended irreversible thermodynamics. Using this model, the dissipation of a piezoceramic stack actuator under harmonic electric or mechanical loadings in linear operation range is studied. The harmonic-balance methods are utilized as solution techniques. In contrast to the existing piezoelectric dissipation models, the dissipation by the developed model is verified to nonlinearly depend on operating frequency, with a peak dissipation occurring at some operating frequency that is related to characteristic relaxation of irreversible processes. The measurements of newly introduced parameters are also discussed. View full abstract»

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  • Single-crystal relaxor ferroelectric piezoactuators with interdigitated electrodes

    Page(s): 1593 - 1599
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (508 KB) |  | HTML iconHTML  

    We report on the fabrication and performance of (1-x) Pb(Zn/sub 1/3/Nb/sub 2/3/)O/sub 3/-xPbTiO/sub 3/ (PZN-PT) single-crystal relaxor piezoactuators with interdigitated electrodes patterned on a single surface. An electric field gradient across the sample thickness induces a differential contraction between opposite faces, and it is responsible for the actuation. The samples are poled by energizing the electrodes at 100/spl deg/C and cooling in a field. Calculations of the piezoelectric response based on a periodically modulated dipolar field yield good agreement with experiment. Discrepancies with the model are ascribed to multidomain formation in the ferroelectric sample as a result of field reversals in the applied electric field along the sample length. View full abstract»

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  • Performance improvement of rectangular-plate linear ultrasonic motors using dual-frequency drive

    Page(s): 1600 - 1606
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    To improve the performances of a rectangular-plate linear ultrasonic motor for specific applications, a dual-frequency drive has been proposed and investigated. Through careful design of the rectangular piezoelectric ceramic plate, its first longitudinal resonant frequency coincides with its second lateral bending resonant frequency and is one-third of its higher lateral bending resonant frequency. When a square-wave voltage is used to drive the motor, its first longitudinal and second bending and the higher bending vibration modes are excited. Experimental results show that the maximum thrust force and maximum velocity of the motor are over 170% of those obtained from the single-frequency sine-wave drive when the voltage performance of the motor becomes saturated. View full abstract»

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  • 1.156-GHz self-aligned vibrating micromechanical disk resonator

    Page(s): 1607 - 1628
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    A new fabrication methodology that allows self-alignment of a micromechanical structure to its anchor(s) has been used to achieve vibrating radial-contour mode polysilicon micromechanical disk resonators with resonance frequencies up to 1.156 GHz and measured Q's at this frequency >2,650 in both vacuum and air. In addition, a 734.6-MHz version has been demonstrated with Q's of 7,890 and 5,160 in vacuum and air, respectively. For these resonators, self-alignment of the stem to exactly the center of the disk it supports allows balancing of the resonator far superior to that achieved by previous versions (in which separate masks were used to define the disk and stem), allowing the present devices to retain high Q while achieving frequencies in the gigahertz range for the first time. In addition to providing details on the fabrication process, testing techniques, and experimental results, this paper formulates an equivalent electrical circuit model that accurately predicts the performance of these disk resonators. View full abstract»

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  • Plane harmonic waves in an infinite piezoelectric plate with dissipation

    Page(s): 1629 - 1638
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    In a previous paper, the three-dimensional equations of linear piezoelectricity with quasielectrostatic approximation were extended to include losses attributed to the mechanical damping in solid and the resistance in current conduction. These equations were used to investigate the plane wave propagation in an unbounded solid and forced thickness vibration of an infinite piezoelectric plate. In the present paper, these equations are used to obtain solutions of plane harmonic wave of arbitrary direction in an infinite and dissipative piezoelectric plate with general crystal symmetry. Dispersion curves are computed and plotted for real frequencies and complex wave numbers. All frequency branches are complex for dissipative plate. There are no longer any pure real or pure imaginary or complex conjugate frequency branches as those existing for nondissipative plates. Effects of dissipation on the wave propagation are examined in detail for AT-cut of quartz as well as barium titanate ceramic plate. View full abstract»

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  • Potential of microbubbles for use as point targets in phase aberration correction

