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Ultrasonics, Ferroelectrics, and Frequency Control, IEEE Transactions on

Issue 6 • Date Nov. 1993

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Displaying Results 1 - 25 of 28
  • A network model for arbitrarily oriented IDT structures

    Publication Year: 1993 , Page(s): 622 - 629
    Cited by:  Papers (14)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (760 KB)  

    A network model approach for analyzing arbitrarily oriented short-circuited SAW grating structures is extended to include interdigital transducers (IDTs) that are also arbitrarily oriented. The IDT structure is divided into cells, each modelled by a sequence of mismatched transmission lines consisting of a metallized and unmetallized region. The model includes: the impedance difference between metallized and free regions, the reflection coefficient at the metallization upstep, the reflection coefficient at the downstep for a counterpropagating wave, all deduced from the Datta-Hunsinger perturbation formula; the velocity difference between the free and metallized regions obtained using SAW propagation calculation software for arbitrarily oriented multilayers; and the energy storage susceptance at each finger discontinuity. Since only ordinary network elements are combined in accordance with the IDT geometry, this model permits good physical insight into the structure's characteristics and allows simple procedures for finding high directivity orientations.<> View full abstract»

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  • An aging model for surface acoustic wave devices

    Publication Year: 1993 , Page(s): 630 - 641
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    The authors present a study of the phase-aging kinetics of a 591.2 MHz quartz-crystal surface acoustic wave (SAW) filter intended for application in an undersea telecommunication system. At aging temperatures from 50 to 140 degrees C, a previously established SAW-device aging model describes the time dependence of the phase aging. The results of an investigation of the temperature dependence of the coefficients in this aging model allows the authors to extend the model, capturing both the time and the temperature dependence of the degradation. They then identify and assess the sources of variation, or error, affecting the data and model, estimate the distributions of the errors, and incorporate these error distributions in the extended aging model. This leads to a composite aging model that describes the time and temperature dependence of the complete phase-aging distribution. The authors use this composite model to predict end-of-life phase-aging distributions, demonstrating that the devices exhibit the high level of stability required by the application.<> View full abstract»

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  • The effect of an SiO/sub 2/ buffer layer on the SAW properties of ZnO/SiO/sub 2//GaAs structure

    Publication Year: 1993 , Page(s): 642 - 647
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (580 KB)  

    The effect of an SiO/sub 2/ buffer layer on the surface acoustic wave (SAW) properties of ZnO/SiO/sub 2//GaAs structure is examined. Both theoretical and experimental results show that the coupling coefficient is increased appreciably by providing an SiO/sub 2/ film between the ZnO film and the GaAs substrate. Adding an SiO/sub 2/ film is also beneficial to the promotion of quality of ZnO thin film. The results could be useful for the further development of monolithic SAW devices.<> View full abstract»

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  • Coupled model analysis of SAW floating electrode type unidirectional transducers

    Publication Year: 1993 , Page(s): 648 - 658
    Cited by:  Papers (17)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (811 KB)  

    The performance of a single-phase unidirectional transducers utilizing the internal reflections of floating electrodes of electrically open and shorted metal strips within an interdigital electrode structure (FEUDT: floating electrode unidirectional transducer) is analyzed using a coupled-mode theory. All four independent parameters (the self and mutual coupling coefficient, the transduction coefficient, and the static capacitance) governing the coupling-mode equation with an electrical transduction term are analytically derived using extended Legendre polynomial expansions of electrical fields and perturbation analysis. Frequency response of radiation admittance and insertion loss, and SAW field distributions in a transducer are calculated from simple closed-form solutions of the coupled-mode equation. The shift effect of reflection and transduction centers due to the asymmetric electrode structure is clarified. Experimental results are given for test devices fabricated on a 128 degrees C YX LiNbO/sub 3/ substrate and compared with theoretical results.<> View full abstract»

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  • Split spectrum algorithms rely on instantaneous phase information-a geometrical approach (US NDE)

    Publication Year: 1993 , Page(s): 659 - 665
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (736 KB)  

    Split spectrum algorithms for suppression of interference noise in ultrasonic nondestructive evaluation are known to work well when properly tuned. However, the algorithms are sensitive to certain parameter values and it is not clear how the algorithms use the phase and amplitude information available. This is partly because most split spectrum algorithms have been suggested heuristically without any detailed signal and noise model. A first step towards a model based approach to split spectrum is initiated. Based on a fairly detailed signal model, geometrical interpretations of the split spectrum concept are presented in an attempt to trace the phase and amplitude information utilized by the algorithms. In the light of gained theoretical knowledge, the conventional algorithms, polarity thresholding, minimization and geometric mean are evaluated. The geometrical approach is related to statistical pattern recognition and neural network approaches and the signal model is verified experimentally on real ultrasonic signals.<> View full abstract»

