Surface acoustic wave device

• US 20040207491A1
• Filed: 03/30/2004
• Published: 10/21/2004
• Est. Priority Date: 03/31/2003
• Status: Active Grant

• Current Assignee: Skyworks Filter Solutions Japan Co., Ltd. (Skyworks Solutions Incorporated)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Nakamura, Hiroyuki, Tsuzuki, Shigeru, Nakaya, Shinobu
• Granted Patent: US 7,019,435 B2
• Time in Patent Office: Days
• US Class Current: 333/195
• CPC Class Codes: H03H 9/0038 the balanced terminals being on the same side of the track
• CPC Class Codes: H03H 9/0071 the balanced terminals being on the same side of the tracks
• CPC Class Codes: H03H 9/02685 Grating lines having particular arrangements
• CPC Class Codes: H03H 9/14588 Horizontally-split transducers
• CPC Class Codes: H03H 9/643 the transfer characteristic being determined by reflective or coupling array characteristics
• CPC Class Codes: H03H 9/6433 Coupled resonator filters
• CPC Class Codes: H03H 9/6469 via two connecting electrodes
• CPC Class Codes: H03H 9/6473 the electrodes being electrically interconnected

Abstract

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.

Claims

1. A surface acoustic wave device comprising:

a plurality of surface acoustic wave elements connected in parallel, wherein each of said surface acoustic wave elements comprises;

at least three interdigital transducer electrodes,

wherein said interdigital transducer electrodes are operable to generate a surface acoustic wave that travels in a propagating direction, and wherein each of said interdigital transducer electrodes is formed of a comb shaped electrode pair;

a first reflector electrode disposed at a first side of said interdigital transducer electrodes; and

a second reflector electrode disposed at a second side of said interdigital transducer electrodes,

wherein said first and second reflector electrodes are disposed in the propagating direction of the surface acoustic wave generated by said interdigital transducer electrodes;

a ground connection electrode that connects together a first part of each comb shaped electrode pair forming said interdigital transducer electrodes; and

a ground pad that is connected to said ground connection electrode.

2. The surface acoustic wave device according to claim 1, further comprising at least one input pad and at least one output pad,

wherein a second part of each comb shaped electrode pair is connected with said at least one input pad or said at least one output pad.

7. The surface acoustic wave device of claim 1, wherein

said plurality of surface acoustic wave elements share in common one of said first reflector electrode and said second reflector electrode.

9. The surface acoustic wave device of claim 1,

wherein at least one of said first and second reflector electrodes is formed of a plurality of strip electrodes and a bus bar electrode, and

wherein different gaps are provided between different adjacent pairs of said strip line electrodes.

12. The surface acoustic wave device of claim 9, wherein

said bus bar electrode comprises a first region and a second region, and

said gap between respective strip line electrodes is different in said first and said second region.

15. The surface acoustic wave device of claim 9, wherein

said gap between respective strip line electrodes is different throughout an entire width of said bus bar electrode.

18. The surface acoustic wave device of claim 1, wherein

at least one of said first and second reflector electrodes is formed of a plurality of strip line electrodes and a bus bar electrode,

said bus bar electrode comprises a plurality of regions,

substantially identical gaps are formed between each adjacent pair of strip line electrodes, and

lengths of the respective strip line electrodes are different in said plurality of regions.

21. The surface acoustic wave device one of claim 2, wherein

said interdigital transducer electrodes are structured so that said at least one input pad and said at least one output pad operate in a balanced state.

24. The surface acoustic wave device of claim 1, wherein

in a case where there are n pieces, or more, of said surface acoustic wave elements, wherein n=an integer of 2 or more, said interdigital transducer electrodes are structured so that each of said surface acoustic wave elements has an impedance of (50×

n )Ω

.

26. The surface acoustic wave device of claim 2, wherein

at least two of said interdigital transducer electrodes are connected together in common with said at least one input pad or said at least one output pad.

31. The surface acoustic wave device of claim 2, wherein

said interdigital transducer electrodes are structured so that impedance as viewed from said input pad or said output pad, is approximately 50Ω

.

34. The surface acoustic wave device of claim 1, wherein said surface acoustic wave elements are formed on a piezoelectric substrate.

3. A surface acoustic wave device comprising:

a first surface acoustic wave element and a second surface acoustic wave element, wherein each of said first and second surface acoustic wave elements comprises;

at least three interdigital transducer electrodes,

wherein each of said interdigital transducer electrodes is formed of a comb shaped electrode pair, and wherein said interdigital transducer electrodes are operable to generate a surface acoustic wave that travels in a propagation direction;

a first reflector electrode disposed at a first side of said interdigital transducer electrodes; and

a second reflector electrode disposed at a second side of said interdigital transducer electrodes,

wherein said first and second reflector electrodes are disposed in the propagating direction of the surface acoustic wave generated by said interdigital transducer electrodes;

at least one ground connection electrode, wherein, in at least one of said first and second surface acoustic wave elements, a first part of each comb shaped electrode pair forming said interdigital transducer electrodes is connected together in common by said at least one ground connection electrode;

a ground pad that connects to said at least one first ground connection electrode;

a first element-to-element connection electrode, wherein a second part of a first comb shaped electrode pair in each of said first and said second surface acoustic wave elements is connected together by said first element-to-element connection electrode; and

a second element-to-element connection electrode, wherein a second part of a second comb shaped electrode pair in each of said first and said second surface acoustic wave elements is connected together by said second element-to-element connection electrode,

wherein said first and second element-to-element electrodes serially connect said first and said second surface acoustic wave elements in two stages.

