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Ultrasonics, Ferroelectrics, and Frequency Control, IEEE Transactions on

Issue 10 • Date October 2006

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

    Page(s): c1 - c2
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  • IEEE Ultrasonics, Ferroelectrics, and Frequency Control Society UFFC

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  • Elected Administrative Committee

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  • Table of contents

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  • Information for Contributors with Multimedia Addition

    Page(s): 1699 - 1703
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  • A multimedia example

    Page(s): 1704
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  • Introduction to the Special Issue on Novel Equipment for Ultrasound Research

    Page(s): 1705 - 1706
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  • A Ring Transducer System for Medical

    Page(s): 1707 - 1718
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    An ultrasonic ring transducer system has been developed for experimental studies of scattering and imaging. The transducer consists of 2048 rectangular elements with a 2.5-MHz center frequency, a 67% -6 dB bandwidth, and a 0.23-mm pitch arranged in a 150-mm-diameter ring with a 25-mm elevation. At the center frequency, the element size is 0.30lambda times 42lambda and the pitch is 0.38lambda. The system has 128 parallel transmit channels, 16 parallel receive channels, a 2048:328 transmit multiplexer, a 2048:16 receive multiplexer, independently programmable transmit waveforms with 8-bit resolution, and receive amplifiers with time variable gain independently programmable over a 40-dB range. Receive signals are sampled at 20 MHz with 12-bit resolution. Arbitrary transmit and receive apertures can be synthesized. Calibration software minimizes system nonidealities caused by noncircularity of the ring and element-to-element response differences. Application software enables the system to be used by specification of high-level parameters in control files from which low-level hardware-dependent parameters are derived by specialized code. Use of the system is illustrated by producing focused and steered beams, synthesizing a spatially limited plane wave, measuring angular scattering, and forming b-scan images View full abstract»

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  • Performance and Characterization of New Micromachined High-Frequency Linear Arrays

    Page(s): 1719 - 1729
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    A new approach for fabricating high frequency (>20 MHz) linear array transducers, based on laser micromachining, has been developed. A 30 MHz, 64-element, 74-mum pitch, linear array design is presented. The performance of the device is demonstrated by comparing electrical and acoustic measurements with analytical, equivalent circuit, and finite-element analysis (FEA) simulations. All FEA results for array performance have been generated using one global set of material parameters. Each fabricated array has been integrated onto a flex circuit for case of handling, and the flex has been integrated onto a custom printed circuit board test card for ease of testing. For a fully assembled array, with an acoustic lens, the center frequency was 28.7 MHz with a one-way -3 dB and -6 dB bandwidth of 59% arid 83%, respectively, arid a -20 dB pulse width of -99 ns. The per-element peak acoustic power, for a plusmn30 V single cycle pulse, measured at the 10 mm focal length of the lens was 590 kPa with a -6 dB directivity span of about 30 degrees. The worst-case total cross talk of the combined array and flex assembly is for nearest neighboring elements and was measured to have an average level -40 dB across the -6 dB bandwidth of the device. Any significant deviation from simulation can be explained through limitations in apparatus calibration and in device packaging View full abstract»

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  • Design of a Multilayer Transducer for Acoustic Bladder Volume Assessment

    Page(s): 1730 - 1738
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    Catheterization remains the "gold standard" for bladder volume assessment, but it is invasive and introduces the risk of infections and traumas. Therefore, noninvasive bladder volume measurement methods have gained interest. In a preceding study a new technique to measure the bladder volume on the basis of nonlinear ultrasound wave propagation was validated. This paper describes a first prototype of a dedicated multilayer transducer to implement this approach. It is composed of a PZT transducer for transmission and a PVDF layer for reception. Acoustical measurements in a water tank and phantom measurements showed that there is a relation between bladder volume and the harmonic contents of the echo obtained from a region of interest behind the bladder. Simulations with an equivalent transducer model on the basis of KLM-circuit modeling closely matched with the results from the acoustical measurements. The results demonstrated the feasibility of the multilayer transducer design for bladder volume assessment on the basis of nonlinear wave propagation View full abstract»

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  • Harmonic 3-d echocardiography with a fast-rotating ultrasound transducer

