By Topic

Ultrasonics, Ferroelectrics, and Frequency Control, IEEE Transactions on

Issue 2 • Date March 1989

Filter Results

Displaying Results 1 - 20 of 20
  • High-rangeability ultrasonic gas flowmeter for monitoring flare gas

    Publication Year: 1989 , Page(s): 144 - 149
    Cited by:  Papers (7)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (495 KB)  

    A transit-time ultrasonic gas flowmeter for high-rangeability requirements, such as those encountered in flare-gas flow-metering, is presented. The concept of ray rescue angle for the orientation of the ultrasonic transducers in single-beam transit-time ultrasonic flowmeters is introduced to overcome the problem of ultrasonic beam drift in high-velocity flows. To overcome problems associated with noise at high velocities, a chirp signal is used. To preserve the accuracy of the meter at low velocities near zero flow, a combination of chirp and continuous-wave signals is used to interrogate the flow. Overall system performance is presented, based on results from extensive wind-tunnel tests.<> View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • ZnO-on-Si mode conversion resonator

    Publication Year: 1989 , Page(s): 150 - 158
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (784 KB)  

    A two-port admittance matrix model is presented to describe the operation of the surface-acoustic-wave (SAW) mode conversion resonator. A unique treatment of the transducer coupling is applied to the specific case of the mode conversion device. The model takes into account the simultaneous presence of propagating Rayleigh and Sezawa waves and allows an equivalent circuit to be constructed to describe the resonator behavior. The model makes it possible to determine the reflector array separation and the interdigital transducer placement necessary for resonance and maximum coupling. Finally, experimental results are shown as verification of the device theory.<> View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Optimized Stoneley wave device by proper choice of glass overcoat

    Publication Year: 1989 , Page(s): 159 - 167
    Cited by:  Papers (2)  |  Patents (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (857 KB)  

    The characteristics of a Stoneley wave propagated along an interface between a piezoelectric material and an isotropic material were investigated both theoretically and experimentally. First, the condition for the existence of Stoneley waves was shown for various piezoelectric materials. A rule of thumb for selecting the combination of the two materials was obtained. Then, LiTaO/sub 3/ was selected as the piezoelectric material and SiO/sub 2/ was selected the isotropic material. After the calculation of the Stoneley wave characteristics, actual devices were fabricated and measured. The experimental results were found to be in good agreement with the theory; zero slope temperature and high electromechanical coupling coefficient (K/sup 2/=1.5%) were obtained for Stoneley wave propagation between SiO/sub 2//X-148 degrees LiTaO/sub 3/. As a result, future surface-acoustic-wave (SAW) devices can be made without any package.<> View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Phase correction of SAW ILRACs and RACs using Langmuir-Blodgett films

    Publication Year: 1989 , Page(s): 168 - 177
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (942 KB)  

    A novel method of adjusting surface-acoustic-wave (SAW) velocity in reflective array pulse compressors (RACs), including in-line devices (ILRACs) and hence correcting fabrication errors, is described. The velocity change is effected by depositing Langmuir-Blodgett films (LBFs) on the surface of the device. An accurate, stepped thickness profile can be created, enabling position-dependent velocity errors to be corrected. Experimental results for the velocity perturbation per LBF layer are first given together with data on temperature, humidity and age dependence. This is followed by the theory required to calculate the necessary thickness profile, including retrofitting to existing devices and allowing for the limitation to positive integer numbers of layers. Finally, experimental results are presented. In one device, simulated compressed pulse sidelobe levels are reduced by 19 dB.<> View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • SAW focusing by circular-arc interdigital transducers on YZ-LiNbO/sub 3/

    Publication Year: 1989 , Page(s): 178 - 184
    Cited by:  Papers (4)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (588 KB)  

    Using the angular spectrum theory and experimental velocity data of surface acoustic waves (SAW) on YZ-LiNbO/sub 3/, the focusing characteristics of a circular-arc interdigital transducer have been demonstrated. The calculated results show that the depth of focus is long and the compressed acoustic beam width is very narrow. The concept of a caustic is shown to be an excellent way of characterizing SAW focusing by a circular-arc interdigital transducer on YZ-LiNbO/sub 3/. Comparison between theoretical and experimental results shows good agreement.<> View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A three-dimensional model of the gas cell atomic frequency standard

    Publication Year: 1989 , Page(s): 185 - 190
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (597 KB)  

