Frequency phase correction system

• US 7,929,928 B2
• Filed: 11/24/2004
• Issued: 04/19/2011
• Est. Priority Date: 05/18/2000
• Status: Expired due to Fees

• Current Assignee: CSR Technology Incorporated (Qualcomm, Inc.)
• Original Assignee: SIRF Technology Incorporated (Qualcomm, Inc.)
• Inventors: Vantalon, Nicolas Patrick, Peng, Leon Kuo-Liang, Pande, Ashutosh, Garin, Lionel, Gronemeyer, Steven A., Babitch, Daniel, Zhang, Gengsheng
• Primary Examiner(s): Urban; Edward
• Assistant Examiner(s): Chen; Junpeng
• Application Number:
  US10/997,797
• Publication Number:
  US 20050162306A1
• Time in Patent Office: 2,337 Days
• Field of Search: 455/118, 455/119, 455/151.1, 455/151.3, 455/264, 455/245.1, 455/255, 455/258, 455/76, 455/164.1, 455/181.1, 455/196.1, 455/259, 455/260, 455/265, 455/456.3, 455/456.1, 455/67.11, 455/67.13, 455/139, 455/147, 4551921-1923, 4551821-1823, 455/71, 375/57.74, 375/376, 375/344, 375/340, 375/355, 375/326, 375/260, 375/145, 375/333, 375/375, 375/226, 375/327, 331/57.74, 331/16, 331/18, 701/216, 701/213, 342/357.15, 342/357.1, 342/357.09, 342/357.06
• US Class Current: 455/139
• CPC Class Codes: G01S 19/05 providing aiding data
• CPC Class Codes: G01S 19/17 Emergency applications
• CPC Class Codes: G01S 19/235 Calibration of receiver components
• CPC Class Codes: G01S 5/021 Calibration, monitoring or correction G01S5/0252 takes precedence
• CPC Class Codes: H03J 2200/12 Radio receiver combined with a GPS receiver
• CPC Class Codes: H03J 7/065 the counter or frequency divider being used in a phase locked loop
• CPC Class Codes: H03L 1/022 by indirect stabilisation, i.e. by generating an electrical correction signal which is a function of the temperature H03L1/021 takes precedence

Abstract

A frequency phase correction system and method are described that provides a receiver with a greater ability to lock onto relatively weak radio frequency signals by determining and estimating an amount of frequency error in a local frequency reference of the receiver, and using the error estimate to maintain frequency coherence with a received signal, thereby allowing tracking over a longer period of time, enabling longer integration times to capture weaker signals without losing frequency coherence.

Claims

1. A frequency phase correction system for use with a communication device utilizing a reference frequency signal and comprising a communication section and a position determination section configured to determine position information of the communication device based on one or more radio frequency signals received by the position determination section, the frequency reference correction system comprising:

a frequency error block, including an adaptive filter, configured to estimate a frequency error, a drift rate, and a phase acceleration in the reference frequency signal during a time interval in the future; and

a frequency and time control block configured to adjust an operating frequency of the reference frequency signal during the time interval by;

a) adjusting the estimate of the drift rate based on the estimated phase acceleration, and

b) adjusting the frequency of the reference frequency signal to counteract the adjusted estimated drift rate.

2. The system of claim 1, wherein said frequency error of the reference frequency signal is obtained by estimating a frequency error based on a measured ambient temperature in which a reference frequency oscillator generating the reference frequency signal is operating.

5. The system of claim 1, wherein said frequency error of the reference frequency signal is obtained utilizing automatic frequency control circuitry to determine a difference between a received communication signal and the frequency reference signal.

6. The system of claim 1, wherein said reference frequency signal is obtained utilizing a reference frequency generator dedicated to the communication receiver.

7. The system of claim 1, wherein said reference frequency signal is obtained utilizing a reference frequency generator shared by the communication receiver and a second communication receiver.

8. The system of claim 1, wherein said frequency error block is further configured to determine signal quality of a communication signal received by the communication receiver and the adaptive filter is configured to filter the communication signal and, based on the determined signal quality of the communication signal, to adjust a level of filtering applied to the communication signal by the adaptive filter.

9. The system of claim 8, wherein said frequency error block is configured to utilize said signal quality information to refine the estimated frequency error and drift rate.

10. The system of claim 1, wherein said frequency error block is configured to determine frequency error at periodic intervals.