    Page(s): 1739 - 1748
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    Although the advantages of three-dimensional (3-D) echocardiography have been acknowledged, its application for routine diagnosis is still very limited. This is mainly due to the relatively long acquisition time. Only recently has this problem been addressed with the introduction of new real-time 3-D echo systems. This paper describes the design, characteristics, and capabilities of an alternative concept for rapid 3-D echocardiographic recordings. The presented fast-rotating ultrasound (FRU) transducer is based on a 64-element phased array that rotates with a maximum speed of 8 Hz (480 rpm). The large bandwidth of the FRU-transducer makes it highly suitable for tissue and contrast harmonic imaging. The transducer presents itself as a conventional phased-array transducer; therefore, it is easily implemented on existing 2-D echo systems, without additional interfacing. The capabilities of the FRU-transducer are illustrated with in-vitro volume measurements, harmonic imaging in combination with a contrast agent, and a preliminary clinical study View full abstract»

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  • Noninvasive field measurement of low-frequency ultrasonic transducers operating in sealed vessels

    Page(s): 1749 - 1758
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    This paper describes a noninvasive technique utilizing the acousto-optic effect, laser interferometry, and tomographic principles that have been implemented to measure the acoustic fields generated by low-frequency ultrasonic transducers operating into sealed, water-loaded vessels commonly used in industrial processing applications. A customized scanning frame, incorporating both linear and rotational stages, has been developed to facilitate manipulation of the laser head and vessel under evaluation. First, transmitted pressure profiles in air are predicted from surface displacement data acquired directly by laser measurement of the vibrating aperture. These profiles were then used to verify the measured fields obtained via conventional tomographic scanning procedures, coupled with laser interferometry, applied within a draft-proof scanning facility under free-field conditions. Next, the finite element code PZFlex was employed for the prediction of pressure fields within cylindrical cell configurations. Finally, precise manipulation of the laser firing angle and position was implemented in order to compensate for the effects of refraction at the cell wall boundaries, and to re-establish the projections required for the reconstruction algorithm. The experimental results demonstrate good corroboration with the PZFlex predictions, validating its application of ultrasound as a virtual prototyping tool for the design of high power ultrasonic test vessels View full abstract»

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  • An ultrasound research interface for a clinical system

    Page(s): 1759 - 1771
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    Under a contract with the National Cancer Institute, we have developed a research interface to an ultrasound system. This ultrasound research interface (URI) is an optional feature providing several basic capabilities not normally available on a clinical scanner. The URI can store high-quality beamformed radio-frequency data to file for off-line processing. Also, through an integrated user interface, the user is provided additional control over the B-mode receive aperture and color flow ensemble size. A third major capability is the ability to record and playback macro files. In this paper, we describe the URI and illustrate its use on three research examples: elastography, computed tomography, and spatial compounding View full abstract»

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  • The ultrasonix 500RP: A commercial ultrasound research interface

    Page(s): 1772 - 1782
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    Unlike researchers in magnetic resonance imaging who have considerable access to high level tools and to data at a very basic level on their scanners, those involved with ultrasound have found little in the way of meaningful and widespread access to even the most basic echo signals in their clinical systems. Interest has emerged, however, in ultrasound research interfaces on commercial scanners to provide access to raw ultrasound data and control of basic research functions. This paper describes initial experience gained on one such ultrasound system. The Ultrasonix 500RP system provides research access to the data at multiple points in the signal processing chain and allows control over most imaging parameters. The Ultrasonix system allows for three methods of research control. One is implemented along with the standard clinical imaging software using "mouseover" screens on the periphery of the application window. These screens are configured by the user to display various signal processing variables, which can be modified in real time. Second, the system can be controlled via a user-written remote control client application interacting through the clinical exam software. Lastly, the user can write a complete application which initializes the basic ultrasound module but need not use the Ultrasonix clinical exam software. All of the modes can be done locally on the scanner itself or via a network, and are based on software developed in C++ with libraries supplied with the scanner. Two examples are presented in this paper from the evaluation of the system in "real world" applications. Measurements of absolute backscatter coefficients and attenuation coefficients versus frequency are shown and elastograms utilizing spatial compounding are described View full abstract»

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  • FEMMINA real-time, radio-frequency echo-signal equipment for testing novel investigation methods