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  • Spatial coherence of ultrasonic speckle in composites

    Publication Year: 1993 , Page(s): 666 - 675
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (897 KB)  

    Pulsed echography in a scattering medium generates speckle noise. Its random nature implies a statistical processing of the backscattered signal. The second-order statistics, such as autocorrelation, can provide information about the structure of the medium and help detect a possible defect. The spatial autocorrelation function is related to the spatial coherence of the backscattered waves, which determines the speckle noise level. Specifically, this spatial coherence approach is applied to anisotropic fiber-reinforced composites. The authors present theoretical as well as experimental results and show how the autocorrelation function changes with the orientation of the layers inside the composite, thus pointing out its anisotropy.<> View full abstract»

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  • Ultrasonic fatigue of nickel-chromium alloys at low temperatures

    Publication Year: 1993 , Page(s): 676 - 679
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    The influence of low temperature ultrasonic deformation on the electrical resistivity and magnetic properties of nickel-chromium dilute solid solutions is examined. It is shown that changes in the electrical resistivity and magnetic properties of prequenched samples after ultrasonic fatigue can be explained by order-disorder processes during fatigue. It is concluded that ordering at low temperatures during the ultrasonic deformation is associated with high strain rate and high vacancy concentration produced by deformation.<> View full abstract»

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  • Effect of periodic surface roughness on V(z) curves for the line-focus acoustic microscope

    Publication Year: 1993 , Page(s): 680 - 686
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (630 KB)  

    A specimen with a periodic surface profile is considered to estimate the effect of surface roughness on the V(z) curve for the line-focus acoustic microscope. The Fourier optics approach is used to obtain the response of the lens and the Rayleigh-Fourier method is used to obtain the reflection coefficients for plane wave incidence from the fluid side on the periodic surface. An integral expression is obtained to calculate V(z) curves for periodic surface profiles. The V(z) curves are used to calculate the leaky Rayleigh wave velocities by applying the fast Fourier technique. Numerical results are presented to display the effect of sinusoidal surface roughness on the V(z) curves and the corresponding leaky Rayleigh wave velocities.<> View full abstract»

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  • Piezoelectric ultrasonic motor using longitudinal-torsional composite resonance vibration

    Publication Year: 1993 , Page(s): 687 - 693
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (714 KB)  

    A piezoelectric ultrasonic motor, which uses longitudinal and torsional composite vibration, is examined in order to obtain high torque characteristics with small diameter. Piezoelectric ceramic elements, oscillating in both longitudinal and torsional modes, respectively, are used as piezoelectric stiffened modes having high electromechanical coupling factors k/sub 33/ and k/sub 15/, respectively. It is found that the resonant frequencies for longitudinal mode and torsional mode could coincide with each other in the ultrasonic motor, according to finite element method analysis and experimental measurement. The motor operating in both resonant vibrations indicated good performance. The 20-mm diameter motor exhibited 4 kgfcm maximum torque, 450 r/min maximum rotational speed, 40% maximum efficiency, and quick responsiveness, within 2.5 ms.<> View full abstract»

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  • Ultrasonic transducers as a black-box: equivalent circuit synthesis and matching network design

    Publication Year: 1993 , Page(s): 694 - 703
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (899 KB)  

    A new modeling technique for ultrasonic transducers is developed in order to build an analytical model in the Laplace s-domain. The model is intended for use in analog circuit CAD system for the front-end electronic design and to visualize the acoustic pulse modifications under different excitation conditions. The transducer is characterized by two analytical functions representing the driving point impedance and the electroacoustic transfer function. The transfer function is obtained as the ratio of the transducer axial response and the excitation voltage. The reference responses of the impedance and transfer function are derived by the Fourier transform of the measured signals. The model is derived by the measurements of the driving point current and voltage, and the field axial response is sensed by a hydrophone. The procedure for the model identification is described. The results of testing 5-MHz transducer for medical applications are presented. An approach for the design of broadband matching networks using a constant resistance network is reported.<> View full abstract»

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  • Theoretical and experimental evaluation of a two-dimensional composite matrix array

    Publication Year: 1993 , Page(s): 704 - 709
    Cited by:  Papers (6)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (593 KB)  

