IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control

Wall losses in microwave cavities will generate a phase difference between the components of the field, and give rise to spatial phase variations which are related to the geometry of complicated shaped metal boundaries. Such effects are important to the design of the cavities used in the field of atomic frequency standards. Past attempts at calculating spatial phase variations in microwave cavitie... View full abstract»

It has been reported that power color Doppler ultrasound has important advantages over conventional color Doppler flow imaging. Some of these advantages are the aliasing free capability, the increased sensitivity to flow, and the angular independence. This last characteristic of power Doppler ultrasound was evaluated to verify if it was still valid in some well-defined flow conditions where porcin... View full abstract»

We address the problem of smooth power spectral density estimation of zero-mean stationary Gaussian processes when only a short observation set is available for analysis. The spectra are described by a long autoregressive model whose coefficients are estimated in a Bayesian regularized least squares (RLS) framework accounting the spectral smoothness prior. The critical computation of the tradeoff ... View full abstract»

Tissue elasticity can be estimated from displacement and strain images acquired under controlled deformation. We extend this approach for coronary arteries, deformed and imaged by an integrated angioplasty balloon and ultrasonic imaging probe. Because the lumen cross section of a severely occluded artery is not circular, we have also developed a technique to perform all motion computations in the ... View full abstract»

Using the incompressibility property of soft tissue, lateral displacements can be reconstructed from axial strain measurements. Results of simulations and experiments on gelatin-based tissue equivalent phantoms are compared with theoretical displacements, as well as estimates derived from traditional speckle tracking. Incompressibility processing greatly improves the accuracy and signal-to-noise r... View full abstract»

A process for manufacturing epoxy-backed integrated poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] transducers using standard microfabrication techniques is reported. The P(VDF-TrFE) is spin-cast over a silicon membrane, which is backfilled with epoxy to yield a wide-band, half-wavelength (/spl lambda//2)-resonant device suitable for pulse-echo use. The main advantages of the fabricatio... View full abstract»

An approach to predict the compressional wave transient radiation in solid load media from elements and arrays comprised of segmented annular apertures is described. The model may also be applied to the simulation of the transient radiation from circular, rectangular, and annular apertures by suitable parameter manipulation. The approach is based on the method developed by Stepanishen to model pro... View full abstract»

We present a theoretical study of guided-wave acoustooptic (AO) Bragg cells produced by a single surface acoustic wave (SAW) in PE:LiNbO/sub 3//LiNbO/sub 3/- and ZnO/GaAs/AlGaAs-based structures. A rigorous modeling of the SAW propagation in multilayered structures has been used and the analysis of the AO interaction has been performed by using a generalized multimode formulation of the coupled-mo... View full abstract»

An improved resonator method is presented for the determination of piezoelectric material constants. The improved method addresses a fundamental limitation of the measurement methods recommended in the current IEEE Standard on Piezoelectricity: the relations between vibrator response and material constants presented in this Standard are based upon the 1-D approximation of an essentially infinite f... View full abstract»

A new solution to the 2-D scalar wave equation is presented which describes an ultrasonic beam maintaining the lateral field response expressed by the sinc function over a finite depth of field. This new beam is realizable with a linear array transducer, and less subject to diffraction spreading than conventional focused beams, physically, it is a superposition of plane waves having the same wavel... View full abstract»

Reconstruction algorithms and their numerical examples of acoustical tomography based on the second-order Born transform perturbation approximation are presented. The reconstruction algorithms in the second-order Born approximation are similar in form to those in the first-order Born approximation. Replacing the angular spectrum of the scattered wave in the first-order case by the result of applyi... View full abstract»

Presents a computational solution to the ultrasonic target-dependent spectral distortion for a finite planar target (FT-SD). The FT-SD predicts the spectrum of the output signal from the receiving transducer generated in response to the insonification of a finite planar specular target, as a function of incident angle. The transducer is assumed to be operating in pulse-echo mode. The development i... View full abstract»

Shear piezoelectric properties of poly(vinylidene fluoride) (PVDF) and copolymer of vinylidene fluoride and trifluoroethylene [P(VDF/TrFE)] have been studied precisely in a wide temperature range from 10 to 400 K. It was found that these polymers have the shear electromechanical coupling factors k/sub 15/ and k/sub 24/ large enough to be utilized for transverse ultrasonic transducers operating in ... View full abstract»

The transverse resonance approach to guided wave analysis is applied to shear horizontal (SH) wave propagation in periodically layered composites. It is found for SH waves that at high values of the guided wavevector /spl beta/, the wave energy is trapped in the slower of the two media and propagates accordingly at the slower wavespeed. At low values of /spl beta/, however, the modes demonstrate a... View full abstract»

We report on a new multifractal type approach of low-frequency noise in oscillators. The time sequence is interrogated by means of a multiscale local stability exponent which acts in a sliding filtering window. Its discontinuities are reflected into a binary coding in which the correlations are analyzed. The mapping of binary data into a devil's staircase is used to emphasize the correlated and po... View full abstract»

Theoretical and experimental investigations of thin-walled tube acoustic wave devices for gravimetric sensing applications are presented. Integrated sensor configurations have been demonstrated by employing a sol-gel processed thin piezoelectric lead zirconate titanate (PZT) film. This was coated coaxially on stainless steel tubes and interdigital transducers (IDT) fabricated as the transmitter an... View full abstract»

Two types of errors resulting from the numerical evaluation of a transducer's spatial impulse response function have been identified, One is geometric and is due to the mismatch between the emulated piston surface (approximated using many small planar elements) and the true surface. The other error is algebraic and is due to the inexact formulation of the response of the emulated surface. The devi... View full abstract»