Decoupled stacked bulk acoustic resonator-based band-pass filter

• US 20050140466A1
• Filed: 02/28/2005
• Published: 06/30/2005
• Est. Priority Date: 10/30/2003
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Avago Technologies Wireless IP Singapore Pte Limited (Broadcom, Inc.)
• Inventors: Larson, John D. III, Ellis, Stephen
• Granted Patent: US 7,242,270 B2
• Time in Patent Office: Days
• US Class Current: 333/187
• CPC Class Codes: H03H 9/132 characterized by a particular shape
• CPC Class Codes: H03H 9/584 Coupled Resonator Filters [CFR]
• CPC Class Codes: H03H 9/587 Air-gaps
• CPC Class Codes: H03H 9/605 consisting of a ladder configuration

Abstract

The band-pass filter has first terminals, second terminals, a first decoupled stacked bulk acoustic resonator (DSBAR), a second DSBAR, and an electrical circuit connecting the first DSBAR and the second DSBAR in series between the first terminals and the second terminals. Each DSBAR has a first film bulk acoustic resonator (FBAR), a second FBAR and an acoustic decoupler between the FBARs. Each FBAR has opposed planar electrodes and a piezoelectric element between the electrodes.

Claims

1. A band-pass filter, comprising:

first terminals;

second terminals;

a first decoupled stacked bulk acoustic resonator (DSBAR) and a second DSBAR, each DSBAR comprising a first film bulk acoustic resonator (FBAR), a second FBAR and an acoustic decoupler between the FBARs, each FBAR comprising opposed planar electrodes and a piezoelectric element between the electrodes; and

an electrical circuit connecting the first DSBAR and the second DSBAR in series between the first terminals and the second terminals.

2. The band-pass filter of claim 1, in which:

the electrical circuit is a first electrical circuit;

the band-pass filter additionally comprises;

a third DSBAR and a fourth DSBAR, each DSBAR comprising a first film bulk acoustic resonator (FBAR), a second FBAR and an acoustic decoupler between the FBARs, each FBAR comprising opposed planar electrodes and a piezoelectric element between the electrodes, and

a second electrical circuit configured to connect the third DSBAR and the fourth DSBAR in series between the first terminals and the second terminals; and

one of the first electrical circuit and the second electrical circuit is phase-inverting relative to the other.

3. The band-pass filter of claim 1, in which:

the first DSBAR, the second DSBAR, the first terminals, the second terminals and the electrical circuit constitute a first filter module in which the electrical circuit is a first electrical circuit;

the band-pass filter additionally comprises a second filter module, comprising;

third terminals;

fourth terminals;

a third DSBAR and a fourth DSBAR, each DSBAR comprising a first film bulk acoustic resonator (FBAR), a second FBAR and an acoustic decoupler between the FBARs, each FBAR comprising opposed planar electrodes and a piezoelectric element between the electrodes; and

a second electrical circuit connecting the third DSBAR and the fourth DSBAR in series between the third terminals and the fourth terminals,

a third electrical circuit connecting the first terminals and the third terminals in parallel, and

a fourth electrical circuit connecting the second terminals and the fourth terminals in series, one of the third electrical circuit and the fourth electrical circuit comprising a phase-inverting connection.

4. A band-pass filter, comprising:

first terminals;

second terminals;

a first decoupled stacked bulk acoustic resonator (DSBAR), a second DSBAR, a third DSBAR and a fourth DSBAR, each DSBAR comprising a first film bulk acoustic resonator (FBAR), a second FBAR and an acoustic decoupler between the FBARs, each FBAR comprising a first electrode, a second electrode and a piezoelectric element between the electrodes;

a first electrical circuit connecting the first DSBAR and the second DSBAR in series between the first terminals and the second terminals; and

a second electrical circuit connecting the third DSBAR and the fourth DSBAR in series between the first terminals and the second terminals, one of the first electrical circuit and the second electrical circuit being phase-inverting relative to the other.

5. The band-pass filter of claim 4, in which the first electrical circuit comprises a phase-inverting connection.

6. The band-pass filter of claim 4, in which the second electrical circuit comprises a phase-inverting connection.

7. The band-pass filter of claim 4, in which:

the first electrical circuit and the second electrical circuit collectively comprise phase-inverting connections; and

the phase-inverting connections differ in number by an odd number between the first electrical circuit and the second electrical circuit.

8. The band-pass filter of claim 4, in which one of the first electrical circuit and the second electrical circuit comprises an electrical connection between electrodes on opposite sides of a common piezoelectric layer.

9. The band-pass filter of claim 4, in which:

the piezoelectric elements are each characterized by a c-axis direction; and

at least one the piezoelectric elements has a c-axis direction opposite the c-axis directions of the remaining piezoelectric elements to provide the phase inversion.

10. The band-pass filter of claim 4, in which:

the first electrical circuit connects one of the first terminals to an electrode on a first side of a piezoelectric layer and connects another of the first terminals to an electrode on a second side of the piezoelectric layer, the second side opposite the first side; and

the second electrical circuit connects the one of the first terminals to an electrode on the second side of the piezoelectric layer and additionally connects the other of the first terminals to an electrode on the first side of the piezoelectric layer.

11. The band-pass filter of claim 4, in which the acoustic decouplers comprise a layer of acoustic decoupling material.

12. The band-pass filter of claim 11, in which the acoustic decoupling material comprises polyimide.

13. The band-pass filter of claim 11, in which the acoustic decoupling material comprises a crosslinked polyphenylene polymer.

14. A band-pass filter, comprising:

first terminals;

second terminals

a first filter module and a second filter module, each filter module comprising;

third terminals,

fourth terminals, and

a first decoupled stacked bulk acoustic resonator (DSBAR) and a second DSBAR electrically connected in series between the third terminals and the fourth terminals;

a first electrical circuit connecting the third terminals of the first filter module and the third terminals of the second filter module in parallel with the first terminals; and

a second electrical circuit connecting the fourth terminals of the first filter module and the fourth terminals of the second filter module in series with the second terminals, one of the electrical circuits comprising a phase-inverting connection.

15. The band-pass filter of claim 14, in which the first electrical circuit comprises the phase-inverting connection.

16. The band-pass filter of claim 14, in which the second electrical circuit comprises the phase-inverting connection.

17. The band-pass filter of claim 14, in which:

each of the DSBARs comprises a first FBAR, a second FBAR stacked on the first FBAR, and an acoustic decoupler between the FBARs;

each of the FBARs comprises opposed planar electrodes and a piezoelectric element between the electrodes; and

the piezoelectric elements of the first FBARs are portions of a common piezoelectric layer.

18. The band-pass filter of claim 17, in which:

the first electrical circuit connects each of the first terminals to ones of the third terminals connected to electrodes located on opposite sides of the piezoelectric layer; and

the second electrical circuit connects each of the second terminals to ones of the fourth terminals connected to electrodes on the same side of the piezoelectric layer.

19. The band-pass filter of claim 17, in which:

the first electrical circuit connects each of the first terminals to ones of the third terminals connected to electrodes located on the same side of the piezoelectric layer; and

the second electrical circuit connects each of the second terminals to ones of the fourth terminals connected to electrodes on opposite sides of the piezoelectric layer.

20. The band-pass filter of claim 17, in which the acoustic decoupler comprises a layer of acoustic decoupling material.