    A theoretical and experimental performance appraisal of a two-dimensional, ceramic-epoxy composite matrix array employing 1-3 connectivity is presented. The linear systems approach is used for temporal and spatial simulation of array performance, with specific regard to three-dimensional synthetic aperture imaging in a fluid load medium. Manufacture and experimental evaluation of a prototype array structure, operating at 1.2 MHz and comprising 100 elements arranged as a 10 by 10 matrix, is described. Close agreement between theory and experiment is obtained, providing a clear indication that the low crosstalk, uniformity, and wideband characteristics of composite array elements offer excellent prospects for such imaging applications.<> View full abstract»

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  • Laser-generated elastic waves in carbon-epoxy composite

    Publication Year: 1993 , Page(s): 710 - 716
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (755 KB)  

    New contactless techniques using laser-generated ultrasound have been applied to the inspection of composite materials. Transient elastic waves were launched thermoelastically in half cylindrical composite samples using a long pulse dye laser or a Q-switched Nd-YAG laser. The waves were detected with piezoelectric transducers or with an optical heterodyne interferometer. The measurements have been carried out on two different lay up design composites: carbon/epoxy: undirectional and cross-ply 0 degrees /45 degrees /90 degrees /-45 degrees . Quasi-longitudinal, quasi-shear, and shear bulk waves and head waves are clearly discerned in the stacking of a large number of waveforms. Velocities of the different types of waves simultaneously generated are compared to the phase and group velocities computed using Christoffel equations and an hexagonal model. It is shown with this point-source measurement technique that the wavefront arrival times agree with the energy velocities rather than with the phase velocities. A pronounced anisotropy is observed in the amplitudes of the wave arrivals. Angular directivity patterns of quasi-longitudinal, quasi-shear, and transverse bulk waves are plotted.<> View full abstract»

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  • Beam transformation techinques for ultrasonic medical imaging

    Publication Year: 1993 , Page(s): 717 - 726
    Cited by:  Papers (13)  |  Patents (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1000 KB)  

    Data acquisition rates in pulsed ultrasound scanners are limited by the speed of sound in the human body. This poses severe limitations to the design of future ultrasound equipment, such as 3-D imaging scanners. The authors describe a technique for higher data acquisition rates based on the simultaneous transmission of multiple beams. By using a linear combination of the received beams, interbeam interference due to the sidelobe energy of the transmitting beams can be significantly reduced. The transformation coefficients are found by using a least squares minimization criterion. A simulation environment used for the evaluation of the authors' methodologies and various simulation results are presented.<> View full abstract»

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  • Two-dimensional array transducers using thick film connection technology

    Publication Year: 1993 , Page(s): 727 - 734
    Cited by:  Papers (22)  |  Patents (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (936 KB)  

    A connection technique for two-dimensional array ultrasound transducers developed by combining a conductive lambda /4 mismatching layer with a multi-layer ceramic (MLC) connector using thick-film microelectronic technology is described. The connector consists of 20 thick films of alumina and screen printed metallization with customized interconnections between the layers called vias. Ten ground layers are interleaved between ten signal layers to reduce elecrical crosstalk. A lambda /4 mismatching layer of conductive epoxy is bonded between each PZT element and the silver metal pad of the MLC connector to provide an effective low impedance backing. In the current configuration, a 16*16 transducer array, 0.6 mm element spacing, is expanded to a 16*16 grid of connector pins at a standard spacing of 2.5 mm. Vector impedance, sensitivity, bandwidth, interelement uniformity, and crosstalk are all in good agreement with arrays of conventional fabrication. However, an array with MLC connector can be fabricated more quickly independent of the number of elements.<> View full abstract»

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  • Sidelobe reduction for limited diffraction pulse-echo systems

    Publication Year: 1993 , Page(s): 735 - 746
    Cited by:  Papers (20)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3775 KB)  

    Conventional focused transducers have a sharp focal spot with low sidelobes, but they also have a short depth of field. Commercial medical scanners obtain increased depth of field by combining several images in a montage, each obtained at a different focal depth. Therefore, to get low sidelobes over a large depth of field several transmits must be used, which decrease the frame rate. Limited diffraction beams such as Bessel beams and X waves obtain good resolution over very large depth of field, but they have high sidelobes. A summation-subtraction method developed for decreasing the sidelobes is presented. The method requires three transmits, decreasing the frame rate to one third. The authors apply this technique to limited diffraction beams and obtain an analytic description.<> View full abstract»

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  • Wavefront amplitude distortion and image sidelobe levels. I. Theory and computer simulations

