Method and system for reducing AM/PM distortion in a polar amplifier

• US 7,957,704 B2
• Filed: 03/09/2007
• Issued: 06/07/2011
• Est. Priority Date: 12/06/2006
• Status: Expired due to Fees

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Zolfaghari, Alireza
• Primary Examiner(s): Trinh; Sonny
• Application Number:
  US11/684,075
• Publication Number:
  US 20080150633A1
• Time in Patent Office: 1,551 Days
• Field of Search: 455/116, 455/126, 455/91, 455/112, 455/115.1, 455/127.1, 455/102, 455/108, 455/110, 330/149, 330/251, 330/295, 330/150, 330/151
• US Class Current: 455/102
• CPC Class Codes: H03F 1/3211 in differential amplifiers
• CPC Class Codes: H03F 1/3276 using the nonlinearity inherent to components, e.g. a diode
• CPC Class Codes: H03F 2203/45482 the CSC comprising offset means
• CPC Class Codes: H03F 2203/45624 the LC comprising balancing means, e.g. trimming means
• CPC Class Codes: H03F 3/45183 Long tailed pairs H03F3/4521, H03F3/45237 take precedence
• CPC Class Codes: H03F 3/45188 Non-folded cascode stages
• CPC Class Codes: H03F 3/45766 by using balancing means

Abstract

Methods and systems for reducing AM/PM distortion in a polar amplifier are disclosed and may comprise adding an offset signal to an amplitude signal in the digital domain and removing the offset signal in the analog domain during polar modulation. A sum of an amplitude signal and an offset signal may be mixed with a phase signal in a first differential amplifier to generate a first voltage signal, and the offset signal may be mixed with the phase signal in a second differential amplifier to generate a second voltage signal, which may be subtracted from the first voltage signal. The amplitude and offset signals may be mixed with the phase signal by modulating a current in the differential amplifiers, which may comprise cascode differential amplifiers. The modulated current may be generated using a current source and a current mirror circuit, which may comprise a cascode current mirror.

Claims

1. A method for controlling a circuit, the method comprising:

in a polar amplifier during polar modulation, adding an offset signal to an amplitude signal in a digital domain;

mixing said added offset signal and amplitude signal with a phase signal to generate a first voltage signal; and

removing said offset signal in an analog domain.

2. The method according to 1, comprising mixing said offset signal with said phase signal to generate a second voltage signal.

3. The method according to 2, comprising subtracting said generated second voltage signal from said generated first voltage signal.

4. The method according to 1, comprising modulating a current in a differential amplifier within said polar amplifier utilizing a sum of said amplitude signal and said offset signal.

5. The method according to 4, wherein said differential amplifier comprises a cascode differential amplifier.

6. The method according to 4, wherein said modulated current is generated using a current source and a current mirror circuit.

7. The method according to 6, wherein said current mirror circuit comprises a cascode current mirror.

8. The method according to 1, comprising modulating a current in a differential amplifier within said polar amplifier utilizing said offset signal.

9. The method according to 8, wherein said differential amplifier comprises a cascode differential amplifier.

10. The method according to 8, wherein said modulated current is generated using a current source and a current mirror circuit.

11. The method according to 10, wherein said current mirror circuit comprises a cascode current mirror.

12. The method according to 1, wherein said polar amplifier is a power amplifier driver.

13. The method according to 1, wherein said polar amplifier is a power amplifier.

14. A method for controlling a circuit, the method comprising:

in a polar amplifier during polar modulation, adding an offset signal to an amplitude signal in a digital domain;

modulating a current in a differential amplifier within said polar amplifier utilizing a sum of said amplitude signal and said offset signal; and

removing said offset signal in an analog domain.

15. The method according to claim 14, wherein said differential amplifier comprises a cascode differential amplifier.

16. The method according to claim 14, wherein said modulated current is generated using a current source and a current mirror circuit.

17. The method according to claim 16, wherein said current mirror circuit comprises a cascode current mirror.

18. The method according to claim 14, comprising modulating a current in a differential amplifier within said polar amplifier utilizing said offset signal.

19. The method according to claim 18, wherein said differential amplifier comprises a cascode differential amplifier.

20. The method according to claim 18, wherein said modulated current is generated using a current source and a current mirror circuit.

21. The method according to claim 20, wherein said current mirror circuit comprises a cascode current mirror.

22. The method according to claim 14, wherein said polar amplifier is a power amplifier driver.

23. The method according to claim 14, wherein said polar amplifier is a power amplifier.

24. A method for controlling a circuit, the method comprising:

in a polar amplifier during polar modulation, adding an offset signal to an amplitude signal in a digital domain;

modulating a current in a differential amplifier within said polar amplifier utilizing said offset signal; and

removing said offset signal in an analog domain.

