DUPLEXER AND METHOD FOR SEPARATING A TRANSMIT SIGNAL AND A RECEIVE SIGNAL

• US 20110080856A1
• Filed: 10/01/2009
• Published: 04/07/2011
• Est. Priority Date: 10/01/2009
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: UBIDYNE, INC
• Inventors: Kenington, Peter
• Granted Patent: US 8,339,216 B2
• Time in Patent Office: Days
• US Class Current: 370/278
• CPC Class Codes: H04B 1/48 in circuits for connecting transmitter and receiver to a common transmission path, e.g. by energy of transmitter H04B1/46 takes precedence

Abstract

The present disclosure provides a duplexer for separating a transmit signal and a receive signal. The duplexer comprises a transmit filter, a receive filter and an analogue quadrature splitter, a first filtering element and a second filtering element. By choosing the first filtering element and the second filtering element substantially identical, it is possible to transform filtering characteristics of the first and second filtering element such that stop bands are substantially transformed into an effective pass band, and vice versa. The analogue quadrature splitter is adapted to increase an attenuation of the transmit signals outside the transmit band, such as in the receive band. Therefore out-of-band emissions by the transmitter will be substantially reduced. The present disclosure further provides a method for separating a transmit signal and a receive signal, and computer program products for the manufacture for carrying out the method of separating transmit signals and receive signals.

Claims

1. A duplexer for separating a transmit signal (Tx) and a receive signal (Rx), the duplexer, comprising:

a transmit filter for substantially forwarding the transmit signal within an at least one transmit band to an antenna;

a receive filter for substantially forwarding the receive signal within at least one receive band from the antenna to a receive path;

an analogue quadrature splitter adapted to split the transmit signal into an in phase component and a quadrature component;

a first filtering element with a first filtering characteristic comprising at least one first pass band and at least one first stop band;

a second filtering element with a second filtering characteristic comprising at least one second pass band and at least one second stop band;

wherein the analogue quadrature splitter is adapted to increase an attenuation of the transmit signal outside the transmit band.

2. The duplexer according to claim 1, wherein the at least one transmit band and the at least one receive band are substantially closely-spaced in frequency.

3. The duplexer according to claim 1, wherein the attenuation of the transmit signal is increased in at least a portion of the receive band.

4. The duplexer according to claim 1, wherein

the analogue quadrature splitter is adapted to substantially transform at least one of the at least one first pass band or the at least one second pass band into at least one effective stop band;

and

the analogue quadrature splitter is adapted to substantially transform at least one of the at least one first stop band or the at least one second stop band into at least one effective pass band;

generating a transmit signal comprising the at least one effective stop band and the at least one effective pass band.

5. The duplexer according to claim 4, wherein the at least one effective stop band that substantially begins at an edge of the at least one transmit band and extends away from the at least one transmit band.

6. The duplexer according to claim 4, wherein the at least one effective pass band is substantially identical to the at least one transmit band.

7. The duplexer according to claim 1, wherein at least one of the first filtering element or the second filtering element is adapted to filter signals at a first power level.

8. The duplexer according to claim 4, wherein at least one of the at least one effective stop band or the at least one effective pass band are adapted to filter the transmit signal at a second power level at the entry of the analogue quadrature splitter;

wherein the second power level is substantially higher than the first power level; and

wherein the analogue quadrature splitter is operable at the second power level.

9. The duplexer according to claim 4, wherein the analogue quadrature splitter is adapted to substantially transform at least one of the first filtering characteristic comprising a first band pass or the second filtering characteristic comprising a second band pass into at least one effective band stop.

10. The duplexer according to claim 4, wherein the analogue quadrature splitter is adapted to substantially transform at least one of the first filtering characteristic comprising a first band stop or the second filtering characteristic comprising a second band stop into at least one effective band pass.

11. The duplexer according to claim 1, wherein the first filtering characteristic and the second filtering characteristic are substantially identical.

12. The duplexer according to claim 1, wherein the first filtering element and the second filtering element comprise a substantially identical response to temperature changes.

