Tunable duplexer

• US 20040127178A1
• Filed: 12/30/2002
• Published: 07/01/2004
• Est. Priority Date: 12/30/2002
• Status: Active Grant

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Kuffner, Stephen L.
• Granted Patent: US 7,212,789 B2
• Time in Patent Office: Days
• US Class Current: 455/133
• CPC Class Codes: H01P 1/15 by semiconductor devices
• CPC Class Codes: H01P 1/18 Phase-shifters H01P1/165 takes precedence
• CPC Class Codes: H01P 1/20 Frequency-selective devices, e.g. filters
• CPC Class Codes: H03H 7/0123 comprising distributed impedance elements together with lumped impedance elements
• CPC Class Codes: H03H 7/0161 Bandpass filters H03H7/12 takes precedence
• CPC Class Codes: H03H 7/463 Duplexers
• CPC Class Codes: H04B 1/0458 Arrangements for matching and coupling between power amplifier and antenna or between amplifying stages matching circuits in general H03H
• 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

The method and apparatus herein identifies tunable duplexer in a communication system. The tunable duplexer includes a tunable receiver filter, a tunable transmitter filter, a variable receiver phase shifter, and variable transmitter phase shifter. Each filter and phase shifter is optimized based on characteristics of impedance within the duplexer. The duplexer may be adjusted to changing environments or desired changes in the frequency of operation, reducing circuitry architecture and providing greater flexibility in communication function. The method commences by tuning tunable filters within the duplexer and then optimizing phase shifters within the duplexer for adjusting impedance matching with antenna and isolating the receiver from the transmitter during duplexing operations. Optimizations and calibration may be performed during manufacture, upon initialization of the system, or during operation of the communication device. The modes of calibration and operation may be generalized as “predefined” (for known environments and frequencies) or “adapt,” where antenna impedance or frequency of operation changes.

Claims

1. In a communication system, a tunable duplexer comprising:

a first variable phase shifter operably connected to an antenna and a receiver; and

a second variable phase shifter operably connected to the antenna and a transmitter, wherein the system isolates the transmitter from the receiver and optimizes impedance matching with the antenna.

2. The communication system in claim 1, the duplexer further comprising:

a transmitter node, a receiver node, and an antenna node;

a first tunable filter operably connected to the first variable phase shifter and the receiver via the receiver node, the first variable phase shifter operably connected to the antenna via the antenna node; and

a second tunable filter operably connected to the second phase shifter and the transmitter via the transmitter node, the second phase shifter operably connected to the antenna via the antenna node.

3. The communication system in claim 2, wherein the first tunable filter comprises a combline filter structure for maintaining a near-constant bandwidth, the structure including at least one resonator.

4. The communication system in claim 3, wherein the second tunable filter comprises a combline filter structure for maintaining a constant bandwidth, the structure including at least three resonators.

5. The communication system in claim 4, wherein the combline structures include a tunable capacitor and a transmission line.

6. The communication system in claim 3, wherein the first variable phase shifter comprises a quadrature hybrid coupler.

7. The communication system in claim 4, wherein the second variable phase shifter comprises a quadrature hybrid coupler.

8. The communication system in claim 6, wherein the first variable phase shifter further includes a variable reactive component.

9. The communication system in claim 7, wherein the first variable phase shifter further includes a variable reactive component.

10. The communication system in claim 6, further comprising:

a first switch operably connected to the first variable phase shifter and the antenna; and

a second switch operably connected to the second variable phase shifter and the antenna, wherein modes of operation of the duplexer includes receive only, transmit only, or full duplex, dependent of the state of the switches.

11. The communication system in claim 10, wherein the first and second switches comprise single pole, single throw switches.

12. The communication system in claim 10, further comprising:

a tuning control unit operably connected to the variable phase shifters and tunable filters, the tuning control unit operably connected to a calibration signal unit, wherein the phase shifters and tunable filters are altered by the tuning control to optimize duplexer operations;

the calibration signal generator further operably connected to the transmitter and the receiver, wherein the calibration signal generator provides multiple frequencies of operation; and

a reflection estimator operably connected to the tuning control unit and the calibration signal unit, the reflection estimator for monitoring and measuring forward and reflected signals within the duplexer.

13. The communication system in claim 12, further comprising:

a first dual directional coupler and a first detector operably connected to the first tunable filter, the reflection estimator, and the receiver, wherein the directional couplers and detector measure a receiver-based forward and reflected signals to determine improvement in duplexer operation; and

a second dual directional coupler and a second detector operably connected to the second tunable filter, the reflection estimator, and the transmitter, wherein the directional couplers and detector measure a transmitter-based forward and reflected signals to determine improvement in duplexer operation.