25. The method according to claim 24, wherein said differential amplifier comprises a cascode differential amplifier.

26. The method according to claim 24, wherein said modulated current is generated using a current source and a current mirror circuit.

27. The method according to claim 26, wherein said current mirror circuit comprises a cascode current mirror.

28. The method according to claim 24, wherein said polar amplifier is a power amplifier driver.

29. The method according to claim 24, wherein said polar amplifier is a power amplifier.

30. A system for controlling transmission of signals in a communication system, the system comprising:

one or more circuits comprising a polar amplifier that adds an offset signal to an amplitude signal in a digital domain during polar modulation;

said one or more circuits mixes said summed offset signal and said amplitude signal with a phase signal to generate a first voltage signal; and

said one or more circuits removes said offset signal in an analog domain.

31. The system according to claim 30, wherein said one or more circuits mixes said offset signal with said phase signal to generate a second voltage signal.

32. The system according to claim 31, wherein said one or more circuits subtracts said generated second voltage signal from said generated first voltage signal.

33. The system according to claim 30, wherein said one or more circuits comprises a differential amplifier integrated within said polar amplifier, and a current in said differential amplifier is modulated utilizing said offset signal.

34. The system according to claim 33, wherein said differential amplifier comprises a cascode differential amplifier.

35. The system according to claim 33, wherein said one or more circuits modulates said current in said differential amplifier using a current source and a current mirror circuit.

36. The system according to claim 35, wherein said current mirror circuit comprises a cascode current mirror.

37. The system according to claim 30, wherein said one or more circuits comprises a differential amplifier integrated within said polar amplifier, and a current in said differential amplifier is modulated utilizing said offset signal.

38. The system according to claim 37, wherein said differential amplifier comprises a cascode differential amplifier.

39. The system according to claim 37, wherein said one or more circuits modulates said current in said differential amplifier using a current source and a current mirror circuit.

40. The system according to claim 39, wherein said current mirror circuit comprises a cascode current mirror.

41. The system according to claim 30, wherein said polar amplifier comprises a power amplifier driver.

42. The system according to claim 30, wherein said polar amplifier comprises a power amplifier.

43. A system for controlling transmission of signals in a communication system, the system comprising:

one or more circuits comprising a polar amplifier that adds an offset signal to an amplitude signal in a digital domain during polar modulation;

said one or more circuits comprises a differential amplifier integrated within said polar amplifier, and a current in said differential amplifier is modulated utilizing said offset signal; and

said one or more circuits removes said offset signal in an analog domain.

44. The system according to claim 43, wherein said differential amplifier comprises a cascode differential amplifier.

45. The system according to claim 43, wherein said one or more circuits modulates said current in said differential amplifier using a current source and a current mirror circuit.

46. The system according to claim 45, wherein said current mirror circuit comprises a cascode current mirror.

47. The system according to claim 43, wherein said one or more circuits comprises a differential amplifier integrated within said polar amplifier, and a current in said differential amplifier is modulated utilizing said offset signal.

48. The system according to claim 47, wherein said differential amplifier comprises a cascode differential amplifier.

49. The system according to claim 47, wherein said one or more circuits modulates said current in said differential amplifier using a current source and a current mirror circuit.

50. The system according to claim 49, wherein said current mirror circuit comprises a cascode current mirror.

51. The system according to claim 43, wherein said polar amplifier comprises a power amplifier driver.

52. The system according to claim 43, wherein said polar amplifier comprises a power amplifier.

53. A system for controlling transmission of signals in a communication system, the system comprising:

one or more circuits comprising a polar amplifier that adds an offset signal to an amplitude signal in a digital domain during polar modulation;

said one or more circuits comprises a differential amplifier integrated within said polar amplifier, and a current in said differential amplifier is modulated utilizing said offset signal; and

said one or more circuits removes said offset signal in an analog domain.

54. The system according to claim 53, wherein said differential amplifier comprises a cascode differential amplifier.

55. The system according to claim 53, wherein said one or more circuits modulates said current in said differential amplifier using a current source and a current mirror circuit.

56. The system according to claim 55, wherein said current mirror circuit comprises a cascode current mirror.

57. The system according to claim 53, wherein said polar amplifier comprises a power amplifier driver.

58. The system according to claim 53, wherein said polar amplifier comprises a power amplifier.