    Initial calculations from a three-dimensional (3-D) model of the gas cell atomic frequency standard are discussed. In particular, a recent suggestion that the short-term stability of a gas cell standard might be improved by varying the microwave power is considered. Though the authors' results generally support the previous conclusion, they show that the degree of sensitivity is less than that predicted by one-dimensional (1-D) gas-cell frequency-standard model. This difference in predicted sensitivity is a manifestation of the three-dimensional model's more accurate treatment of the clock-cavity microwave field distribution. The more accurate treatment is highlighted by the three-dimensional model's determination of isoefficiency contours (contours showing spatial regions in the clock cavity that have equal efficiency for producing clock signal), and noting their spatial dependence on microwave power.<> View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Thermal modeling in cylindrical coordinates using effective conductivity

    Publication Year: 1989 , Page(s): 191 - 196
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (466 KB)  

    Predictive thermometry, utilizing minimally invasive sampling techniques, is an essential ingredient in the development of hyperthermia treatment planning capabilities. The authors demonstrate a powerful, but simple approach toward predicting temperature distributions in tissues, based on analytic solution, using in cylindrical symmetry, of the heat diffusion equation. Conduction and localized perfusion effects are combined as an effective conductivity term, readily measurable, and parametrized in a general exponential form. The proposed approach allows a first-order approximation to modeling three typical situations: hypoxic or necrotic tumor core with homogeneously perfused periphery; highly perfused periphery (in rapidly growing tumors); or perfused central cover with a less well-supplied periphery (such as for some invasive tumors). The utility and strength of this approach is that it provides a rapid, accurate model of directly observing the technical quality to be expected for different heating methods, making it possible to optimally configure source distributions in a treatment planning setting.<> View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Acoustic attenuation estimation for soft tissue from ultrasound echo envelope peaks

    Publication Year: 1989 , Page(s): 197 - 203
    Cited by:  Papers (6)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (633 KB)  

    A theoretical framework of a modified EP (envelope peak) method is developed. In this method, a wideband echo signal from each A line (one echo sequence) is first filtered in parallel by a bank of narrow-bandpass filters using a split-spectrum processing. The attenuation is then estimated from the EPs of each filtered signal using a narrowband technique. The combination of the split-spectrum processing with the narrowband technique enables the accuracy of the attenuation estimation to be well controlled without the precise measurements of the spectral shape and parameters of the transmitted pulses. On the other hand, the precision of the estimation is still determined by the bandwidth of the original echo signal, and is not affected by the split-spectrum processing. As a result, the modified EP method improves the accuracy of the attenuation estimation while retaining the high precision of the original EP method. Results from phantom experiments supported the theoretical analysis.<> View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • An improved theory for the prediction of microcavitation thresholds

    Publication Year: 1989 , Page(s): 204 - 208
    Cited by:  Papers (8)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (474 KB)  

    An approximate analytical formulation is presented that allows for the calculation of acoustic pressure thresholds for transient cavitation over a variety of frequencies and host fluid parameters. Specifically, R.E. Apfel's (1986) theory is extended to include an estimate of the time delay associated with the Laplace pressure, 2 sigma /R/sub 0/, where sigma is the surface tension and R/sub 0/ is the initial radius. Also presented is a correction factor for the time-averaged pressure difference, across the bubble wall during growth. An optimum size distribution of nuclei for the predisposition of a sample to microcavitation is exhibited. The role of transient cavitation in medical ultrasound is discussed.<> View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Focusing ultrasound in biological media

    Publication Year: 1989 , Page(s): 209 - 215
    Cited by:  Papers (4)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (707 KB)  

    The authors present a formulation for calculating the field distributions for an ultrasonic imaging system when focusing in biological media. A biological medium is characterized in terms of its complex and frequency-dependent compressibility that, in turn, depends on the medium relaxation time and specific heat ratio. The analysis is based on a spatial/temporal transfer function formalism and can predict the effects of dispersion, frequency-dependent attenuation, aperture apodization and pulse shape. These effects can be observed on a 'snapshot' of the field in time and space. A number of simulations for a 3-MHz broadband system are presented. The results indicate that, aside from geometrical considerations (F/number), the pulse-width and the dispersive processes can play a major role in imaging performance.<> View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Power spectrum equalization for ultrasonic image restoration

    Publication Year: 1989 , Page(s): 216 - 222
    Cited by:  Papers (22)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (799 KB)  

