Matsushita Electric Industrial Co., Ltd.

Shinobu Nakaya

Hiroyuki Nakamura

Hiroshi Kushitani

Toru Yamada

Takeo Yasuho

Shigeru Tsuzuki

Shunichi Seki

Akio Tsunekawa

A surface acoustic wave (SAW) filter includes a first SAW resonator, a second SAW resonator connected in series to the first SAW resonator at a first node, a third SAW resonator connected in series to the second SAW resonator at a second node, a fourth SAW resonator connected in series to the third SAW resonator at a third node, a fifth SAW resonator connected between the first node and ground, a sixth SAW resonator connected between the third node and ground, and a first capacitance element connected between the second node and ground. Further, the SAW filter includes a first inductance element connected in series to the fifth SAW resonator, and a second inductance element connected in series to the sixth SAW resonator. This SAW filter has a sharp attenuation at a high frequency of a pass band, thereby widening the pass band and reducing the loss thereof.

Surface acoustic wave filter and device employing it

A surface acoustic wave filter having a plurality of the transmission lines, each with one end connected to the surface acoustic wave element and the other end thereof connected to a ground. The transmission lines are divided by an additional transmission line which has multiple connections to a ground electrode at an interval equal to or lower than a wavelength of a using frequency. This structure provides grounds among a plurality of transmission lines and thus isolation among terminals can be increased to improve the filter characteristic.

Surface acoustic wave filter

In a SAW device containing two or more longitudinal mode coupling type SAW elements connected in parallel, each SAW element includes at least three comb shaped electrode pairs and a reflector electrode provided at both sides of the comb shaped electrodes. One part of respective comb shaped electrode pairs forming IDT electrodes is connected together in common by a ground connection electrode and connected with a ground pad. This configuration enables the number of connection pads to be minimized, thus providing a SAW device that is small in size and superior in filter characteristics.

Surface acoustic wave device

A longitudinally coupled surface acoustic wave filter includes a first, second and third IDT electrodes and a first and second reflector electrodes on a piezoelectric substrate. The IDT electrodes each include a primary excitation region having &#x3bb;/2 electrode finger pitches, where &#x3bb; is the wavelength of a surface acoustic wave. The primary excitation region is phase-shifted by a certain amount in accordance with a desired passband frequency response. The IDT electrodes further include a plurality of secondary excitation regions each having electrode finger pitches different from the &#x3bb;/2 pitches. All of the electrode finger pitches of the surface acoustic wave filter thus range from 0.8&#x3bb;/2 to 1.2&#x3bb;/2, so that a loss increase caused by discontinuity between the IDT electrodes is prevented.

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Osaka, Japan

Shinobu Nakaya