    Publication Year: 1993 , Page(s): 747 - 753
    Cited by:  Papers (15)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (828 KB)  

    The quality of an imaging system is degraded by propagation anomalies that distort wavefronts propagating through the medium. Adaptive phase-deaberration algorithms compensate for phase errors in the wavefront. The algorithms suffer, however, when the wavefront is also significantly distorted. A theory which shows that the rise of image background level, which is the average sidelobe floor (ASF), in a single point-like source image is proportional to the amplitude distortion of the wavefront and inversely proportional to the effective number of array elements is derived. From the theory, the tolerance to the amplitude distortion, after the phasefront has been corrected by a deaberration algorithm, can be calculated based on the design requirement of the sidelobe floor for a given array. Computer simulations show good agreement with the theory.<> View full abstract»

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  • Wavefront amplitude distortion and image sidelobe levels. II. In vivo experiments

    Publication Year: 1993 , Page(s): 754 - 762
    Cited by:  Papers (15)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (966 KB)  

    For part I, see ibid., vol.40, no.6, p.747-753 (1993). In vivo measurements of the rise of the sidelobe level in a single-source image obtained through the female breast as a function of the distortion of the wavefront amplitude are described. The measured sidelobe levels are the average sidelobe floor (ASF) and the peak sidelobe level (PSL). The ASF is shown to be proportional to the variance of the modulus of the wavefront normalized to the square of its mean value, with a proportionality constant close to the value predicted by theory. The PSL similarly increases linearly. The average ratio of PSL to ASF is 5 (7 dB).<> View full abstract»

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  • A simple equivalent circuit for interdigital transducers based on the coupled-mode approach

    Publication Year: 1993 , Page(s): 763 - 767
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (444 KB)  

    The coupled-mode approach is a powerful tool for analyzing surface acoustic wave (SAW) periodic structures such as reflectors and interdigital transducers. The relations among the terminal quantities at two acoustical ports and one electrical port of an interdigital transducer (IDT) are derived from coupled-mode equations. A simple distributed-parameter equivalent circuit representing the entire IDT is proposed. A few examples of applications of this equivalent circuit to analysis of SAW devices are presented.<> View full abstract»

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  • A real-time ultrasound time-domain correlation blood flowmeter. I. Theory and design

    Publication Year: 1993 , Page(s): 768 - 775
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (907 KB)  

    A real-time ultrasound time-domain correlation (UTDC) blood flowmeter has been developed. Real-time performance has been achieved through the implementation of a custom-designed high-speed residue-number system (RNS) hardware correlator. The flowmeter is interfaced to a commercial ultrasound imager and can produce one-dimensional velocity versus range graphs at a rate of three per second. It has been validated in a blood flow phantom under a variety of conditions along with in vivo measurements in the human carotid artery. The theory of the time-domain correlation technique, design and implementation of flowmeter hardware, and the important correlation parameters which affect the performance of the flowmeter are described.<> View full abstract»

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  • A real-time ultrasound time-domain correlation blood flowmeter. II. Performance and experimental verification

    Publication Year: 1993 , Page(s): 776 - 785
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1130 KB)  

    For Part I, see ibid., vol.40, no.6, p.768-775 (1993). The performance of a real-time ultrasound time-domain correlation (UTDC) flowmeter employing a high-speed residue number system correlator under various flow conditions for different correlation parameter settings is evaluated. Previous work has incorporated a weighted-averaging scheme to estimate the flow velocity over a wide number of echo signal spacings. The present evaluation indicates that a linear averaging of 50 adjacent echo signal pairs produces equivalent accuracy and precision at real-time processing speed as compared to previous non-real time systems incorporating weighted averaging.<> View full abstract»

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  • Experimental evaluation of intrinsic and nonstationary ultrasonic Doppler spectral broadening in steady and pulsatile flow loop models

    Publication Year: 1993 , Page(s): 786 - 795
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1059 KB)  

    Intrinsic and nonstationary Doppler spectral broadening, and the skewness of the spectral representation, were evaluated experimentally using porcine red cell suspensions as ultrasonic scatterers. Theoretically, the relative Doppler bandwidth, defined as the intrinsic bandwidth divided by the mean Doppler frequency shift, should be velocity independent. The relative Doppler bandwidth invariance theorem was experimentally verified with an in vitro steady laminar blood flow model. It is shown that the relative bandwidth is both independent of the flow velocity and blood hematocrit. Using a pulsatile laminar flow model, the authors demonstrated that the relative Doppler bandwidth invariance theorem did not hold during flow acceleration and deceleration. In addition, a positive skewness of the Doppler spectra was observed during acceleration while a negative skewness was measured during the deceleration of blood. The effect of the window duration used in the Fourier spectral computation, on nonstationary broadening, is characterized.<> View full abstract»

