System for closed loop power control using a linear or a non-linear power amplifier

• US 6,670,849 B1
• Filed: 08/30/2000
• Issued: 12/30/2003
• Est. Priority Date: 08/30/2000
• Status: Active Grant

• Current Assignee: Skyworks Solutions Incorporated
• Original Assignee: Skyworks Solutions Incorporated
• Inventors: Damgaard, Morten, Rozenblit, Dmitriy, Domino, William J., Clark, Ricke W.
• Primary Examiner(s): NGUYEN, PATRICIA T
• Application Number:
  US09/650,987
• Time in Patent Office: 1,217 Days
• Field of Search: 330/85, 330/129, 330/140, 455/126, 455/127, 455/522
• US Class Current: 330/129
• CPC Class Codes: H03F 1/02 Modifications of amplifiers to raise the efficiency, e.g. gliding Class A stages, use of an auxiliary oscillation
• CPC Class Codes: H03F 2200/294 the amplifier being a low noise amplifier [LNA]
• CPC Class Codes: H03F 2200/372 Noise reduction and elimination in amplifier
• 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: H04W 52/52 using AGC [Automatic Gain Control] circuits or amplifiers

Abstract

A system for a closed power control feedback loop allows for the use of a non-linear amplifier for amplifying a phase modulated (PM) signal while introducing an inverse version of the desired amplitude modulated (AM) signal into the feedback loop using a variable gain element. By introducing an inverse version of the desired AM portion of the signal into the power control feedback loop, the non-linear, and highly efficient, power amplifier may be used to amplify only the PM portion of the signal, while the AM portion is introduced by the power control feedback loop. In another aspect of the invention, an inverse version of the AM portion of the desired transmit signal is introduced into the power control feedback loop of an amplifier that is amplifying both a phase modulated signal and an amplitude modulated signal. By introducing an inverse version of the desired AM signal into the power control feedback loop, the power control feedback loop may not cancel the AM component present at the output of the power amplifier. In yet another aspect of the invention, the desired AM signal is injected into the feedback loop along with the power control reference signal.

Claims

1. A method for controlling output power from an amplifier using a closed power control feedback loop, comprising the steps of:

supplying a first modulated signal to a power amplifier;

detecting a portion of an output of the power amplifier using a power detector in a closed power control feedback loop;

adjusting the output power of the power amplifier based upon the detected portion of the output of the power amplifier and a reference signal; and

injecting a second modulated signal into the feedback loop using a variable gain element, wherein the second modulated signal is an inverse of a desired second modulated signal.

2. The method of claim 1, wherein the variable gain element is an amplifier.

3. The method of claim 1, wherein the variable gain element is an attenuator.

4. The method of claim 1, wherein the first modulated signal is a phase modulated signal.

5. The method of claim 1, wherein the second modulated signal is an amplitude modulated signal.

6. The method of claim 1, wherein the variable gain element operates on a radio frequency (RF) signal.

7. The method of claim 1, wherein the variable gain element operates on a baseband signal representing the radio frequency (RF) power level of the output power of the power amplifier.

8. A method for controlling output power from an amplifier using a closed power control feedback loop, comprising the steps of:

supplying a combined modulated signal to a power amplifier, the combined modulated signal including a first portion and a second portion;

detecting a portion of an output of the power amplifier using a power detector in a closed power control feedback loop;

adjusting the output power of the power amplifier based upon the difference between the detected portion of the output of the power amplifier and a reference signal; and

injecting a second modulated signal into the feedback loop using a variable gain element, the second modulated signal being an inverse of the second portion of the combined modulated signal.

9. The method of claim 8, wherein the variable gain element is an amplifier.

10. The method of claim 8, wherein the variable gain element is an attenuator.

11. The method of claim 8, wherein the first portion of the combined modulated signal is phase modulated.

12. The method of claim 8, wherein the second portion of the combined modulated signal is amplitude modulated.

13. The method of claim 8, wherein the variable gain element operates on a radio frequency (RF) signal.

14. The method of claim 8, wherein the variable gain element operates on a baseband signal representing the radio frequency (RF) power level of the output power of the power amplifier.

15. A system for controlling output power from an amplifier using a closed power control feedback loop, comprising:

a power amplifier configured to receive a first modulated signal;

a power detector located in a closed power control feedback loop and configured to detect a portion of an output of the power amplifier;

a comparator configured to develop an error signal used to adjust the output power of the power amplifier based upon the difference between the detected portion of the output of the power amplifier and a reference signal; and

a variable gain amplifier configured to inject a second modulated signal into the feedback loop, wherein the second modulated signal is an inverse of a desired second modulated signal.

