SURFACE ACOUSTIC WAVE ELEMENT AND SURFACE ACOUSTIC WAVE DEVICE COMPRISING THE ELEMENT

Abstract

A surface acoustic wave element comprises a first surface acoustic wave element unit formed on a surface of a piezo-electric substrate, and a second surface acoustic wave element unit formed on the surface of said piezo-electric substrate adjacent to said first surface acoustic wave element unit. Each of said first surface acoustic wave element unit and said second surface acoustic wave element unit includes a signal input terminal, a signal output terminal, a ground terminal, a signal path for coupling said signal input terminal to the signal output terminal, series arm resonators connected in series on said signal path, a branch line branched from said signal path to said ground terminal, and parallel arm resonators connected on said branch line. The signal path of at least one of the first surface acoustic wave element unit and second surface acoustic wave element unit is extended outside of the center line of said surface acoustic wave element unit.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, features, and advantages of the present invention will become apparent from the following description of embodiments of the present invention taken in conjunction with the drawings, where the same reference numerals designate the same or corresponding parts.

FIG. 1 is a block diagram illustrating a SAW device (duplexer) according to a first embodiment of the present invention;

FIG. 2 is a circuit diagram illustrating a transmission filter contained in the SAW device according to the first embodiment;

FIG. 3A is a circuit diagram illustrating an example of a reception filter contained in the SAW device according to the first embodiment;

FIG. 3B is a circuit diagram illustrating another example of the reception filter contained in the SAW device according to the first embodiment;

FIG. 4A is a cross-sectional view illustrating an example of the SAW device according to the first embodiment;

FIG. 4B is a cross-sectional view illustrating another example of the SAW device according to the first embodiment;

FIG. 5 is a top plan view schematically illustrating a SAW element contained in the SAW device according to the first embodiment;

FIG. 6 is a graphic representation showing frequency—attenuation characteristics (simulation result) of the duplexer according to the first embodiment in comparison with a conventional SAW element structure;

FIG. 7 is a graphic representation showing isolation characteristics between the transmission and reception filters in the first embodiment;

FIG. 8 is a top plan view schematically illustrating a SAW element contained in a SAW device according to a second embodiment of the present invention;

FIG. 9 is a graphic representation showing frequency—attenuation characteristics (simulation result) of a duplexer according to the second embodiment in comparison with a conventional SAW element structure;

FIG. 10 is a graphic representation showing isolation characteristics between the transmission and reception filters in the second embodiment;

FIG. 11 is a top plan view schematically illustrating another exemplary configuration of a SAW device according to the present invention; and

FIG. 12 is a top plan view schematically illustrating the configuration of a conventional SAW element structure.

Claims

1. A surface acoustic wave element comprising: a first surface acoustic wave element unit formed on a surface of a piezo-electric substrate; anda second surface acoustic wave element unit formed on the surface of said piezo-electric substrate adjacent to said first surface acoustic wave element unit,wherein each of said first surface acoustic wave element unit and said second surface acoustic wave element unit includes:an input terminal for inputting a signal therethrough;an output terminal for outputting a signal therethrough;a ground terminal connected to a ground;a signal path for coupling said input terminal and said output terminal;one or more series arm resonators connected in series on said signal path;a branch line branched from said signal path to said ground terminal; andone or more parallel arm resonators connected on said branch line,wherein said signal path of at least one of said first surface acoustic wave element unit and said second surface acoustic wave element unit is extended outside of a center line of said surface acoustic wave element unit.

2. A surface acoustic wave element according to claim 1, wherein: said signal path of the other of said first surface acoustic wave element unit and said second surface acoustic wave element unit is partially extended outside of the center line of said surface acoustic wave element unit.

3. A surface acoustic wave element according to claim 1, wherein: said signal path of each of said first surface acoustic wave element unit and said second surface acoustic wave element unit is extended outside of the center line of each surface acoustic wave element unit.

4. A surface acoustic wave element according to claim 1, wherein: said branch line is arranged to interpose between the signal path of said first surface acoustic wave element unit and the signal path of said second surface acoustic wave element unit.

5. A surface acoustic wave element according to claim 2, wherein: said branch line is arranged to interpose between the signal path of said first surface acoustic wave element unit and the signal path of said second surface acoustic wave element unit.

6. A surface acoustic wave element according to claim 3, wherein: said branch line is arranged to interpose between the signal path of said first surface acoustic wave element unit and the signal path of said second surface acoustic wave element unit.

7. A surface acoustic wave device comprising: a base substrate on which a surface acoustic wave element can be mounted;a surface acoustic wave element flip-chip mounted on said based substrate; anda lid for hermetically sealing said surface acoustic wave element,wherein said surface acoustic wave element comprises:a first surface acoustic wave element unit formed on a surface of a piezo-electric substrate; anda second surface acoustic wave element unit formed on the surface of said piezo-electric substrate adjacent to said first surface acoustic wave element unit,each of said first surface acoustic wave element unit and said second surface acoustic wave element unit includes:an input terminal for inputting a signal therethrough;an output terminal for outputting a signal therethrough;a ground terminal connected to a ground;a signal path for coupling said input terminal and said output terminal;one or more series arm resonators connected in series on said signal path;a branch line branched from said signal path to said ground terminal; andone or more parallel arm resonators connected on said branch line, andsaid signal path of at least one of said first surface acoustic wave element unit and said second surface acoustic wave element unit is extended outside of a center line of said surface acoustic wave element unit.

8. A surface acoustic wave device according to claim 7, wherein: said signal path of the other of said first surface acoustic wave element unit and said second surface acoustic wave element unit is partially extended outside of the center line of said surface acoustic wave element unit.

9. A surface acoustic wave device according to claim 7, wherein: said signal path of each of said first surface acoustic wave element unit and said second surface acoustic wave element unit is extended outside of the center line of each surface acoustic wave element unit.

10. A surface acoustic wave device according to claim 7, wherein: said branch line is arranged to interpose between the signal path of said first surface acoustic wave element unit and the signal path of said second surface acoustic wave element unit.

11. A surface acoustic wave device according to claim 8, wherein: said branch line is arranged to interpose between the signal path of said first surface acoustic wave element unit and the signal path of said second surface acoustic wave element unit.

12. A surface acoustic wave device according to claim 9, wherein: said branch line is arranged to interpose between the signal path of said first surface acoustic wave element unit and the signal path of said second surface acoustic wave element unit.

13. A surface acoustic wave device according to claim 7, wherein said lid does not comprise a ground conductor.

14. A surface acoustic wave device according to claim 8, wherein said lid does not comprise a ground conductor.

15. A surface acoustic wave device according to claim 9, wherein said lid does not comprise a ground conductor.

16. A surface acoustic wave device according to claim 10, wherein said lid does not comprise a ground conductor.

17. A surface acoustic wave device according to claim 11, wherein said lid does not comprise a ground conductor.

18. A surface acoustic wave device according to claim 12, wherein said lid does not comprise a ground conductor.