Michio Kadota

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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. To realize a high-frequency device(More)
Al-electrodes on 36&#x2013;48&#x00B0;YX-LiTaO<inf>3</inf> substrates have been widely used in surface acoustic wave (SAW) filters and SAW duplexers because of having an optimum electro-mechanical coupling factor, reflection coefficient and good Q-factor. In this paper, authors proposed and constructed a new SAW structure composed of upper Al-electrodes(More)
Authors previously proposed a SAW PCS-duplexer with an excellent temperature coefficient of frequency (TCF) and a good frequency characteristic composed of a thick-SiO<sub>2</sub>/thin-Au-electrodes/LiTaO<sub>3</sub> structure. However, a sheet resistance of thin Au electrode is large, compared with thick Al-electrode, so thin Au-electrode is not suitable(More)
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(More)
Authors report a new structure of a shear horizontal (SH) type boundary acoustic wave for cellular phone applications. Such a structure composed of electrodes with a low shear wave velocity between two materials, namely, the SiO<sub>2</sub> film/high density electrode/LiNbO <sub>3</sub> substrate, is proposed. The unique feature of this structure is that it(More)
The Lamb wave type of high frequency resonator was proposed. But any Lamb wave resonator operating really above 3 GHz, which is difficult to be realized with conventional surface acoustic wave (SAW), have been not reported. Authors have tried to realize the high frequency device by using A<sub>1</sub> mode of Lamb wave propagating in the X-axis direction on(More)
The full material constants of a 40% Sc-AlN thin film were systematically determined. First, 4 kinds of MEMS resonators and a Lamb wave resonator were used to determine the material constants as much as possible. The other unknown material constants together with the material constants which needed more accurate estimation were determined based on(More)
Radio frequency (RF) filters in high frequency using surface acoustic wave (SAW) such as MediaFLO<sup>TM</sup>, time division synchronous code division multiple access (TDSCDMA) in China handy phone system, and global positioning system (GPS) in cars require a narrow bandwidth. So, the SAW substrates for their RF filters are also required to have a very(More)
There are various types of electron cyclotron resonance (ECR) sputtering systems, DC-mode, RF-mode, etc. We reported that zinc oxide (ZnO) films on glass substrates deposited by DC-mode ECR and RF-mode ECR sputtering systems had shown excellent piezoelectric properties and c-axis orientations. The RF-mode ECR sputtering system was capable of depositing ZnO(More)
This paper reviews recent progress of temperature compensated surface acoustic wave (SAW) devices for wireless communications. First, temperature compensation techniques based on the SiO<sub>2</sub> deposition and the wafer bonding are explained, and their implementation into real devices are discussed. Finally, we will show how high performances have been(More)