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Ultrasonics, Ferroelectrics, and Frequency Control, IEEE Transactions on

Issue 4 • Date April 2002

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Displaying Results 1 - 23 of 23
  • Synthetic aperture imaging with arrays of arbitrary shape. Part I. General case

    Publication Year: 2002 , Page(s): 399 - 403
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (175 KB) |  | HTML iconHTML  

    The problem of synthesizing full-aperture resolution with linear transmitting and receiving arrays of arbitrary shape is considered. The arrays are assumed to lie in the same plane and can be open (e.g., curved or straight line segments) or closed (e.g., circles). It is shown that a full (area) aperture can be synthesized by suitably weighting the transmitted and received signals. This weighting turns out to be the Jacobian of a transformation that yields uniform coverage in the spatial-frequency domain. If the Jacobian is factorable, then full-aperture resolution can be achieved in a single transmission. The theory is illustrated with two annular arrays of different diameter: one that transmits and one that receives. If the radii of the annular arrays are a and b, then the synthesized point-spread function (PSF) is shown to be equivalent to that of a filled circular aperture of radius a+b. View full abstract»

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  • Synthetic aperture imaging with arrays of arbitrary shape. II. The annular array

    Publication Year: 2002 , Page(s): 404 - 408
    Cited by:  Papers (7)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (211 KB) |  | HTML iconHTML  

    For pt.I, see ibid., vol.4, no.2, p.399-403 (Apr. 2002). It has been previously shown that full aperture resolution can be achieved with an annular transducer array by transmitting and receiving between all pairs of elements around the array circumference and applying an appropriate weighting function . If there are N elements in the array, this requires N transmissions. This paper shows that full aperture resolution can be obtained with a much smaller number of transmissions (two to four) by using a certain aperture phase weighting on transmit and receive. Thus, full aperture, real-time imaging from an annular array should be feasible. View full abstract»

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  • Supercritical parametric wave phase conjugation as an instrument for narrowband analysis in ultrasonic harmonic imaging

    Publication Year: 2002 , Page(s): 409 - 414
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (381 KB) |  | HTML iconHTML  

    Supercritical parametric wave phase conjugation (SWPC) is used for selection and phase conjugation of harmonic components of a nonlinear incident wave. The amplitude of the phase conjugate wave in a supercritical mode is high enough for acoustic nonlinearity of the propagation medium to appear. As a result, in particular, doubled and quadrupled frequencies of the incident wave become available for image formation at the same order of the medium nonlinearity. The improvement of the imaging system resolution because of harmonic analysis of the received acoustic signal and compensation of phase distortions caused by wave phase conjugation were observed simultaneously when the propagation medium was inhomogeneous. View full abstract»

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  • Intracardiac catheter 2-D arrays on a silicon substrate

    Publication Year: 2002 , Page(s): 415 - 425
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (406 KB) |  | HTML iconHTML  

    The design, fabrication, and characterization of a 7 MHz, two-dimensional (2-D) array transducer built on a silicon substrate is described. The array fits inside a 9-French (2.9 mm O.D.) catheter for use in real-time intracardiac volumetric imaging. The -6 dB fractional bandwidth of the transducer is 30%, the 50 /spl Omega/ pitch-catch insertion loss is 78 dB, and the interelement crosstalk is -25 dB. Realtime volumetric images in phantoms and in-vitro images of a sheep heart have been acquired yielding measured spatial resolution of 2 mm at a depth of 1 cm. The cardiac structures imaged include ventricular chambers, interventricular septum, mitral and tricuspid valves and real-time 3-D rendered volumes of the tricuspid valve in the open and closed position. View full abstract»

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  • Shear modulus imaging with 2-D transient elastography

    Publication Year: 2002 , Page(s): 426 - 435
    Cited by:  Papers (40)  |  Patents (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1327 KB) |  | HTML iconHTML  

