Single stack coupled resonators having differential output

• US 7,791,435 B2
• Filed: 09/28/2007
• Issued: 09/07/2010
• 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
• Primary Examiner(s): Summons; Barbara
• Application Number:
  US11/863,720
• Publication Number:
  US 20090086654A1
• Time in Patent Office: 1,075 Days
• Field of Search: 333/133, 333/189
• US Class Current: 333/189
• 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

A coupled acoustic resonator adapted for single-ended input to differential output signal transformation, comprises a single stack. The single stack comprises: a first film bulk acoustic resonator (FBAR) comprising a single-ended input; 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 comprising a resonant inductor and a parasitic capacitor connected in parallel. The resonant element is connected to the first differential output and is operative to substantially balance a signal from the first differential output with a signal from the second differential output. 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.

Claims

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

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

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 comprising a resonant inductor and a parasitic capacitor connected in parallel, the resonant element being connected to the first differential output and operative to substantially balance a signal from the first differential output with a signal from the second differential output, 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.

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

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

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

5. A coupled acoustic resonator as claimed in claim 1, wherein the parasitic impedance comprises a parasitic inductor, and the parasitic inductor is connected in series with a tank circuit comprising the parasitic capacitor and the resonant inductor.

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

7. A communication device, comprising:

a transmitter;

a receiver; and

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

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

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 comprising a resonant inductor and a parasitic capacitor connected in parallel, the resonant element being connected to the first differential output and operative to substantially balance a signal from the first differential output with a signal from the second differential output, 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.

8. A communication device as claimed in claim 7, wherein the parasitic impedance comprises a parasitic inductor, and the parasitic inductor is connected in series with a tank circuit comprising the parasitic capacitor and the resonant inductor.

9. A communications device as claimed in claim 7, wherein the resonant inductor is connected between the first differential output and a ground.

10. A communications device as claimed in claim 7, wherein the parasitic capacitor comprises the acoustic decoupling layer, an upper electrode of the first FBAR and a lower electrode of the second FBAR form a parasitic capacitor.

11. A communications device as claimed in claim 7, 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. An electronic device, comprising:

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

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

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 comprising a resonant inductor and a parasitic capacitor connected in parallel, the resonant element being connected to the first differential output and operative to substantially balance a signal from the first differential output with a signal from the second differential output, 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.

13. An electronic device as claimed in claim 12, wherein the electronic device is one of an oscillator circuit;

a mixer;

or a transformer.

14. A coupled acoustic resonator adapted for single-ended to differential signal transformation, comprising a single stack, the single stack comprising:

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

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 comprising a resonant inductor and the parasitic capacitor connected in parallel, the resonant element being connected to the first differential output and operative to substantially balance a signal from the first differential output with a signal from the second differential output, 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.

15. A communication device, comprising:

a transmitter;

a receiver; and

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

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

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 comprising a resonant inductor and a parasitic capacitor connected in parallel, the resonant element being 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, 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.

16. 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 input;

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, 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.

17. A communication device, comprising:

a transmitter;

a receiver; and

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

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

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, 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.