Michio Kadota 교수

The author and coengineers have developed, put to practical use, mass-produced, and commercialized various surface acoustic wave (SAW) devices. Their success depended largely on the development of SAW substrate materials, SAW device structures, and the processes of producing with the cooperation of many engineers. The author reports the development and practical applications of several SAW devices: (1) ZnO/glass structure SAW filters for video intermediate frequency (VIF) for televisions (TVs) o

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 operating at 3 GHz or higher using a Lamb wave, a very thin (less than 0.5 μm thick) single-crystal plate must be used. It is difficult to f

A small surface acoustic wave (SAW) duplexer for a wide-band code-division multiple access (W-CDMA) system with a good temperature coefficient of frequency (TCF) has been required. However, the conventional SAW duplexer for W-CDMA using Al electrode/50–70° YX-LiNbO3 is large (3.8×3.8 mm2) and its TCF is not good (-80 ppm/°C). When a SiO2 film is deposited on this substrate to improve its TCF, good frequency characteristics cannot be realized. Thus, by using a new structure such as a flattened Si

The transmission (Tx) and receiving (Rx) passbands of the Personal Communication Services (PCS) mobile phone system in the US are 1850–1910 MHz and 1930–1990 MHz, respectively. The transition bandwidth between Tx and Rx is very narrow, 20 MHz. A duplexer for the US-PCS employing surface acoustic waves (SAWs) requires a substrate which has good temperature stability, an optimum electromechanical coupling factor, a large reflection coefficient, and a good resonant mechanical Q value. Previously, t

A cognitive radio system operating at frequencies from 400 MHz to 6 GHz requires tunable filters with a wide variable frequency range. Wide band resonators are required to realize such tunable filters consisting of resonators. However, it is difficult to fabricate a very high frequency and wide band resonator, such as 6 GHz and wider than 10%, respectively. The first antisymmetric (A 1 ) mode of a Lamb wave on a LiNbO 3 thin plate or film having a high velocity and a large electromechanical coup

"Hetero acoustic layer (HAL) surface acoustic wave (SAW) device" is a new type of SAW device using a single crystal piezoelectric thin plate supported by a substrate. In this study, a HAL SAW resonator using a LiNbO3 (LN) thin plate and a multi-layer acoustic film was designed by finite element method (FEM) and fabricated. The thickness of LN is 3.6 µm and the pitch of an interdigital transducer (IDT) (λ) is 5.24 µm for a resonance frequency of 600 MHz. The multi-layer acoustic film is composed

This article reports a new concept of surface-acoustic-wave (SAW) resonator, which uses shear horizontal (SH) wave confined in a thin LiTaO₃ (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. Excellent TCFs of 2

A substrate having a suitable electromechanical coupling factor ( k s ) value and a good temperature coefficient of frequency (TCF) is required for an applications of resonator surface acoustic wave (SAW) filters and rudder-type SAW filters requiring a specific bandwidth, because their bandwidth largely depends on the coupling factor of the substrate. Although a quartz substrate for SAW devices provides a good TCF, the electromechanical coupling factor obtained is small. The author speculated th

It has been considered that it is difficult to realize a high-frequency device of 3 GHz or more, for instance, for a fourth generation mobile phone system in Japan, using a conventional surface acoustic wave (SAW) substrate. In this study, we attempted to fabricate a high-frequency resonator using Lamb waves, which has a high velocity and consists of a thin LiNbO3 film deposited by chemical vapor deposition (CVD). As a result, a 1-port Lamb wave resonator composed of an electrode/thin epitaxial

A cognitive radio system requires a tunable filter with a wide tunable range to compose a simple front-end. Because the tunable range is limited by the bandwidth (BW) of resonators, an ultra-wideband resonator is an important device to implement the tunable filter. The authors previously obtained low frequency resonators with a wide BWs of 26 to 29% and a large impedance ratios of 92 to 98 dB between resonance (fr) and anti-resonance frequencies (fa) using 0-th mode shear horizontal (SH0 mode) p

In this paper, we describe a new type of magnetic surface acoustic wave (SAW) sensor that consists of interdigital transducers made of a magnetostrictive material, Ni, on a quartz substrate. This sensor can be used as an element of a resonator-type wireless SAW sensor system because it has a high Q . Moreover, it has the merits of being fabricated easily using the existing process for SAW devices because its structure is the same as that of general SAW resonators. When an external magnetic field

For mobile communication, acoustic wave filters are being continuously required better steepness of a passband and a smaller temperature coefficient of frequency (TCF). Recently, various Hetero Acoustic Layer (HAL) types of surface acoustic wave (SAW) devices were reported by different groups including us [1-5]. HAL SAW devices inherently have many variations of structure and a lot of potentials. In this study, we report the bandwidth (BW) and impedance ratio (Z ratio) of different designs of HA

A leaky surface acoustic wave (LSAW) and a leaky pseudo SAW (LPSAW) of various rotated Y-cut langasite substrates grown by the Czochralski method were measured by an ultrasonic microscope. The measured results agreed well with the values calculated using Ilyaeve's material constants of five kinds of material. Rayleigh SAW transversal filters, having various aluminum (Al) thicknesses of interdigital transducers (IDT), were constituted on (0°, 140–150°, 24–25°) and (12°, 150–153°, 36–37°) plates.

Compared to conventional RF magnetron sputtering systems, electron cyclotron resonance (ECR) sputtering systems are characterized by the ability to generate high-density plasma under low gas pressure. (1120)-plane oriented epitaxial ZnO films were deposited on an R-plane sapphire substrate using the RF-magnetron-mode ECR sputtering equipment. As the results of the measurement, the films showed a good orientation and excellent effective electromechanical coupling factors ( k eff ) for the Rayleig

Currently, miniature surface acoustic wave (SAW) devices (filters and duplexers) with a good temperature stability are strongly required. In order to realize its requirement, various SAW substrates combining a high density metal electrode and a substrate were researched. Combination of SAW substrates using high density metal electrodes offers excellent properties such as large electrode reflection coefficient, large mechanical coupling factor, low velocity, and good temperature stability. This p