    In previous work, we have shown that time-resolved 2-D transient elastography is a promising technique for characterizing the elasticity of soft tissues. It involves the measurement of the displacements induced by the propagation of low frequency (LF) pulsed shear waves in biological tissues. In this paper, we present a novel apparatus that contains a LF vibrating device surrounding a linear array of 128 ultrasonic transducers that performs ultrafast ultrasonic imaging (up to 10,000 frames/s) and that is able to follow in real time the propagation of a LF shear wave in the human body. The vibrating device is made of two rods, fixed to electromagnetic vibrators, that produce in the ultrasonic image area a large amplitude shear wave. The geometry has been chosen both to enhance the sensitivity and to create a quasi linear shear wave front in the imaging plane. An inversion algorithm is used to recover the shear modulus map from the spatio-temporal data, and the first experimental results obtained from tissue-equivalent materials are presented. View full abstract»

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  • Shear elasticity probe for soft tissues with 1-D transient elastography

    Publication Year: 2002 , Page(s): 436 - 446
    Cited by:  Papers (33)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (748 KB) |  | HTML iconHTML  

    Important tissue parameters such as elasticity can be deduced from the study of the propagation of low frequency shear waves. A new method for measuring the shear velocity in soft tissues is presented in this paper. Unlike conventional transient elastography in which the ultrasonic transducer and the low frequency vibrator are two separated parts, the new method relies on a probe that associates the vibrator and the transducer, which is built on the axis of the vibrator. This setup is easy to use. The low frequency shear wave is driven by the transducer itself that acts as a piston while it is used in pulse echo mode to acquire ultrasonic lines. The results obtained with the new method are in good agreement with those obtained with the conventional one. View full abstract»

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  • Micro-receiver guided transcranial beam steering

    Publication Year: 2002 , Page(s): 447 - 453
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1246 KB) |  | HTML iconHTML  

    A new method for focusing ultrasound energy in brain tissue through the skull is investigated. The procedure is designed for use with a therapeutic transducer array and a small catheter-inserted hydrophone receiver placed in the brain to guide the array's focus. When performed at high-intensity, a focal intensity on the order of several hundred watts per centimeter-squared is achieved, and cells within a target volume are destroyed. The present study tests the feasibility and range of the method using an ex vivo human skull. Acoustic phase information is obtained from the stationary receiver and used to electrically shift the beam to new locations as well as correct for aberrations due to the skull. The method is applied to a 104-element 1.1 MHz array and a 120-element 0.81 MHz array. Using these array configurations, it is determined that the method can reconstruct and steer a focus over a distance of 50 mm. Application of this minimally invasive technique for ultrasound brain therapy and surgery also is investigated in vitro with a 64-element 0.664 MHz hemisphere array designed for transskull surgery. Tissue is placed inside of a skull and a catheter-inserted receiver is inserted into the tissue. A focus intense enough to coagulate the tissue is achieved at a predetermined location 10 mm from the receiver, the maximum distance that this large element array can electronically steer the focus. View full abstract»

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  • Standardized evaluation of chemical compositions of LiTaO/sub 3/ single crystals for SAW devices using the LFB ultrasonic material characterization system

    Publication Year: 2002 , Page(s): 454 - 465
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (522 KB) |  | HTML iconHTML  

