SH-mode SAW and its acousto-optic interaction in KNbO/sub 3/

A multi-mode P-matrix formalism accounting for energy conservation, causality and reciprocity is presented. The P-matrix of an electrode is represented as product of P-matrices for propagation, excitation and reflection. Reflection considers the interaction of forward and backward propagating waves of the same mode as well as different modes. Model parameters are determined by fitting to dispersion relation [1] and harmonic admittance, both obtained from finite element (FEM)computations. For a temperature compensated SAW (TCSAW)system a two-mode model of interacting Rayleigh and shear horizontal (SH)mode is determined. It is shown that the excitation of the SH mode is mainly determined by mode interaction, rather than direct excitation of the mode. A multi-mode model for leaky SAW (LSAW)systems is set up by considering the interaction of a single guided mode and a quasicontinuum of bulk acoustic wave (BAW)modes. In this way the surface bulk hybrid (SBH)mode and other characteristic features of LSAW devices automatically emerge in the simulation result.

Development of a linear array electromagnetic acoustic transducer for shear horizontal guided wave inspection

To meet the demands of highly integrated and miniaturized radio frequency front-end (RFFE) modules, multi-passband filters which support multi-channel compounding come to the foreground. In this work, we proposed a new design of a dual-passband surface acoustic wave (SAW) filter based on a 32°YX-LiNbO3 (LN)/SiO2/SiC multilayered structure. The filter is of a standalone ladder topology and comprises dual-mode resonators, in which the shear horizontal (SH) mode and high-order SH mode are simultaneously excited through electrode thickness modulation. The impact of electrode thickness on the performance of the dual-mode resonator was systematically investigated by the finite element method (FEM), and resonators were prepared and verified the simulation results. The electromechanical coupling coefficients (K2) of the SH modes are 15.1% and 17.0%, while the maximum Bode-Q (Qmax) values are 150 and 247, respectively, for the fabricated resonators with wavelengths of 1 μm and 1.1 μm. In terms of the high-order SH modes in these resonators, the K2 values are 9.8% and 8.4%, and Qmax values are 190 and 262, respectively. The fabricated dual-band filter shows the center frequencies (fc) of 3065 MHz and 4808 MHz as two bands, with 3-dB fractional bandwidths (FBW) of 5.1% and 5.9%, respectively. Such a dual-band SAW filter based on a conventional ladder topology is meaningful in terms of its compact layout and diminished area occupancy. This work provides a promising avenue to constitute a high-performance dual-passband SAW filter for sub-6 GHz RF application.

A cognitive radio system using a vacant frequency band of digital TV channels (TV white space) requires a tunable filter with wide tunable ranges of center frequency and bandwidth. An ultra-wideband resonator is a key device to implement the tunable filter, because the tunable range is limited by the bandwidth (BW) of the resonators. A 0-th shear horizontal (SH0) mode plate wave resonator using an ultra-thin LiNbO3 plate is known to have a large electromechanical coupling factor, i.e., a large BW, but the structural fragility of the ultra-thin LiNbO3 plate is problematic. In this study, the feasibility of solidly mounted resonator type SH0 mode plate wave resonator was investigated systematically by finite element method simulation. The design parameters including the Euler angle, thickness of a LiNbO3 plate, and the material and thickness of an interdigital transducer were optimized. With the best design, a BW as wide as 26% is obtained.

Detection of kissing bond type defects and evaluation of the bonding quality in metal/adhesive/composite structures by a wavenumber-frequency insensitive SH mode

Propagation characteristics of the zeroth-order symmetric (S0) mode shear-horizontal (SH) wave in a cell structure containing a thermotropic liquid crystal layer with chiral smectic-C (SmC*), smectic-A (SmA), chiral nematic (N*) and isotropic (Iso) phase states, are examined. The SH wave propagation is numerically analyzed with consideration of the directional dependence of the viscosity and elastic constant of the SmA liquid crystal. Temperature dependencies of acoustic phase delay and propagation loss of the SH wave are observed. The critical behavior of the acoustic phase delay and the propagation loss of the S0 mode SH wave in the vicinity of the N*-SmA phase transition temperature are explained by the existence of the elastic constant related to layer compression. The layer compression elasticity is predominant in the SmA phase, and is determined from the comparison of numerical analysis with experimental results.

A theoretical model is derived to extend existing work on the theory of acoustoelasticity in isotropic materials subjected to uniaxial or hydrostatic loadings, up to the case of arbitrary triaxial loading. The model is applied to study guided wave propagation in a plate. The semi-analytical finite element method is adapted to deal with the present theory. Effects of triaxial loading on velocities of Lamb and shear horizontal (SH) modes are studied. They are non-linearly dependent on stress, and this nonlinearity is both frequency-dependent and anisotropic. Velocity changes induced by the effect of stress on the plate thickness are shown to be non-negligible. When a stress is applied, both Lamb and SH modes lose their simple polarization characteristics when they propagate in directions different from the principal directions of stress. The assumption that effects induced by a multiaxial stress equal the sum of effects induced by each of its components independently is tested. Its validity is shown to depend on frequency and propagation direction. Finally, the model is validated by comparing its predictions to theoretical and experimental results of the literature. Its predictions agree very well with measurements and are significantly more accurate than those of existing theories.