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  • A new adaptive mean frequency estimator: application to constant variance color flow mapping

    Publication Year: 1993 , Page(s): 796 - 804
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1004 KB)  

    A class of adapted mean frequency estimators is proposed for color flow mapping. These estimators can be fitted to the specific characteristics of a given Doppler signal to optimize the compromise between the range of analysable frequencies and the variance of mean frequency estimation. A sub-optimal estimator is derived for real-time applications, and an adaptive criterion based on the Doppler signal variance is developed for color flow mapping applications. Its performance is compared to that of the usual correlation phase estimator on simulated Doppler signals and on synthetic Doppler images. An improvement in image quality is achieved, mainly for low signal-to-noise ratio Doppler signals.<> View full abstract»

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  • A stereoscopic technique for seafloor statistical characterization by acoustic remote sensing

    Publication Year: 1993 , Page(s): 805 - 813
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (920 KB)  

    The authors present a new method for performing statistical characterization of underwater surfaces by acoustic remote sensing. A wideband technique is outlined that, by exploiting stereoscopic observation, estimates the roughness height of underwater surfaces however oriented with respect to the instrument. The surface is ensonified by a wideband signal and simultaneously viewed from two or more slightly different directions of view. The corresponding echoes are compared in the frequency domain, and a roughness estimate is obtained. Once the instrument centerband frequency has been fixed, the scale factor in the estimation can be adjusted by varying the differences between the view directions. This permits a wide estimation interval, ranging from a small fraction to many times the wavelength corresponding to the centerband frequency. Preliminary experiments have been carried out in a water tank, and the estimated roughness values are in agreement with the theory.<> View full abstract»

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  • Suppression of sidelobe levels for guided-wave acousto-optic tunable filters using weighted coupling

    Publication Year: 1993 , Page(s): 814 - 818
    Cited by:  Papers (6)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (479 KB)  

    An analysis of guided-wave acousto-optic tunable filters (AOTFs) that employ simple acousto-optic (AO) weighted coupling techniques for sidelobe reduction and the calculated and experimental results from a specific example that involves only variation of the width of a surface acoustic wave (SAW) slot waveguide are presented. The calculations on single- and multi-stage AOTFs consisting of an optical channel waveguide and a SAW slot waveguide in LiNbO/sub 3/ substrate show that waveguide width weighting using generalized Hamming functions would provide significant improvement in sidelobe suppression. Calculated results together with the design, fabrication, and measured performance characteristics of a single-stage AOTF that utilizes a weighted-aperture SAW slot waveguide in YX-LiNbO/sub 3/ substrate at the optical wavelength of 1.55 mu m and the acoustic center frequency of 175 MHz are reported. The measured sidelobe level is -13.6 dB and the measured FWHM bandwidth is 26 AA, as compared to the theoretical values of -15.0 dB and 15 AA, respectively. The RF drive power was measured to be 1.0 W at a mode-conversion efficiency of 100%.<> View full abstract»

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  • Curie temperatures and dielectric properties of doped and undoped KTiOPO/sub 4/ and isomorphs

    Publication Year: 1993 , Page(s): 819 - 824
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (646 KB)  

    The Curie temperatures and dielectric properties of KTiOPO/sub 4/ (KTP), RbTiOPO/sub 4/, KTiOAsO/sub 4/, RbTiOAsO/sub 4/, CsTiOAsO/sub 4/, Ba:KTP, and Ga:KTP were measured with small-signal relative dielectric permittivity ( kappa ) analysis, piezoelectric resonance analysis, and optical second harmonic generation. All the isomorphs and the doped KTP exhibit lower Curie temperatures than KTP, ranging from 637 degrees C for CsTiOAsO/sub 4/ to 955 degrees C for hydrothermally (HT) grown KTP. The Curie-Weiss law is obeyed in all samples. With the exception of CsTiOAsO/sub 4/, all doped and undoped crystals show large dielectric relaxation at frequencies below 100 KHz throughout the temperature range of 500 degrees C-800 degrees C. For the barium-doped KTP, it was found that the Curie temperature decreases with increasing Ba/sup ++/-doping concentration. Barium doping also significantly modifies dielectric and piezoelectric properties of KTP.<> View full abstract»

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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