This article describes a new transverse edge structure with double busbar for surface acoustic wave (SAW) devices employing a 42°YX-lithium tantalate thin plate such as incredible high-performance (I.H.P.) SAW. This design offers good energy confinement and scattering loss suppression for a wide frequency range. First, preexisting transverse edge designs are reviewed, and their difficulties are pointed out using the dispersion relation for lateral SAW propagation. Then, numerical simulations are performed using the periodic 3-D finite-element method (FEM) powered by the hierarchical cascading technique, and effectiveness of the proposed structure is revealed. In addition, we also provide a possible solution to expand the frequency range giving well energy confinement and demonstrate effectiveness of manipulating the SAW slowness curve shape for transverse mode suppression.

This paper describes application of the hierarchical cascading technique (HCT) to the 3D FEM analysis of transverse mode behaviors in surface acoustic wave (SAW) devices. Mirror cascading is proposed as a speed up technique for the HCT operation using the general purpose graphic processing unit (GPGPU). Two methods are implemented for the analysis; one is impedance calculation, and the other is calculation of SAW scattering coefficients at boundaries. It is demonstrated that HCT enables rapid calculation for successive simulation with scanning design parameters. Thus, techniques discussed in the paper are quite effective for optimization of device structures. It is also shown that GPGPU can accelerate HCT calculation dramatically, especially for 3D cases discussed in this paper.

Phononic crystals (PnC) are a remarkable example of acoustic metamaterials with superior wave attenuation mechanisms for piezoelectric micro-electro-mechanical systems (MEMS) resonators to reduce the energy dissipation. Herein, a spider web-like PnC (SW-PnC) is proposed to sufficiently isolate the wave vibration. Finite-element analysis is performed to gain insight into the transmission property of finite PnC, and band characteristics by infinite periods. In comparison with the circle hole PnC at a similar bandgap, due to its already very lightweight PnC structure compared with previously reported PnCs, the proposed PnC offers a significantly lighter weight, smaller lattice constant, and greater energy leakage inhibition. More specifically, the resonator with the SW-PnC plate as the anchoring substrate exhibited a quality factor as high as 66569.7 at 75.82 MHz.

This paper compares three different piston mode designs for temperature-compensated surface acoustic wave (TC-SAW) resonators using SiO ₂ /LiNbO ₃ structure. It was shown that in rough approximation, phase shift given by extra elements for the piston mode operation is determined by the total mass of extra elements and SiO ₂ which overlaid on piston region. The hammer head design without additional metal layers does not work properly due to the weaker impact of the extra elements when the SiO ₂ layer is thick. On the other hand, piston mode designs using metal dots or stripes are effective to suppress the transverse mode resonances even when the SiO ₂ layer is thick. Although larger metal thickness is preferable for the wideband operation, it also makes the split of main resonance. Thus, the optimal metal thickness can be found from this trade-off, and then the optimal metal width can be found to achieve good transverse mode suppression.

This article investigates a spurious resonance appearing near the antiresonance when the double-busbar configuration is applied to layered surface acoustic wave (SAW) resonators using 42 $^\circ$ YX-LiTaO $_3$ thin plates, and possible mitigation methods are studied both theoretically and experimentally. First, the origin of the spurious resonance is revealed, and the influence of structural parameters is studied using the periodic 3-D finite-element method (FEM) powered by the hierarchical cascading technique (HCT). Then, possible methods are discussed for spurious mitigation. Finally, experimental data are provided for validation of the present analysis.