14. The communication system in claim 13, further comprising:

a third switch operably connected to the receiver, the first dual directional coupler, and the first detector;

a fourth switch operably connected to the transmitter, the second dual directional coupler, and the second detector; and

a fifth switch operably connected to the calibration signal unit, the transmitter, and the receiver.

15. The communication system in claim 14, further comprising:

a signal generated by the reflection estimator based on a ratio of forward and reflected signals within the duplexer; and

an optimization algorithm, wherein the tuning control unit adjusts the variable phase shifters and tunable filters according to an optimization algorithm and the reflection estimator signal.

16. The communication system in claim 15, wherein the third, fourth, and fifth switches comprise single pole, double throw switches.

17. A method of calibrating a tunable duplexer, the method comprising:

tuning a tunable receiver filter;

tuning a tunable transmitter filter;

operably connecting the tunable receiver filter to a receiver and an antenna via a variable receiver phase shifter;

operably connecting the tunable transmitter filter to a transmitter and the antenna via a variable transmitter phase shifter;

tuning a variable receiver phase shifter, while terminating the tunable transmitter filter; and

tuning a variable transmitter phase shifter, while terminating the tunable receiver filter.

18. The method in claim 17, wherein the tuning of the variable receiver phase shifter further comprises:

analyzing a signal between the antenna and the transmitter;

determining a reflection coefficient based on the terminated tunable transmitter filter; and

determining a tuning value for the variable receiver phase shifter based on the reflection coefficient.

19. The method in claim 18, wherein the tuning of the variable transmitter phase shifter further comprises:

analyzing a signal between the antenna and the receiver;

determining a reflection coefficient based on the terminated tunable receiver filter; and

determining a tuning value for the variable transmitter phase shifter based on a reflection coefficient.

20. A method of calibrating a tunable duplexer, the method comprising:

applying an initial tuning value to a tunable transmitter filter based on a pre-determined communication system design;

applying an initial tuning value to a tunable receiver filter based on the pre-determined communication system design;

determining at least one transmitter tuning value for the tunable transmitter filter based on a pre-determined frequency of operation and temperature;

determining at least one receiver tuning value for the tunable receiver filter based on the pre-determined frequency of operation and temperature;

tuning the tunable transmitter filter based on the transmitter tuning value; and

tuning the tunable receiver filter based on the receiver tuning value.

21. The method in claim 20, further comprising:

optimizing a receiver variable phase shifter for a transmitter signal in a duplexer environment, wherein the duplexer environment includes an antenna, a transmitter, a receiver, and the tuned filters, the optimizing based on the tuned transmitter filter; and

optimizing a transmitter variable phase shifter for a receiver signal in the duplexer environment, the optimizing based on the tuned receiver filter.

22. The method in claim 21, wherein optimizing the receiver phase shifter comprises:

analyzing a signal from the transmitter filter and the antenna; and

adjusting the receiver variable phase shifter to minimize the receiver'"'"'s impact on the tuned transmitter filter.

23. The method in claim 22, wherein optimizing the transmitter phase shifter comprises:

analyzing a signal from the receiver filter and the antenna; and

adjusting the transmitter variable phase shifter to minimize the transmitter'"'"'s impact on the tuned receiver filter.

24. The method in claim 23, further comprising:

repeating the steps of determining transmitter and receiver tuning values to generate a set of tuning values and to optimize the tunable filters; and

recording a set of tuning values.

25. The method in claim 24, further comprising:

determining an optimum receiver tuning value from the set of tuning values;

determining an optimum transmitter tuning value from the set of tuning values;

applying the optimum receiver tuning value to the tunable receiver filter; and

applying the optimum transmitter tuning value to the tunable transmitter filter.

26. The method in claim 25, further comprises:

performing the steps of determining tuning values for the tunable filters within a duplexer module.

27. The method of claim 25, wherein determining tuning values comprises random methods of optimization.

28. The method of claim 25, wherein determining tuning values comprises gradient methods of optimization.

29. The method in claim 23, further comprising:

repeating the steps of determining transmitter tuning values for a range of frequencies and temperatures to generate a set of transmitter tuning values and to optimize the tunable transmitter filter;

repeating the steps of determining receiver tuning values for a range of frequencies and temperatures to generate a set of receiver tuning values and to optimize the tunable receiver filter; and

recording the set of transmitter and receiver tuning values.

30. The method in claim 29, further comprising:

determining an optimum receiver tuning value from the set of tuning values;

determining an optimum transmitter tuning value from the set of tuning values;

applying the optimum receiver tuning value to the tunable receiver filter; and

applying the optimum transmitter tuning value to the tunable transmitter filter.

31. The method in claim 30, further comprising:

performing the steps of determining tuning values for the tunable filters within a duplexer module.

32. The method of claim 30, wherein determining tuning values comprises random methods of optimization.

33. The method of claim 30, wherein determining tuning values comprises gradient methods of optimization.