    The line-focus-beam ultrasonic material characterization (LIFB-UMC) system is applied to compare and evaluate tolerances provided independently for the Curie temperature T/sub C/ and lattice constant /spl alpha/ to evaluate commercial LiTaO/sub 3/ single crystals by measuring the Rayleigh-type leaky surface acoustic wave (LSAW) velocities V/sub LSAW/. The relationships between VLSAW, and T/sub C/ and /spl alpha/ measured by individual manufacturers were obtained experimentally using 42/spl deg/YX-LiTaO/sub 3/ wafers as specimens from three crystal manufacturers. In addition, the relationship between VLSAW and SH-type SAW velocities V/sub SAW/ that are actually used for the SAW device wafers was obtained through calculations, using the chemical composition dependences of the acoustical physical constants for LiTaO/sub 3/ crystals reported previously. The result of a comparison between the T/sub C/ tolerance of /spl plusmn/3/spl deg/C and the /spl alpha/ tolerance of /spl plusmn/0.00002 nm through the common scale of VLSAW or VSAW demonstrated that the /spl alpha/ tolerance is 1.6 times larger than the T/sub C/ tolerance. Furthermore, we performed a standardized comparison of statistical data of T/sub C/ and /spl alpha/ for LiTaO/sub 3/ crystals grown by two manufacturers during 1999 and 2000, using VLSAW. The results clarified the differences of the average chemical compositions and of the chemical composition distributions among the crystal ingots between the two manufacturers. A guideline for the standardized evaluation procedure has been established for the SAW-device wafer specifications by the LFB-UMC system. View full abstract»

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  • Design on semiconductor coupled SAW convolver

    Publication Year: 2002 , Page(s): 466 - 474
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (541 KB) |  | HTML iconHTML  

    This paper presents results of a design study on a semiconductor coupled surface acoustic wave (SAW) convolver in which bi-directionally propagating SAWs, on a piezoelectric substrate with a high coupling coefficient, couple with bonded semiconductor diodes through multistrips. To obtain convolution signals with a high efficiency, we adopted a diode-balanced bridge structure for the nonlinear operation. We also found that the tapping pitches of the multi-strip electrodes have robustness against operation frequency variation and temperature-dependent variation on the delay of the SAW. We verified the effectiveness of the device in. a circuit simulation and an experiment on a test circuit, which was fabricated by using an epitaxial lift-off film-bonding process. View full abstract»

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  • The influence of fabrication errors on the stopband magnitude responses of SAW devices

    Publication Year: 2002 , Page(s): 475 - 483
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (196 KB) |  | HTML iconHTML  

    This article is devoted to an analysis of the influence of manufacturing errors on the magnitude responses of surface acoustic wave (SAW) devices. Analytical analysis of these random errors provides statistical distributions of the relevant responses and their parameters. It allows significant reduction in the modeling computations compared to the Monte Carlo method, and it provides possibilities for further analytical analysis. After the application of the statistical analysis to different potential structures of SAW devices, it is possible to choose the least sensitive one during the design process without the need of costly trials. Experimental analysis confirmed the existence of some of the features predicted both theoretically and by modeling. The experimental procedure for the evaluation of the fabrication error variances is described. The application of these results to the design process of the SAW devices allows simplification of the requirements for the manufacturing equipment and/or improvement of the devices' parameters, especially stopband suppression. View full abstract»

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  • Efficiency of excitation of piezoceramic transducers at antiresonance frequency

    Publication Year: 2002 , Page(s): 484 - 494
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (260 KB) |  | HTML iconHTML  

    The efficiency of piezoceramic transducers excited at both the resonance and antiresonance frequency was investigated. Losses in piezoceramics are phenomenologically considered to have three coupled mechanisms: dielectric, mechanical, and piezoelectric losses. Expressions for the resonance and antiresonance quality factors, which ultimately determine transducer efficiency, have been received on the basis of complex material constants for both stiffened and unstiffened vibration modes. Comparison of electric and mechanical fields, thermal and electrical losses of power supply, and their distribution in the transducer volume have been made. For a given constant mechanical displacement of the transducer top, the required electric voltage applied to the transducer at the antiresonance frequency is proportional to the resonance quality factor, but the changes in the intrinsic electric and mechanical field characteristics in the common case are not too essential. The requirements on the piezoceramic parameters, types of transducer vibration, and especially on the factor of piezoelectric losses in a range of physically valid values were established to provide maximal quality factors at the antiresonance frequency. View full abstract»

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  • A piezoelectric motor using two orthogonal bending modes of a hollow cylinder

    Publication Year: 2002 , Page(s): 495 - 500
    Cited by:  Papers (25)  |  Patents (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1227 KB) |  | HTML iconHTML  

