Method of frequency and phase locking in a plurality of temporal frames

• US 6,088,414 A
• Filed: 12/18/1997
• Issued: 07/11/2000
• Est. Priority Date: 12/18/1997
• Status: Expired due to Term

• Current Assignee: WSOU Investments, LLC (WSOU Holdings, LLC)
• Original Assignee: Alcatel USA Sourcing L.P. (Nokia Corporation)
• Inventors: Witchey, John, Dove, Jason W.
• Primary Examiner(s): TSE, YOUNG TOI
• Application Number:
  US08/993,288
• Time in Patent Office: 936 Days
• Field of Search: 375/354, 375/368, 375/371, 375/373, 375/375, 375/376, 327/147, 327/156
• US Class Current: 375/376
• CPC Class Codes: H03D 3/241 the oscillator being part of a phase locked loop
• CPC Class Codes: H03L 7/06 using a reference signal applied to a frequency- or phase-locked loop
• CPC Class Codes: H03L 7/087 using at least two phase detectors or a frequency and phase detector in the loop
• CPC Class Codes: H04L 7/033 using the transitions of the received signal to control the phase of the synchronising-signal-generating means, e.g. using a phase-locked loop
• CPC Class Codes: H04L 7/10 Arrangements for initial synchronisation

Abstract

A frequency and phase locking method for fine phase locking of a plurality of temporal frames, such as synchronous optical network (SONET) frames, includes the steps of fine phase tracking of the first frame and setting the phases of the subsequent frames in coherence with the phase of the first frame, for example, by a plurality of drop clock signals.

Claims

1. A method of phase locking in a plurality of temporal frames including a first frame and at least one subsequent frame, each frame characterized by a frequency and a phase, the phase of the first frame referenced by a first reference frequency, the method comprising the steps of:

(a) adjusting the first reference frequency to obtain a phase lock in the first frame;

(b) setting the phase of the at least one subsequent frame in coherence with the phase of the first frame;

(c) tracking the phase of the first frame;

(d) determining whether the phase lock of the first frame is lost; and

(e) repeating steps (a) through (b) if the phase lock of the first frame is lost.

2. The method of claim 1, wherein the frequency of the first frame is referenced by a second reference frequency, further comprising the step of adjusting the second reference frequency to obtain a frequency lock in the first frame.

3. The method of claim 2, further comprising the steps of:

(f) determining whether the phase lock of the first frame is lost for more than a predetermined time; and

(g) repeating the step of adjusting the second reference frequency if the phase lock of the first frame is lost for more than the predetermined time.

4. The method of claim 2, further comprising the step of providing a reference clock frequency adapted to provide the first and second reference frequencies.

5. The method of claim 4, further comprising the steps of:

dividing the reference clock frequency by a first divisor to obtain the first reference frequency; and

dividing the reference clock frequency by a second divisor to obtain the second reference frequency.

6. The method of claim 5, wherein the first divisor is less than the second divisor.

7. The method of claim 1, wherein the step of setting the phase of the at least one subsequent frame comprises the steps of:

(i) generating at least one drop clock signal corresponding to the at least one subsequent frame; and

(ii) shifting the phase of the at least one subsequent frame respectively according to the at least one drop clock signal while holding the phase and frequency of the first frame constant.

8. The method of claim 7, wherein the step of generating the at least one drop clock signal comprises the step of providing a predetermined phase shift for the at least one subsequent frame.

9. The method of claim 1, wherein the at least one subsequent frame comprises a plurality of subsequent frames, and the step of setting the phase of the at least one subsequent frame comprises the step of setting the phases of the plurality of subsequent frames.

10. The method of claim 9, wherein the frequency of the first frame is referenced by a second reference frequency, further comprising the step of adjusting the second reference frequency to obtain a frequency lock in the first frame.

11. The method of claim 10, further comprising the steps of:

(f) determining whether the phase lock of the first frame is lost for more than a predetermined time; and

(g) repeating the step of adjusting the second reference frequency if the phase lock of the first frame is lost for more than the predetermined time.

12. The method of claim 9, wherein the step of setting the phases of the plurality of subsequent frames comprises the steps of:

(i) generating a plurality of drop clock signals respectively for the plurality of subsequent frames; and

(ii) shifting the phases of the subsequent frames respectively according to the plurality of drop clock signals while holding the phase and frequency of the first frame constant.

13. The method of claim 12, wherein the step of generating the plurality of drop clock signals comprises the step of providing a predetermined phase shift for each of the subsequent frames.

14. The method of claim 13, wherein the predetermined phase shift is 0°

.

15. The method of claim 13, wherein the step of providing the predetermined phase shift comprises the step of providing a fixed phase shift between immediately adjacent frames in the plurality of frames.

16. A method of frequency and phase locking in a plurality of temporal frames including a first frame and at least one subsequent frame, each frame characterized by a frequency and a phase, the phase of the first frame referenced by a first reference frequency and the frequency of the first frame referenced by a second reference frequency, the method comprising the steps of:

(a) adjusting the second reference frequency to obtain a frequency lock in the first frame;

(b) adjusting the first reference frequency to obtain a phase lock in the first frame;

(c) setting the phase of the at least one subsequent frame in coherence with the phase of the first frame;

(d) tracking the phase of the first frame;

(e) determining whether the phase lock of the first frame is lost; and

(f) repeating steps (b) through (c) if the phase lock of the first frame is lost.

17. The method of claim 16, further comprising the steps of:

(g) determining whether the phase lock of the first frame is lost for more than a predetermined time; and

(h) repeating steps (a) through (c) if the phase lock of the first frame is lost for more than the predetermined time.

