Fujitsu Corporation

Kazushi Hashimoto

Masanori Ueda

Osamu Ikata

Yoshiro Fujiwara

Yoshio Satoh

Hideki Ohmori

Nobuo Hirasawa

Kiyoshi Satoh

A filter device includes at least two filter elements provided in a package, each of the filter elements passing only signals within a predetermined frequency band, the predetermined frequency bands of the filter elements having center frequencies which are distinct from each other. An input terminal is connected to and shared by respective inputs of the filter elements. An output terminal is connected to and shared by respective outputs of the filter elements.

Filter device and dual-band radio system in which the filter device is

A surface acoustic wave filter element is formed by replacing with a single parallel resonator having a driving electrode whose area is equal to the sum total of the areas of driving electrodes of a plurality of consecutive parallel resonators arranged in a ladder shape, together with serial resonators, for structuring a surface acoustic wave resonator. Also, in a surface acoustic wave filter formed by packaging the surface acoustic wave filter element, ground electrodes of the parallel resonators of the filter element are electrically insulated from each other and are connected to different electrode pads for grounding.

Surface acoustic wave filter with larger driving electrode areas in some

In a duplexer, phase matching circuit patterns corresponding to filter chips are formed on a surface layer of a multi-layer ceramic package provided with filter chips having different central frequencies. An end of each of the phase matching circuit patterns is connected to a common terminal pattern.

Surface acoustic wave filter duplexer comprising a multi-layer package

An acoustic surface wave element having an oscillation frequency stable against temperature changes, and a wide range of oscillation frequency adjustment, is provided by an acoustic surface wave element comprising: a substrate of a 36.degree. rotated Y-cut single crystal lithium tantalate having X, Y and Z crystal axes and a top surface and side walls; electrodes formed on the top surface of the substrate such that an acoustic surface wave is propagated in a direction of the X-axis of the substrate and an oscillation of the acoustic surface wave occurs at a predetermined frequency, the electrodes having a thickness equal to 1 to 4% of a wavelength of the acoustic surface wave at the oscillation; and a plasma CVD-deposited layer of silicon dioxide covering the electrodes and the substrate, the silicon dioxide layer having a refractive index of 1.445 to 1.486 and a thickness equal to 16 to 26% of the wavelength of the acoustic surface wave at the oscillation.

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Kawasaki, Japan

Kazushi Hashimoto