    Page(s): 1783 - 1795
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    Fast echographic multiparameter multi-image novel apparatus (FEMMINA), is a hardware and software platform dedicated to ultrasonic signal and image processing. FEMMINA is able to operate with sequences of radio-frequency (RF) frames. Its architecture is designed to be modular, expandable, and aimed at implementing different ultrasonic investigation techniques. The first experimental characteristic of this system is in its capability to operate in real time with ultrasonic RF signals, starting from acquisition up to processing, storage, and visualization. The second characteristic is the user-system interactivity that allows one to modify the operation appropriately while observing results. Currently, FEMMINA works in both typical experimental situations to study novel investigation techniques and clinical field to validate the proposed methods in different human districts View full abstract»

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  • High frame rate imaging system for limited diffraction array beam imaging with square-wave aperture weightings high frame rate imaging system for limited diffraction array beam imaging with square-wave aperture weightings

    Page(s): 1796 - 1812
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    A general-purpose high frame rate (HFR) medical imaging system has been developed. This system has 128 independent linear transmitters, each of which is capable of producing an arbitrary broadband (about 0.05-10 MHz) waveform of up to plusmn144 V peak voltage on a 75-ohm resistive load using a 12-bit/40-MHz digital-to-analog converter. The system also has 128 independent, broadband (about 0.25-10 MHz), and time-variable-gain receiver channels, each of which has a 12-bit/40-MHz analog-to-digital converter and up to 512 MB of memory. The system is controlled by a personal computer (PC), and radio frequency echo data of each channel are transferred to the same PC via a standard USB 2.0 port for image reconstructions. Using the HFR imaging system, we have developed a new limited-diffraction array beam imaging method with square-wave aperture voltage weightings. With this method, in principle, only one or two transmitters are required to excite a fully populated two-dimensional (2-D) array transducer to achieve an equivalent dynamic focusing in both transmission and reception to reconstruct a high-quality three-dimensional image without the need of the time delays of traditional beam focusing arid steering, potentially simplifying the transmitter subsystem of an imager. To validate the method, for simplicity, 2-D imaging experiments were performed using the system. In the in vitro experiment, a custom-made, 128-element, 0.32-mm pitch, 3.5-MHz center frequency linear array transducer with about 50% fractional bandwidth was used to reconstruct images of an ATS 539 tissue-mimicking phantom at an axial distance of 130 mm with a field of view of more than 90deg. In the in vivo experiment of a human heart, images with a field of view of more than 90deg at 120-mm axial distance were obtained with a 128-element, 2.5-MHz center frequency, 0.15-mm pitch Acusori V2 phased array. To ensure that the system was operated under the limits set by the U.S. Food and Drug Administration, th- - e mechanical index, thermal index, and acoustic output were measured. Results show that higher-quality images can be reconstructed with the square-wave aperture weighting method due to an increased penetration depth as compared to the exact weighting method developed previously, and a frame rate of 486 per second was achieved at a pulse repetition frequency of about 5348 Hz for the human heart View full abstract»

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  • A programmable real-time system for development and test of new ultrasound investigation methods

    Page(s): 1813 - 1819
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    In vitro and/or in vivo experimental tests represent a crucial phase in the development of new ultrasound (US) investigation methods for biomedical applications. Such tests frequently are made difficult by the lack of flexibility of general purpose instruments and commercial US machines typically available in research laboratories. This paper presents a novel, real-time development system specifically designed for US research purposes. Main features of the system are the limited dimensions (it is based on a single electronic board), the capability of transmitting arbitrary waveforms to two probes, of storing the received radio-frequency (RF) echo data in a file and/or of processing them in real-time according to programmable algorithms. As an example of application, results of simultaneous hemodynamic and mechanic investigations in human arteries are reported. However, the high system flexibility and portability make it suitable for a large class of US applications View full abstract»

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  • The progressive focusing correction technique for ultrasound beamforming

    Page(s): 1820 - 1831
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    This work presents a novel method for digital ultrasound beamforming based on programmable table look-ups, in which vectors containing coded focusing information are efficiently stored, achieving an information density of a fraction of bit per acquired sample. Timing errors at the foci are within half the period of a master clock of arbitrarily high frequency to improve imaging quality with low resource requirements. The technique is applicable with conventional as well as with DeltaSigma converters. The bit-width of the focusing code and the number of samples per focus can be defined to improve both memory size and F# with controlled timing errors. In the static mode, the number of samples per focus is fixed, and in the dynamic approach that figure grows progressively, taking advantage of the increasing depth of focus. Furthermore, the latter has the lowest memory requirements. The technique is well suited for research purposes as well as for real-world applications, offering a degree of freedom not available with other approaches. It allows, for example, modifying the sampling instants to phase aberration correction, beamforming in layered structures, etc. The described modular and scalable prototype has been built using low-cost field programmable gate arrays (FPGAs). Experimental measurements are in good agreement with the theoretically expected errors View full abstract»

