Coupled resonator bulk acoustic wave filter

• US 6,720,844 B1
• Filed: 11/16/2001
• Issued: 04/13/2004
• Est. Priority Date: 11/16/2001
• Status: Expired due to Term

• Current Assignee: Qorvo US, Inc. (Qorvo, Inc.)
• Original Assignee: Qorvo Oregon, Inc. (Qorvo, Inc.)
• Inventors: Lakin, Kenneth Meade
• Primary Examiner(s): Summons, Barbara
• Application Number:
  US09/990,923
• Time in Patent Office: 879 Days
• Field of Search: 333/186-192, 333/133, 310/323, 310/328, 310/334, 310/335
• US Class Current: 333/189
• CPC Class Codes: H03H 9/0095 using bulk acoustic wave devices
• CPC Class Codes: H03H 9/583 comprising a plurality of piezoelectric layers acoustically coupled
• CPC Class Codes: H03H 9/584 Coupled Resonator Filters [CFR]
• CPC Class Codes: H03H 9/589 Acoustic mirrors

Abstract

A microwave filter made of acoustically coupled, bulk wave acoustic resonators. The resonators utilize piezoelectric materials sandwiched between conducting electrodes. Layers of material that intervene between the resonators control the amount of acoustic coupling between the resonators and the amount of coupling is selected to obtain desired filter characteristics. The resonators and the intervening layers may be supported upon a substrate by means of a series of layers of material that function as an acoustic mirror or reflector.

Claims

1. A microwave filter comprising:

a first piezoelectric acoustic, bulk wave, resonator having a piezoelectric layer made of an insulating material;

a second piezoelectric acoustic, bulk wave, resonator having a piezoelectric layer made of an insulating material, the second acoustic resonator being acoustically coupled to the first acoustic resonator and disposed above or below the first acoustic resonator; and

a plurality of contiguous intervening layers of differing materials located between the first acoustic resonator and the second acoustic resonator, the contiguous intervening layers acoustically coupling the first acoustic resonator with the second acoustic resonator.

2. The microwave filter of claim 1 wherein the first acoustic resonator and the second acoustic resonator are acoustically either approximately critically coupled or over-coupled.

3. The microwave filter of claim 2 having a signal input port and a signal output port, the first acoustic resonator being electrically connected to the signal input port and the second acoustic resonator being electrically connected to the signal output port.

4. The microwave filter of claim 1 and further comprising:

a substrate;

an acoustic reflector; and

the first and second acoustic resonators and the plurality of intervening layers being supported upon the substrate by the acoustic reflector.

5. A microwave filter comprising:

a first piezoelectric acoustic, bulk wave, resonator;

a second piezoelectric acoustic, bulk wave, resonator acoustically coupled to the first acoustic resonator and disposed above or below the first acoustic resonator;

a third piezoelectric acoustic, bulk wave, resonator electrically connected to the second acoustic resonator;

a fourth piezoelectric acoustic, bulk wave, resonator acoustically coupled to the third acoustic resonator and disposed above or below the third acoustic resonator;

a first plurality of contiguous intervening layers of differing materials located between the first acoustic resonator and the second acoustic resonator and affecting the amount of the acoustic coupling between the first and second acoustic resonators; and

a second plurality of intervening layers of material located between the third acoustic resonator and the fourth acoustic resonator and affecting the amount of the acoustic coupling between the third and fourth acoustic resonators.

6. The microwave filter of claim 5 and further comprising:

a substrate;

an acoustic reflector; and

the first, second, third and fourth acoustic resonators and the first and second plurality of intervening layers being supported upon the substrate by the acoustic reflector.

7. The microwave device of claim 5 in which the first, second, third and fourth acoustic resonators each has a piezoelectric layer made of an insulating material.

8. The microwave device of claim 5 having a signal input port and a signal output port, the first acoustic resonator being connected to the signal input port and the fourth acoustic resonator being connected to the signal output port.

