Systems and methods for controlling output power in a communication device

• US 6,710,651 B2
• Filed: 10/22/2001
• Issued: 03/23/2004
• Est. Priority Date: 10/22/2001
• Status: Expired due to Fees

• Current Assignee: Kyocera Corporation
• Original Assignee: Kyocera Wireless Corporation (Kyocera Corporation)
• Inventors: Forrester, Tim
• Primary Examiner(s): Tokar, Michael
• Assistant Examiner(s): NGUYEN, KHAI M
• Application Number:
  US10/035,596
• Publication Number:
  US 20030076168A1
• Time in Patent Office: 883 Days
• Field of Search: 330/129, 330/207.P, 455/115, 455/117, 455/126, 455/69, 455/70, 455/522
• US Class Current: 330/129
• CPC Class Codes: H03G 3/001 Digital control of analog signals
• CPC Class Codes: H03G 3/3042 in modulators, frequency-changers, transmitters or power amplifiers transmission power control in bidirectional transmission systems H04W52/04
• CPC Class Codes: H04B 1/3838 Arrangements for reducing RF exposure to the user, e.g. by changing the shape of the transceiver while in use
• CPC Class Codes: H04B 17/103 Reflected power, e.g. return loss

Abstract

A wireless communication device comprises a power amplifier configured to amplify a power level of a transmit signal to a required transmit power level and a transmission line coupled with the power amplifier. The transmission line is configured to convey the amplified transmit signal. The wireless communication device also comprises a power control circuit that includes a bi-directional coupler detector coupled with the transmission line. The bi-directional coupler detector is configured to sense a forward power level and a reflected power level in the transmission line. The power control circuit may be configured to adjust the required transmit power level based at least in part on the forward and reflected power levels sensed by the bi-directional coupler detector. The power control circuit may also adjust an impedance of an impedance matching circuit based at least in part on the reflected power level sensed by the bi-directional coupler detector.

Claims

1. A power control circuit comprising a bi-directional coupler detector configured to couple the power control circuit with a transmission line and to sense a forward power level and a reflected power level in the transmission line, the power control circuit configured to:

determine the amount of transmit signal power being radiated by an antenna interfaced with the transmission line;

determine if the radiated signal power exceeds a first threshold;

if the radiated signal power does exceed the first threshold, then decrease a transmit signal power level;

determine if the radiated signal power exceeds a second threshold; and

if the radiated signal power does exceed the second threshold, then decrease the transmit signal power level.

2. The power control circuit of claim 1, configured to decrease the transmit signal power level by controlling the amplification of a power amplifier.

3. The power control circuit of claim 1, configured to decrease the transmit signal power level by controlling the amplification of an in-phase transmission path and an out-of-phase transmission path of a power amplifier.

4. The power control circuit of claim 3, wherein decreasing the transmit signal power level can include turning off one of the in-phase and out-of-phase transmission paths.

5. The power control circuit of claim 1, configured to decrease the transmit signal power level by controlling a variable gain amplifier.

6. The power control circuit of claim 5, wherein controlling the variable gain amplifier comprises varying a gain of the variable gain amplifier.

7. The power control circuit of claim 1, wherein the first threshold is based on SAR requirements.

8. The power control circuit of claim 1, wherein the second threshold is based on ACPR requirements.

9. The power control circuit of claim 1, wherein determining the radiated signal power comprises comparing the sensed forward and reflected 1 power levels.

10. The power control circuit of claim 1, wherein the power control circuit is configured to operate at low transmit signal power levels used in CDMA systems.

11. A wireless communication device, comprising:

a power amplifier configured to amplify a power level of a transmit signal to a required transmit power level;

a transmission line coupled with the power amplifier, the transmission line configured to convey the amplified transmit signal; and

a power control circuit including a bi-directional coupler detector coupled with the transmission line, the bi-directional coupler detector configured to sense a forward power level and a reflected power level in the transmission line, the power control circuit configured to;

determine the amount of transmit signal power being radiated by an antenna interfaced with the transmission line;

determine if the radiated signal power exceeds a first threshold;

if the radiated signal power does exceed the first threshold, then decrease a transmit signal power level;

determine if the radiated signal power exceeds a second threshold; and

if the radiated signal power does exceed the second threshold, then decrease the transmit signal power level.

12. The wireless communication device of claim 11, further comprising an antenna coupled with the transmission line, wherein the transmission line is configured to convey the amplified transmit signal from the power amplifier to the antenna, and wherein the antenna is configured to transmit the amplified transmit signal.

13. The wireless communication device of claim 12, further comprising an impedance matching circuit configured to match an impedance of the transmission line to an impedance of the antenna in order to reduce a magnitude of the reflected power level.

14. The wireless communication device of claim 11, wherein the power control circuit is configured to decrease the transmit signal power level by controlling the amplification provided by the power amplifier.

15. The wireless communication device of claim 14, wherein the power amplifier comprises an in-phase transmission path and an-out-of phase transmission path, and wherein the power control circuit is configured to decrease the transmit signal power level by controlling the amplification provided by the in-phase transmission path and the out-of-phase transmission path.

16. The wireless communication device of claim 15, wherein decreasing the transmit signal power level can include turning off one of the in-phase and out-of-phase transmission paths.

17. The wireless communication device of claim 11, further comprising a variable gain amplifier coupled with the power amplifier, the variable gain amplifier configured to generate the transmit signal, wherein the power control circuit is configured to decrease the transmit signal power level by controlling the variable gain amplifier.

18. The wireless communication device of claim 17, wherein controlling the variable gain amplifier comprises varying a gain of the variable gain amplifier.