    A method of image restoration for ultrasonic B-scan images has been proposed that need no a priori knowledge on the PSF (point spread function) of the imaging system and is feasible for in vivo applications. The entire system's response, including the interposed medium and possible transducer defects, is estimated from the degraded image itself with a few simple operations. The ultrasonic image is restored based only on a knowledge of the estimated PSF and on the spectral characteristics of the resultant echo signal. The proposed method does not modify the phase relations between echoes from multiple scatterers since the restoration filter is phaseless and the display operation does not involve nonlinear detection. The effectiveness of the restoration filter was tested on simulated ultrasonic images in the absence and in the presence of interposed tissue. Then the filter was tested on a phantom made of scatterers randomly distributed in nonattenuating gel with and without an interposed medium whose attenuation linearly increases with frequency. A good correspondence between simulations and experimental results was found: both tests show an exceptional improvement of image resolution.<> View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Electromechanical coupling to Lamb and shear-horizontal modes in piezoelectric plates

    Publication Year: 1989 , Page(s): 223 - 230
    Cited by:  Papers (8)  |  Patents (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (555 KB)  

    Recent theoretical studies and experiments have been shown that interdigital transducers can couple strongly to plate modes in piezoelectric materials and in piezoelectric-on-nonpiezoelectric composite membranes. The calculated velocity dispersion and electromechanical coupling factors for plate modes in representative piezoelectric materials are described. The frequency dependence of velocity and electromechanical coupling factors are given, under different metallization conditions, for generalized stiffened-Lamb, pure stiffened-Lamb, and stiffened-shear (shear-horizontal) modes, for various plate orientations in lithium niobate, lithium tantalate, quartz, bismuth germanium oxide, and zinc oxide. For lithium niobate, electromechanical-coupling values as high as 15% are found under narrowband bandpass conditions, and 5% under wideband low-pass conditions. For lithium tantalate, bismuth germanium oxide, coupling values of 0.5, 2, and 4% are obtained. For quartz with its weaker piezoelectricity, the coupling is still made smaller.<> View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Thin-film induced effects on the stability of SAW devices

    Publication Year: 1989 , Page(s): 231 - 241
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1023 KB)  

    Measurements show an upward shift on the order of 50 ppm in the resonant frequency of a surface acoustic wave (SAW) resonator, as taken before and after the device is hermetically sealed in vacuum following a certain glass-frit sealing process. The authors analyze some of the thin-film phenomena that are potential sources of the observed frequency shift and that may affect the long-term stability of such devices. Various factors contributing to the shifts include: 1) intrinsic or structural stresses in the bonding layers as well as in the interdigital transducer (IDT) fingers; 2) thermal stresses due to the differences in thermal expansion coefficients of the metallic IDT fingers and the bonding agent (glass frits) from those of quartz; 3) partial oxidation of the IDT fingers and transmission lines during the frit glazing process; and 4) possible metal diffusion into quartz. Quantitative estimates of the contribution of two factors to the total observed frequency shift after a certain glass-frit sealing process are provided. Rough estimates of the frequency shifts due to the oxidized film are made from the dispersion curves for a uniform thin aluminum film and for its oxide film as fully plated on a quartz substrate. It is concluded that the results may provide a way of estimating the magnitude of the intrinsic stress for a given long-term stability of the SAW device.<> View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Sound field calculation for rectangular sources

    Publication Year: 1989 , Page(s): 242 - 248
    Cited by:  Papers (47)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (560 KB)  

    A method is presented for calculation of the sound field from a rectangular continuous-wave source surrounded by a plane grid baffle. The approach is illustrated for square sources of 0.5, 1, 2, 5, 10, 20, and 100 lambda on a side. These results are compared to the sound fields produced by similarly sized circular sources. The beam widths and locations of on-axis minima are similar for the two sources, but the transverse pressure distribution is more uniform in the near-field of the square source. The effects of attenuation on the sound field of a square source are examined.<> View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • The sector-vortex phased array: acoustic field synthesis for hyperthermia

    Publication Year: 1989 , Page(s): 249 - 257
    Cited by:  Papers (29)  |  Patents (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (990 KB)  

    A sector-vortex phased array capable of generating directly annular-shape foci is analyzed. By driving the sectors of the array with signals whose phase rotates M times around the circular track, annular foci with the same acoustic-signal-phase rotation are produced in the geometrical focal plane of the array. Because of this phase modulation around the focal annuli and the resulting high-spatial-frequency content, the produced acoustic fields are free from secondary foci both behind and in front of the focal plane. The diameter of the focal annuli can be increased by increasing the mode number M. By providing the array with multiple tracks, it is possible to get larger focal annuli than with a single track with the same mode number M. It is also possible to achieve some control of the power deposition patterns in the depth direction in this way. Using a dual track sector-vortex array with practical ranges of the aperture size and number of elements, acoustic power deposition patterns capable of heating the peripheral and central regions of a nonsuperficial tumor a few centimeters in diameter are obtained by computer simulation.<> View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Wideband acoustic microscopy of tissue

