Bulk acoustic wave resonator with two piezoelectric layers as balun in filters and duplexers

• US 20030128081A1
• Filed: 01/09/2002
• Published: 07/10/2003
• Est. Priority Date: 01/09/2002
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Nokia Corporation
• Inventors: Aigner, Robert, Ella, Juha
• Granted Patent: US 6,670,866 B2
• Time in Patent Office: Days
• US Class Current: 333/133
• CPC Class Codes: H03H 7/42 Networks for transforming balanced signals into unbalanced signals and vice versa, e.g. baluns
• CPC Class Codes: H03H 9/0095 using bulk acoustic wave devices
• CPC Class Codes: H03H 9/0571 including bulk acoustic wave [BAW] devices
• CPC Class Codes: H03H 9/589 Acoustic mirrors
• CPC Class Codes: H03H 9/706 Duplexers

Abstract

A bulk acoustic wave device having two resonators in a stacked-up configuration separated by a dielectric layer. The device can be coupled to a lattice filter or a ladder filter to form a passband filter with an unbalanced input port and two balanced output ports. One or more such passband filters can be used, together with another lattice or ladder filter, to form a duplexer having an unbalanced antenna port, two balanced ports for one transceiver part and two balanced ports for another transceiver part.

Claims

1. A bulk acoustic wave device having a resonant frequency and an acoustic wavelength characteristic of the resonant frequency, said device comprising:

a first resonator having a first electrode, a second electrode and a first piezoelectric layer disposed between the first and second electrodes;

a second resonator having a third electrode, a fourth electrode and a second piezoelectric layer disposed between the third and fourth electrodes; and

an electrically insulating layer, wherein the first resonator and the second resonator are arranged in a stack with the electrically insulating layer disposed between the second electrode and the third electrode.

2. The bulk acoustic wave device of claim 1, wherein the electrically insulating layer comprises a dielectric layer.

3. The bulk acoustic wave device of claim 2, wherein the dielectric layer has a thickness substantially equal to one half of the acoustic wavelength.

4. The bulk acoustic wave device of claim 1, wherein the device has a signal input port, a first signal output port, a second signal output port and a device ground, and wherein

the first electrode is coupled to the signal input port,

the second electrode is electrically connected to the device ground,

the third electrode is coupled to the first signal output port, and

the fourth electrode is coupled to the second signal output port.

5. The bulk acoustic wave device of claim 4, further comprising a capacitive element coupled between the fourth electrode and the device ground for adjusting the parasitic capacitance therebetween.

6. The bulk acoustic wave device of claim 4, further comprising an inductance element coupled between the first and second signal output ports for impedance matching and bandwidth widening.

7. The bulk acoustic wave device of claim 4, further comprising an inductance element coupled between the signal input port and the device ground for impedance matching and bandwidth widening.

8. The bulk acoustic wave device of claim 1, wherein the first piezoelectric layer has a thickness substantially equal to one half of the acoustic wavelength.

9. The bulk acoustic wave device of claim 1, wherein the second piezoelectric layer has a thickness substantially equal to one half of the acoustic wavelength.

10. The bulk acoustic wave device of claim 2, wherein the first and second piezoelectric layers are made of a material having a negative temperature coefficient, and the dielectric layer is made of a material having a positive temperature coefficient for compensating for the temperature effect on the bulk acoustic wave device.

11. The bulk acoustic device of claim 2, wherein the dielectric layer is made of silicon oxide.

12. A bulk acoustic wave device having a signal input port, a first signal output port, a second signal output port and a device ground, said device having a resonant frequency and an acoustic wavelength characteristic of the resonant frequency, said device comprising:

a first resonator having a first electrode, a second electrode and a first piezoelectric layer disposed between the first and second electrodes;

a second resonator having a third electrode, a fourth electrode and a second piezoelectric layer disposed between the third and fourth electrodes; and

a dielectric layer, wherein the first resonator and the second resonator are arranged in a stack with the dielectric layer disposed between the second electrode and the third electrode, and wherein

the first electrode is coupled to the signal input port,

the second electrode is electrically connected to the device ground,

the third electrode is coupled to the first signal output port, and

the fourth electrode is coupled to the second signal output port.

