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A novel type of hybrid resonator based on BAW transformation into SAW in a ridged layered structure was fabricated and characterized. Bulk waves are excited by micromachined piezoelectric AlScN pillars located on the non-piezoelectric Si and sapphire substrates. The effect of film thickness and etching depth on the electromechanical coupling and velocity dispersion were calculated by finite element...
This contribution is concerned with a technique to precisely measure the physical dimensions of flaws in solid specimen by pulse-echo mode acoustic microscopy. We have implemented a synthetic aperture focusing technique (SAFT), which is based on a semi-numerical simulation approach (SIRFEM). In acoustic microscopy, one normally applies single-element transducers with center frequencies above 10MHz...
Phononic crystals (PnC) consist of two or more materials arranged in a spatially periodic manner. Introduction of a defect into the crystal lattice is a technique to create resonant modes. The idea behind the application of a PnC as sensor element is the dependence of the characteristic features of those modes on speed of sound. Currently the sensor designs are based on common 2D phononic crystal...
In this work a causal P-matrix method for leaky SAW(LSAW) devices and the determination of the thereto needed COM-parameters slowness s and reflection r are presented. As a consequence of causality s and r in general are complex. The imaginary parts of reflection and slowness are interpreted as the exchange of energy between SAW and BAW. A relation of energy conservation between imaginary parts of...
In ultrasound imaging, cross coupling of transducer elements through the medium has significant effect on the frequency response, thus affecting the quality of the ultrasound image. In Side-Looking Intravascular Ultrasound (SL-IVUS) imaging a radial image of the vessel wall is formed using a transducer array in a cylindrical configuration. Recent advances in Capacitive Micromachined Ultrasound Transducer...
In this paper, we present piezoelectric co-doped (Mg,Hf)xAl1−xN thin films, where the dopant concentration x is in the range of 0–0.13. The (Mg,Hf)xAl1−xN thin films were prepared on Si (100) substrates with a dual magnetron with AC power applied between two ring targets. The compositions of the targets were pure Al and Al-Mg-Hf metals. The composition of the films was controlled by adjusting a DC...
This paper describes lateral propagation of surface acoustic waves (SAWs) when two types of SAWs are coupled. For the analysis, the thin plate model proposed by the authors is extended to include interaction between two SAW modes. Firstly, lateral wave propagation in an infinitely long periodic grating is modelled and discussed, it is found that SAW slowness curves can be changed by mode coupling...
An ultrasonic transducer technology to generate wideband impulses using a one-dimensional chain of spheres was previously presented. The Hertzian contact between the spheres causes the nonlinearity of the system to increase, which transforms high amplitude narrowband sinusoidal input into a train of wideband impulses. Generation of short duration ultrasonic pulses is desirable both in diagnostic and...
As more LTE bands are squeezed into the crowded global RF spectrum interference becomes a major concern. Some cases require profoundly steep transitions from passband to the tightly packed neighboring bands. The most demanding high frequency LTE bands may only be served with high-performance BAW resonators that have been temperature compensated to have essentially zero temperature drift. There is...
Under specific ultrasound excitation, contrast microbubbles undergo nonlinear oscillations. Considering the size and the complexity of the phenomenon, expensive and complex experiments and/or simulations are required. To overcome this, the use of an analogy has been proposed and validated. A chain of coupled oscillators has been optimized in order to re-scale the bubble ultrasonic oscillation at the...
Research on electrically-small antennas has been active for a long time, but so far it is still challenging to approach the Chu's limit that sets a constraint between the quality factor and the size of an antenna. Some researchers have made efforts to generate electromagnetic (EM) radiation by driving the magnetization of ferri-/ferro-magnetic materials, which can be efficiently realized via mechanical...
Photoacoustic imaging systems are now commercially available and built into traditional ultrasound hardware. However, unlike ultrasound imaging, the choice of coupling gel may potentially alter attenuation and fluency of the laser transmission. Hence, the objective of this study was to determine the attenuating effects of various ultrasound coupling gels on photoacoustic signals. Signals from 3 tissue...
The 0-th shear horizontal (SH0) mode plate wave has an electromechanical coupling factor k2 larger than 50% in a (0°, 120°, 0°) LiNbO3 (LN) plate thinner than 0.1λ, where λ is a pitch of an intergidital transducer (IDT). In the previous study, ultra-wide-band ladder filters composed of cavity type resonators recorded 6 dB bandwidth from 41% to 51% in a digital TV band. However, the structure is fragile,...
In 2D 360° Spatial Compounding (SC) envelope detected pulse-echo data from a conventional linear probe is superimposed from 360° in parallel cross-sectional planes to improve B mode image quality. Latest research of our group has shown that extending this concept to 3D by utilizing a motorized 1D array (3D probe) brings along substantial gain in image quality and significance of 360°-SC for diagnosis...
This work deals with the possibility to create a high temperature surface acoustic waves (SAW) sensor based on the use of a new piezoelectric material : Ba2TiSi2O8.The wave propagation in the material is at first studied and compared to another material used for harsh environment : LiTaO3. Then a SAW resonator on Ba2TiSi2O8 is designed.
Bubbles insonified by ultrasound can exhibit shape deformations and no more oscillate upon a purely spherical mode. Understanding and predicting the appearance of surface oscillations is essential for typical applications based on the acoustic response of bubbles (e.g. the use of contrast agents in echographic imaging), partly because shape modes can contribute to the monopole emission of sound by...
Shear wave inspection is generated from mode conversion of longitudinal waves, using a selected, angled wedge positioned between the transducer and the test specimen. However, in certain scenarios where access is restricted the combination of the transducer and the wedge can be too cumbersome for in situ deployment. In this work, a low profile, linear ultrasound array transducer is proposed to generate...
Row-column-addressed CMUT arrays suffer from low receive sensitivity of the bottom elements due to a capacitive coupling to the substrate. The capacitive coupling increases the parasitic capacitance. A simple approach to reduce the parasitic capacitance is presented, which is based on depleting the semiconductor substrate. To reduce the parasitic capacitance by 80% the bulk doping concentration should...
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