    Publication Year: 1989 , Page(s): 258 - 263
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (803 KB)  

    A scanning acoustic microscope (SAM) has been used to measure the elastic properties of tissue with a resolution of around 8 mu m. This is achieved by broadband excitation of the acoustic lens, and the recording of an undemodulated returning signal. A method of analyzing this information to yield sound velocity, acoustic impedance, section thickness, and acoustic attenuation is described. Results from a sample of skin tissue are presented and compared with data from a computer simulation of the experiment.<> View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Improvement of anisotropy sensitivity in the scanning acoustic microscope

    Publication Year: 1989 , Page(s): 264 - 273
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (871 KB)  

    The response of the conventional scanning acoustic microscope (SAM) to anisotropic materials is theoretically investigated. For this purpose, the reflection coefficient of plane acoustic waves incident on a liquid-solid interface is numerically calculated for a general anisotropic solid oriented in any arbitrary direction. In general, the reflection coefficient depends on polar and azimuthal angles of incidence. For the case of a circularly symmetric acoustic microscope lens, a mean reflectance function can be defined that depends only on the polar angle. With this mean reflectance function, it is very easy to predict the anisotropic material response of the acoustic microscope. It is found that, under certain conditions, the amplitude response of the acoustic microscope can depend heavily on the orientation of the solid material under investigation. The amplitude of the acoustic microscope signal is influenced by the orientation of the material because there is a cancellation of acoustic rays reflected from the object surface at different azimuthal angles. This cancellation is revealed as a minimum in the mean reflectance function. It is shown by numerical simulation that the sensitivity to orientation can be increased by the use of a ring-shaped insonification at the back of the acoustic lens.<> View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Experimental observation of plastic deformation areas, using an acoustic microscope

    Publication Year: 1989 , Page(s): 274 - 279
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (743 KB)  

    Novel techniques are described for the observation of plastic deformation areas by using an acoustic microscope. On a test piece subjected to plastic deformation, an area was found that had an abnormal contrast in the crystal grain and a pointed end at the V notch. Calculation of the propagation velocity of the surface acoustic wave (SAW) showed a difference of several percent between this area and the rest of the test piece. It has been presumed that this difference reflects the local plastic deformation, and that the abnormal contrast area corresponds to the image of the two-dimensionally distributed plastic deformation area of metals.<> View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Reciprocal relations for transmission coefficients: theory and application

    Publication Year: 1989 , Page(s): 280 - 286
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (551 KB)  

    The authors present a rigorous proof of certain intuitively plausible reciprocal relations for time harmonic plane-wave transmission and reflection at the interface between a fluid and an anisotropic elastic solid. Precise forms of the reciprocity relations for the transmission coefficients and for the transmitted energy fluxes are derived, based on the reciprocity theorem of elastodynamics. It is shown that the reciprocity relations can be used in conjunction with measured values of peak amplitudes for transmission through a slab of the solid (water-solid-water) to obtain the water-solid coefficients. Experiments were performed for a slab of a unidirectional fiber-reinforced composite. Good agreement of the experimentally measured transmission coefficients with theoretical values was obtained.<> View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Shear-horizontal surface waves on piezoelectric ceramics with depolarized surface layer

    Publication Year: 1989 , Page(s): 287 - 293
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (581 KB)  

    Theoretical analysis and numerical results describing the propagation of SH (shear-horizontal) surface waves on piezoelectric ceramics with a depolarized surface layer are described. SH surface waves propagating in piezoelectric ceramics with a depolarized surface layer are shown to be a mixture of the Bleustein-Gulyaev surface wave, electrical potential, and the Love surface-wave mechanical displacement. Depolarization of the surface layer in piezoelectric ceramics produces strong dispersion and a multimode structure of the SH surface wave. The penetration depth of the SH surface waves propagating on an electrically free surface of a piezoelectric ceramic with a depolarized surface layer can be significantly smaller than that of the Bleustein-Gulyaev surface waves propagating on a free piezoelectric half-space. It is concluded that piezoelectric ceramics with a depolarized surface layer can be used in hybrid piezoelectric semiconductor convolvers of reduced size.<> View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.

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.

Full Aims & Scope

Meet Our Editors

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