13. The duplexer according to claim 1, further comprising:

a first impedance matching network coupled to the first filtering element; and

a second impedance matching network coupled to the second filtering element.

14. The duplexer according to claim 1, further comprising:

a first load for terminating the in phase component; and

a second load for terminating the quadrature component.

15. The duplexer according to claim 1, further comprising at least one auxiliary termination network adapted to increase an attenuation in the at least one effective stop band.

16. The duplexer according to claim 1, wherein at least one of the first filtering element or the second filtering element is a low-power, high-performance filter.

17. The duplexer according to claim 1, wherein the analogue quadrature splitter is implemented in strip line technology.

18. The duplexer according to claim 1, wherein the transmit filter comprises

a first transmit filter element upstream of the analogue quadrature splitter;

and

a second transmit filter element downstream of the analogue quadrature splitter.

19. The duplexer according to claim 1, with an isolator downstream of the analogue quadrature splitter, the isolator comprising:

a circulator; and

a circulator load.

20. A method for separating a transmit signal and a receive signal, the method comprising:

forwarding the transmit signal within at least one transmit band in a transmit direction;

forwarding a receive signal within at least one receive signal in a receive direction;

splitting the transmit signal into an in phase component and a quadrature component;

filtering at least one of the in phase component or the quadrature component;

wherein the filtering increases an attenuation of the transmit signal outside the transmit band.

21. The method according to claim 20, wherein the attenuation of the transmit signal is increased at least partially within the receive band.

22. The method according to claim 20 wherein the filtering comprises:

filtering the in phase component according to at least one first pass band and at least one first stop band; and

filtering the quadrature component according to at least one second pass band and at least one second stop band.

23. The method according to claim 22, wherein the filtering further comprises:

transforming at least one of the at least one first pass band or the at least one second pass band substantially into at least one effective stop band,

transforming at least one of the at least one first stop band or the at least one second stop band substantially into at least one effective pass band.

24. The method according to claim 22, the filtering further comprising:

impedance matching the in phase component; and

impedance matching the quadrature component.

25. The method according to claim 22, the filtering further comprising:

terminating the in phase component; and

terminating the quadrature component.

26. The method according to claim 22, the filtering further comprising:

auxiliary matching an attenuation in the at least one effective stop band.

27. The method according to claim 22, wherein the filtering of the in phase component and the filtering of the quadrature component comprise using a substantially identical filtering characteristic.

28. The method according to claim 22, wherein the filtering of the in phase component and the filtering of the quadrature component comprise a substantially identical response to temperature changes.

29. The method according to claim 22, wherein the filtering of the in phase component and the filtering of the quadrature component is implemented using filtering elements operable at a first power level.

30. The method according to claim 23, wherein at least one of the at least one effective pass band or the at least one effective stop band is adapted to substantially filter signals at a second power level, the second power level being substantially higher than the first power level.

31. A computer program product embodied on a computer-readable medium and the computer-readable medium comprising executable instructions for the execution of a manufacture of a duplexer for separating a transmit signal and a receive signal, the duplexer comprising:

a transmit filter substantially forwarding the transmit signal within an at least one transmit band to an antenna;

a receive filter substantially forwarding the receive signal within at least one receive band from the antenna to a receive path;

an analogue quadrature splitter adapted to split the transmit signal into an in phase component and a quadrature component;

a first filtering element with a first filtering characteristic comprising at least one first pass band and at least one first stop band;

a second filtering element with a second filtering characteristic comprising at least one second pass band and at least one second stop band;

wherein the analogue quadrature splitter is adapted to increase an attenuation of the transmit signal outside the transmit band.

32. A computer program product embodied on a computer-readable medium and the computer-readable medium comprising executable instructions for the execution of a method of separating a transmit signal and a receive signal, the method comprising:

forwarding the transmit signal within at least one transmit band in a transmit direction;

forwarding a receive signal within at least one receive signal in a receive direction;

splitting the transmit signal into an in phase component and a quadrature component;

filtering at least one of the in phase component or the quadrature component;

wherein an attenuation of the transmit signal outside the transmit band is increased.