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  • Adaptive imaging on a diagnostic ultrasound scanner at quasi real-time rates

    Page(s): 1832 - 1843
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    Constructing an ultrasonic imaging system capable of compensating for phase errors in real-time is a significant challenge in adaptive imaging. We present a versatile adaptive imaging system capable of updating arrival time profiles at frame rates of approximately 2 frames per second (fps) with 1-D arrays and up to 0.81 fps for 1.75-D arrays, depending on the desired near-field phase correction algorithm. A novel feature included in this system is the ability to update the aberration profile at multiple beam locations for 1-D arrays. The features of this real-time adaptive imaging system are illustrated in tissue-mimicking phantoms with physical near-field phase screens and evaluated in clinical breast tissue with a 1.75-D array. The contrast-to-noise ratio (CNR) of anechoic cysts was shown to improve dramatically in the tissue-mimicking phantoms. In breast tissue, the width of point-like targets showed significant improvement: a reduction of 26.2% on average. Brightness of these targets, however, marginally decreased by 3.9%. For larger structures such as cysts, little improvement in features and CNR were observed, which is likely a result of the system assuming an infinite isoplariatic patch size for the 1.75-D arrays. The necessary requirements for constructing a real-time adaptive imaging system are also discussed View full abstract»

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  • Intravascular ultrasound tissue harmonic imaging in vivo

    Page(s): 1844 - 1852
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    Tissue harmonic imaging (THI) has been shown to increase image quality of medical ultrasound in the frequency range from 2 to 10 MHz and might, therefore, also be used to improve image quality in intravascular ultrasound (IVUS). In this study we constructed a prototype IVUS system that could operate in both fundamental frequency and second harmonic imaging modes. This system uses a conventional, continuously rotating, single-element IVUS catheter and was operated in fundamental 20 MHz, fundamental 40 MHz, and harmonic 40 MHz modes (transmit 20 MHz, receive 40 MHz). Hydrophone beam characterization measurements demonstrated the build-up of a second harmonic signal as a function of increasing pressure. Imaging experiments were conducted in both a tissue-mimicking phantom and in an atherosclerotic animal model in vivo. Acquisitions of fundamental 20 and 40 MHz and second harmonic acquisitions resulted in cross sections of the phantom and a rabbit aorta. The harmonic results of the imaging experiments showed the feasibility of intravascular THI with a conventional IVUS catheter both in a phantom and in vivo. The harmonic acquisitions also showed the potential of THI to reduce image artifacts compared to fundamental imaging View full abstract»

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  • Multigate transcranial doppler ultrasound system with real-time embolic signal identification and archival

    Page(s): 1853 - 1861
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    An integrated system for acquisition and processing of intracranial and extracranial Doppler signals and automatic embolic signal detection has been developed. The hardware basis of the system is a purpose-built acquisition/processing board that includes a multigate Doppler unit controlled through a computer. The signal-processing engine of the system contains a fast Fourier transform (FFT)-based, spectral-analysis unit and an embolic signal-detection unit using expert system reasoning theory. The system is designed so that up to four receive gates from a single transducer can be used to provide useful reasoning information to the embolic signal-detection unit. Alternatively, two transducers can be used simultaneously, either for bilateral transcranial Doppler (TCD) investigations or for simultaneous intraand extracranial investigation of different arteries. The structure of the software will allow the future implementation of embolus detection algorithms that use the information from all four channels when a single transducer is used, or of independent embolus detection in two sets of two channels when two transducers are used. The user-friendly system has been tested in-vitro, and it has demonstrated a 93.6% sensitivity for micro-embolic signal (MES) identification. Preliminary in-vivo results also are encouraging View full abstract»

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  • High reliability outdoor sonar prototype based on efficient signal coding

