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Ultrasonics, Ferroelectrics, and Frequency Control, IEEE Transactions on

Issue 5 • Date May 2010

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Displaying Results 1 - 25 of 33
  • "IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control - Front cover"

    Page(s): C1 - C2
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  • IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control - List staff

    Page(s): i
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  • IEEE Ultrasonics, Ferroelectrics, and Frequency Control Society - Elected Administrative Committee

    Page(s): ii
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  • Table of contents

    Page(s): iii - v
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  • Information for contributors with multimedia addition

    Page(s): 995 - 998
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  • A multimedia example

    Page(s): 999
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  • Electromagnetic-acoustic high-Q silicon resonators for liquid phase sensing

    Page(s): 1000 - 1002
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    Piezoelectric and electrostatic excitation are the standard transduction methods of ultrasonic sensors. However, electromagnetic-acoustic transduction has been demonstrated as a suitable alternative with unique advantages of noncontact excitation and multi-mode vibration in inexpensive materials, such as thin metal plates. We have also demonstrated the use of high-Q silicon membranes as resonator elements. Here, we report on the utilization of these devices as liquid phase sensors for density and viscosity measurements. View full abstract»

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  • 2-D green's functions for semi-infinite orthotropic piezothermoelastic plane

    Page(s): 1003 - 1010
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    Green's functions play an important role in electroelastic analyses of piezoelectric media. However, most works available on the topic are for the case of uniform temperature. Based on the compact 2-D general solution of orthotropic piezothermoelectric material, which is expressed in harmonic functions, and employing the trial-and-error method, the 2-D Green's function for a steady line heat source in a semi-infinite piezothermoelectric plane is presented by four newly induced harmonic functions. All components of the coupled field are expressed in terms of elementary functions and are convenient to use. Numerical results are given graphically by contours. View full abstract»

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  • Stability variances: a filter approach

    Page(s): 1011 - 1028
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    We analyze the Allan variance estimator as the combination of discrete-time linear filters. We apply this analysis to the different variants of the Allan variance: the overlapping Allan variance, the modified Allan variance, the Hadamard variance and the overlapping Hadamard variance. Based upon this analysis, we present a new method to compute a new estimator of the Allan variance and its variants in the frequency domain. We show that the proposed frequency domain equations are equivalent to extending the data by periodization in the time domain. Like the total variance, which is based on extending the data manually in the time domain, our frequency domain variance estimators have better statistics than the estimators of the classical variances in the time domain. We demonstrate that the previous well-know equation that relates the Allan variance to the power spectrum density (PSD) of continuous-time signals is not valid for real world discrete-time measurements and we propose a new equation that relates the Allan variance to the PSD of the discrete-time signals and allows computation of the Allan variance and its different variants in the frequency domain. View full abstract»

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  • Characterization of doped BST thin films deposited by sol-gel for tunable microwave devices

    Page(s): 1029 - 1033
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    BST thin films with various dopants were grown by the sol-gel method on platinized silicon and MgO substrates. Their dielectric properties were investigated at low frequency (up to 1 MHz) on silicon with parallel-plate capacitors and at high frequency (up to 15 GHz) with interdigitated capacitors on MgO substrate. The results depend on the nature of the dopant and show that Mg is a very good candidate to reduce dielectric losses. On the other hand, K is a good candidate as dopant of BST thin film to drastically increase the tunability. View full abstract»

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  • Cryogenic sapphire oscillator using a low- vibration design pulse-tube cryocooler: first results

    Page(s): 1034 - 1038
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    A cryogenic sapphire oscillator (CSO) has been implemented at 11.2 GHz using a low-vibration design pulse-tube cryocooler. Compared with a state-of-the-art liquid helium cooled CSO in the same laboratory, the square root Allan variance of their combined fractional frequency instability is ??y = 1.4 ?? 10-5??-1/2 for integration times 1 < ?? < 10 s, dominated by white frequency noise. The minimum ??y = 5.3 ?? 10-16 for the two oscillators was reached at ?? = 20 s. Assuming equal contributions from both CSOs, the single oscillator phase noise S?? ?? -96 dB.rad2/Hz at 1 Hz set from the carrier. View full abstract»

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  • Segmented motion compensation for complementary coded ultrasonic imaging