    Page(s): 1639 - 1648
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    Bubbles can be produced by vaporization of perfluorocarbon droplets of a few /spl mu/m diameter. These bubbles can reach over 100 /spl mu/m in diameter and their backscatter is calculated to be well more than 10 dB above that of several organ tissues. At appropriate sizes, small acoustic amplitudes, and diagnostic frequencies (2-15 MHz), bubbles can be approximated by the nonrigid sphere-scattering solution employed here. This paper concerns the bubble size and its implications on the backscatter amplitude and the phase error introduced in diagnostic ultrasound when assuming that the bubble acts as a point target for phase aberration correction. View full abstract»

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  • Comparisons of lesion detectability in ultrasound images acquired using time-shift compensation and spatial compounding

    Page(s): 1649 - 1659
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    The effects of aberration, time-shift compensation, and spatial compounding on the discrimination of positive-contrast lesions in ultrasound b-scan images are investigated using a two-dimensional (2-D) array system and tissue-mimicking phantoms. Images were acquired within an 8.8/spl times/12-mm/sup 2/ field of view centered on one of four statistically similar 4-mm diameter spherical lesions. Each lesion was imaged in four planes offset by successive 45/spl deg/ rotations about the central scan line. Images of the lesions were acquired using conventional geometric focusing through a water path, geometric focusing through a 35-mm thick distributed aberration phantom, and time-shift compensated transmit and receive focusing through the aberration phantom. The views of each lesion were averaged to form sets of water path, aberrated, and time-shift compensated 4:1 compound images and 16:1 compound images. The contrast ratio and detectability index of each image were computed to assess lesion differentiation. In the presence of aberration representative of breast or abdominal wall tissue, time-shift compensation provided statistically significant improvements of contrast ratio but did not consistently affect the detectability index, and spatial compounding significantly increased the detectability index but did not alter the contrast ratio. Time-shift compensation and spatial compounding thus provide complementary benefits to lesion detection. View full abstract»

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  • Ultrasonic ranging sensor using simultaneous emissions from different transducers

    Page(s): 1660 - 1670
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    In recent applications based on ultrasound, several ultrasonic transducers have been geometrically and electronically associated to constitute a global sensor. There are several different methods used to process the ultrasonic signals obtained from these transducers. In this work, multimode techniques using Golay complementary sequences are proposed for processing the ultrasonic signal. The system increases scan rate, precision, and reliability. It is also capable of echo discrimination, allowing simultaneous measurements to be made and detection of the same obstacle by different transducers without cross-talk problems. The real-time implementation of the algorithm is presented on a field-programmable gate array (FPGA) device. View full abstract»

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  • Phases of the SAW reflection and transmission coefficients for short reflectors on 128/spl deg/ LiNbO/sub 3/

    Page(s): 1671 - 1682
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    We study numerically the phase of surface acoustic waves reflected by or transmitted through short reflectors comprising only 1-3 aluminium electrodes on 128/spl deg/ YX-cut lithium niobate (LiNbO/sub 3/). The electrodes have a finite thickness, and they are either open-circuited or grounded. The center-to-center distance between adjacent electrodes d corresponds roughly either to half of the characteristic wavelength d/spl prop//spl lambda//sub 0//2 or to d/spl prop//spl lambda//sub 0/, for the reflectors operating at the fundamental and second harmonic modes, respectively. We use software based on the finite-element and boundary-element methods (FEM/BEM) for numerical experiments with a tailored test structure having 3 interdigital transducers (IDTs), simulating experimental conditions with an incident wave and reflected and transmitted surface acoustic wave (SAW). Using artificial enhancement of time resolution in conjunction with the fast Fourier transform (FFT) and time-gating, calculation of the Y-parameters in a relatively wide frequency range allows us to determine the phase of the reflection and transmission coefficients. View full abstract»

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  • Simulation of characteristics of a SiO/sub 2//c-axis-oriented LiNbO/sub 3//diamond surface acoustic wave