    Page(s): 1862 - 1872
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    Many mobile robots and autonomous vehicles designed for outdoor operation have incorporated ultrasonic sensors in their navigation systems, whose function is mainly to avoid possible collisions with very close obstacles. The use of these systems in more precise tasks requires signal encoding and the incorporation of pulse compression techniques that have already been used with success in the design of high-performance indoor sonars. However, the transmission of ultrasonic encoded signals outdoors entails a new challenge because of the effects of atmospheric turbulence. This phenomenon causes random fluctuations in the phase and amplitude of traveling acoustic waves, a fact that can make the encoded signal completely unrecognizable by its matched receiver. Atmospheric turbulence is investigated in this work, with the aim of determining the conditions under which it is possible to assure the reliable outdoor operation of an ultrasonic pulse compression system. As a result of this analysis, a novel sonar prototype based on complementary sequences coding is developed and experimentally tested. This encoding scheme provides the system with very useful additional features, namely, high robustness to noise, multi-mode operation capability (simultaneous emissions with minimum cross talk interference), and the possibility of applying an efficient detection algorithm that notably decreases the hardware resource requirements View full abstract»

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  • Trajectory tracking of piezoelectric positioning stages using a dynamic sliding-mode control

    Page(s): 1872 - 1882
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    Trajectory tracking performance of a piezoelectric positioning stage almost depends on whether the tracking controller can effectively compensate the inherent hysteresis phenomenon. In this paper, a dynamic sliding-mode control (DSMC) with backstepping is proposed for the trajectory tracking of the piezoelectric positioning stage, which is suitable for a component of scanning microscopes. An equivalent model developed from a linear motion dynamics with addition of the hysteresis nonlinearity and strain-dependent function first is proposed to approximately represent the dynamics of motion of a one-dimensional piezoelectric positioning stage. Then, based on the equivalent model, the DSMC with an asymptotical sliding surface is proposed for the trajectory tracking control of the piezoelectric positioning stage. Moreover, the analysis of stability can be completed by mathematics, and the convergence rate of the tracking error can be governed by the choice of the control parameter values. Using the DSMC to trajectory tracking control, the piezoelectric positioning stage becomes more suitable for practical applications, especially with the need of various trajectories tracking in microscopy. To validate the proposed control scheme. a computer-based controller arid a piezoelectric positioning stage with a capacitive displacement sensor are implemented. Experimental results illustrate the feasibility of the proposed controller for trajectory tracking applications View full abstract»

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  • Complex permittivity measurements of ferroelectrics employing composite dielectric resonator technique

    Page(s): 1883 - 1888
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    Composite cylindrical TE0n1 mode dielectric resonator has been used for the complex permittivity measurements of ferroelectrics at frequency about 8.8 GHz. Rigorous equations have been derived that allowed us to find a relationship between measured resonance frequency and Q-factor and the complex permittivity. It has been shown that the choice of appropriate diameter of a sample together with rigorous complex angular frequency analysis allows precise measurements of various ferroelectric. Proposed technique can be used for materials having both real and imaginary part of permittivity as large as a few thousand. Variable temperature measurements were performed on a PbMg1/3Nb2/3O3 (PMN) ceramic sample, and the measured complex permittivity have shown good agreement with the results of measurements obtained on the same sample at lower frequencies (0.1 1.8 GHz) View full abstract»

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  • Merits of PM noise measurement over noise figure: a study at microwave frequencies

    Page(s): 1889 - 1894
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    This paper primarily addresses the usefulness of phase-modulation (PM) noise measurements versus noise figure (NF) measurements in characterizing the merit of an amplifier. The residual broadband (white PM) noise is used as the basis for estimating the NF of an amplifier. We have observed experimentally that many amplifiers show an increase in the broadband noise of 1 to 5 dB as the signal level through the amplifier increases. This effect is linked to input power through the amplifier's nonlinear intermodulation distortion. Consequently, this effect is reduced as linearity is increased. We further conclude that, although NF is sometimes used as a selection criteria for an amplifier for low-level signal, NF yields no information about potentially important close-to-carrier 1/f noise of an amplifier nor broadband noise in the presence of a high-level signal, but a PM noise measurements does. We also have verified experimentally that the single-sideband PM noise floor of an amplifier due to thermal noise is -177 dBc/Hz, relative to a carrier input power of 0 dBm 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