    Page(s): 1039 - 1050
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    Ultrasonic imaging using complementary coded pulses offers the SNR improvements of signal coding without the filter side-lobes introduced by single-transmit codes. Tissue motion between coded pulse emissions, however, can introduce high side-lobes caused by misalignment of complementary filter outputs. This paper presents a method for filtering and motion compensation of complementary coded signals appropriate for use in medical imaging. The method is robust to the effects of non-ideal transducers on the imaging signals, includes mirrored compensation stages to reduce the impact of motion estimation error, and has been shown to reduce side-lobes to levels that compare favorably to systems using FM-coded signals of similar length and bandwidth while providing increased coding gain and range resolution. In addition, motion compensation allows the received data to be used without the frame-rate penalty usually incurred by complementary-coded imaging. The method has been verified using simulated point and speckle targets with both homogeneous and inhomogeneous motion profiles. Selected results have been verified experimentally. View full abstract»

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  • Three-dimensional synthetic aperture focusing using a rocking convex array transducer

    Page(s): 1051 - 1063
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    Volumetric imaging can be performed using 1-D arrays in combination with mechanical motion. Outside the elevation focus of the array, the resolution and contrast quickly degrade compared with the lateral plane, because of the fixed transducer focus. This paper shows the feasibility of using synthetic aperture focusing for enhancing the elevation focus for a convex rocking array. The method uses a virtual source (VS) for defocused multi-element transmit, and another VS in the elevation focus point. This allows a direct time-of-flight to be calculated for a given 3-D point. To avoid artifacts and increase SNR at the elevation VS, a plane-wave VS approach has been implemented. Simulations and measurements using an experimental scanner with a convex rocking array show an average improvement in resolution of 26% and 33%, respectively. This improvement is also seen in in vivo measurements. An evaluation of how a change in transducer design will affect the resolution improvement shows a potential for using a modified transducer for 3-D imaging with improved elevation focusing and contrast. View full abstract»

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  • A new method for blood velocity measurements using ultrasound FMCW signals

    Page(s): 1064 - 1076
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    The low peak power of frequency-modulated continuous wave (FMCW) radar makes it attractive for various applications, including vehicle collision warning systems and airborne radio altimeters. This paper describes a new ultrasound Doppler measurement system that measures blood flow velocity based on principles similar to those of FMCW radar. We propose a sinusoidal wave for FM modulation and introduce a new demodulation technique for obtaining Doppler information with high SNR and range resolution. Doppler signals are demodulated with a reference FMCW signal to adjust delay times so that they are equal to propagation times between the transmitter and the receiver. Analytical results suggest that Doppler signals can be obtained from a selected position, as with a sample volume in pulse wave Doppler systems, and that the resulting SNR is nearly identical to that obtained with continuous wave (CW) Doppler systems. Additionally, clutter power is less than that of CW Doppler systems. The analytical results were verified by experiments involving electronic circuits and Doppler ultrasound phantoms. View full abstract»

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  • Demonstration of second-harmonic IVUS feasibility with focused broadband miniature transducers

    Page(s): 1077 - 1085
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    Focused broadband miniature polyvinylidene fluoride-trifluoroethylene (PVDF TrFE) ultrasonic transducers were investigated for intravascular (IVUS) second-harmonic imaging. Modeling and experimental studies demonstrated that focused transducers, unlike conventional flat transducers, build up second harmonic peak pressures faster and stronger, leading to an increased SNR of second harmonic content within the coronary geometry. Experimental results demonstrated that focused second harmonic pressures could be controlled to occur at specific depths by controlling the f-number of the transducer. The experimental results were in good agreement with the modeled results. Experiments were conducted using three imaging modalities: fundamental 20 MHz (F20), second harmonic 40 MHz (H40), and fundamental 40 MHz (F40). The lateral resolutions for a 1-mm transducer (f-number 3.2) at F20, F40, and H40 were experimentally measured to be 162, 123, and 124 ??m, respectively, which agreed well with the theoretical calculations with <8% error. Lateral resolution was further characterized in the three modes, using a micromachined phantom consisting of fixed bars and spaces with widths ranging from 20 to 160 ??m. H40 exhibited better lateral resolution, clearly displaying 40- and 60-??m bars with about ~4 dB and ~7 dB greater signal strength compared with F20. Ex vivo human aorta images were obtained in the second-harmonic imaging mode to show the feasibility of high-resolution second-harmonic IVUS using focused transducers. View full abstract»