4. The surface acoustic wave device of claim 3, further comprising a third surface acoustic wave element and a fourth surface acoustic wave element,

wherein each of said third and said fourth surface acoustic wave elements comprises a second plurality of interdigital transducer electrodes, wherein each of said second plurality of interdigital electrodes is formed of a comb shaped electrode pair,

wherein said first and said third surface acoustic wave elements are disposed in said propagating direction of said surface acoustic wave, and are connected in parallel, and

wherein said second and said fourth surface acoustic wave elements are disposed in the propagating direction of the surface acoustic wave, and are connected in parallel.

5. The surface acoustic wave device according to claim 4, further comprising at least one input pad and at least one output pad,

wherein a second part of at least one comb shaped electrode pair is connected with said at least one input pad or said at least one output pad.

6. The surface acoustic wave device of claim 5,

wherein, in at least one of said third and fourth surface acoustic wave elements, a first part of each comb shaped electrode pair forming said interdigital transducer electrodes is connected together in common by said ground connection electrode, and

further comprising:

a third element-to-element connection electrode, wherein a second part of a first comb shaped electrode pair in each of said third and said fourth surface acoustic wave elements is connected together by said third element-to-element connection electrode;

a fourth element-to-element connection electrode, wherein a second part of a second comb shaped electrode pair in each of said third and said fourth surface acoustic wave elements is connected together by said fourth element-to-element connection electrode; and

wherein said third and fourth element-to-element electrodes serially connect said third and said fourth surface acoustic wave elements in two stages.

8. The surface acoustic wave device of claim 6, wherein

said first and said third surface acoustic wave elements share in common one of said first reflector electrode and said second reflector electrodes.

10. The surface acoustic wave device of claim 3,

wherein at least one of said first and second reflector electrodes is formed of a plurality of strip line electrodes and a bus bar electrode, and

wherein different gaps are provided between different adjacent pairs of said strip line electrodes.

11. The surface acoustic wave device of claim 4,

wherein at least one of said first and second reflector electrodes is formed of a plurality of strip line electrodes and a bus bar electrode, and

wherein different gaps are provided between different adjacent pairs of said strip line electrodes.

13. The surface acoustic wave device of claim 10, wherein

said bus bar electrode comprises a first region and a second region, and

said gap between respective strip line electrodes is different in said first and said second region.

14. The surface acoustic wave device of claim 11, wherein

said bus bar electrode comprises a first region and a second region, and

said gap between respective strip line electrodes is different in said first and said second region.

16. The surface acoustic wave device of claim 10, wherein

said gap between respective strip line electrodes is different throughout an entire width of said bus bar electrode.

17. The surface acoustic wave device of claim 11, wherein

said gap between respective strip line electrodes is different throughout an entire width of said bus bar electrode.

19. The surface acoustic wave device of claim 3, wherein

at least one of said first and second reflector electrodes is formed of a plurality of strip line electrodes and a bus bar electrode,

said bus bar electrode comprises a plurality of regions,

substantially identical gaps are formed between each adjacent pair of strip line electrodes, and

lengths of the respective strip line electrodes are different in said plurality of regions.

20. The surface acoustic wave device of claim 4, wherein

at least one of said first and second reflector electrodes is formed of a plurality of strip line electrodes and a bus bar electrode,

said bus bar electrode comprises a plurality of regions,

substantially identical gaps are formed between each adjacent pair of strip line electrodes, and

lengths of the respective strip line electrodes are different said plurality of regions.

22. The surface acoustic wave device of claim 5, wherein

said interdigital transducer electrodes are structured so that said at least one input pad and said at least one output pad operate in a balanced state.

23. The surface acoustic wave device of claim 6,

wherein

said interdigital transducer electrodes are structured so that said at least one input pad and said at least one output pad operate in a balanced state.

25. The surface acoustic wave device of claim 3, wherein

in a case where there are n pieces, or more, of said surface acoustic wave elements, wherein n=an integer of 2 or more, said interdigital transducer electrodes are structured so that each of said surface acoustic wave elements has an impedance of (50×

n )Ω

.

27. The surface acoustic wave device of claim 5, wherein

at least two of said interdigital transducer electrodes are connected together in common with said at least one input pad or said at least one output pad.

28. The surface acoustic wave device of claim 6, wherein

at least two of said interdigital transducer electrodes are connected together in common with said at least one input pad or said at least one output pad.

29. The surface acoustic wave device of claim 3, wherein

signals in said element-to-element connection electrodes are reverse-phased to each other.

30. The surface acoustic wave device of claim 3, further comprising an electrode for connecting said first element-to-element connection electrode with said second element-to-element connection electrode.

32. The surface acoustic wave device of claim 3, wherein

said ground connection electrode which connects together in common said first part of the comb shaped electrode pair forming each of said interdigital transducer electrodes, and said ground pad, are disposed to be symmetrical to each other.

33. The surface acoustic wave device of claim 4, wherein

said ground connection electrode which connects together in common said one part of the comb shaped electrode pair forming each of said interdigital transducer electrodes, and said ground pad, are disposed to be symmetrical to each other.

35. The surface acoustic wave device of claim 3, wherein said surface acoustic wave elements are formed on a piezoelectric substrate.

36. The surface acoustic wave device of claim 6, wherein

one of said first and said second element-to-element connection electrodes, and one of said third and said fourth element-to-element connection electrodes, oppose each other, and

signals in said element-to-element connection electrodes that oppose each other have the same phase.

37. The surface acoustic wave device of claim 6, further comprising:

a connection electrode which connects one of said first and said second element-to-element connection electrodes with one of said third and said fourth element-to-element connection electrodes.

38. The surface acoustic wave device of claim 6, further comprising:

a connection electrode which connects together in common said first, second, third and fourth element-to-element connection electrodes.