Direct conversion digital domain control

• US 20020132597A1
• Filed: 12/10/2001
• Published: 09/19/2002
• Est. Priority Date: 01/12/2001
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Peterzell, Paul E., Sahota, Gurkanwal
• Granted Patent: US 6,694,129 B2
• Time in Patent Office: Days
• US Class Current: 455/130
• CPC Class Codes: H03D 3/008 Compensating DC offsets
• CPC Class Codes: H03D 3/009 Compensating quadrature phase or amplitude imbalances
• CPC Class Codes: H04B 1/109 by improving strong signal performance of the receiver when strong unwanted signals are present at the receiver input
• CPC Class Codes: H04B 1/406 with more than one transmission mode, e.g. analog and digital modes

Abstract

A system and method for a multi-band direct conversion wireless communication receiver is presented. The system incorporates a low noise amplifier (LNA) configured to amplify received RF signals, a local oscillator (LO) configured to output a frequency, and I and Q channel mixers. Each mixer has a first input operatively coupled to the LNA, a second input operatively coupled to the LO output, and an output. The system further includes an adjustment mechanism configured to adjust drive level of the LO depending on a level of jammers detected by the receiver. Thus, the receiver may operate in multiple wireless communication bands and modes and meet the associated specifications.

Claims

1. A method for suppressing jammer leakage in a multi-band direct conversion wireless communication device, the method comprising:

providing a receiver configured to receive RF signals, the receiver including a low noise amplifier (LNA), a mixer having an input and an output, and a local oscillator (LO); and

adjusting drive level of the LO depending on a level of jammers detected by the receiver.

2. The method of claim 1, wherein the adjusting drive level comprises increasing the LO drive level as the level of jammers increases.

3. The method of claim 2, wherein the LO drive level is stepped up.

4. The method of claim 1, further comprising removing a DC offset from a downconverted baseband signal.

5. The method of claim 4, wherein the removing the DC offset comprises providing an analog DC cancellation loop.

6. The method of claim 4, wherein the removing the DC offset comprises providing a digital DC cancellation module.

7. The method of claim 1, wherein the adjusting LO drive level comprises:

measuring signal power of baseband signals;

measuring power of the received RF signals;

comparing the signal power of baseband signals with the power of the received RF signals; and

adjusting a setpoint of the LO based on the comparing.

8. The method of claim 7, further comprising adjusting gain of the LNA and the mixer based on the measured signal power of baseband signals.

9. The method of claim 8, wherein the adjusting the LNA and mixer gain comprises lowering the gain as the signal power of the received RF signals increases.

10. The method of claim 1, further comprising controlling, via a digital automatic gain control (AGC) mechanism, power of baseband signals inputted to a demodulator of the receiver.

11. A system for suppressing jammer leakage in a multi-band direct conversion wireless communication receiver, the system comprising:

a low noise amplifier (LNA) configured to amplify received RF signals;

a local oscillator (LO) configured to output a frequency;

a mixer having a first input operatively coupled to the LNA, a second input operatively coupled to the LO output, and an output; and

an adjustment mechanism configured to adjust drive level of the LO depending on a level of jammers detected by the receiver.

12. The system of claim 11, wherein the adjustment mechanism comprises:

a first measurement mechanism configured to measure total power of the received RF signals;

a second measurement mechanism configured to measure signal power of baseband signals;

a comparison mechanism configured to compare the total power of the received RF signals with the signal power of baseband signals; and

an adjustor configured to adjust a setpoint of the LO based on the comparison.

13. The system of claim 12, wherein the first measurement mechanism includes:

an RF power detector configured to output an analog signal representing power of the received RF signals;

an analog-to-digital converter (ADC) having an output and an input coupled to the RF power detector output; and

a summer having a first input coupled to the ADC output and a second input coupled to an offset signal, the summer being configured to produce an output signal that represents the total power of the received RF signals.