13. A bulk acoustic wave device structure formed on a substrate having an upper section, said structure comprising:

a first electrode provided on the upper section;

a first piezoelectric layer provided on top of at least part of the first electrode;

a second electrode provided on top of at least part of the first piezoelectric layer, wherein the first electrode, the first piezoelectric layer and the second electrode have an overlapping area for forming a first acoustic resonator;

a dielectric layer disposed on top of at least part of the second electrode;

a third electrode disposed on top of at least part of the dielectric layer such that the third electrode and the second electrode are electrically insulated by the dielectric layer,

a second piezoelectric layer provided on top of at least part of the third electrode, and

a fourth electrode provided on top of at least part of the second piezoelectric layer, wherein the third electrode, the second piezoelectric layer and the fourth electrode have a further overlapping area for forming a second resonator.

14. The bulk acoustic wave device structure of claim 13, further having an acoustic mirror structure provided between part of the first electrode and the upper section of the substrate.

15. The bulk acoustic wave device structure of claim 13, wherein the structure has a signal input port, a first signal output port, a second signal output port and a device ground, and wherein

the first electrode is coupled to the signal input port,

the second electrode is electrically connected to the device ground,

the third electrode is coupled to the first signal output port, and

the fourth electrode is coupled to the second signal output port.

16. The bulk acoustic wave device of claim 15, further comprising a capacitive element coupled between the fourth electrode and the device ground for adjusting the parasitic capacitance therebetween.

17. The bulk acoustic wave device of claim 16, wherein the first acoustic resonator and the second acoustic resonator have a further overlapping area for defining an active area of the bulk acoustic wave device structure, and wherein

the second electrode has an extended portion located outside the active area,

the fourth electrode has a further extended portion located outside the active area, wherein the extended portion and the further extended portion have yet another overlapping area for forming said capacitive element.

18. The bulk acoustic wave device of claim 15, further comprising an inductance element coupled between the first and second signal output ports for impedance matching and bandwidth widening.

19. The bulk acoustic wave device of claim 15, further comprising an inductance element coupled between the signal input port and the device ground for impedance matching and bandwidth widening.

20. An acoustic wave apparatus formed on a substrate having an upper surface, said apparatus having a device ground, a signal input, a first signal output, a second signal output and a device ground, said structure comprising:

a first bulk acoustic wave device; and

a second bulk acoustic wave device coupled to the first bulk acoustic wave device, wherein

the first bulk acoustic wave device comprising;

a first resonator having a first electrode, a second electrode and a first piezoelectric layer disposed between the first and second electrodes; and

a second resonator having a third electrode, a fourth electrode and a second piezoelectric layer disposed between the third and fourth electrodes, wherein the first resonator and the second resonator are arranged in a stack with a first dielectric layer disposed between the second and third electrode for electrically insulating the second electrode from the third electrode, and the second bulk acoustic wave device comprising;

a first resonator having a first electrode, a second electrode and a first piezoelectric layer disposed between the first and second electrodes; and

a second resonator having a third electrode, a fourth electrode and a second piezoelectric layer disposed between the third and fourth electrodes, wherein the first resonator and the second resonator are arranged in a stack with a first dielectric layer disposed between the second and third electrode for electrically insulating the second electrode from the third electrode, and wherein

the fourth electrode of the first bulk acoustic wave device is coupled to the first signal output of the structure,

the fourth electrode of the second bulk acoustic wave device is coupled to the second signal output of the structure,

the first electrode of the first bulk acoustic wave device is coupled to the signal input of the structure and is electrically connected to the second electrode of the second bulk acoustic wave device, and

the second electrode and the third electrode of the first bulk acoustic wave device are electrically connected to the device ground and the first electrode of the second bulk acoustic wave device.