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  • Interstitial thermal ablation with a fast rotating dual-mode transducer

    Page(s): 1066 - 1095
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    Interstitial ultrasound applicators can be a minimally invasive alternative for treating targets that are unresectable or are inaccessible by extracorporeal methods. Dualmode transducers for ultrasound imaging and therapy were developed to address the constraints of a miniaturized applicator and real-time treatment monitoring. We propose an original treatment strategy that combines ultrasound imaging and therapy using a dual-mode transducer rotating at 8 revolutions per second. Real-time B-mode imaging was interrupted to emit high-intensity ultrasound over a selected therapy aperture. A full 360?? image was taken every 8th rotation to image the therapy aperture. Numerical simulations were performed to study the effect of rotation on tissue heating, and to study the effect of the treatment sequence on transducer temperature. With the time-averaged transducer surface intensity held at 12 W/ cm2 to maintain transducer temperature below 66??C, higher field intensities and deeper lesions were produced by narrower therapy apertures. A prototype system was built and tested using in vitro samples of porcine liver. Lesions up to 8 mm were produced using a time-averaged transducer surface intensity of 12 W/cm2 applied for a period of 240 s over a therapy aperture of 40??. Apparent strain imaging of the therapy aperture improved the contrast between treated and spared tissues, which could not be differentiated on B-mode images. With appropriate limits on the transducer output, real-time imaging and deep thermal ablation are feasible and sustainable using a rotating dual-mode transducer. View full abstract»

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  • Eigen-based clutter filter design for ultrasound color flow imaging: a review

    Page(s): 1096 - 1111
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    Proper suppression of tissue clutter is a prerequisite for visualizing flow accurately in ultrasound color flow imaging. Among various clutter suppression methods, the eigen- based filter has shown potential because it can theoretically adapt its stopband to the actual clutter characteristics even when tissue motion is present. This paper presents a formative review on how eigen-based filters should be designed to improve their practical efficacy in adaptively suppressing clutter without affecting the blood flow echoes. Our review is centered around a comparative assessment of two eigen-filter design considerations: 1) eigen-component estimation approach (single-ensemble vs. multi-ensemble formulations), and 2) filter order selection mechanism (eigenvalue-based vs. frequencybased algorithms). To evaluate the practical efficacy of existing eigen-filter designs, we analyzed their clutter suppression level in two in vivo scenarios with substantial tissue motion (intra-operative coronary imaging and thyroid imaging). Our analysis shows that, as compared with polynomial regression filters (with or without instantaneous clutter downmixing), eigen-filters that use a frequency-based algorithm for filter order selection generally give Doppler power images with better contrast between blood and tissue regions. Results also suggest that both multi-ensemble and single-ensemble eigen-estimation approaches have their own advantages and weaknesses in different imaging scenarios. It may be beneficial to develop an algorithmic way of defining the eigen-filter formulation so that its performance advantages can be better realized. View full abstract»

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  • Intima-media thickness: setting a standard for a completely automated method of ultrasound measurement

    Page(s): 1112 - 1124
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    The intima-media thickness (IMT) of the common carotid artery is a widely used clinical marker of severe cardiovascular diseases. IMT is usually manually measured on longitudinal B-mode ultrasound images. Many computer-based techniques for IMT measurement have been proposed to overcome the limits of manual segmentation. Most of these, however, require a certain degree of user interaction. In this paper we describe a new, completely automated layer extraction technique (named CALEXia) for the segmentation and IMT measurement of the carotid wall in ultrasound images. CALEXia is based on an integrated approach consisting of feature extraction, line fitting, and classification that enables the automated tracing of the carotid adventitial walls. IMT is then measured by relying on a fuzzy K-means classifier. We tested CALEXia on a database of 200 images. We compared CALEXia?s performance with those of a previously developed methodology that was based on signal analysis (CULEXsa). Three trained operators manually segmented the images and the average profiles were considered as the ground truth. The average error from CALEXia for lumen-intima (LI) and media- adventitia (MA) interface tracings were 1.46 ? 1.51 pixel (0.091 ? 0.093 mm) and 0.40 ? 0.87 pixel (0.025 ? 0.055 mm), respectively. The corresponding errors for CULEXsa were 0.55 ? 0.51 pixels (0.035 ? 0.032 mm) and 0.59 ? 0.46 pixels (0.037 ? 0.029 mm). The IMT measurement error was equal to 0.87 ? 0.56 pixel (0.054 ? 0.035 mm) for CALEXia and 0.12 ? 0.14 pixel (0.01 ? 0.01 mm) for CULEXsa. Thus, CALEXia showed limited performance in segmenting the LI interface, but outperformed CULEXsa in the MA interface and in the number of images correctly processed (190 for CALEXia and 184 for CULEXsa). Based upon two complementary strategies, we anticipate fusing them for further IMT improvements. View full abstract»