11. The system of claim 1, wherein said frequency error block configured to determine a frequency error of the reference frequency signal is configured to receive frequency error information from a source external to the frequency error block.

12. The system of claim 1, wherein said frequency error block configured to determine a frequency error of the reference frequency signal is configured to compute, at least partially, the frequency error of the reference frequency signal.

13. The system of claim 1, wherein said frequency error block configured to determine a frequency error of the reference frequency signal is configured to compare a determined frequency estimate to a previous frequency estimate, and determine a difference between the determined frequency estimate and the previous frequency estimate.

14. The system of claim 1, wherein said frequency error block is implemented as a Kalman filter.

15. The system of claim 1, wherein said frequency error block is further configured to filter broadband noise from an incoming signal.

16. The system of claim 1, wherein said time and frequency block is implemented using a processor.

17. The system of claim 16, wherein said processor is implemented using a digital signal processor.

3. A frequency phase correction system for use with a communication device utilizing a reference frequency signal and comprising a communication section and a position determination section configured to determine position information of the communication device based on one or more radio frequency signals received by the position determination section, the frequency reference correction system comprising:

a frequency error block configured to estimate a frequency error, a drift rate, and a phase acceleration in the reference frequency signal during a time interval in the future; and

a frequency and time control block configured to adjust an operating frequency of the reference frequency signal during the time interval by;

a) adjusting the estimate of the drift rate based on the estimated phase acceleration, and

b) adjusting the frequency of the reference frequency signal to counteract the adjusted estimated drift rate,

wherein said frequency error of the reference frequency signal is obtained utilizing a phase-locked loop to determine a difference between a received communication signal and the frequency reference signal.

4. A frequency phase correction system for use with a communication device utilizing a reference frequency signal and comprising a communication section and a position determination section configured to determine position information of the communication device based on one or more radio frequency signals received by the position determination section, the frequency reference correction system comprising:

a frequency error block, configured to estimate a frequency error, a drift rate, and phase acceleration in the reference frequency signal during a time interval in the future; and

a frequency and time control block configured to adjust an operating frequency of the reference frequency signal during the time interval by;

a) adjusting the estimate of the drift rate based on the estimated phase acceleration, and

b) adjusting the frequency of the reference frequency signal to counteract the adjusted estimated drift rate.

18. An aided location communication device (ALCD), comprising:

a reference frequency oscillator providing a reference frequency signal;

a communication section providing radio frequency communication with one or more communication devices;

a position determination section configured to determine position information of the ALCD based on one or more received radio frequency signals received by the position determination section; and

a frequency phase correction system, including an adaptive filter configured to filter the one or more radio frequency signals received by the position determination section, the frequency phase correction system configured to correlate the reference frequency signal with the one or more adaptively filtered radio frequency signals,

wherein the adaptive filter estimates a frequency error, a drift rate, and a phase acceleration in the reference frequency signal during a time interval in the future, and the frequency phase correction system adjusts an operating frequency of the reference frequency signal during the time interval by;

a) adjusting the estimate of the drift rate based on the estimated phase acceleration, and

b) adjusting the frequency of the reference frequency signal to counteract the adjusted estimated drift rate.

19. The system of claim 18, wherein said communication section comprises a wireless communication device.

20. The system of claim 19, wherein the wireless communication device is a cellular telephone.

21. The system of claim 18, wherein said position determination section comprises a GPS receiver.

22. The system of claim 18, wherein said frequency phase correction system comprises:

a frequency error block, including the adaptive filter, the frequency error block being configured to determine a frequency error of the reference frequency signal, one or more frequency characteristics of the reference frequency signal, and an estimate of the frequency error in the reference frequency signal at a time in the future; and

a frequency and time control block configured to adjust an operating frequency of the reference frequency signal to account for said estimate of the frequency error in reference frequency signal.

23. The system of claim 22, wherein the frequency error of the reference frequency signal is obtained by estimating a frequency error based on the measured ambient temperature in which the reference frequency oscillator is operating.

24. The system of claim 22, wherein the frequency error of the reference frequency signal is obtained utilizing a phase-locked loop to determine a difference between a received communication signal and the frequency reference signal.

25. The system of claim 22, wherein the frequency error of the reference frequency signal is obtained utilizing automatic frequency control circuitry to determine a difference between a received communication signal and the frequency reference signal.

26. The system of claim 22, wherein the frequency characteristics comprise at least one of a rate of change of the frequency error, and frequency jerk.

