Piezoelectric resonator

• US 6,437,482 B1
• Filed: 04/11/2000
• Issued: 08/20/2002
• Est. Priority Date: 04/19/1999
• Status: Expired due to Term

• Current Assignee: Murata Manufacturing Co Limited
• Original Assignee: Murata Manufacturing Co Limited
• Inventors: Shibata, Akihiko
• Primary Examiner(s): Nguyen, Tran
• Assistant Examiner(s): MEDLEY, PETER M
• Application Number:
  US09/547,193
• Time in Patent Office: 861 Days
• Field of Search: 310/320, 310/324, 310/357, 310/330, 310/331, 310/332
• US Class Current: 310/320
• CPC Class Codes: H03H 9/02015 Characteristics of piezoelectric layers, e.g. cutting angles
• CPC Class Codes: H03H 9/02078 the vibration mode being overmoded
• CPC Class Codes: H03H 9/171 implemented with thin-film techniques, i.e. of the film bulk acoustic resonator [FBAR] type
• CPC Class Codes: H03H 9/178 of a laminated structure of multiple piezoelectric layers with inner electrodes

Abstract

A piezoelectric resonator using a thickness extensional vibration mode, comprises a vibrator portion made up of two or more layers of piezoelectric thin-films where the piezoelectric thin-films and a plurality of insulating thin films are alternately laminated. An alternating voltage is independently applied to each layer of the piezoelectric thin-films for a higher-order vibration mode to be dominantly excited.

Claims

1. A piezoelectric resonator using a thickness extensional vibration mode, the piezoelectric resonator comprising a vibrator portion made up of n layers of piezoelectric thin-film, n being an integer greater than or equal to 2, each of the piezoelectric thin-film layers being separated by a respective insulating thin-film layer, the distance d_n to the center of each of the n piezoelectric thin-film layers from a first side of the vibrator portion, being determined by the formula

2. A piezoelectric resonator as claimed in claim 1, wherein each of the piezoelectric thin-film layers comprises a generally planar piezoelectric thin-film having electrodes formed on opposite sides thereof.

3. A piezoelectric resonator as claimed in claim 2, wherein each of the piezoelectric thin-film layers and each of the insulating thin-film layers are generally planar and extend parallel to one another.

4. A piezoelectric resonator as claimed in claim 2, wherein the piezoelectric thin-films and the insulating thin film layers are made up of materials having temperature coefficients of the elastic constant whose sign is opposite to one another.

5. A piezoelectric resonator as claimed in claim 1, wherein adjacent piezoelectric thin-film layers are polarized in the same direction.

6. A piezoelectric resonator as claimed in claim 1, wherein adjacent piezoelectric thin-films are polarized in opposite directions.

7. A piezoelectric resonator as claimed in claim 1, wherein the thickness t is equal to one half of the wave length of the first resonance wavelength of the thickness extension vibration mode.

8. The combination of a piezoelectric resonator and a voltage source, the combination comprising:

a piezoelectric resonator using a thickness extensional vibration mode, the piezoelectric resonator comprising a vibrator portion made up of n layers of piezoelectric thin-film, n being an integer greater than or equal to 2, each of the piezoelectric thin-film layers being separated by a respective insulating thin-film layer; and

a voltage source for applying alternating voltages to the piezoelectric resonator in such a manner that the predominant vibration mode excited in the piezoelectric resonator is a higher-order vibration mode.

9. The combination according to claim 8, wherein the alternating voltages are independently applied to each of the piezoelectric thin-film layers.

10. The combination of claim 8, wherein the higher-order vibration mode is the nth vibration mode.

11. The combination of claim 10, wherein the distance d_n to the center of each of the n piezoelectric thin-film layers from a first side of the vibrator portion is determined by the formula

12. The combination of claim 11, wherein the thickness t is equal to one half of the wave length of the first resonance wavelength of the thickness extension vibration mode.

13. The combination of claim 11, wherein each of the piezoelectric thin-film layers comprises a generally planar piezoelectric thin-film having electrodes formed on opposite sides thereof.

