Acoustic galvanic isolator incorporating series-connected decoupled stacked bulk acoustic resonators

• US 20070086080A1
• Filed: 10/18/2005
• Published: 04/19/2007
• Est. Priority Date: 10/18/2005
• 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: Hardcastle, Ian, Larson, John
• Granted Patent: US 7,737,807 B2
• Time in Patent Office: Days
• US Class Current: 359/341.330
• 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 9/60 Electric coupling means therefor H03H9/0095 takes precedence

Abstract

Embodiments of the acoustic galvanic isolator comprise a carrier signal source, a modulator connected to receive an information signal and the carrier signal, a demodulator, and an electrically-isolating acoustic coupler connected between the modulator and the demodulator. The electrically-isolating acoustic coupler comprises series-connected decoupled stacked bulk acoustic resonators (DSBARs).

Claims

1. A galvanic isolator, comprising:

a carrier signal source;

a modulator connected to receive an information signal and the carrier signal;

a demodulator; and

connected between the modulator and the demodulator, an electrically-isolating acoustic coupler comprising series-connected decoupled stacked bulk acoustic resonators (DSBARs).

2. The galvanic isolator of claim 1, in which the acoustic coupler comprises:

a first decoupled stacked bulk acoustic resonator (DSBAR) and a second DSBAR, each of the DSBARs comprising a first film bulk acoustic resonator (FBAR), a second FBAR and an acoustic decoupler between the first FBAR and the second FBAR; and

an electrical circuit connecting the DSBARs in series.

3. The galvanic isolator of claim 2, in which the electrical circuit additionally connects the first FBAR of the first DSBAR to the modulator and the first FBAR of the second DSBAR to the demodulator.

4. The galvanic isolator of claim 3, in which the electrical circuit connects the second FBARs of the DSBARs in parallel to connect the DSBARs in series.

5. The galvanic isolator of claim 4, in which:

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

the electrical circuit comprises;

a first electrical connection between a first one of the electrodes of the second FBAR of the first DSBAR and a first one of the electrodes of the second FBAR of the second DSBAR, and

a second electrical connection between a second one of the electrodes of the second FBAR of the first DSBAR and a second one of the electrodes of the second FBAR of the second DSBAR, the second ones of the electrodes being closer to the acoustic decouplers of the DSBARs than the first ones of the electrodes.

6. The galvanic isolator of claim 3, in which the electrical circuit connects the second FBARs of the DSBARs in anti-parallel to connect the DSBARs in series.

7. The galvanic isolator of claim 6, in which:

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

the electrical circuit comprises;

a first electrical connection between a first one of the electrodes of the second FBAR of the first DSBAR and a second one of the electrodes of the second FBAR of the second DSBAR, and

a second electrical connection between a second one of the electrodes of the second FBAR of the first DSBAR and a first one of the electrodes of the second FBAR of the second DSBAR, the second ones of the electrodes being closer to the acoustic decouplers of the DSBARs than the first ones of the electrodes.

8. The galvanic isolator of claim 2, in which each of the DSBARs additionally comprises an acoustically-resonant electrical insulator.

9. The galvanic isolator of claim 8, in which the acoustically-resonant electrical insulator comprises a layer of electrically-insulating material differing in acoustic impedance from the FBARs by less than one order of magnitude.

10. The galvanic isolator of claim 8, in which the acoustically-resonant electrical insulator comprises a layer of electrically-insulating material matched in acoustic impedance with the FBARs.

11. The galvanic isolator of claim 8, in which:

each of the DSBARs additionally comprises an additional acoustic decoupler between the FBARs; and

the acoustically-resonant electrical insulator comprises a quarter-wave layer of electrically-insulating material located between the acoustic decoupler and the additional acoustic decoupler.

12. The galvanic isolator of claim 8, in which each of the DSBARs additionally comprises a half-wave acoustically-resonant electrical insulator interposed between the acoustic decoupler and each the FBARs.

13. The galvanic isolator of claim 8, in which:

the acoustically-resonant electrical insulator is a first half-wave acoustically-resonant electrical insulator;

the each of the DSBARs additionally comprises a second half-wave acoustically-resonant electrical insulator; and

the acoustic decoupler is located between the first half-wave acoustically-resonant electrical insulator and the second half-wave acoustically-resonant electrical insulator.

14. The galvanic isolator of claim 13, in which the half-wave acoustically-resonant electrical insulator comprises a half-wave layer of electrically-insulating material.

15. A method for galvanically isolating an information signal, the method comprising:

providing an electrically-isolating acoustic coupler comprising series-connected decoupled stacked bulk acoustic resonators;

providing a carrier signal;

modulating the carrier signal with the information signal to form a modulated electrical signal;

acoustically coupling the modulated electrical signal through the electrically-insulating acoustic coupler; and

recovering the information signal from the modulated electrical signal acoustically coupled through the electrically-isolating acoustic coupler.

16. The method of claim 15, in which the electrically-isolating acoustic coupler comprises a first decoupled stacked bulk acoustic resonator (DSBAR) and a second DSBAR, each of the DSBARs comprising a first film bulk acoustic resonator (FBAR), a second FBAR and an acoustic decoupler between the FBARs.

17. The method of claim 16, in which the coupling comprises:

applying the modulated electrical signal to the first FBAR of the first DSBAR, and

receiving the modulated electrical signal from the first FBAR of the second DSBAR.

18. The method of claim 17, in which the coupling comprises:

converting the modulated electrical signal to an acoustic signal;

transmitting the acoustic signal through an electrical insulator; and

converting the acoustic signal back to a modulated electrical signal.

19. The method of claim 16, in which each of the DSBARs additionally comprises a an acoustically-resonant electrical insulator between the FBARs.

20. The method of claim 16, in which the second FBARs of the DSBARs are electrically connected in anti-parallel to connect the DSBARs in series.