Experimental Study of Transverse Mode Suppression on Wideband Hetero Acoustic Layer Surface Acoustic Wave Resonator.

Transverse mode suppression is a great challenge for high-performance surface acoustic wave (SAW) resonators. Conventional methods work well on narrowband resonators, but their performances on wideband resonator have not been demonstrated. In this article, we give an in-depth study on the transverse mode suppression of wideband resonators using 11° YX-LiNbO3 (LN)/70 Y90X -quartz (Qz) hetero acoustic layer structure as a platform.

Hetero Acoustic Layer Surface Acoustic Wave Resonator Composed of LiNbO and Quartz.

In this work, a shear-horizontal (SH) mode surface acoustic wave (SAW) resonator based on LiNbO3 (LN)/Quartz (Qz) hetero acoustic layer (HAL) structure was studied by simulation and experiment. By this HAL structure, the displacement and electric displacement are well confined in the piezoelectric layer. A lower mechanical loss of Qz than that of lossy amorphous SiO2 further enhances the quality ( Q ) factor.

Surface Acoustic Wave Resonators With Hetero Acoustic Layer (HAL) Structure Using Lithium Tantalate and Quartz.

This article reports a new concept of surface-acoustic-wave (SAW) resonator, which uses shear horizontal (SH) wave confined in a thin LiTaO (LT) layer supported by a quartz (Qz) substrate. The LT layer is 35-50°YX LT, and the quartz substrate is 35-60°Y90°X Qz. A negative temperature coefficient of frequency (TCF) of the SH SAW in the LT layer is compensated by the quartz substrate, which shows a wide range of positive TCF depending on the crystalline orientation.

High-Frequency Resonator Using A Lamb Wave Mode in LiTaO Plate.

Acoustic wave devices utilizing plate waves in thin lithium tantalate (LiTaO) have the potential of achieving high resonance frequency with a suitable electromechanical coupling factor and a relatively small temperature coefficient of frequency (TCF). The influence of Euler angle and plate thickness on the characteristics of plate waves has been investigated. High-frequency resonators using first antisymmetric Lamb wave mode (A) in (0°, 42°, 0°) LiTaO thin plates have been fabricated and optimized.

Investigation of Material Constants of CaTiO₃ Doped (K,Na)NbO₃ Film by MEMS-Based Test Elements.

A CaTiO₃-doped (K,Na)NbO₃ (KNN-CT) film is a lead-free piezoelectric film that is expected to substitute Pb(Zr,Ti)O₃ (PZT) film in piezoelectric micro electro mechanical systems (MEMS). However, the full set of the material constants (elastic constants, piezoelectric constants and dielectric constants) of the KNN-CT film have not been reported yet. In this study, all the material constants of a sputter-deposited blanket KNN-CT film were investigated by the resonance responses of MEMS-based piezoelectric resonators and the phase velocities of leaky Lamb waves on a self-suspended membrane.

Ultra-wideband ladder filter using SH(0) plate wave in thin LiNbO(3) plate and its application to tunable filter.

A cognitive radio terminal using vacant frequency bands of digital TV (DTV) channels, i.e., TV white space, strongly requires a compact tunable filter covering a wide frequency range of the DTV band (470 to 710 MHz in Japan).

Tunable filters using wideband elastic resonators.

Currently, an ultra-wideband resonator is greatly needed to realize a tunable filter with a wide tunable range, because mobile phones with multiple bands and cognitive radio systems require such tunable filters to simplify their circuits. Although tunable filters have been studied using SAW resonators, their tunable range was insufficient for the filters even when wideband SAW resonators with a bandwidth of 17% were used. Therefore, the fabrication of wider-bandwidth resonators has been attempted with the goal of realizing tunable filters with wide tunable ranges.

High-frequency Lamb wave device composed of MEMS structure using LiNbO3 thin film and air gap.

High-frequency devices operating at 3 GHz or higher are required, for instance, for future 4th generation mobile phone systems in Japan. Using a substrate with a high acoustic velocity is one method to realize a high-frequency acoustic or elastic device. A Lamb wave has a high velocity when the substrate thickness is thin.

Small and low-loss IF SAW filters using zinc oxide film on quartz substrate.

It was previously reported that a Rayleigh wave propagating on a zinc oxide film (ZnO)/ST-cut 35 degrees X propagation quartz substrate structure has the characteristics of an excellent temperature coefficient of frequency (TCF) and a large electromechanical coupling factor k(s). This substrate was applied to various intermediate-frequency (IF) stage filters. During the filter development, it was clarified that a spurious response due to the Love wave was generated.

Resonator filters using shear horizontal-type leaky surface acoustic wave consisting of heavy-metal electrode and quartz substrate.

The authors have succeeded in exciting a new type of leaky surface acoustic wave (LSAW) having only a shear horizontal (SH) component that has a large electromechanical coupling factor, a large reflection coefficient, and excellent temperature stability, by combining interdigital transducers (IDTs) and reflectors made of heavy-metal films such as gold (Au), tantalum (Ta), and tungsten (W) on the ST-cut 90 degrees X propagation (direction perpendicular to the X-axis) quartz substrate. This LSAW does not have a propagation decay. The square of the electromechanical coupling factor is 2.

Very small IF resonator filters using reflection of shear horizontal wave at free edges of substrate.

A shear horizontal (SH) wave has the characteristic of complete reflection at the free edges of a substrate with a large dielectric constant. A conventional surface acoustic wave (SAW) resonator filter requires reflectors consisting of numerous grating fingers on both sides of interdigital transducers (IDTs). On the contrary, it is considered that small-sized and low loss resonator filters without reflectors consisting of grating fingers can be realized by exploiting this characteristic of the SH wave or the Bleustein-Gulyaev-Shimizu (BGS) wave.