14. The system of claim 12, wherein the second measurement mechanism includes:

a calculator configured to determine instantaneous power of baseband signals;

an integrator having an input coupled to the calculator, the integrator determining average signal power of the baseband signals and outputting an automatic gain control (AGC) signal; and

a summer configured to sum a log power representation of the AGC signal with an RF offset, the RF offset accounting for adjustments to gain of the LNA and the mixer, the summer being configured to output signal power of baseband signals.

15. The system of claim 14, wherein the calculator includes a multiplier configured to square signal levels of the I channel of the receiver.

16. The system of claim 14, wherein the calculator includes a look-up table including instantaneous power values associated with signal levels of the I channel of the receiver.

17. The system of claim 12, wherein the comparison mechanism subtracts the total power of the received RF signals from the signal power of the baseband signals.

18. The system of claim 11, wherein the adjustment mechanism sends a control signal to the LO, the control signal adjusting a setpoint of the LO.

19. The system of claim 11, further comprising a buffer amplifier coupled to the LO and to the second mixer input, wherein the adjustment mechanism adjusts gain of the buffer amplifier to adjust the LO drive level.

20. The system of claim 11, wherein the adjustment mechanism is further configured to adjust gain of the LNA and the mixer as the signal level of the received RF signals increases.

21. The system of claim 11, wherein the receiver incorporates differential RF and LO signal paths.

22. The system of claim 11, further comprising a DC cancellation mechanism configured to remove a DC offset from a downconverted baseband signal.

23. The system of claim 22, wherein the DC cancellation mechanism includes an analog DC cancellation loop.

24. The system of claim 22, wherein the DC cancellation mechanism includes a digital DC cancellation module configured to subtract the DC offset from the downconverted baseband signal.

25. The system of claim 24, wherein the digital DC cancellation module is configured to operate in a fast and a slow mode, the modes having different integration rates.

26. The system of claim 11, further comprising a demodulator configured to remove a frequency offset from an FM-modulated digital baseband signal.

28. The method of claim 27, further comprising adjusting the bit width of digital signals in the baseband portion of the receiver.

29. The method of claim 28, wherein the adjusting the bit width comprises truncating bits off digital baseband signals when signal power of the received RF signals is strong.

30. The method of claim 28, wherein the adjusting the bit width comprises adjusting the resolution of an analog-to-digital converter (ADC) in the baseband portion of the receiver.

31. The method of claim 28, wherein the adjusting the bit width comprises adjusting the resolution of a digital filter in the baseband portion of the receiver.

32. The method of claim 27, further comprising adjusting a sample rate of an ADC in the baseband portion of the receiver.

33. The method of claim 27, wherein the step of providing comprises providing a baseband portion that includes a baseband amplifier.

34. The method of claim 33, further comprising adjusting gain of the baseband amplifier based on one of part-to-part variations of the receiver and frequency of an operating band.

35. The method of claim 34, wherein the gain of the baseband amplifier is adjusted over a 6 dB range.

36. The method of claim 27, wherein the step of providing comprises providing a baseband portion that includes a baseband analog filter.

38. The system of claim 37, wherein the adjustment mechanism is further configured to adjust the bit width of digital signals in the baseband portion of the receiver.

39. The system of claim 38, wherein the adjustment mechanism is configured to truncate bits off digital baseband signals when signal power of the received RF signals is strong.

40. The system of claim 38, wherein the adjustment mechanism is configured to adjust the resolution of an analog-to-digital converter (ADC) in the baseband portion of the receiver.

41. The system of claim 38, wherein the adjustment mechanism is configured to adjust the resolution of a digital filter in the baseband portion of the receiver.

42. The system of claim 37, wherein the adjustment mechanism is configured to adjust a sample rate of an ADC in the baseband portion of the receiver.

43. The system of claim 37, wherein the baseband portion comprises a baseband amplifier.

44. The system of claim 43, wherein the adjustment mechanism is configured to adjust gain of the baseband amplifier based on one of part-to-part variations of the receiver and frequency of an operating band.

