Oki Electric Industry Co., Ltd.

Tdk Corporation

Yoshikazu Kihara

Kazushige Noguchi

Tomokazu Komazaki

Yoshiaki Fujita

Masaki Sobu

Katsunori Osanai

Hisanori Ehara

Satoshi Terada

Yukio Hirokawa

A SAW device comprises a single crystal piezo-electric strate (made, for example, of LiTaOor LiNbO), and an interdigital transducer (IDT) formed of a material mainly containing Al and disposed on the piezo-electric substrate. The piezo-electric strate contains an additive (for example, Fe, Mn, Cu, Ti), and an orientation rotated by an angle in a range of 42&#xb0; to 48&#xb0; (more preferably 46&#xb0;&#xb1;0.3&#xb0;) from a Y-axis toward a Z-axis about an X-axis. The IDT presents a normalized thickness h/&#x3bb; (h: thickness of electrode, and &#x3bb;: spacing between digits of the IDT) of 7% to 11%. A more appropriate substrate cut angle can be shown for the SAW device which employs a piezo-electric substrate containing an additive, to improve the electric characteristics thereof.

Surface acoustic wave device

A polar SAW (Surface Acoustic Wave) filter includes a band-pass ladder type SAW filter having a SAW resonator. A two-terminal pair circuit is serially connected to the band-pass ladder type SAW filter and includes a plurality of inductors. The polar SAW filter has attenuation poles in each of the higher-frequency and lower-frequency attenuation ranges of a pass band.

Saw filter with an attenuation pole including a band-pass ladder type of saw filter having a saw resonator

In a differential surface acoustic wave resonator, when an unbalanced electric signal is inputted between an input terminal and an output terminal connected to a ground potential, this electric signal is inputted to two-terminal-pair surface acoustic wave resonators and . The electric signal inputted to the two-terminal-pair surface acoustic wave resonator is converted into a surface acoustic wave, and thereafter it is again converted into an electric signal to be outputted to a two-terminal-pair surface acoustic wave resonator . The electric signal inputted to the two-terminal-pair surface acoustic wave resonator is converted into a surface acoustic wave, and thereafter it is again converted into an electric signal to be outputted from an output terminal of the differential surface acoustic wave filter as a balanced signal. On the other hand, the electric signal inputted to the two-terminal-pair surface acoustic wave resonator is converted into a surface acoustic wave, and thereafter it is again converted into an electric signal to be outputted to a two-terminal-pair surface acoustic wave resonator . The electric signal inputted to the two-terminal-pair surface acoustic wave resonator is converted into a surface acoustic wave, and thereafter it is again converted into an electric signal to be outputted from an output terminal of the differential surface acoustic wave filter as a balanced signal. Here, in the respective two-terminal-pair surface acoustic wave resonators to , the phase of the electric signal to be inputted is substantially &deg; different from that of the electric signal to be outputted. The balanced signals having the same phase and the same amplitude are outputted from the two output terminals of the differential surface acoustic wave filter.

Differential surface acoustic wave filter

Growing community of inventors

Tokyo, Japan

Yoshikazu Kihara