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  • Laser ultrasonic inspection of plates using zero-group velocity lamb modes

    Page(s): 1125 - 1132
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    A noncontact laser-based ultrasonic technique is proposed for detecting small plate thickness variations caused by corrosion and adhesive disbond between two plates. The method exploits the resonance at the minimum frequency of the S1 Lamb mode dispersion curve. At this minimum frequency, the group velocity vanishes, whereas the phase velocity remains finite. The energy deposited by the laser pulse generates a local resonance of the plate. This vibration is detected at the same point by an optical interferometer. First experiments show the ability to image a 1.5-??m deep corroded area on the back side of a 0.5-mm-thick duralumin plate. Because of the finite wavelength of the S1- zero group velocity (ZGV) mode, the spatial resolution is limited to approximately twice the plate thickness. With the same technique we investigate the state of adhesive bonds between duralumin and glass plates. The S1-Lamb mode resonance is strongly attenuated when plates are rigidly bonded. In the case of thin adhesive layers, we observed other resonances, associated with ZGV modes of the multi-layer structure, whose frequencies and amplitudes vary with adhesive thickness. Experiments were carried out on real automotive adhesively bonded structures and the results were compared with images obtained by X-ray radiography. View full abstract»

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  • Ultrasonic viscosity measurement using the shear-wave reflection coefficient with a novel signal processing technique

    Page(s): 1133 - 1139
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    Real-time viscosity measurement remains a necessity for highly automated industry. To resolve this problem, many studies have been carried out using an ultrasonic shear wave reflectance method. This method is based on the determination of the complex reflection coefficient's magnitude and phase at the solid-liquid interface. Although magnitude is a stable quantity and its measurement is relatively simple and precise, phase measurement is a difficult task because of strong temperature dependence. A simplified method that uses only the magnitude of the reflection coefficient and that is valid under the Newtonian regimen has been proposed by some authors, but the obtained viscosity values do not match conventional viscometry measurements. In this work, a mode conversion measurement cell was used to measure glycerin viscosity as a function of temperature (15 to 25??C) and corn syrup-water mixtures as a function of concentration (70 to 100 wt% of corn syrup). Tests were carried out at 1 MHz. A novel signal processing technique that calculates the reflection coefficient magnitude in a frequency band, instead of a single frequency, was studied. The effects of the bandwidth on magnitude and viscosity were analyzed and the results were compared with the values predicted by the Newtonian liquid model. The frequency band technique improved the magnitude results. The obtained viscosity values came close to those measured by the rotational viscometer with percentage errors up to 14%, whereas errors up to 96% were found for the single frequency method. View full abstract»

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  • Vibration characteristics of besocke-style scanning systems

    Page(s): 1140 - 1145
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    A vibration model of Besocke-style scanners is given based on Timoshenko beam theory. The model is applied to investigate the flexural vibration characteristics of piezotubes in the scanners, in which the effects of affiliated components of the piezo-tubes are considered. The calculated results show that several factors in addition to the piezo-tubes themselves influence the flexural vibration frequencies of the scanners. An example is the balls which support the piezo-tubes. These play important roles in influencing the flexural vibration characteristics of the scanners and can result in high-flexural resonance frequencies. The local resonance of the scanner disk can also influence the flexural vibration characteristics of the piezo-tubes. Finally, we show that the effects of the local resonance on the vibration characteristics of the scanners can be decreased or eliminated by improving the rigidity of connection between the scanner disk and the piezo-tube. View full abstract»

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  • Frequency spectra of AT-cut quartz plates with electrodes of unequal thickness