16. The system of claim 15, wherein the variable gain element is an amplifier.

17. The system of claim 15, wherein the variable gain element is an attenuator.

18. The system of claim 15, wherein the first modulated signal is a phase modulated signal.

19. The system of claim 15, wherein the second modulated signal is an amplitude modulated signal.

20. The system of claim 15, wherein the variable gain element operates on a radio frequency (RF) signal.

21. The system of claim 15, wherein the variable gain element operates on a baseband signal representing the radio frequency (RF) power level of the output power of the power amplifier.

22. A system for controlling output power from an amplifier using a closed power control feedback loop, comprising:

a power amplifier configured to receive a combined modulated signal, the combined modulated signal including a first portion and a second portion;

a power detector located in a closed power control feedback loop and configured to detect a portion of an output of the power amplifier;

a comparator configured to develop an error signal used to adjust the output power of the power amplifier based upon the difference between the detected portion of the output of the power amplifier and a reference signal; and

a variable gain element configured to inject a second modulated signal into the feedback loop, the second modulated signal being an inverse of the second portion of the combined modulated signal.

23. The system of claim 22, wherein the variable gain element is an amplifier.

24. The system of claim 22, wherein the variable gain element is an attenuator.

25. The system of claim 22, wherein the first portion of the combined modulated signal is phase modulated.

26. The system of claim 22, wherein the second portion of the combined modulated signal is amplitude modulated.

27. The system of claim 22, wherein the variable gain element operates on a radio frequency (RF) signal.

28. The system of claim 22, wherein the variable gain element operates on a baseband signal representing the radio frequency (RF) power level of the output power of the power amplifier.

29. A computer readable medium having a program for controlling output power from an amplifier using a closed power control feedback loop, the program comprising logic configured to perform the steps of:

supplying a first modulated signal to a power amplifier;

detecting a portion of an output of the power amplifier using a power detector in a closed power control feedback loop;

adjusting the output power of the power amplifier based upon the detected portion of the output of the power amplifier and a reference signal; and

injecting a second modulated signal into the feedback loop using a variable gain element, wherein the second modulated signal is an inverse of a desired second modulated signal.

30. The program of claim 29, wherein the variable gain element is an amplifier.

31. The program of claim 29, wherein the variable gain element is an attenuator.

32. The program of claim 29, wherein the first modulated signal is a phase modulated signal.

33. The program of claim 29, wherein the second modulated signal is an amplitude modulated signal.

34. The program of claim 29, wherein the variable gain element operates on a radio frequency (RF) signal.

35. The program of claim 29, wherein the variable gain element operates on a baseband signal representing the radio frequency (RF) power level of the output power of the power amplifier.

36. A computer readable medium having a program for controlling output power from an amplifier using a closed power control feedback loop, the program comprising logic configured to perform the steps of:

supplying a combined modulated signal to a power amplifier, the combined modulated signal including a first portion and a second portion;

detecting a portion of an output of the power amplifier using a power detector in a closed power control feedback loop;

adjusting the output power of the power amplifier based upon the difference between the detected portion of the output of the power amplifier and a reference signal; and

injecting a second modulated signal into the feedback loop using a variable gain element, the second modulated signal being an inverse of the second portion of the combined modulated signal.

37. The program of claim 36, wherein the variable gain element is an amplifier.

38. The program of claim 36, wherein the variable gain element is an attenuator.

39. The program of claim 36, wherein the first portion of the combined modulated signal is phase modulated.

40. The program of claim 36, wherein the second portion of the combined modulated signal is amplitude modulated.

41. The program of claim 36, wherein the variable gain element operates on a radio frequency (RF) signal.

42. The program of claim 36, wherein the variable gain element operates on a baseband signal representing the radio frequency (R-F) power level of the output power of the power amplifier.

43. A system for controlling output power from an amplifier using a closed power control feedback loop, comprising:

means for supplying a first modulated signal to a power amplifier;

means for detecting a portion of an output of the power amplifier using a power detector in a closed power control feedback loop;

means for adjusting the output power of the power amplifier based upon the detected portion of the output of the power amplifier and a reference signal; and

means for injecting a second modulated signal into the feedback loop using a variable gain element, wherein the second modulated signal is an inverse of a desired second modulated signal.

44. A system for controlling output power from an amplifier using a closed power control feedback loop, comprising:

means for receiving a first modulated signal in a power amplifier;

means for detecting a portion of an output of the power amplifier,

means for developing an error signal used to adjust the output power of the power amplifier based upon the difference between the detected portion of the output of the power amplifier and a reference signal; and

means for injecting a second modulated signal into the feedback loop wherein the second modulated signal is an inverse of a desired second modulated signal.