19. The wireless communication device of claim 11, wherein the first threshold is based on SAR requirements.

20. The wireless communication device of claim 11, wherein the second threshold is based on ACPR requirements.

21. The wireless communication device of claim 11, wherein determining the radiated signal power comprises comparing the sensed forward and reflected 1 power levels.

22. The wireless communication device of claim 11, wherein the power control circuit is configured to operate at low transmit signal power levels used in CDMA systems.

23. A wireless communication device, comprising:

a transmission line configured to convey a transmit signal;

an impedance matching circuit coupled with the transmission line, the impedance matching circuit configured to match the impedance of the transmission line with a required output impedance; and

a power control circuit including a bi-directional coupler detector coupled with the transmission line, the bi-directional coupler detector configured to sense a reflected power level in the transmission line, the power control circuit configured to;

determine the amount of transmit signal power being radiated by an antenna interfaced with the transmission line;

determine if the radiated signal power exceeds a first threshold;

if the radiated signal power does exceed the first threshold, then adjust the impedance of the impedance matching circuit;

determine if the radiated signal power exceeds a second threshold; and

if the radiated signal power does exceed the second threshold, then adjust the impedance of the impedance matching circuit.

24. The wireless communication device of claim 23, wherein the impedance matching circuit comprises a ferro-electric tunable matching circuit, and wherein the power control circuit is configured to adjust the impedance of the impedance matching circuit by tuning the ferro-electric tunable matching circuit.

25. The wireless communication device of claim 23, further comprising a power amplifier coupled with the transmission line, the power amplifier configured to amplify a signal power level of the transmit signal to a required transmit signal power level and to drive the amplified transmit signal down the transmission line.

26. The wireless communication device of claim 25, wherein the power control circuit is configured to adjust the required transmit signal power level by controlling the amplification provided by the power amplifier.

27. The wireless communication device of claim 26, wherein the power amplifier comprises an in-phase transmission path and an-out-of phase transmission path, and wherein the power control circuit is configured to adjust the required transmit signal power level by controlling the amplification provided by the in-phase transmission path and the out-of-phase transmission path.

28. The wireless communication device of claim 27, wherein adjusting the required transmit signal power level can include turning off one of the in-phase and out-of-phase transmission paths.

29. The wireless communication device of claim 25, further comprising a variable gain amplifier coupled with the power amplifier, the variable gain amplifier configured to generate the transmit signal, wherein the bi-directional coupler detector is configured to adjust the required transmit signal power level by controlling the variable gain amplifier.

30. The wireless communication device of claim 29, wherein controlling the variable gain amplifier comprises varying a gain of the variable gain amplifier.

31. The wireless communication device of claim 23, wherein the bi-directional coupler detector is further configured to sense a forward power level in the transmission line, and wherein the power control circuit is configured to adjust a transmit power level based at least in part on the forward and reflected power levels sensed by the bi-directional coupler detector.

32. The wireless communication device of claim 23, further comprising an antenna coupled with the transmission line, the antenna configured to transmit the amplified transmit signal, and wherein the matching circuit is configured to match the impedance of the transmission line to the impedance of the antenna.

33. The wireless communication device of claim 23, wherein the first threshold is based on SAR requirements.

34. The wireless communication device of claim 23, wherein the second threshold is based on ACPR requirements.

35. The wireless communication device of claim 23, wherein determining the radiated signal power comprises comparing a sensed forward and reflected power levels.

36. The wireless communication device of claim 23, wherein the power control circuit is configured to operate at low transmit signal power levels used in CDMA systems.

37. A method of controlling output power in a wireless communication device, comprising:

sensing a forward power level of a transmit signal as the transmit signal travels from a power amplifier to an antenna of the wireless communication device;

sensing a power level of a portion of the transmit signal that is reflected back toward the power amplifier;

determine the amount of transmit signal power being radiated by an antenna interfaced with the transmission line;

determine if the radiated signal power exceeds a first threshold;

if the radiated signal power does exceed the first threshold, then decrease a transmit signal power level;

determine if the radiated signal power exceeds a second threshold; and

if the radiated signal power does exceed the second threshold, then decrease the transmit signal power level.

38. The method of claim 37, further comprising adjusting an impedance of an impedance matching circuit based at least in part on the sensed reflected power level.

39. The method of claim 37, wherein decreasing the transmit signal power level-comprises adjusting a bias voltage of the power amplifier.

40. The method of claim 37, wherein decreasing the transmit signal power level comprises adjusting a gain of a variable gain amplifier.

41. The method of claim 37, wherein the first threshold is based on SAR requirements.

42. The method of claim 37, wherein the second threshold is based on ACPR requirements.

43. The method of claim 37, wherein determining the radiated signal power comprises comparing the sensed forward and reflected power levels.

44. A wireless communication device configured to communicate using low power level CDMA signals, comprising a power control circuit including a bi-directional coupler detector coupled with the transmission line, the bi-directional coupler detector configured to sense a forward power level and a reflected power level in the transmission line, the power control circuit configured to:

determine the amount of transmit signal power being radiated by an antenna interfaced with the transmission line;

determine if the radiated signal power exceeds a first threshold;

if the radiated signal power does exceed the first threshold, then decrease a transmit signal power level;

determine if the radiated signal power exceeds a second threshold; and

if the radiated signal power does exceed the second threshold, then decrease the transmit signal power level.

45. The wireless communication device of claim 44, wherein the first threshold is based on SAR requirements.

46. The wireless communication device of claim 44, wherein the second threshold is based on ACPR requirements.

47. The wireless communication device of claim 44, wherein determining the radiated signal power comprises comparing the sensed forward and reflected power levels.