    This paper proposes a compact ultrasonic motor with low manufacturing costs, a simpler driving circuit, and scalability. The stator of the motor presented in this paper consists of a hollow metal cylinder, whose outside surface was flattened on two sides at 90 degrees to each other, on which two rectangular piezoelectric plates were bonded. Because the cylinder has a partially square/partially circular outside surface, the stator has two degenerated bending modes that are orthogonal to each other. A wobbling motion is generated on the cylinder when only one piezoelectric plate is excited at a frequency between the two orthogonal bending modes. A rod through a pair of ferrules was used as the rotor of this motor. The prototype motor, whose stator was 2.4 mm in diameter and 10 mm in length, operated at 69.5 kHz, was experimentally characterized, and a maximum torque of 1.8 mNm was obtained. View full abstract»

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  • A low-flicker scheme for the real-time measurement of phase noise

    Publication Year: 2002 , Page(s): 501 - 507
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (622 KB) |  | HTML iconHTML  

    This paper presents a new scheme for the measurement of phase noise in real time, based on carrier suppression and synchronous detection of the noise sidebands of the device being tested. In the instruments of the interferometric type, the carrier is suppressed by adding an equal and opposite signal that must be adjusted with a phase shifter and an attenuator. The proposed scheme makes use of a dual adjustment of the carrier suppression, coarse and fine. The former is by-step; the latter is continuous. Because of the higher stability of the by-step adjustment and the lower weight of the continuous adjustment in the suppression circuit, the instrument exhibits intrinsically low residual flicker and low microphonicity. A prototype shows a residual flicker as low as -160 dBrad/sup 2//Hz at 1 Hz off the 100 MHz carrier. Applications include the noise characterization of components and the design of innovative ultrastable oscillators. View full abstract»

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  • Application of the moment condition to noise simulation and to stability analysis

    Publication Year: 2002 , Page(s): 508 - 513
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (201 KB) |  | HTML iconHTML  

    It is well-known that low frequency noises (flicker FM and random walk FM) are not stationary; it is not possible to define either the mean value or the (true) variance. Therefore, the use of a stationary approach yields convergence problems unless a low cut-off frequency is introduced, the physical meaning of which is not clear. The moment condition explains the link between insensitivity to drifts and convergence for low frequency noises in a stationary approach. This condition may be summarized by the following consideration: the divergence effect of a low frequency noise for the lowest frequencies induces a false drift with random drift coefficients; the lower the low cut-off frequency, the higher the variance of the coefficients of this drift. These variances may be known by theoretical calculations. The order of the drift is directly linked to the power law of the noise. The moment condition is demonstrated and applied for creating new estimators (new variances) and for simulating low frequency noises with a very low cut-off frequency. View full abstract»

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  • Isochronism defect for various doubly rotated cut quartz resonators

    Publication Year: 2002 , Page(s): 514 - 518
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (338 KB) |  | HTML iconHTML  

    It has been shown in earlier works that the amplitude-frequency effect [also called isochronism defect (ID) or anisochronism] could be a limitation factor on ultrastable oscillators. Theoretical studies based on the nonlinear theory of piezoelectricity have already been developed to explain the amplitude-frequency effect. So, it is possible to estimate the dependence of the ID versus various parameters of the resonator design (overtone rank, radius of curvature, electrodes diameter, etc.). However, because of the lack of available fourth-order elastic coefficients, it is not possible to predict the ID of any resonant frequency of a given trapped energy resonator. To tentatively find orientations of plates exhibiting a quasi-null ID, we have realized electroded resonators with different orientations and curvatures. We present results that verify, particularly, the R/sup -1/2/ dependence of the amplitude-frequency effect versus radius of curvature. Moreover, we show that the ID can be positive or negative, that it can vary from one orientation to other one of about one order of magnitude, and that there exists a thermal compensated mode for which the amplitude-frequency effect is null. View full abstract»

