Surface acoustic wave device and communication apparatus using the same

A surface acoustic wave device comprising:

• a first longitudinally coupled resonator type surface acoustic wave element including at least three interdigital transducers arranged along the direction of transmission of a surface acoustic wave, each of the interdigital transducers being provided with a plurality of electrode fingers;
• and
• a second longitudinally coupled resonator type surface acoustic wave element including at least three interdigital transducers arranged along the direction of transmission of the surface acoustic wave, each of the interdigital transducers of the second longitudinally coupled resonator type surface acoustic wave element being provided with a plurality of electrode fingers, the first longitudinally coupled resonator type surface acoustic wave element and the second longitudinally coupled resonator type surface acoustic wave element being cascaded to each other and being arranged on a piezoelectric substrate;
• wherein
• at least one of the interdigital transducers of each of the first and second longitudinally coupled resonator type surface acoustic wave elements has a narrow pitch electrode finger portion located near the adjacent interdigital transducer, the pitch of the electrode fingers of the narrow pitch electrode finger portion being smaller than the pitch of the other electrode fingers;
• and
• N1 is not equal to N2, where N1 represents the number of the electrode fingers of the narrow pitch electrode finger portion of the first longitudinally coupled resonator type surface acoustic wave element and N2 represents the number of the electrode fingers of the narrow pitch electrode finger portion of the second longitudinally coupled resonator type surface acoustic wave element.

A surface acoustic wave device comprising:

• a first longitudinally coupled resonator type surface acoustic wave element including at least three interdigital transducers arranged along the direction of transmission of a surface acoustic wave, each of the interdigital transducers being provided with a plurality of electrode fingers;
• and
• a second longitudinally coupled resonator type surface acoustic wave element including at least three interdigital transducers arranged along the direction of transmission of the surface acoustic wave, each of the interdigital transducers of the second longitudinally coupled resonator type surface acoustic wave element being provided with a plurality of electrode fingers, the first longitudinally coupled resonator type surface acoustic wave element and the second longitudinally coupled resonator type surface acoustic wave element being cascaded to each other and being arranged on a piezoelectric substrate;
• wherein
• at least one of the interdigital transducers of each of the first and second longitudinally coupled resonator type surface acoustic wave elements has a narrow pitch electrode finger portion located near the adjacent interdigital transducer, the pitch of the electrode fingers of the narrow pitch electrode finger portion being smaller than the pitch of the other electrode fingers;
• and
• wherein P1 is not equal to P2, where P1 represents the pitch of the electrode fingers of the narrow pitch electrode finger portion of the first longitudinally coupled resonator type surface acoustic wave element and P2 represents the pitch of the electrode fingers of the narrow pitch electrode finger portion of the second longitudinally coupled resonator type surface acoustic wave element.

A surface acoustic wave device comprising:

• a first surface acoustic wave filter element including a first longitudinally coupled resonator type surface acoustic wave element provided with at least three interdigital transducers arranged along the direction of transmission of a surface acoustic wave, each of the interdigital transducers being provided with a plurality of electrode fingers, and a second longitudinally coupled resonator type surface acoustic wave element provided with at least three interdigital transducers arranged along the direction of transmission of the surface acoustic wave, each of the interdigital transducers being provided with a plurality of electrode fingers, the first longitudinally coupled resonator type surface acoustic wave element and the second longitudinally coupled resonator type surface acoustic wave element being cascaded to each other and being arranged on a piezoelectric substrate;
• and
• a second surface acoustic wave filter element including a third longitudinally coupled resonator type surface acoustic wave element provided with at least three interdigital transducers arranged along the direction of transmission of the surface acoustic wave, each of the interdigital transducers being provided with a plurality of electrode fingers, and a fourth longitudinally coupled resonator type surface acoustic wave element provided with at least three interdigital transducers arranged along the direction of transmission of the surface acoustic wave, each of the interdigital transducers being provided with a plurality of electrode fingers, the third longitudinally coupled resonator type surface acoustic wave element and the fourth longitudinally coupled resonator type surface acoustic wave element being cascaded to each other and being arranged on the piezoelectric substrate, the phase of input and output signals of the second surface acoustic wave filter element being approximately 180 degrees different from the phase of input and output signals of the first surface acoustic wave filter element, one terminal of the first surface acoustic wave filter element and one terminal of the second surface acoustic wave filter element being electrically connected in parallel, the other terminal of the first surface acoustic wave filter element and the other terminal of the second surface acoustic wave filter element being electrically connected in series;
• wherein
• at least one of the interdigital transducers of each of the first, second, third, and fourth longitudinally coupled resonator type surface acoustic wave elements has a narrow pitch electrode finger portion located near the adjacent interdigital transducer, the pitch of the electrode fingers of the narrow pitch electrode finger portion being smaller than the pitch of the other electrode fingers;
• the number and the pitch of the electrode fingers of the narrow pitch electrode finger portion of the first longitudinally coupled resonator type surface acoustic wave element are different from the number and the pitch of the electrode fingers of the narrow pitch electrode finger portion of the second longitudinally coupled resonator type surface acoustic wave element;
• and
• the number and the pitch of the electrode fingers of the narrow pitch electrode finger portion of the third longitudinally coupled resonator type surface acoustic wave element are different from the number and the pitch of the electrode fingers of the narrow pitch electrode finger portion of the fourth longitudinally coupled resonator type surface acoustic wave element.