Recent communication equipment such as mobile and cellular phones, radio systems, pagers, LANs, have demanded high performance components. Among these components, the last generation of SAW filters and signal processing devices, presenting low loss, flexible frequency and phase response characteristics, control of spurious, etc., have played a major role in designing new equipment and redesigning existing systems. The highest frequency obtainable with SAW technology in practical devices is limited to a couple of GHz, usually due to restrictions in the fabrication process involved and SAW propagation characteristics. Pseudo-SAW (PSAW) and shear horizontal (SH) mode, presenting phase velocities circa 40% superior than the SAW and low attenuation along certain directions, have permitted the construction of devices operating at higher frequencies. The High Velocity Pseudo-SAW (HVPSAW), with phase velocities about 100% higher than the SAW and low attenuation in many materials along certain directions, extends the high operating limit of SAW devices even further. In this paper the major characteristics of this new type of wave are reviewed. Extended topics such as: the boundary function magnitude behavior; the relationship between the growing tilted bulk-like partial waves and the bulk slowness; the number of roots (uncoupling of modes); the Poynting vector behavior with depth; are explored, enlightening the solution and behavior of this new type of high velocity pseudo-SAW.

We present a 3D-RSWEI characterization of a polyvinyl alcohol phantom with applied uniaxial stretch at multiple transducer tilt angles (0<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">◦</sup>, 15<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">◦</sup>, 30<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">◦</sup>, and 45<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">◦</sup>), building on previous work [1]. We have observed shear horizontal (SH) and complex shear vertical (SV) wave mode propagation at large stretch ratios and at 15<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">◦</sup> and 30<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">◦</sup> of tilt. We have compared analytically calculated shear wave speeds assuming an Isihara material model to experimentally measured speeds in the PVA phantom to re-derive estimates of uniaxial stretch ratios. This analysis indicates the potential for 3D-RSWEI in higher order nonlinear elasticity characterization methods.

Ultrasonic guided wave defect detection method for tank bottom plate based on SH0 mode multichannel magnetostrictive sensor

By composing interdigital transducers (IDTs) and reflectors consisting of films made of a heavy metal such as Au, Ta or W on an ST cut 90°X propagation (direction perpendicular to X-axis) quartz substrate, the authors realized a new type of shear horizontal (SH) wave. This wave has an excellent temperature characteristic, a large electromechanical coupling factor (k), and a large reflection coefficient at reflector electrodes. The square of this electromechanical coupling factor (k2=0.28∼0.34%) and the reflection coefficient at reflector electrodes are 2.2∼2.6 times and 30∼35 times, respectively, as large as those of a Rayleigh wave on an ST cut X propagation quartz substrate. The authors applied this technology to filters for the first intermediate frequency (first IF) stage of a global system for mobile communications (GSM) in the nominal center frequency from 200 to 400 MHz. As a result, we succeeded in developing the first IF filter having a low insertion loss, an excellent temperature characteristic (frequency shift: 1 ppm/°C) and a small package size (3×3 mm2), which is as small as a radio frequency (RF) surface acoustic wave (SAW) filter, for the first time.

A semi-analytical approach for SH guided wave mode conversion from evanescent into propagating

The present problem aims to study the propagation behaviour of Shear Horizontal (SH) surface waves in a composite structure comprising of functionally graded piezoelectric plate fused with a porous piezoelectric plate. The material properties of the functionally graded piezoelectric material (FGPM) are assumed to be vary in quadratic manner. Method of separation of variables is used to obtain the solutions for the displacement and stress components in both the media. Solutions are obtained in terms of modified Bessel functions of first and second kinds. Dispersion relations are obtained for both the electrically open and short cases. Effects of thickness of the plates, gradient parameter, dielectric coefficient and piezoelectric coefficient on dispersion curve have been marked distinctly and portrayed through graphs. The electromechanical coupling factor is also plotted against wave number. Findings of the present investigation may set guidelines for the designing of more efficient Surface acoustic wave (SAW) devices.

GHz AlN-based multiple mode SAW temperature sensor fabricated on PEN substrate

This paper describes the shear horizontal (SH) wave devices for frequency modulation and demodulation in the HF band. By means of a numerical analysis, it is found that the zeroth‐order symmetric SH mode in a horizontally poled piezoelectric ceramic plate is useful for this purpose. It has a low dispersion, low velocity and high coupling coefficient. SH wave devices as small as IC chips are useful in the HF band. The frequency characteristics of the frequency modulator and demodulator are from dc to 200 kHz and their linear conversion bandwidth is 60 kHz. These devices are useful for signal processing devices and sensors in the HF band.