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  • Analysis of general multi-channel planar waveguides

    Publication Year: 2002 , Page(s): 519 - 527
    Cited by:  Papers (2)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (882 KB) |  | HTML iconHTML  

    Using the planar waveguide concept in surface acoustic wave (SAW) technology is often advantageous when the modeling of transversely distributed phenomena is indispensable for an accurate design of SAW devices. This is especially true when complex multi-track structures such as transversely coupled resonator filters (TCRFs) are under consideration where, e.g., transverse velocity and stiffness profiles have to be incorporated in the device simulation. The interdigital transducers (IDTs) and the reflector gratings composing those devices behave as planar waveguides, supporting, in principle, all kinds of modes such as bound, semi-bound, and radiation modes. Therefore, to model these SAW propagation effects, we subdivide the SAW structures in transverse direction into several parallel waveguiding channels (N regions), and take, as the wave-describing quantity, a two-dimensional scalar potential function. By doing so, we obtain a complete set of orthonormal modes into which an arbitrary transverse excitation function can be expanded to study its propagation. The general mode spectrum includes a discrete spectrum of bound modes and continuous spectra of semi-bound and radiation modes. We calculate all types of modes by making use of the stack matrix technique. The present work, which arose from the requirement of creating an efficient mathematical tool for the simulation of TCRFs, provides the complete analysis of general SAW multi-channel structures. View full abstract»

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  • Harmonic admittance and dispersion equations-the theorem [SAWs in periodic electrode arrays]

    Publication Year: 2002 , Page(s): 528 - 534
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (216 KB) |  | HTML iconHTML  

    The harmonic admittance is known as a powerful tool for analyzing the excitation and propagation of surface acoustic waves (SAWs) in periodic electrode arrays. In particular, the dispersion relationships for open- and short-circuited systems are indicated, respectively, by the zeros and poles of the harmonic admittance. Here, we show that a strict reverse relationship also exists: the harmonic admittance of a periodic system of electrodes may always be expressed as the ratio of two determinants, which have been specifically constructed to describe the eigenmodes of the open- and short-circuited systems. There is no need to solve these equations to find the admittance. The existence of a connection between the excitation and propagation problems was recognized within the coupling-of-modes theory by Chen and Haus (1985) and was recently used to model surface transverse waves by Koskela et al. (1998), but a rigorous mathematical proof was only found later by Biryukov (2000). Here, we reproduce this theorem in detail, give some examples of calculations based on this theorem, and compare the results with measured admittance curves. View full abstract»

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  • Thin film bulk acoustic wave filter

    Publication Year: 2002 , Page(s): 535 - 539
    Cited by:  Papers (15)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (394 KB) |  | HTML iconHTML  

    Thin film bulk acoustic wave (BAW) resonators (FBAR) are fabricated on a silicon nitride bridge using a ZnO piezolayer on a glass substrate and surface micromachining by standard thin film technology. These resonators exhibit a coupling constant k/sub t//sup 2/=7.8% at the first thickness extensional wave mode and are used as impedance elements in a ladder filter in the 1-GHz frequency band of mobile telecommunications. An electrical equivalent circuit is used to characterize the properties of the resonators and to show how the performance of the filter depends on the parameters of the resonators. 2.5% bandwidth, 2.8-dB insertion loss, and 35-dB selectivity are obtained in a filter with six resonators. The technology can be used to manufacture miniature microwave filters without any additional inductances. View full abstract»

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  • [Front cover]

    Publication Year: 2002 , Page(s): i
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    Freely Available from IEEE
  • [Inside front cover]

    Publication Year: 2002 , Page(s): ii
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    Freely Available from IEEE
  • [Inside back cover]

    Publication Year: 2002 , Page(s): iii
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  • Table of contents

    Publication Year: 2002 , Page(s): iv
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  • Final Call for Papers

    Publication Year: 2002 , Page(s): 540 - 543
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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
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