Duplexer with negative phase shifting circuit

• US 8,193,877 B2
• Filed: 11/30/2009
• Issued: 06/05/2012
• Est. Priority Date: 11/30/2009
• Status: Expired due to Fees

• Current Assignee: Avago Technologies General IP PTE Limited (Broadcom, Inc.)
• Original Assignee: Avago Technologies Wireless IP Singapore Pte Limited (Broadcom, Inc.)
• Inventors: Fritz, Martin, Handtmann, Martin, Liang, Ji-Fuh, Gebauer, Bernhard
• Primary Examiner(s): Takaoka, Dean O
• Application Number:
  US12/627,122
• Publication Number:
  US 20110128092A1
• Time in Patent Office: 918 Days
• Field of Search: 333/133, 333/187, 333/188, 333/189, 333/191, 333/192, 333/193, 333/194, 333/195
• US Class Current: 333/133
• CPC Class Codes: H03H 7/19 Two-port phase shifters providing a predetermined phase shift, e.g. "all-pass" filters
• CPC Class Codes: H03H 9/706 Duplexers
• CPC Class Codes: H04B 1/0057 using diplexing or multiplexing filters for selecting the desired band
• CPC Class Codes: H04B 1/18 Input circuits, e.g. for coupling to an antenna or a transmission line coupling networks between antennas or lines and receivers independent of the nature of the receiver H03H
• CPC Class Codes: H04B 1/52 Hybrid arrangements, i.e. arrangements for transition from single-path two-direction transmission to single-direction transmission on each of two paths or vice versa

Abstract

A duplexer includes first and second acoustic filters and a phase shifter. The first acoustic filter is connected between an antenna and the transmitter, and has a first passband. The second acoustic filter is connected between the antenna and the receiver, and has a second passband. The phase shifter includes at least one series capacitor connected in series with the antenna and at least one shunt inductor connected between the at least one capacitor and ground. The phase shifter is connected between the antenna and the first filter when the first passband is higher than the second passband, and provides a negative phase shift of an output impedance of the first filter. The phase shifter is connected between the antenna and the second filter when the second passband is higher than the first passband, and provides a negative phase shift of an input impedance of the second filter.

Claims

1. A duplexer interfacing a receiver and a transmitter with a common antenna, the duplexer comprising:

a first acoustic filter connected in series between the antenna and the transmitter, the first acoustic filter having a first passband;

a second acoustic filter connected in series between the antenna and the receiver, the second acoustic filter having a second passband; and

a phase shifter comprising at least one series capacitor connected in series with the antenna and at least one shunt inductor connected between the at least one capacitor and ground,

wherein the phase shifter is connected between the antenna and the first acoustic filter when the first passband is higher than the second passband, and provides a negative phase shift of an output impedance of the first acoustic filter, and

wherein the phase shifter is connected between the antenna and the second acoustic filter when the second passband is higher than the first passband, and provides a negative phase shift of an input impedance of the second acoustic filter.

2. The duplexer of claim 1, wherein the first acoustic filter comprises a plurality of first series resonators connected in series between the antenna and the transmitter and a plurality of first shunt resonators respectively connected between at least one of the series resonators and ground;

and

wherein the second acoustic filter comprises a plurality of second series resonators connected in series between the antenna and the receiver and a plurality of second shunt resonators respectively connected between at least one of the second series resistors and the ground.

3. The duplexer of claim 2, wherein the second passband is higher than the first passband, and a resonator of the second acoustic filter located closest to the antenna is one of the plurality of second shunt resonators.

4. The duplexer of claim 2, wherein the second passband is higher than the first passband, and a resonator of the second acoustic filter located closest to the antenna is one of the plurality of second series resonators.

5. The duplexer of claim 1, wherein the second passband is higher than the first passband, and the phase shifter comprises at least one series capacitor connected between the antenna and the input of the second acoustic filter, and two shunt inductors connected between ground and each side of the series capacitor, respectively.