27. The system of claim 22, wherein the reference frequency signal is obtained utilizing a reference frequency generator dedicated to the position determination section.

28. The system of claim 22, wherein the reference frequency signal is obtained utilizing a reference frequency generator utilized by at least one of the position determination section and the communication section of the ALCD.

29. The system of claim 22, wherein said frequency error block is further configured to determine signal quality of a communication signal received by a communication receiver and the adaptive filter is configured to filter the communication signal and, based on the determined signal quality of the communication signal, to adjust a level of filtering applied to the communication signal by the adaptive filter.

30. The system of claim 29, wherein the signal quality is that of a communication signal received by the communication section of the ALCD.

31. The system of claim 29, wherein the frequency reference correction system is configured to utilize said signal quality information to refine the determined frequency characteristics.

32. The system of claim 22, wherein said frequency error block is configured to determine frequency error at periodic intervals.

33. The system of claim 22, wherein said frequency error block configured to determine a frequency error of the reference frequency signal is configured to receive frequency error information from the communication section of the ALCD.

34. The system of claim 33, wherein the received frequency error information is at least one of a hardware signal and a software word.

35. The system of claim 22, wherein said frequency error block configured to determine a frequency error of the reference frequency signal is configured to compute, at least partially, the frequency error of the reference frequency signal.

36. The system of claim 22, wherein said reference frequency error block configured to determine a frequency error of the reference frequency signal is configured to compare a determined frequency estimate to a previous frequency estimate, and determine a difference between the determined frequency estimate and the previous frequency estimate.

37. The system of claim 22, wherein the adaptive filter of the frequency error block is a Kalman filter.

38. The system of claim 22, wherein the adaptive filter is further configured to filter broadband noise from a received frequency error signal.

39. The system of claim 22, wherein said time and frequency block is implemented using a processor.

40. The system of claim 39, wherein said processor is utilized by at least one of the communication section and the position determination section.

41. The system of claim 39, wherein said processor is a digital signal processor.

42. A method for receiving wireless signals at a communication device utilizing a reference frequency signal and comprising a communication section and a position determination section configured to determine position information of the communication device based on one or more radio frequency signals received by the position determination section, the method comprising:

adaptively filtering the one or more radio frequency signals received by the position determination section;

correlating the reference frequency signal with the one or more adaptively filtered radio frequency signals received by the position determination section to determine a frequency error of the reference frequency signal,

determining one or more frequency characteristics of the reference frequency signal,

determining an estimate of the frequency error, a drift rate, and a phase acceleration in the reference frequency signal during a time interval in the future; and

adjusting an operating frequency of the reference frequency signal during the time interval by;

a) adjusting the estimate of the drift rate based on the estimated phase acceleration, and

b) adjusting the frequency of the reference frequency signal to counteract the adjusted estimated drift rate.

43. The method of claim 42, wherein said determining the frequency error of the reference frequency signal comprises estimating a frequency error based on the measured ambient temperature in which a reference frequency oscillator generating the reference frequency signal is operating.

44. The method of claim 42, wherein said determining the frequency error of the reference frequency signal comprises utilizing a phase-locked loop to determine a difference between a received communication signal and the frequency reference signal.

45. The method of claim 42, wherein the frequency characteristics comprise at least one of a rate of change of the frequency error, and frequency jerk.

46. The method of claim 42, wherein said determining the frequency error of the reference frequency signal comprises utilizing automatic frequency control circuitry to determine a difference between a received communication signal and the frequency reference signal.

47. The method of claim 42, further comprising generating the reference frequency signal utilizing a reference frequency generator dedicated to the communication receiver.

48. The method of claim 42, further comprising generating the reference frequency signal utilizing a reference frequency generator shared by the communication receiver and a second communication receiver.

49. The method of claim 42, further comprising determining a signal quality of a communication signal received by the receiver and changing the adaptive filtering of the one or more radio-frequency signals responsive to the determined signal quality.

50. The method of claim 49, further comprising utilizing said signal quality information to refine the determined frequency characteristics.

51. The method of claim 42, wherein said determining the frequency error further comprises determining the frequency error at periodic intervals.

52. The method of claim 42, wherein said determining the frequency error further comprises receiving frequency error information from a source external to the frequency error block.

53. The method of claim 42, wherein said determining the frequency error further comprises computing, at least partially, the frequency error of the reference frequency signal.