9. The microwave device of claim 5 in which at least two of the acoustic resonators include piezoelectric layers of material and electrodes, each of said resonators having a resonant frequency, at least one electrode of the first one of said at least two acoustic resonators having a thickness that differs from the thickness of at least one of the electrodes in the second resonator of said at least two acoustic resonators thereby offsetting the resonant frequency of the first one of said at least two acoustic resonators from the resonant frequency of the second one of said at least two acoustic resonators.

10. A microwave filter having a signal input port and a signal output port and comprising:

a first acoustic, bulk wave, resonator that includes a piezoelectric layer of insulating material, the first acoustic resonator being electrically connected to the signal input port;

a second acoustic, bulk wave, resonator acoustically coupled to the first resonator and disposed above or below the first acoustic resonator;

a third acoustic, bulk wave, resonator that includes a piezoelectric layer of insulating material and that is acoustically coupled to the second resonator and disposed above or below the second acoustic resonator, the third acoustic resonator being electrically connected to the signal output port and the second acoustic resonator being located between the first and third acoustic resonators;

a first plurality of contiguous intervening layers of differing materials located between the first acoustic resonator and the second acoustic resonator, the first plurality of contiguous intervening layers acoustically coupling the first acoustic resonator with the second acoustic resonator;

a second plurality of contiguous intervening layers of differing materials located between the second and third acoustic resonators, the second plurality of contiguous intervening layers acoustically coupling the second acoustic resonator with the third acoustic resonator.

11. The microwave filter of claim 10 in which the second acoustic resonator includes a piezoelectric layer of material and bounding electrodes and in which the second acoustic resonator is electrically connected to an external load.

12. The microwave filter of claim 10 and further comprising:

a substrate;

an acoustic reflector; and

the first, second and third acoustic resonators and the first and second plurality of intervening layers being supported upon the substrate by the acoustic reflector.

13. A microwave filter comprising:

a first piezoelectric acoustic, bulk wave, resonator;

a second piezoelectric acoustic, bulk wave, resonator, the second acoustic resonator being acoustically coupled to the first acoustic resonator and disposed above or below the first acoustic resonator; and

a plurality of contiguous intervening layers of differing materials located between the first acoustic resonator and the second acoustic resonator, the contiguous intervening layers acoustically coupling the first acoustic resonator with the second acoustic resonator and the first acoustic resonator and the second acoustic resonator being acoustically either approximately critically coupled or over-coupled.

14. The microwave filter of claim 13 having a signal input port and a signal output port, the first acoustic resonator being electrically connected to the signal input port and the second acoustic resonator being electrically connected to the signal output port.

15. The microwave filter of claim 13 and further comprising:

a substrate;

an acoustic reflector; and

the first and second acoustic resonators and the plurality of intervening layers being supported upon the substrate by the acoustic reflector.

16. An microwave acoustic device fabricated upon a wafer comprising:

a first microwave filter fabricated upon the wafer and having a pass-band frequency and the first microwave filter comprising;

a first piezoelectric acoustic, bulk wave, resonator having a conducting electrode;

a second piezoelectric acoustic, bulk wave, resonator, the second acoustic resonator being acoustically coupled to the first acoustic resonator and disposed above or below the first acoustic resonator; and

a plurality of contiguous intervening layers of differing materials located between the first acoustic resonator and the second acoustic resonator and affecting the amount of the acoustic coupling between the first and second acoustic resonators;

and a second microwave filter fabricated upon the wafer and having a pass-band frequency and the second microwave filter comprising;

a first piezoelectric acoustic, bulk wave, resonator having a conducting electrode;

a second piezoelectric acoustic, bulk wave, resonator, the second acoustic resonator being acoustically coupled to the first acoustic resonator and disposed above or below the first acoustic resonator; and

a plurality of contiguous intervening layers of differing materials located between the first acoustic resonator and the second acoustic resonator and affecting the amount of the acoustic coupling between the first and second acoustic resonators;

wherein the thickness of the conducting electrode in the first piezoelectric resonator of the first microwave filter differs from the thickness of the conducting electrode in the first piezoelectric resonator of the second microwave filter, whereby said difference in thicknesses causes the pass-band frequency of the first microwave filter to be shifted relative to the pass-band frequency of the second microwave filter.