    Page(s): 1146 - 1151
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    We study vibrations of an AT-cut quartz plate with electrodes of unequal thickness. Mindlin's first-order plate theory is used. Dispersion relations for straight-crested waves in an unbounded plate and frequency spectra of modes in a finite plate are obtained. Results show that, because of the unequal thickness of the electrodes, the two originally uncoupled groups of modes are now coupled. One group consists of thickness-shear, flexure, and face-shear. The other has thickness-twist and extension. This coupling by asymmetric electrodes changes the frequency spectra and affects resonator performance. To avoid the effects of this coupling, a series of discrete values of the length/thickness ratio of the crystal plate need to be excluded. View full abstract»

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  • Noncontact ultrasonic transportation of small objects over long distances in air using a bending vibrator and a reflector

    Page(s): 1152 - 1159
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    Ultrasonic manipulation of small particles, including liquid droplets, over long distances is discussed. It is well known that particles can be trapped at the nodal points of an acoustic standing wave if the particles are much smaller than the wavelength of the standing wave. We used an experimental setup consisting of a 3-mm-thick, 605-mm-long duralumin bending vibrating plate and a reflector. A bolt-clamped Langevin transducer with horn was attached to each end of the vibrating plate to generate flexural vibrations along the plate. A plane reflector with the same dimensions as the vibrating plate was installed parallel to the plate at a distance of approximately 17 mm to generate an ultrasonic standing wave between them and to trap the small particles at the nodal lines. The acoustic field and acoustic radiation force between the vibrator and reflector were calculated by finite element analysis to predict the positions of the trapped particles. The sound pressure distribution was measured experimentally using a scanning laser Doppler vibrometer. By controlling the driving phase difference between the two transducers, a flexural traveling wave can be generated along the vibrating plate, and the vertical nodal lines of the standing wave and the trapped particles can be moved. The flexural wave was excited along the vibrator at 22.5 kHz. A lattice standing wave with a wavelength of 35 mm in the length direction could be excited between the vibrator and the reflector, and polystyrene spheres with diameters of several millimeters could be trapped at the nodal lines of the standing wave. The experimental and calculated results showed good agreement for the relationship between the driving phase difference and the positions of the trapped particles. Noncontact transportation of the trapped particles over long distances could be achieved by changing the driving phase difference. The position of the trapped particles could be controlled to an accuracy of 0.046 mm/deg. An - thanol droplet could also be trapped and moved. View full abstract»

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  • A new traveling wave ultrasonic motor using thick ring stator with nested PZT excitation

    Page(s): 1160 - 1168
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    To avoid the disadvantages of conventional traveling wave ultrasonic motors¿lower efficiency PZT working mode of d31, fragility of the PZT element under strong excitation, fatigue of the adhesive layer under harsh environmental conditions, and low volume of the PZT material in the stator- a new type of traveling wave ultrasonic motor is presented in this paper. Here we implement the stator by nesting 64 PZT stacks in 64 slots specifically cut in a thick metal ring and 64 block springs nested within another 64 slots to produce preloading on the PZT stacks. In this new design, the d33 mode of the PZT is used to excite the flexural vibrations of the stator, and fragility of the PZT ceramics and fatigue of the adhesive layer are no longer an issue. The working principle, FEM simulation, fabrication, and performance measurements of a prototype motor were demonstrated to validate the proposed ideas. Typical output of the prototype motor is no-load speed of 15 rpm and maximum torque of 7.96 N¿m. Further improvement will potentially enhance its features by increasing the accuracy in fabrication and adopting appropriate frictional material into the interface between the stator and the rotor. View full abstract»

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  • Measuring the photodetector frequency response for ultrasonic applications by a heterodyne system with difference- frequency servo control

    Page(s): 1169 - 1174
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    A technique for the calibration of photodiodes in ultrasonic measurement systems using standard and cost-effective optical and electronic components is presented. A heterodyne system was realized using two commercially available distributed feedback lasers, and the required frequency stability and resolution were ensured by a difference-frequency servo control scheme. The frequency-sensitive element generating the error signal for the servo loop comprised a delay-line discriminator constructed from electronic elements. Measurements were carried out at up to 450 MHz, and the uncertainties of about 5% (k = 2) can be further reduced by improved radio frequency power measurement without losing the feature of using only simple elements. The technique initially dedicated to the determination of the frequency response of photodetectors applied in ultrasonic applications can be transferred to other application fields of optical measurements. 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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Meet Our Editors

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