SINGLE STACK COUPLED RESONATORS HAVING DIFFERENTIAL OUTPUT

• US 20090086654A1
• Filed: 09/28/2007
• Published: 04/02/2009
• Est. Priority Date: 09/28/2007
• 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: Jamneala, Tiberiu
• Granted Patent: US 7,791,435 B2
• Time in Patent Office: Days
• US Class Current: 370/284
• 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 9/60 Electric coupling means therefor H03H9/0095 takes precedence

Abstract

An acoustic resonator and a communication device with an acoustic resonator are described.

Claims

1. A coupled acoustic resonator adapted for single-ended to differential signal transformation, comprising a single stack, which comprises:

a first film bulk acoustic resonator (FBAR) comprising a single-ended output;

a second FBAR disposed over the first FBAR comprising a first differential output and a second differential output;

an acoustic decoupling layer disposed between the first FBAR and the second FBAR; and

a resonant element connected to the first differential output and operative to balance substantially a signal from the first differential output with a signal from the second differential output.

2. A coupled acoustic resonator as claimed in claim 1, wherein the resonant element comprises an inductor, which is connected between the first differential output and a ground.

3. A coupled acoustic resonator as claimed in claim 1, wherein the decoupling layer, an upper electrode of the first FBAR and a lower electrode of the second FBAR form a parasitic capacitor.

4. A coupled acoustic resonator as claimed in claim 3, wherein the resonant element comprises a resonant inductor and the parasitic capacitor connected in parallel.

5. A coupled acoustic resonator as claimed in claim 1, wherein the resonant element has a passband selected to match substantially a passband of the resonator.

6. A coupled acoustic resonator as claimed in claim 4, wherein:

the first differential output is connected to an external circuit comprising a parasitic impedance; and

the resonant inductor has an inductance selected to substantially maintain the balance.

7. A coupled resonator circuit as claimed in claim 1, wherein:

the second differential output is connected to an external circuit comprising a parasitic impedance; and

the resonant inductor has an inductance selected to substantially maintain the balance.

8. A coupled acoustic resonator as claimed in claim 6, wherein the parasitic impedance is a parasitic inductor, and the parasitic inductor is connected in parallel with a tank circuit comprising the parasitic capacitor and the resonant inductor.

9. A coupled acoustic resonator as claimed in claim 7, wherein the parasitic impedance is a parasitic inductor, and the parasitic inductor is connected in parallel with a tank circuit comprising the parasitic capacitor and the resonant inductor.

10. A coupled acoustic resonator as claimed in claim 1, wherein the coupled acoustic resonator is a coupled resonator filter (CRF).

11. A coupled acoustic resonator as claimed in claim 1, wherein an S parameter of the signal of the first differential output and an S parameter of the signal of the second differential output have a differential of less than approximately 1.0 dB to approximately 0.3 dB.

12. A communication device, comprising:

a transmitter;

a receiver; and

a single stack coupled resonator filter (CRF), adapted for single-ended to differential signal transformation, which comprises;

a first film bulk acoustic resonator (FBAR) comprising a single-ended output;

a second FBAR disposed over the first FBAR comprising a first differential output and a second differential output;

an acoustic decoupling layer disposed between the first FBAR and the second FBAR; and

a resonant element connected to the first differential output and operative to balance substantially a signal from the first differential output with a signal from the second differential output.

13. A communications device as claimed in claim 12, wherein the resonant element comprises an inductor, which is connected between the first differential output and a ground.

14. A communications device as claimed in claim 12, wherein the decoupling layer, an upper electrode of the first FBAR and a lower electrode of the second FBAR form a parasitic capacitor.

15. A communications device as claimed in claim 14, wherein the resonant element comprises a resonant inductor and the parasitic capacitor connected in parallel.

16. A coupled resonator circuit as claimed in claim 15, wherein:

the first differential output is connected to an external circuit comprising a parasitic impedance; and

the resonant inductor has an inductance selected to substantially maintain the balance.

17. A communications device as claimed in claim 15, wherein:

the second differential output is connected to an external circuit comprising a parasitic impedance; and

the and the resonant inductor has an inductance selected to substantially maintain the balance.

18. A communications device as claimed in claim 12, wherein an S parameter of the signal of the first differential output and an S parameter of the signal of the second differential output have a differential of less than approximately 1.0 dB to approximately 0.3 dB.

19. An electronic device, comprising:

a single stack coupled resonator filter (CRF), adapted for single-ended to differential signal transformation, which comprises;

a first film bulk acoustic resonator (FBAR) comprising a single-ended output;

a second FBAR disposed over the first FBAR comprising a first differential output and a second differential output;

an acoustic decoupling layer disposed between the first FBAR and the second FBAR; and

a resonant element connected to the first differential output and operative to balance substantially a signal from the first differential output with a signal from the second differential output.

20. An electronic device as claimed in claim 19, wherein the electronic device is one of an oscillator circuit;

a mixer;

or a transformer.