    Page(s): 1683 - 1689
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    High-frequency surface acoustic wave (SAW) devices based on diamond that have been realized to date utilize c-axis-oriented ZnO as the piezoelectric thin film. This material, with SiO/sub 2/ overlay, shows excellent characteristics of a high phase velocity of over 10,000 m/s and a zero temperature coefficient, and it has been successfully applied to high-frequency SAW filters and resonators. To expand on materials used on diamond, the theoretical calculation has been carried out for LiNbO/sub 3//diamond, and a high electromechanical coupling coefficient up to 9.0% is expected. In this work, the characteristics of SiO/sub 2//LiNbO/sub 3//diamond were studied by computer simulation, emphasizing a zero temperature coefficient with a high coupling coefficient. Calculations are carried out for the phase velocity, the electromechanical coupling coefficient, and the temperature coefficient of the Rayleigh wave and its higher mode Sezawa wave. As a result, SiO/sub 2//IDT/LiNbO/sub 3//diamond is found to offer a zero temperature coefficient with a very high coupling coefficient up to 10.1% in conjunction with a high phase velocity of 12,100 m/s. View full abstract»

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  • A P-matrix based model for SAW grating waveguides taking into account modes conversion at the reflection

    Page(s): 1690 - 1696
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    Several models exist for analyzing the wave-guiding effect of a reflective grating. On the one hand, there are models based on scalar waveguide theory. These models consider that a device can be described as being made of several regions having different velocities. On the other hand, an extension of the coupling of modes (COM) model taking into account the transverse dimension has been developed. This paraxial COM model predicts that guidance is possible even when there is no velocity difference between the interior and the exterior of the grating region. Guidance, under such circumstances, is due only to differences in reflectivity between regions. Following from this insight, a new approach has been developed: guided modes and the continuum of radiating modes are first determined. At each period, reflections then are considered as occurring only in the reflective regions, so that the modes are truncated. Thus, at each reflection (and transmission), each mode is converted into a distribution of all modes. Dispersion curves very similar to those shown by other researchers are obtained by this method. They show, in particular, the existence of guided modes even when the wave velocity in all regions is identical. This model can be used to more easily analyze practical devices and exhibits a good agreement with experimental results. View full abstract»

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  • SPUDT filters for the 2.45 GHz ISM band

    Page(s): 1697 - 1703
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    Filters based on using single-phase, unidirectional transducers (SPUDT) consisting of /spl lambda//4 and wider electrodes are presented. The design variants exploit the significant difference between the reflectivity of short-circuited /spl lambda//4 electrodes and that of floating wide electrodes on 128/spl deg/ lithium niobate (LiNbO/sub 3/). The surface acoustic wave (SAW) devices operating at 2.45 GHz have critical dimensions of about 0.3-0.4 /spl mu/m, accessible to standard optical lithography. When matched, the fabricated SPUDT filters exhibit minimum insertion losses of 5.5-7.9 dB together with 3 dB passbands of 89-102 MHz. The majority of the insertion loss can be attributed to the attenuation on free surface and inside the grating, and to the resistivity of the electrodes. View full abstract»

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  • Effect of diamond nucleation process on propagation losses of AlN/diamond SAW filter

    Page(s): 1704 - 1709
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    In this work, the effect of a diamond nucleation process on freestanding aluminium nitride (AlN)/diamond surface acoustic wave (SAW) device performances was studied. Before diamond deposition, silicon (Si) substrates have been mechanically nucleated, using an ultrasonic vibration table with submicron diamond slurry, and bias-enhanced nucleated (BEN). Freestanding diamond layers obtained on mechanically scratched Si substrates exhibit a surface roughness of R/sub MS/=13 nm, whereas very low surface roughness (as low as R/sub MS//spl les/1 nm) can be achieved on a freestanding BEN diamond layer. Propagation losses have been measured as a function of the operating frequency for the two nucleation techniques. Dispersion curves of phase velocities and electromechanical coupling coefficient (K/sup 2/) were determined experimentally and by calculation as a function of normalized thickness AlN film (kh/sub AlN/=2/spl pi/h/sub AlN///spl lambda/). Experimental results show that the propagation losses strongly depend on the nucleation technique, and that these losses are weakly increased with frequency when the BEN technique is used. View full abstract»

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  • Index

    Page(s): 1710 - 1734
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Aims & Scope

IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control focuses on the theory, design, and application on generation, transmission, and detection of bulk and surface mechanical waves.

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Editor-in-Chief
Steven Freear
s.freear@leeds.ac.uk