Film acoustically-coupled transformer

• US 20050093655A1
• Filed: 10/13/2004
• Published: 05/05/2005
• 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: Ruby, Richard C., Larson, John D. III, Ellis, Stephen L.
• Granted Patent: US 7,391,285 B2
• Time in Patent Office: Days
• US Class Current: 333/189
• CPC Class Codes: H03H 9/02102 of temperature influence cutting angles H03H9/02015
• CPC Class Codes: H03H 9/132 characterized by a particular shape
• CPC Class Codes: H03H 9/175 Acoustic mirrors
• CPC Class Codes: H03H 9/584 Coupled Resonator Filters [CFR]
• CPC Class Codes: H03H 9/587 Air-gaps
• CPC Class Codes: H03H 9/589 Acoustic mirrors
• CPC Class Codes: H03H 9/605 consisting of a ladder configuration

Abstract

One embodiment of the film acoustically-coupled transformer (FACT) includes a decoupled stacked bulk acoustic resonator (DSBAR) having a lower film bulk acoustic resonator (FBAR) an upper FBAR stacked on the lower FBAR, and, between the FBARs, an acoustic decoupler comprising a layer of acoustic decoupling material. Each FBAR has opposed planar electrodes with a piezoelectric element between them. The FACT additionally has first terminals electrically connected to the electrodes of one FBAR and second terminals electrically connected to the electrodes of the other FBAR. Another embodiment has decoupled stacked bulk acoustic resonators (DSBARs), each as described above, a first electrical circuit interconnecting the lower FBARs, and a second electrical circuit interconnecting the upper FBARs. The FACT provides impedance transformation, can linking single-ended circuitry with balanced circuitry or vice versa and electrically isolates primary and secondary. Some embodiments are additionally electrically balanced.

Claims

1. A film acoustically-coupled transformer (FACT), comprising:

a decoupled stacked bulk acoustic resonator (DSBAR), comprising;

a lower film bulk acoustic resonator (FBAR), an upper FBAR stacked on the lower FBAR, each of the FBARs comprising opposed planar electrodes and a piezoelectric element between the electrodes, and

between the FBARs, an acoustic decoupler comprising a layer of acoustic decoupling material;

first terminals electrically connected to the electrodes of the lower FBAR; and

second terminals electrically connected to the electrodes of the upper FBAR.

2. The FACT of claim 1, in which the acoustic decoupling material is lower in acoustic impedance than the piezoelectric element.

3. The FACT of claim 2, in which the acoustic decoupling material is intermediate in acoustic impedance between the piezoelectric element and air.

4. The FACT of claim 2, in which the acoustic decoupling material has an acoustic impedance in the range from about 2 Mrayl to about 8 Mrayl.

5. The FACT of claim 2, in which the acoustic decoupling material comprises plastic.

6. The FACT of claim 2, in which the acoustic decoupling material comprises polyimide.

7. The FACT of claim 2, in which the acoustic decoupling material comprises poly(para-xylylene).

8. The FACT of claim 2, in which the acoustic decoupling material comprises a crosslinked polyphenylene polymer.

9. The FACT of claim 8, in which the crosslinked polyphenylene polymer is formed from a precursor solution sold by The Dow Chemical Company under the trademark SiLK.

10. The FACT of claim 1, in which:

the FACT has a pass band characterized by a center frequency; and

the layer of acoustic decoupling material has a nominal thickness equal to an odd integral multiple of one quarter of the wavelength in the acoustic decoupling material of an acoustic signal equal in frequency to the center frequency.

11. The FACT of claim 10, in which odd integral multiple is unity.

19. The FACT of claim 11, in which the acoustic decoupling material comprises a crosslinked polyphenylene polymer.

20. The FACT of claim 19, in which the crosslinked polyphenylene polymer is formed from a precursor solution sold by The Dow Chemical Company under the trademark SiLK.

12. A film acoustically-coupled transformer (FACT), comprising:

decoupled stacked bulk acoustic resonators (DSBARs), each of the DSBARs comprising;

a lower film bulk acoustic resonator (FBAR), an upper FBAR stacked on the lower FBAR, each FBAR comprising opposed planar electrodes and a piezoelectric element between the electrodes, and

between the FBARs, an acoustic decoupler comprising a layer of acoustic decoupling material;

a first electrical circuit interconnecting the lower FBARs; and

a second electrical circuit interconnecting the upper FBARs.

13. The FACT of claim 12, in which:

the first electrical circuit interconnects the lower FBARs in one of (a) series and (b) anti-parallel; and

the second electrical circuit interconnects the upper FBARs in one of (c) series and (d) anti-parallel.

14. The FACT of claim 13, in which:

the FACT additionally comprises first terminals and second terminals;

the first electrical circuit additionally connects the lower FBARs to the first terminals; and

the second electrical circuit additionally connects the upper FBARs to the second terminals.

15. The FACT of claim 14, in which:

the first electrical circuit connects the lower FBARs in one of (a) parallel and (b) anti-series; and

the second electrical circuit connects the upper FBARs in one of (c) parallel and (d) anti-series.

16. The FACT of claim 12, in which the acoustic decoupling material comprises plastic.

17. The FACT of claim 12, in which the acoustic decoupling material comprises polyimide.

18. The FACT of claim 12, in which the acoustic decoupling material comprises poly(para-xylylene).

21. A film acoustically-coupled transformer (FACT), comprising:

a decoupled stacked bulk acoustic resonator (DSBAR), comprising;

a lower film bulk acoustic resonator (FBAR), an upper FBAR stacked on the lower FBAR, each of the FBARs comprising opposed planar electrodes and a piezoelectric element between the electrodes, and

between the FBARs, an acoustic decoupler comprising a layer of acoustic decoupling material having an acoustic impedance of about 2 Mrayl;

first terminals electrically connected to the electrodes of the lower FBAR; and

second terminals electrically connected to the electrodes of the upper FBAR.

22. The FACT of claim 21, in which:

the FACT has a pass band characterized by a center frequency; and

the layer of acoustic decoupling material has a nominal thickness equal to an odd integral multiple of one quarter of the wavelength in the acoustic decoupling material of an acoustic signal equal in frequency to the center frequency.

23. The FACT of claim 22, in which the odd integral multiple is unity.

24. The FACT of claim 22, in which:

the DSBAR is a first DSBAR; and

the FACT additionally comprises;

a second DSBAR, comprising;

a lower film bulk acoustic resonator (FBAR), an upper FBAR stacked on the lower FBAR, each of the FBARs comprising opposed planar electrodes and a piezoelectric element between the electrodes; and

between the FBARs, an acoustic decoupler comprising a layer of acoustic decoupling material having an acoustic impedance of about 2 Mrayl,

a first electrical circuit interconnecting the lower FBARs, and

a second electrical circuit interconnecting the upper FBARs.

25. The FACT of claim 24, in which:

the FACT has a pass band characterized by a center frequency; and

the layer of acoustic decoupling material has a nominal thickness equal to an odd integral multiple of one quarter of the wavelength in the acoustic decoupling material of an acoustic signal equal in frequency to the center frequency.

26. The FACT of claim 25, in which the odd integral multiple is unity.