45. The system of claim 44, wherein the baseband amplifier is configured to be adjusted over a 6 dB range.

46. The system of claim 44, wherein the baseband amplifier is configured to be adjusted with a digital-to-analog (DAC) voltage or current adjustment.

47. The system of claim 37, wherein the baseband portion comprises a baseband analog filter.

49. The method of claim 48, wherein the adjusting comprises adjusting the gain continuously.

50. The method of claim 48, wherein the adjusting comprises stepping down the gain.

51. The method of claim 48, wherein the step of providing comprises providing a mixer having a terminated output.

52. The method of claim 48, further comprising running a frequency synthesizer of the LO at a multiple of the frequency of the received RF signals.

53. The method of claim 52, wherein the multiple equals M/N, wherein M and N are positive integers.

54. The method of claim 53, wherein the multiple equals 2.

55. The method of claim 52, further comprising dividing down an output frequency of the frequency synthesizer by the multiple.

57. The receiver of claim 56, wherein the gain is adjusted continuously.

58. The receiver of claim 56, wherein the gain is stepped down.

59. The receiver of claim 56, wherein a frequency synthesizer of the LO runs at a multiple of the frequency of the received RF signals.

60. The receiver of claim 59, wherein the multiple equals M/N, wherein M and N are positive integers.

61. The receiver of claim 59, wherein the multiple is 2.

62. The receiver of claim 59, wherein an output frequency of the frequency synthesizer is divided down by the multiple.

63. The receiver of claim 56, wherein the receiver is integrated in a wireless communication transceiver.

64. The receiver of claim 56, wherein the adjustment mechanism includes a serial bus interface configured to convey control signals that adjust the LNA and mixer gain.

65. The receiver of claim 56, further comprising differential RF and LO signal paths.

66. The receiver of claim 56, wherein an output of the mixer is terminated.

67. The receiver of claim 56, wherein the mixer output is terminated with a 50 ohm RF load.

68. The receiver of claim 56, wherein a band of received RF signals is PCS.

69. The receiver of claim 56, wherein a band of received RF signals is Cellular.

70. The receiver of claim 56, wherein the LNA includes high gain, bypass, and mid-gain states.

27. A method for optimizing dynamic range in a multi-band direct conversion wireless communication device, the method comprising:

providing a receiver configured to receive RF signals, the receiver including a low noise amplifier (LNA), a mixer having an input and an output, a local oscillator (LO), and a baseband portion;

adjusting gain of the LNA and the mixer depending on a level of the received RF signals; and

adjusting drive level of the LO depending on a level of jammers detected by the receiver.

37. A system for optimizing dynamic range in a multi-band direct conversion wireless communication receiver, the system comprising:

a low noise amplifier (LNA) configured to amplify received RF signals;

a local oscillator (LO) configured to output a frequency;

a mixer having a first input operatively coupled to the LNA, a second input operatively coupled to the LO output, and an output;

a baseband portion coupled to the mixer output; and

an adjustment mechanism configured to adjust gain of the LNA and the mixer depending on a level of the received RF signals and drive level of the LO depending on a level of jammers detected by the receiver.

48. A method for reducing local oscillator leakage in a multi-band direct conversion wireless communication device, the method comprising:

providing a receiver configured to receive RF signals, the receiver including a low noise amplifier (LNA), a mixer, and a local oscillator (LO); and

adjusting gain of the LNA and the mixer as the signal level of the received RF signals increases, the adjusting balancing the reverse isolation of active components in the receiver.

56. A multi-band direct conversion wireless communication receiver, comprising:

a low noise amplifier (LNA) configured to amplify received RF signals;

a local oscillator (LO) configured to output a frequency;

a mixer having a first input operatively coupled to the LNA and a second input operatively coupled to the LO output; and

an adjustment mechanism configured to adjust gain of the LNA and the mixer as the signal level of the received RF signals increases, the adjusting balancing the reverse isolation of active components in the RF path of the receiver.