54. The method of claim 42, further comprising comparing a determined frequency estimate to a previous frequency estimate, and determining a difference between the determined frequency estimate and the previous frequency estimate.

55. The method of claim 42, further comprising tuning a frequency error block configured to determine the frequency error, said tuning based on expected noise in the frequency estimates.

56. The method of claim 42, further comprising tuning a frequency error block configured to determine the frequency error, said tuning based on signal quality received by the communication device.

57. The method of claim 42, further comprising determining at least one of phase acceleration, frequency acceleration, phase jerk and frequency jerk over time.

58. The method of claim 42, further comprising filtering the frequency reference signal.

59. The method of claim 42, further comprising storing the frequency characteristics in one or more registers or other locations utilized by a processor.

60. The method of claim 42, further comprising determining a signal quality measure using received signal strength, phase noise in the loop or other characteristics that can be used to indicate the quality of the received signal.

61. The method of claim 60, further comprising using said signal quality measure to determine a level of filtering applied in determining the frequency error.

62. A system for receiving wireless signals at a communication device utilizing a reference frequency signal and comprising a communication section and a position determination section configured to determine position information of the communication device based on one or more radio frequency signals received by the position determination section, the system comprising:

means for adaptively filtering the one or more radio frequency signals received by the position determination section;

means for correlating the reference frequency signal with the one or more adaptively filtered radio frequency signals received by the position determination section to determine a frequency error of the reference frequency signal;

means for determining one or more frequency characteristics of the reference frequency signal;

means for determining an estimate of the frequency error, a drift rate, and a phase acceleration in the reference frequency signal during a time interval in the future; and

means for adjusting an operating frequency of the reference frequency signal during the time interval by;

a) adjusting the estimate of the drift rate based on the estimated phase acceleration, and

b) adjusting the frequency of the reference frequency signal to counteract the adjusted estimated drift rate.

63. The system of claim 62, wherein said means for determining the frequency error of the reference frequency signal comprises means for estimating a frequency error based on the measured ambient temperature in which a reference frequency oscillator generating the reference frequency signal is operating.

64. The system of claim 62, wherein said means for determining the frequency error of the reference frequency signal comprises means for determining a difference between a received communication signal and the frequency reference signal.

65. The system of claim 62, wherein the frequency characteristics comprise at least one of a rate of change of the frequency error, and frequency jerk.

66. The system of claim 62, wherein said means for determining the frequency error of the reference frequency signal comprises means for determining a difference between a received communication signal and the frequency reference signal.

67. The system of claim 62, further comprising means dedicated to the communication receiver for generating the reference frequency signal.

68. The system of claim 62, further comprising means shared by the communication receiver and a second communication receiver for generating the reference frequency signal.

69. The system of claim 62, further comprising means for determining a signal quality of a communication signal received by the receiver and for changing the adaptive filtering of the one or more radio-frequency signals, by the means for adaptively filtering, responsive to the determined signal quality.

70. The system of claim 69, further comprising means for utilizing said signal quality information to refine the determined frequency characteristics.

71. The system of claim 62, wherein said means for determining the frequency error further comprises means for determining the frequency error at periodic intervals.

72. The system of claim 62, wherein said means for determining the frequency error further comprises means for receiving frequency error information from an external source.

73. The system of claim 62, wherein said means for determining the frequency error further comprises means for computing, at least partially, the frequency error of the reference frequency signal.

74. The system of claim 62, further comprising means for comparing a determined frequency estimate to a previous frequency estimate, and for determining a difference between the determined frequency estimate and the previous frequency estimate.

75. The system of claim 62, further comprising means for tuning a frequency error block to determine the frequency error based on expected noise in the frequency estimates.

76. The system of claim 62, further comprising means for tuning a frequency error block to determine the frequency error based on signal quality received by the communication device.

77. The system of claim 62, further comprising means for determining at least one of phase acceleration, frequency acceleration, phase jerk, and frequency jerk over time.

78. The system of claim 62, further comprising means for filtering the frequency reference signal.

79. The system of claim 62, further comprising means for storing the frequency characteristics in one or more registers or other locations utilized by a processor.

80. The system of claim 62, further comprising means for determining a signal quality measure using received signal strength, phase noise in the loop or other characteristics that can be used to indicate the quality of the received signal.

81. The method of claim 80, further comprising means for determining a level of filtering applied based on said signal quality measure.