Impedance transformation ratio control in film acoustically-coupled transformers

• US 7,173,504 B2
• Filed: 10/13/2004
• Issued: 02/06/2007
• 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 L., Sarkeshik, Naghmeh
• Primary Examiner(s): Summons; Barbara
• Application Number:
  US10/965,474
• Publication Number:
  US 20050128030A1
• Time in Patent Office: 846 Days
• Field of Search: 333187-189, 333/133
• US Class Current: 333/189
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/49175 Parallel arrangements
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• 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
• CPC Class Codes: Y10T 29/42 Piezoelectric device making

Abstract

The film acoustically-coupled transformer (FACT) has decoupled stacked bulk acoustic resonators (DSBARs), a first electrical circuit and a second electrical circuit. Each of the DSBARs has a lower film bulk acoustic resonator (FBAR), an upper FBAR and an acoustic decoupler. The upper FBAR is stacked on the lower FBAR and the acoustic decoupler is located between the FBARs. Each FBAR has opposed planar electrodes and a piezoelectric element between the electrodes. The first electrical circuit interconnects the lower FBARs. The second electrical circuit interconnects the upper FBARs. The FBARs of one of the DSBARs differ in electrical impedance from the FBARs of another of the DSBARs. The FACT has an impedance transformation ratio greater than 1:m², where m is the number of DSBARs. The actual impedance transformation ratio depends on the ratio of the impedances of the FBARs.

Claims

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

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

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

a first electrical circuit interconnecting the lower FBARs; and

a second electrical circuit interconnecting the upper FBARs;

in which;

the FBARs of one of the DSBARs differ in impedance from the FBARs of another of the DSBARs.

2. The FACT of claim 1, in which the electrodes of the FBARs of the one of the DSBARS differ in area from the electrodes of the FBARs of the other of the DSBARS.

3. The FACT of claim 1, in which the piezoelectric elements of the FBARs of the one of the DSBARs differ in thickness from the piezoelectric elements of the FBARs of the other of the DSBARS.

4. The FACT of claim 1, in which the piezo electric elements of the FBARs of the one of the DSBARs differ in dielectric constant from the piezoelectric elements of the FBARs of the other of the DSBARs.

5. The FACT of claim 1, in which:

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

the second electrical circuit connects the upper FBARs in the other of (a) series and (b) anti-parallel.

6. The FACT of claim 1, in which the DSBARS are more than two in number.

7. The FACT of claim 1, in which:

the FACT has a pass band having a center frequency, and each of the acoustic decouplers comprises a layer of acoustic decoupling material having a nominal thickness equal to one quarter of the wavelength in the acoustic decoupling material of an acoustic signal equal in frequency to the center frequency.

8. The FACT of claim 7, in which the acoustic decoupling material comprises one of polyimide, paralene and a crosslinked polyphenylene polymer.

9. The FACT of claim 1, in which:

the FACT has a pass band having a center frequency; and

each of the acoustic decouplers comprises layers of different acoustic decoupling materials and is structured to impose a nominal phase change of π

/2 on an acoustic signal equal in frequency to the center frequency.

10. The FACT of claim 1, in which:

the DSBARs are more than two in number and one of the electrical circuits provides series and parallel connections among the respective one of the lower FBARs and the upper FBARs.

11. The FACT of claim 1, in which the FACT has an impedance transformation ratio of (1+r)²/r, where r is the ratio between the impedance of the FBARs of the one of the DSBARs and the impedance of the FBARs of the other of the DSBARs.

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

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

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

a first electrical circuit interconnecting the first FBARs of the DSBARs; and

a second electrical circuit interconnecting the second FBARs of the DSBARS.

13. The FACT of claim 12, in which the first electrical circuit provides series and parallel connections among the first FBARs.

14. The FACT of claim 13, in which:

the DSBARs comprise a first DSBAR, a second DSBAR and a third DSBAR; and

the first electrical circuit connects the first FBAR of the first DSBAR and the first FBAR of the second DSBAR in series to form a series combination and connects the first FBAR of the third DSBAR in parallel with the series combination.

15. The FACT of claim 14, in which:

the DSBARs additionally comprise a fourth DSBAR and the first electrical circuit additionally connects the first FBAR of the fourth DSBAR in parallel with the first FBAR of the third DSBAR and the series combination.

16. The FACT of claim 14, in which:

the DSBARS additionally comprise a fourth DSBAR; and

the first electrical circuit additionally connects the first FBAR of the fourth DSBAR in series with the first FBAR of the first DSBAR and the first FBAR of the second DSBAR to form the series combination.

17. The FACT of claim 14, in which:

the DSBARs additionally comprise a fourth DSBAR and the first electrical circuit additionally connects the first FBAR of the fourth DSBAR in series with the first FBAR of the third DSBAR connected in parallel with the series combination.

18. The FACT of claim 13, in which:

the DSBARs comprise a first DSBAR, a second DSBAR and a third DSBAR and the first electrical circuit connects the first FBAR of the first DSBAR and the first FBAR of the second DSBAR in parallel to form a parallel combination and connects the first FBAR of the third DSBAR in series with the parallel combination.

19. The FACT of claim 18, in which:

the DSBARs additionally comprise a fourth DSBAR and the first electrical circuit additionally connects the first FBAR of the fourth DSBAR in parallel with the first FBAR of the first DSBAR and the first FBAR of the second DSBAR to form the parallel combination.

20. The FACT of claim 18, in which:

the DSBARs additionally comprise a fourth DSBAR and the first electrical circuit additionally connects the first FBAR of the fourth DSBAR in series with the first FBAR of the third DSBAR and the parallel combination.

21. The FACT of claim 12, in which:

the first electrical circuit interconnects the first FBARs in a first circuit arrangement; and

the second electrical circuit interconnects the second FBARs in a second circuit arrangement different from the first circuit arrangement.

22. The FACT of claim 12, in which the first electrical circuit connects the first FBARS of all the DSBARs in parallel.

23. The FACT of claim 12, in which the first electrical circuit connects the first FBARS of all the DSBARS in series.

24. The FACT of claim 12, in which the FBARs of one of the DSBARS differ in impedance from the FBARs of another of the DSBARs.

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

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

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

a first electrical circuit interconnecting the first FBARs; and

a second electrical circuit interconnecting the second FBARs;

in which;

the FACT has an impedance transformation ratio that differs from 1;

1 and 1;

m², where m is the number of the DSBARS.

26. The FACT of claim 25, in which the FBARs of one of the DSBARs differ in impedance from the FBARs of another of the DSBARS.

27. The FACT of claim 25, in which:

the DSBARS number more than two;

the first electrical circuit interconnects the first FBARs in a first circuit arrangement comprising series and parallel connections among the first FBARs; and

the second electrical circuit interconnects the second FBARs in a second circuit arrangement, different from the first circuit arrangement.