6. The duplexer of claim 1, wherein the second passband is higher than the first passband, and the phase shifter comprises at least two series capacitors connected between the antenna and the input of the second acoustic filter, and one shunt inductor connected between ground and each of the two series capacitors.

7. The duplexer of claim 1, wherein the first passband is higher than the second passband, and the phase shifter comprises at least one series capacitor connected between the antenna and the output of the first acoustic filter, and two shunt inductors connected between ground and each side of the series capacitor, respectively.

8. The duplexer of claim 1, wherein the first passband is higher than the second passband, and the phase shifter comprises at least two series capacitors connected between the antenna and the output of the first acoustic filter, and one shunt inductor connected between ground and each of the two series capacitors.

9. The duplexer of claim 2, wherein each of the first and second series resonators and the first and second shunt resonators comprises a film bulk acoustic resonator (FBAR) or a bulk acoustic wave (BAW) resonator device.

10. The duplexer of claim 1, wherein at least one of the series capacitor and the shunt inductor of the phase shifter is implemented within a die of the first acoustic filter or the second acoustic filter.

11. The duplexer of claim 1, wherein at least one of the series capacitor and the shunt inductor of the phase shifter is implemented on a silicon or polymer capping of the first acoustic filter or the second acoustic filter.

12. The duplexer of claim 2, wherein at least one of the series capacitor and the shunt inductor of the phase shifter is implemented on a common substrate with the first series resonators and the first shunt resonators of the first acoustic filter.

13. The duplexer of claim 2, wherein at least one of the series capacitor and the shunt inductor of the phase shifter is implemented on a common substrate with the second series resonators and the second shunt resonators of the second acoustic filter.

14. The duplexer of claim 2, wherein one of the series capacitor and the shunt inductor of the phase shifter is implemented on a common substrate with the first series resonators and the first shunt resonators of the first acoustic filter, and the other one of the series capacitor and the shunt inductor of the phase shifter is implemented on a common substrate with the second series resonators and the second shunt resonators of the second acoustic filter.

15. A duplexer, comprising:

a transmit filter connected in series between an antenna terminal and a transmitter terminal;

a receive filter connected in series between the antenna terminal and a receiver terminal, the receive filter having a higher passband center frequency than the transmit filter; and

a phase shifter connected in series between the antenna terminal and an input of the receive filter, the phase shifter comprising a capacitor connected in series between the antenna terminal and the input of the receive filter, a first inductor connected between a first end of the capacitor and ground, and a second inductor connected between a second end of the capacitor and ground, wherein the phase shifter provides a negative phase shift of an input impedance of the receive filter.

16. The duplexer of claim 15, wherein the receive filter comprises a plurality of series resonators connected in series between the antenna terminal and the receiver terminal, and a plurality of shunt resonators respectively connected between at least one of the series resistors and ground.

17. The duplexer of claim 16, wherein at least one of the capacitor, the first inductor and second inductor of the phase shifter is implemented on a common substrate with the series resonators and the shunt resonators of the receive filter.

18. A duplexer, comprising:

a transmit filter connected in series between an antenna terminal and a transmitter terminal;

a receive filter connected in series between the antenna terminal and a receiver terminal, the receive filter having a higher passband center frequency than the transmit filter; and

a phase shifter connected in series between the antenna terminal and an input of the receive filter, the phase shifter comprising first and second capacitors connected in series between the antenna terminal and the input of the receive filter, and one shunt inductor having a first end connected between the first and second series capacitors and a second end connected to a ground voltage, wherein the phase shifter provides a negative phase shift of an input impedance of the receive filter.

19. The duplexer of claim 18, wherein the receive filter comprises a plurality of series resonators connected in series between the antenna terminal and the receiver terminal, and a plurality of shunt resonators respectively connected between at least one of the series resistors and the ground voltage.

20. The duplexer of claim 19, wherein at least one of the first capacitor, the second capacitor and the inductor of the phase shifter is implemented on a common substrate with the series resonators and the shunt resonators of the receive filter.