A surface acoustic wave device comprising:

• a first surface acoustic wave filter element including a first longitudinally coupled resonator type surface acoustic wave element provided with at least three interdigital transducers arranged along the direction of transmission of a surface acoustic wave, each of the interdigital transducers being provided with a plurality of electrode fingers, and a second longitudinally coupled resonator type surface acoustic wave element provided with at least three interdigital transducers arranged along the direction of transmission of the surface acoustic wave, each of the interdigital transducers being provided with a plurality of electrode fingers, the first longitudinally coupled resonator type surface acoustic wave element and the second longitudinally coupled resonator type surface acoustic wave element being cascaded to each other and being arranged on a piezoelectric substrate;
• and
• a second surface acoustic wave filter element including a third longitudinally coupled resonator type surface acoustic wave element provided with at least three interdigital transducers arranged along the direction of transmission of the surface acoustic wave, each of the interdigital transducers being provided with a plurality of electrode fingers, and a fourth longitudinally coupled resonator type surface acoustic wave element provided with at least three interdigital transducers arranged along the direction of transmission of the surface acoustic wave, each of the interdigital transducers being provided with a plurality of electrode fingers, the third longitudinally coupled resonator type surface acoustic wave element and the fourth longitudinally coupled resonator type surface acoustic wave element being cascaded to each other and being arranged on the piezoelectric substrate, the phase of input and output signals of the second surface acoustic wave filter element being approximately 180 degrees different from the phase of input and output signals of the first surface acoustic wave filter element, one terminal of the first surface acoustic wave filter element and one terminal of the second surface acoustic wave filter element being electrically connected in parallel, the other terminal of the first surface acoustic wave filter element and the other terminal of the second surface acoustic wave filter element being electrically connected in series;
• wherein
• at least one of the interdigital transducers of each of the first, second, third, and fourth longitudinally coupled resonator type surface acoustic wave elements has a narrow pitch electrode finger portion near the adjacent interdigital transducer, the pitch of the electrode fingers of the narrow pitch electrode finger portion being smaller than the pitch of the other electrode fingers;
• the number of the electrode fingers of the narrow pitch electrode finger portion of the first longitudinally coupled resonator type surface acoustic wave element is different from the number of the electrode fingers of the narrow pitch electrode finger portion of the second longitudinally coupled resonator type surface acoustic wave element;
• and
• wherein the number of the electrode fingers of the narrow pitch electrode finger portion of the third longitudinally coupled resonator type surface acoustic wave element is different from the number of the electrode fingers of the narrow pitch electrode finger portion of the fourth longitudinally coupled resonator type surface acoustic wave element.

A surface acoustic wave device comprising:

• a first surface acoustic wave filter element including a first longitudinally coupled resonator type surface acoustic wave element provided with at least three interdigital transducers arranged along the direction of transmission of a surface acoustic wave, each of the interdigital transducers being provided with a plurality of electrode fingers, and a second longitudinally coupled resonator type surface acoustic wave element provided with at least three interdigital transducers arranged along the direction of transmission of the surface acoustic wave, each of the interdigital transducers being provided with a plurality of electrode fingers, the first longitudinally coupled resonator type surface acoustic wave element and the second longitudinally coupled resonator type surface acoustic wave element being cascaded to each other and being arranged on a piezoelectric substrate;
• and
• a second surface acoustic wave filter element including a third longitudinally coupled resonator type surface acoustic wave element provided with at least three interdigital transducers arranged along the direction of transmission of the surface acoustic wave, each of the interdigital transducers being provided with a plurality of electrode fingers, and a fourth longitudinally coupled resonator type surface acoustic wave element provided with at least three interdigital transducers arranged along the direction of transmission of the surface acoustic wave, each of the interdigital transducers being provided with a plurality of electrode fingers, the third longitudinally coupled resonator type surface acoustic wave element and the fourth longitudinally coupled resonator type surface acoustic wave element being cascaded to each other and being arranged on the piezoelectric substrate, the phase of input and output signals of the second surface acoustic wave filter element being approximately 180 degrees different from the phase of input and output signals of the first surface acoustic wave filter element, one terminal of the first surface acoustic wave filter element and one terminal of the second surface acoustic wave filter element being electrically connected in parallel, the other terminal of the first surface acoustic wave filter element and the other terminal of the second surface acoustic wave filter element being electrically connected in series;
• wherein
• at least one of the interdigital transducers of each of the first, second, third, and fourth longitudinally coupled resonator type surface acoustic wave elements has a narrow pitch electrode finger portion located near the adjacent interdigital transducer, the pitch of the electrode fingers of the narrow pitch electrode finger portion being smaller than the pitch of the other electrode fingers;
• the pitch of the electrode fingers of the narrow pitch electrode finger portion of the first longitudinally coupled resonator type surface acoustic wave element is different from the pitch of the electrode fingers of the narrow pitch electrode finger portion of the second longitudinally coupled resonator type surface acoustic wave element;
• and
• the pitch of the electrode fingers of the narrow pitch electrode finger portion of the third longitudinally coupled resonator type surface acoustic wave element is different from the pitch of the electrode fingers of the narrow pitch electrode finger portion of the fourth longitudinally coupled resonator type surface acoustic wave element.