21. A bulk acoustic wave filter having a signal input terminal, a first signal output terminal, a second signal output terminal and a device ground, said bulk acoustic wave filter comprising:

a balun having at least two resonators in a stacked-up configuration including

a first resonator coupled between a signal input end and the device ground, and

a second resonator coupled between a first signal output end and a second signal output end, wherein

the first signal output end is coupled to the first signal output terminal,

the second signal output end is coupled to the second signal output terminal; and

at least one acoustic filter segment having

a series element having a first end and a second end, and

a shunt element having a first end and a second end, wherein

the first end the series element is connected to the signal input end of the balun,

the second end of the series element is connected to signal input terminal,

the first end of the shunt element is connected to the second end of the series element, and

the second end of the shunt element is connected to the device ground.

22. The bulk acoustic wave filter of claim 21, wherein

the first resonator of the balun comprises

a first electrode connected to the signal input end,

a second electrode connected to the device ground, and

a first piezoelectric layer disposed between the first and second electrodes, and the second resonator of the balun comprises

a third electrode connected to the first signal output end,

a fourth electrode connected to the second signal output end, and

a second piezoelectric layer disposed between the third and fourth electrodes, and wherein

the balun further comprises a dielectric layer disposed between the second electrode of the first resonator and the third electrode of the second resonator.

23. A bulk acoustic wave filter having a signal input terminal, a first signal output terminal, a second signal output terminal and a device ground, said bulk acoustic wave filter comprising:

at least one acoustic filter segment having

a first terminal coupled to the first signal output terminal,

a second terminal coupled to the second signal output terminal,

a third terminal,

a fourth terminal,

a first series element having a first end connected to the first terminal and a second end connected to the third terminal,

a second series element having a first end connected to the second terminal and a second end connected to the fourth terminal,

a first shunt element having a first end connected to the third terminal and a second end connected to the second terminal, and

a second shunt element having a first end connected to the first terminal and a second end connected to the fourth terminal; and

a balun having at least two resonators in a stacked-up configuration including

a first resonator coupled between a signal input end and the device ground, and

a second resonator coupled between a first signal output end and a second signal output end, wherein

the signal input end is coupled to the signal input terminal,

the first signal output end is connected to the fourth terminal of the acoustic filter segment, and

the second signal output end is connected to the third terminal of the acoustic filter segment.

24. The bulk acoustic wave filter of claim 23, wherein

the first resonator of the balun comprises

a first electrode connected to the signal input end,

a second electrode connected to the device ground, and

a first piezoelectric layer disposed between the first and second electrodes, and the second resonator of the balun comprises

a third electrode connected to the first signal output end,

a fourth electrode connected to the second signal output end, and

a second piezoelectric layer disposed between the third and fourth electrodes, and wherein

the balun further comprises a dielectric layer disposed between the second electrode of the first resonator and the third electrode of the second resonator.

25. The bulk acoustic wave filter of claim 23, wherein each of the first and second series elements has a first active area and each of the first and second shunt elements has a second active area different from the first active area in size.

26. The bulk acoustic wave filter of claim 25, wherein the first active area is greater than the second active area.

27. The bulk acoustic wave filter of claim 25, wherein the ratio of the first active area to the second active area is substantially equal to 1.2.

28. A duplexer comprising:

a first port;

a second port;

a third port;

a device ground;

a lattice bulk acoustic wave filter, disposed between the first port and the second port, said lattice bulk acoustic wave filter having

a first end, and

a second end coupled to the first port;

a balun coupled between the second port and the second end of the lattice filter;

a further bulk acoustic wave filter having

a first end coupled to the third port, and

a second end coupled to the second port; and

a phase shifting means coupled between the lattice bulk acoustic wave filter and the further bulk acoustic wave filter for matching the lattice bulk acoustic wave filter and the further bulk acoustic wave filter, wherein the balun having at least two resonators in a stacked-up configuration including

a first resonator coupled between a signal input end and the device ground, and

a second resonator coupled between a first signal output end and a second signal output end, wherein

the signal input end is connected to the second port, and

the first and second signal output ends are connected to the second end of the lattice bulk acoustic wave filter.

29. The duplexer of claim 28, wherein the further bulk acoustic wave filter comprises a further lattice bulk acoustic wave filter.

30. The duplexer of claim 28, further comprising a further balun coupled between the phase shifting means and the further lattice bulk acoustic wave filter, wherein said further balun having at least two resonators in a stacked-up configuration including

a first resonator coupled between a signal input end and the device ground, and

a second resonator coupled between a first signal output end and a second signal output end, wherein the signal input end is connected to the phase shifting means and the signal output ends are connected to the second end of the further lattice filter.

