Acoustic galvanic isolator incorporating single decoupled stacked bulk acoustic resonator

• US 7,675,390 B2
• Filed: 10/18/2005
• Issued: 03/09/2010
• 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: Larson, John D III
• Primary Examiner(s): Summons; Barbara
• Application Number:
  US11/253,851
• Publication Number:
  US 20070090892A1
• Time in Patent Office: 1,603 Days
• Field of Search: 333/187, 333/189, 310/311, 310/320, 310/324, 310/326, 310/327
• US Class Current: 333/189
• CPC Class Codes: H03H 9/584 Coupled Resonator Filters [CFR]
• CPC Class Codes: H03H 9/587 Air-gaps

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 acoustic coupler comprises no more than one decoupled stacked bulk acoustic resonator (DSBAR). An electrically-isolating acoustic coupler based on a single DSBAR is physically small and is inexpensive to fabricate yet is capable of passing information signals having data rates in excess of 100 Mbit/s and has a substantial breakdown voltage between its inputs and its outputs.

Claims

1. An acoustic 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 exactly one decoupled stacked bulk acoustic resonator (DSBAR),

wherein the DSBAR comprises a first film bulk acoustic resonator (FBAR), a second FBAR, and an electrically-insulating acoustic decoupler between the FBARs, and

wherein the electrically-insulating acoustic decoupler comprises at least one of;

(1) an electrically-insulating acoustic Bragg structure;

(2) a quarter-wave thick layer of acoustic coupling material; and

(3) at least one layer of crosslinked polyphenylene polymer.

2. The acoustic galvanic isolator of claim 1, additionally comprising:

a first electrical circuit electrically connecting the modulator to the first FBAR; and

a second electrical circuit electrically connecting the demodulator to the second FBAR.

3. The acoustic galvanic isolator of claim 2, in which:

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

the first electrical circuit electrically connects the modulator to the electrodes of the first FBAR; and

the second electrical circuit electrically connects demodulator to the electrodes of the second FBAR.

4. The acoustic galvanic isolator of claim 1, wherein the electrically-insulating acoustic decoupled comprises the electrically-insulating acoustic Bragg structure, and wherein the electrically-insulating acoustic Bragg structure comprises first, second, and third Bragg elements, the second Bragg element being disposed in between the first and third Bragg elements and having a lower acoustic impedance than the first and third Bragg elements, respectively, at least one of the Bragg elements comprising a layer of electrically-insulating material.

5. The acoustic galvanic isolator of claim 4, wherein the first Bragg element is a quarter-wave thick layer of a same material as an electrode of the first FBAR, and the third Bragg element is a quarter-wave thick layer of a same material as an electrode of the second FBAR.

6. The acoustic galvanic isolator of claim 1, wherein the electrically-insulating acoustic decoupler comprises the electrically-insulating acoustic Bragg structure, and wherein the electrically-insulating acoustic Bragg structure comprises one or more layers of crosslinked polyphenylene polymer interleaved with layers of silicon dioxide.

7. The acoustic galvanic isolator of claim 1, wherein the electrically-insulating acoustic decoupler comprises the quarter-wave thick layer of acoustic coupling material.

8. The acoustic galvanic isolator of claim 1, wherein the electrically-insulating acoustic decoupler comprises the at least one layer of crosslinked polyphenylene polymer.

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

providing an electrically-isolating acoustic coupler comprising exactly one decoupled stacked bulk acoustic resonator (DSBAR), the DSBAR comprising a first film bulk acoustic resonator (FBAR), a second FBAR, and an electrically-insulating acoustic decoupler between the FBARs, wherein the electrically-insulating acoustic decoupler comprises at least one of;

(1) an electrically-insulating acoustic Bragg structure;

(2) a quarter-wave thick layer of acoustic coupling material; and

(3) at least one layer of crosslinked polyphenylene polymer;

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-isolating acoustic coupler; and

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

10. The method of claim 9, in which the recovering comprises performing clock and data recovery on the modulated electrical signal acoustically coupled through the electrically-isolating acoustic coupler.

11. The method of claim 9, wherein the electrically-insulating acoustic decoupler comprises the electrically-insulating acoustic Bragg structure, and wherein the electrically-insulating acoustic Bragg structure comprises first, second, and third Bragg elements, the second Bragg element being disposed in between the first and third Bragg elements and having a lower acoustic impedance than the first and third Bragg elements, respectively, at least one of the Bragg elements comprising a layer of electrically-insulating material.

12. The method of claim 11, wherein the first Bragg element is a quarter-wave thick layer of a same material as an electrode of the first FBAR, and the third Bragg element is a quarter-wave thick layer of a same material as an electrode of the second FBAR.

13. The method of claim 9, wherein the electrically-insulating acoustic decoupler comprises the quarter-wave thick layer of acoustic coupling material.

14. The method of claim 9, wherein the electrically-insulating acoustic decoupler comprises the at least one layer of crosslinked polyphenylene polymer.

15. An acoustic galvanic isolator, comprising:

a semiconductor substrate having an insulating layer formed on a top surface thereof;

a carrier signal source disposed on the substrate;

a modulator disposed on the substrate and connected to receive an information signal and the carrier signal and to modulate the information signal onto the carrier signal to produce a modulated signal;

a demodulator disposed on the substrate; and

an electrically-isolating acoustic coupler disposed on the substrate and connected between the modulator and the demodulator, the electrically-isolating acoustic coupler comprising exactly one decoupled stacked bulk acoustic resonator (DSBAR),

wherein the demodulator is adapted to receive the modulated signal from the electrically-isolating acoustic coupler and in response thereto outputs the information signal.

16. The acoustic galvanic isolator of claim 15, wherein the DSBAR comprises a first film bulk acoustic resonator (FBAR), a second FBAR, and an electrically-insulating acoustic decoupler between the FBARs the electrically-insulating acoustic decoupler comprises at least one of:

(1) an electrically-insulating acoustic Bragg structure;

(2) a quarter-wave thick layer of acoustic coupling material; and

(3) at least one layer of crosslinked polyphenylene polymer.

17. The acoustic galvanic isolator of claim 16, wherein the electrically-insulating acoustic decoupler comprises the quarter-wave thick layer of acoustic coupling material.

18. The acoustic galvanic isolator of claim 16, wherein the electrically-insulating acoustic decoupler comprises the at least one layer of crosslinked polyphenylene polymer.

19. The acoustic galvanic isolator of claim 16, wherein the electrically-insulating acoustic decoupler comprises the electrically-insulating acoustic Bragg structure, and wherein the electrically-insulating acoustic Bragg structure comprises first, second, and third Bragg elements, the second Bragg element being disposed in between the first and third Bragg elements and having a lower acoustic impedance than the first and third Bragg elements, respectively, at least one of the Bragg elements comprising a layer of electrically-insulating material.

20. The acoustic galvanic isolator of claim 19, wherein the first Bragg element is a quarter-wave thick layer of a same material as an electrode of the first FBAR, and the third Bragg element is a quarter-wave thick layer of a same material as an electrode of the second FBAR.