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 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.

This paper discusses combination of tetragonal crystals with LiTaO ₃ (LT) thin plate for complete transverse resonance suppression of surface acoustic wave devices without k ² deterioration by manipulating the slowness shape. Besides, better lateral energy confinement is achieved as well by the use of double busbar structure. First, the mechanism of slowness shape manipulation by combining tetragonal crystals is studied. By comparison, YZ-lithium tetraborate (LBO) shows better performance than 69°Y90°X quartz. Then numerical simulations are carried out using periodic three-dimensional finite method assisted by hierarchical cascading technique, and the effectiveness of transverse mode suppression by flattening the slowness shape is revealed. And the possibility to realize temperature compensation is discussed owing to the unique material property of LBO. Moreover, the capability of other tetragonal crystals for slowness manipulation are compared, and LBO is the best choice among these tetragonal crystals.

Thin-film piezoelectric-on-silicon (TPoS) microelectromechanical (MEMS) resonators are required to have high Q-factor to offer satisfactory results in their application areas, such as oscillator, filter, and sensors. This paper proposed a phononic crystal (PnC)-reflector composite structure to improve the Q factor of TPoS resonators. A one-dimensional phononic crystal is designed and deployed on the tether aiming to suppress the acoustic leakage loss as the acoustic wave with frequency in the range of the PnC is not able to propagate through it, and a reflector is fixed on the anchoring boundaries to reflect the acoustic wave that lefts from the effect of the PnC. Several 10 MHz TPoS resonators are fabricated and tested from which the Q-factor of the proposed 10 MHz TPoS resonator which has PnC-reflector composite structure on the tether and anchoring boundaries achieved offers a loaded Q-factor of 4682 which is about a threefold improvement compared to that of the conventional resonator which is about 1570.

This paper discusses the applicability of double busbar design to surface acoustic wave (SAW) devices employing low-cut lithium tantalate (LT) with a multi-layered structure. This design offers good energy confinement, scattering loss suppression and transverse mode suppression for a wide frequency range. In addition, the effectiveness of manipulating the slowness curve shape for transverse mode suppression is demonstrated. First, three different lateral edge designs are applied to the layered SAW configuration on low-cut LT, and their performances are compared using the periodic three-dimensional finite-element method powered by the hierarchical cascading technique. Then, the discussion is extended to the influence of the SAW slowness shape to the transverse mode suppression.

This letter investigates impact of the surface acoustic wave (SAW) slowness curvature on anti-resonance quality factor ( Q _a ) of RF SAW resonators. First, variation of SAW resonance characteristics with aperture width W is studied using periodic three dimensional finite-element method for three structures with different slowness curvature. It is shown that the slowness shape affects the frequency ( f ) dependence of Bode Q , and smaller slowness curvature makes the Bode Q less sensitive to both f and W . This means that when the curvature is small, SAWs propagate like parallel beams on the substrate surface and are scarcely influenced by discontinuities at side boundaries such as electrode tips. Since loss mechanisms in the aperture region mainly contribute to the Bode Q reduction, high Q _a and maximum Bode Q are achievable. Finally, series of I.H.P. SAW resonators using 42°YX-LiTaO ₃ are fabricated, and it is verified that the Bode Q is not sensitive to W when the electrode ohmic loss is ignored.