31. The duplexer of claim 28, wherein the further bulk acoustic wave filter comprises a ladder bulk acoustic wave filter.

32. The duplexer of claim 31, further comprising a further balun disposed between the ladder bulk acoustic wave filter and the third port, wherein said further balun having at least two resonators in a stacked-up configuration including

a first resonator coupled between a signal input end and the device ground, and

a second resonator coupled between a first signal end and a second signal end, wherein the signal input end is connected to the first end of the lattice bulk acoustic device, and the signal output ends are connected to the third port.

33. The duplexer of claim 28, wherein

the lattice bulk acoustic wave filter comprises a plurality of series elements and shunt elements, each element including a piezoelectric layer having a first thickness,

the further bulk acoustic wave filter comprises at least one series element and one shunt element, each element including a piezoelectric layer having a second thickness different from the first thickness,

the first resonator of the balun includes a piezoelectric layer having a third thickness substantially equal to the first thickness, and

the second resonator of the balun includes a piezolectic layer having a fourth thickness substantially equal to the second thickness.

34. The duplexer of claim 28, wherein

the lattice bulk acoustic wave filter comprises a plurality of series elements and shunt elements, each element including a piezoelectric layer having a first thickness,

the further bulk acoustic wave filter comprises at least one series element and one shunt element, each element including a piezoelectric layer having a second thickness different from the first thickness,

the first resonator of the balun includes a piezoelectric layer having a third thickness substantially equal to the second thickness, and

the second resonator of the balun includes a piezolectic layer having a fourth thickness substantially equal to the first thickness.

35. The duplexer of claim 33, wherein the first thickness is greater than the second thickness.

36. The duplexer of claim 33, wherein the first thickness is smaller than the second thickness.

37. The duplexer of claim 34, wherein the first thickness is greater than the second thickness.

38. The duplexer of claim 34, wherein the first thickness is smaller than the second thickness.

39. The duplexer of claim 30, wherein

the lattice bulk acoustic wave filter comprises a plurality of series elements and shunt elements, each element including a piezoelectric layer having a first thickness,

the further bulk acoustic wave filter comprises at least one series element and one shunt element, each element including a piezoelectric layer having a second thickness different from the first thickness,

the first resonator of the balun includes a piezoelectric layer having a third thickness substantially equal to the first thickness,

the second resonator of the balun includes a piezoelectric layer having a fourth thickness substantially equal to the second thickness,

the first resonator of the further balun includes a piezoelectric layer having a fifth thickness substantially equal to the third thickness, and

the second resonator of the further balun includes a piezoelectric layer having a sixth thickness substantially equal to the fourth thickness.

40. The duplexer of claim 30, wherein

the lattice bulk acoustic wave filter comprises a plurality of series elements and shunt elements, each element including a piezoelectric layer having a first thickness,

the further bulk acoustic wave filter comprises at least one series element and one shunt element, each element including a piezoelectric layer having a second thickness different from the first thickness,

the first resonator of the balun includes a piezoelectric layer having a third thickness substantially equal to the second thickness,

the second resonator of the balun includes a piezoelectric layer having a fourth thickness substantially equal to the first thickness,

the first resonator of the further balun includes a piezoelectric layer having a fifth thickness substantially equal to the third thickness, and

the second resonator of the further balun includes a piezoelectric layer having a sixth thickness substantially equal to the fourth thickness.

41. The duplexer of claim 39, wherein the first thickness is greater than the second thickness.

42. The duplexer of claim 39, wherein the first thickness is smaller than the second thickness.

43. The duplexer of claim 40, wherein the first thickness is greater than the second thickness.

44. The duplexer of claim 40, wherein the first thickness is smaller than the second thickness.

45. The duplexer of claim 32, wherein

the lattice bulk acoustic wave filter comprises a plurality of series elements and shunt elements, each element including a piezoelectric layer having a first thickness,

the further bulk acoustic wave filter comprises at least one series element and one shunt element, each element including a piezoelectric layer having a second thickness different from the first thickness,

the first resonator of the balun includes a piezoelectric layer having a third thickness substantially equal to the first thickness,

the second resonator of the balun includes a piezoelectric layer having a fourth thickness substantially equal to the second thickness,

the first resonator of the further balun includes a piezoelectric layer having a fifth thickness substantially equal to the third thickness, and

the second resonator of the further balun includes a piezoelectric layer having a sixth thickness substantially equal to the fourth thickness.