14. The combination of claim 13 wherein each of the piezoelectric thin-film layers and each of the insulating thin-film layers are generally planar and extend parallel to one another.

15. The combination of claim 14, wherein the piezoelectric thin-films and the insulating thin film layers are made up of materials having temperature coefficients of the elastic constant whose sign is opposite to one another.

16. The combination of claim 15, wherein adjacent piezoelectric thin-film layers are polarized in the same direction and the voltage source applies alternating voltages of the opposite phase to adjacent piezoelectric thin-film layers.

17. The combination of claim 15 wherein adjacent piezoelectric thin-film layers are polarized in opposite directions and the voltage source applies alternating voltages of the same phase to each of the piezoelectric thin-film layers.

18. The combination of claim 15, wherein the voltage source applies alternating voltages to the piezoelectric thin-film layers in such a manner that vibrations of opposite phase are induced in adjacent piezoelectric thin-film layers.

19. The combination of claim 8, wherein adjacent piezoelectric thin-film layers are polarized in the same direction and the voltage source applies alternating voltages of the opposite phase to adjacent piezoelectric thin-film layers.

20. The combination of claim 8 wherein adjacent piezoelectric thin-film layers are polarized in opposite directions and the voltage source applies alternating voltages of the same phase to each of the piezoelectric thin-film layers.

21. The combination of claim 8, wherein the voltage source applies alternating voltages to the piezoelectric thin-film layers in such a manner that vibrations of opposite phase are induced in adjacent piezoelectric thin-film layers.

22. A method for exciting a piezoelectric resonator in a thickness extensional vibration mode, the piezoelectric resonator comprising a vibrator portion made up of n layers of piezoelectric thin-film, n being an integer greater or equal to 2, each of the piezoelectric thin-film layers being separated by a respective insulating thin-film layer, the method comprising:

applying alternating voltages to the piezoelectric thin film layers in such a manner that the predominant vibration mode excited in the piezoelectric resonator is a higher-order vibration mode.

23. The method of claim 22, wherein the alternating voltages are independently applied to each of the piezoelectric thin-film layers.

24. The method of claim 22, wherein the higher-order vibration mode is the nth vibration mode.

25. The method of claim 24, wherein the distance d_n to the center of each of the n piezoelectric thin-film layers from a first side of the vibrator portion is determined by the formula

26. The method of claim 25, wherein each of the piezoelectric thin-film layers comprises a generally planar piezoelectric thin-film having electrodes formed on opposite sides thereof.

27. The method of claim 26 wherein each of the piezoelectric thin-film layers and each of the insulating thin-film layers are generally planar and extend parallel to one another.

28. The method of claim 27, wherein the piezoelectric thin-films and the insulating thin film layers are made up of materials having temperature coefficients of the elastic constant whose sign is opposite to one another.

29. The method of claim 28, wherein adjacent piezoelectric thin-film layers are polarized in the same direction and alternating voltages of the opposite phase are applied to adjacent piezoelectric thin-film layers.

30. The method of claim 28, wherein adjacent piezoelectric thin-film layers are polarized in opposite directions and alternating voltages of the same phase are applied to each of the piezoelectric thin-film layers.

31. The method of claim 28, wherein alternating voltages are applied to the piezoelectric thin-film layers in such a manner that vibrations of opposite phase are induced in adjacent piezoelectric thin-film layers.

32. The method of claim 25, wherein the thickness t is equal to one half of the wave length of the first resonance wavelength of the thickness extension vibration mode.

33. The method of claim 22, wherein adjacent piezoelectric thin-film layers are polarized in the same direction and alternating voltages of the opposite phase are applied to adjacent piezoelectric thin-film layers.

34. The method of claim 22, wherein adjacent piezoelectric thin-film layers are polarized in opposite directions and alternating voltages of the same phase are applied to each of the piezoelectric thin-film layers.

35. The method of claim 22, wherein alternating voltages are applied to the piezoelectric thin-film layers in such a manner that vibrations of opposite phase are induced in adjacent piezoelectric thin-film layers.