Tunable resonator element, filter circuit and method

Patent metadata

Field	Value
Publication number	US-11018652-B2
Application number	US-201816210756-A
Country	US
Kind code	B2
Filing date	Dec 5, 2018
Priority date	Dec 7, 2017
Publication date	May 25, 2021
Grant date	May 25, 2021

Abstract

A resonator element for use in a filter is provided. The resonator element includes a first resonator acoustically coupled to a second or third resonator or both. The first resonator has terminals for incorporation in a filter structure. A tuning circuit is coupled to the second or third resonator or both to enable tuning of the resonator element. The tuning circuit includes a variable capacitor and an inductor.

First claim

What is claimed is:

1. A resonator element for a filter, comprising:
a first resonator having a first terminal and a second terminal for coupling to a filter structure;
a second resonator having a third terminal and a fourth terminal, wherein the second resonator is acoustically coupled to the first resonator; and
a tuning circuit coupled to the third and fourth terminals,
wherein the first resonator comprises a first piezoelectric material, and the second resonator comprises a second piezoelectric material, and wherein a piezoelectric electromechanical coupling constant k T 2 of the first piezoelectric material is smaller than 10%.

2. The resonator element of claim 1 , wherein the first resonator and the second resonator are implemented as a resonator stack.

3. The resonator element of claim 2 , wherein one of the first resonator or the second resonator is formed on an acoustically decoupled region of a substrate, and the other one of the first resonator and the second resonator is formed on the one of the first resonator or second resonator.

4. The resonator element of claim 1 , further comprising a further tuning circuit coupled to the first and second terminals.

5. The resonator element of claim 1 , wherein a piezoelectric coupling of the first piezoelectric material is lower than a piezoelectric coupling of the second piezoelectric material.

6. The resonator element of claim 1 , wherein the second terminal and third terminal are implemented as a common terminal or are electrically coupled to each other.

7. The resonator element of claim 1 , wherein a piezoelectric electromechanical coupling constant k T 2 of the second piezoelectric material is larger than 10%.

8. The resonator element of claim 1 , wherein the first piezoelectric material comprises at least one of aluminum nitride or scandium-doped aluminum nitride.

9. The resonator element of claim 1 , wherein the second piezoelectric material comprises at least one of lithium niobate, potassium niobate or scandium-doped aluminum nitride.

10. The resonator element of claim 1 , wherein the tuning circuit comprises an impedance network.

11. The resonator element of claim 10 , wherein the impedance network comprises at least one of a variable capacitance, a switch, a switch with a fixed capacitance or a switch in parallel to a fixed capacitance.

12. The resonator element of claim 10 , wherein the impedance network comprises at least one inductor.

13. The resonator element of claim 12 , wherein the at least one inductor has an inductivity below 50 nH.

14. The resonator element of claim 12 , wherein the at least one inductor has a Q-factor of at least 10.

15. A filter device, comprising:
a signal input;
a signal output; and
a resonator element coupled between the signal input and the signal output, wherein the resonator element comprises
a first resonator having a first terminal and a second terminal,
a second resonator having a third terminal and a fourth terminal, wherein the second resonator is acoustically coupled to the first resonator, and
a tuning circuit coupled to the third and fourth terminals,

wherein the first resonator comprises a first piezoelectric material, and the second resonator comprises a second piezoelectric material, and wherein a piezoelectric electromechanical coupling constant k T 2 of the first piezoelectric material is smaller than 10%.

16. The filter device of claim 15 , wherein the first terminal of the first resonator is coupled to the signal input, and the second terminal of the first resonator is coupled to the signal output.

17. The filter device of claim 15 , wherein the first terminal of the first resonator is coupled to the signal input and the signal output, and the second terminal is coupled to ground.

18. A method of providing a resonator element for a filter, the method comprising:
providing a first resonator having a first terminal and a second terminal for coupling to a filter structure;
providing a second resonator having a third terminal and a fourth terminal, wherein the second resonator is acoustically coupled to the first resonator; and
providing a tuning circuit coupled to the third and fourth terminals,
wherein the first resonator comprises a first piezoelectric material, and the second resonator comprises a second piezoelectric material, and wherein a piezoelectric electromechanical coupling constant k T 2 of the first piezoelectric material is set to be smaller than 10%.

19. The method of providing a resonator element of claim 18 , wherein the first resonator and the second resonator are implemented as a resonator stack.

20. The method of providing a resonator element of claim 19 , wherein one of the first resonator or the second resonator is formed on an acoustically decoupled region of a substrate, and the other one of the first resonator and the second resonator is formed on the one of the first resonator or second resonator.

21. The method of providing a resonator element of claim 18 , wherein a piezoelectric coupling of the first piezoelectric material is lower than a piezoelectric coupling of the second piezoelectric material.

22. The method of providing a resonator element of claim 18 , wherein a piezoelectric electromechanical coupling constant k T 2 of the second piezoelectric material is set to be larger than 10%.

23. The method of providing a resonator element of claim 18 , wherein the first piezoelectric material comprises at least one of aluminum nitride or scandium-doped aluminum nitride.

24. The method of providing a resonator element of claim 18 , wherein the second piezoelectric material comprises at least one of lithium niobate, potassium niobate or scandium-doped aluminum nitride.

25. The method of providing a resonator element of claim 18 , wherein the tuning circuit comprises an impedance network.

26. The method of providing a resonator element of claim 25 , wherein the impedance network comprises at least one of a variable capacitance, a switch, a switch with a fixed capacitance or a switch in parallel to a fixed capacitance.

27. The method of providing a resonator element of claim 25 , wherein the impedance network comprises at least one inductor.

28. The method of providing a resonator element of claim 27 , wherein the at least one inductor has an inductivity below 50 nH.

Assignees

• Infineon Technologies Ag

Inventors

• Timme Hans-Joerg
• Bauder Ruediger

Classifications

• H03H9/205

  having multiple resonators (crystal tuning forks H03H9/21) · CPC title

• H03H9/131

  consisting of a multilayered structure · CPC title

• H03H7/12

  Bandpass or bandstop filters with adjustable bandwidth and fixed centre frequency (H03H7/09 takes precedence) · CPC title

• H03H7/0161

  Bandpass filters (H03H7/12 takes precedence) · CPC title

• H03H7/0115 Primary

  comprising only inductors and capacitors (H03H7/075, H03H7/09, H03H7/12, H03H7/13 take precedence) · CPC title