46. The duplexer of claim 32, wherein

the lattice bulk acoustic wave filter comprises a plurality of series elements and shunt elements, each element including a piezoelectric layer having a first thickness,

the further bulk acoustic wave filter comprises at least one series element and one shunt element, each element including a piezoelectric layer having a second thickness different from the first thickness,

the first resonator of the balun includes a piezoelectric layer having a third thickness substantially equal to the second thickness,

the second resonator of the balun includes a piezoelectric layer having a fourth thickness substantially equal to the first thickness,

the first resonator of the further balun includes a piezoelectric layer having a fifth thickness substantially equal to the third thickness, and

the second resonator of the further balun includes a piezoelectric layer having a sixth thickness substantially equal to the fourth thickness.

47. The duplexer of claim 45, wherein the first thickness is greater than the second thickness.

48. The duplexer of claim 45, wherein the first thickness is smaller than the second thickness.

49. The duplexer of claim 46, wherein the first thickness is greater than the second thickness.

50. The duplexer of claim 46, wherein the first thickness is smaller than the second thickness.

51. A duplexer comprising:

an antenna port;

a first transceiver port;

a second transceiver port;

a device ground;

a balun coupled between the antenna port and the first transceiver port;

a bulk acoustic wave filter having

a first filter end coupled to the second transceiver port, and

a second filter end coupled to the antenna port; and

a phase shifting means coupled between the balun and bulk acoustic wave filter at the antenna port for matching the balun and the bulk acoustic wave filter, wherein the balun having at least two resonators in a stacked-up configuration including

a first resonator coupled between a signal input end and the device ground, and

a second resonator coupled between a first signal output end and a second signal output end, wherein

the signal input end is connected to the antenna port, and

the first and second signal output ends are connected to first transceiver port.

52. The duplexer of claim 51, wherein the bulk acoustic wave filter comprises at least one lattice filter including two elements and two shunt elements connected to the series elements in a cross-connection fashion.

53. The duplexer of claim 51, wherein the bulk acoustic wave filter comprises at least one ladder filter including

a series element having a first end connected to the first filter end, and a second end coupled to the antenna port via the phase shifter, and

a shunt element having a first end connected to the second end of the series element, and a second end connected to the device ground.

54. The duplexer of claim 52, further comprising a further balun coupled between the bulk acoustic wave filter and the antenna port, wherein the further balun has at least two resonators in a stacked-up configuration including

a first resonator coupled between a signal input end and the device ground, and

a second resonator coupled between a first signal output end and a second signal output end, wherein

the signal input end is connected to the antenna port via the phase shifting means, and

the first and second signal output ends are connected to the second filter end bulk acoustic wave filter.

55. The duplexer of claim 53, further comprising a further balun coupled between the bulk acoustic wave filter and the second transceiver port, wherein the further balun has at least two resonators in a stacked-up configuration including

a first resonator coupled between a signal input end and the device ground, and

a second resonator coupled between a first signal output end and a second signal output end, wherein

the signal input end is connected to the first filter end of the bulk acoustic wave filter, and

the first and second signal output ends are connected to the second transceiver port.

56. A duplexer comprising:

an antenna port;

a first transceiver port;

a second transceiver port;

a device ground;

a first balun coupled between the antenna port and the first transceiver port;

a second balun coupled between the antenna port and the second transceiver port; and

a phase shifting means coupled between the first balun and the second balun at the antenna port, wherein each of the baluns has at least two resonators in a stacked-up configuration including

a first resonator coupled between a signal input end and the device ground, and

a second resonator coupled between a first signal output end and a second signal output end, wherein

the signal input end is connected to the antenna port, and

the first and second signal output ends of each balun are connected to each of the first and second transceiver ports.