18. The method of claim 16, wherein the step of setting the phase of the at least one subsequent frame comprises the steps of:

(i) generating at least one drop clock signal corresponding to the at least one subsequent frame; and

(ii) shifting the phase of the at least one subsequent frame respectively according to the at least one drop clock signal while holding the phase and frequency of the first frame constant.

19. The method of claim 18, wherein the step of generating the at least one drop clock signal comprises the step of providing a predetermined phase shift for the at least one subsequent frame.

20. The method of claim 16, wherein the at least one subsequent frame comprises a plurality of subsequent frames, and the step of setting the phase of the at least one subsequent frame comprises the step of setting the phases of the plurality of subsequent frames.

21. The method of claim 20, further comprising the steps of:

(g) determining whether the phase lock of the first frame is lost for more than a predetermined time; and

(h) repeating steps (a) through (c) if the phase lock of the first frame is lost for more than the predetermined time.

22. The method of claim 20, wherein the step of setting the phases of the plurality of subsequent frames comprises the steps of:

(i) generating a plurality of drop clock signals respectively for the plurality of subsequent frames; and

(ii) shifting the phases of the subsequent frames respectively according to the plurality of drop clock signals while holding the phase and frequency of the first frame constant.

23. The method of claim 22, wherein the step of generating the plurality of drop clock signals comprises the step of providing a predetermined phase shift for each of the subsequent frames.

24. The method of claim 23, wherein the predetermined phase shift is 0°

.

25. The method of claim 23, wherein the step of providing the predetermined phase shift comprises the step of providing a fixed phase shift between immediately adjacent frames in the plurality of frames.

26. The method of claim 16, further comprising the step of providing a reference clock frequency adapted to provide the first and second reference frequencies.

27. The method of claim 26, further comprising the steps of:

dividing the reference clock frequency by a first divisor to obtain the first reference frequency; and

dividing the reference clock frequency by a second divisor to obtain the second reference frequency.

28. The method of 27, wherein the first divisor is less than the second divisor.

29. A method of frequency and phase locking in a plurality of temporal frames including a first frame and at least one subsequent frame, each frame characterized by a frequency and a phase, the phase of the first frame referenced by a first reference frequency and the frequency of the first frame referenced by a second reference frequency, the method comprising the steps of:

(a) adjusting the second reference frequency to obtain a frequency lock in the first frame;

(b) adjusting the first reference frequency to obtain a phase lock in the first frame;

(c) setting the phase of the at least one subsequent frame in coherence with the phase of the first frame;

(d) tracking the phase of the first frame;

(e) determining whether the phase lock of the first frame is lost;

(f) repeating steps (b) through (c) if the phase lock of the first frame is lost;

(g) determining whether the phase lock of the first frame is lost for more than a predetermined time; and

(h) repeating steps (a) through (c) if the phase lock of the first frame is lost for more than the predetermined time.

30. The method of claim 29, wherein the step of setting the phase of the at least one subsequent frame comprises the steps of:

(i) generating at least one drop clock signal corresponding to the at least one subsequent frame; and

(ii) shifting the phase of the at least one subsequent frame respectively according to the at least one drop clock signal while holding the phase and frequency of the first frame constant.

31. The method of claim 30, wherein the step of generating the at least one drop clock signal comprises the step of providing a predetermined phase shift for the at least one subsequent frame.

32. The method of claim 29, wherein the at least one subsequent frame comprises a plurality of subsequent frames, and the step of setting the phase of the at least one subsequent frame comprises the step of setting the phases of the plurality of subsequent frames.

33. The method of claim 32, wherein the step of setting the phases of the plurality of subsequent frames comprises the steps of:

(i) generating a plurality of drop clock signals respectively for the plurality of subsequent frames; and

(ii) shifting the phases of the plurality of subsequent frames respectively according to the drop clock signals while holding the phase and frequency of the first frame constant.

34. The method of claim 33, wherein the step of generating the plurality of drop clock signals comprises the step of providing a predetermined phase shift for each of the subsequent frames.

35. The method of claim 34, wherein the predetermined phase shift is 0°

.

36. The method of claim 34, wherein the step of providing the predetermined phase shift comprises the step of providing a fixed phase shift between immediately adjacent frames in the plurality of frames.

37. The method of claim 29, further comprising the step of providing a reference clock frequency adapted to provide the first and second reference frequencies.

38. The method of claim 37, further comprising the steps of:

dividing the reference clock frequency by a first divisor to obtain the first reference frequency; and

dividing the reference clock frequency by a second divisor to obtain the second reference frequency.

39. The method of claim 38, wherein the first divisor is less than the second divisor.

40. A method of frequency and phase locking in a plurality of temporal frames including a first frame and at least one subsequent frame, each frame characterized by a frequency and a phase, the method comprising the steps of:

(a) providing a first reference frequency adapted to reference the phase of the first frame;

(b) providing a second reference frequency adapted to reference the frequency of the first frame;

(c) adjusting the second reference frequency to obtain a frequency lock in the first frame;

(d) adjusting the first reference frequency to obtain a phase lock in the first frame;

(e) setting the phase of the at least one subsequent frame in coherence with the phase of the first frame;

(f) tracking the phase of the first frame;

(g) determining whether the phase lock of the first frame is lost;

(h) repeating steps (d) through (e) if the phase lock of the first frame is lost;

(i) determining whether the phase lock of the first frame is lost for more than a predetermined time; and

(j) repeating steps (c) through (e) if the phase lock of the first frame is lost for more than the predetermined time.

41. The method of claim 40, wherein the step of setting the phase of the at least one subsequent frame comprises the steps of:

generating at least one drop clock signal corresponding to the at least one subsequent frame; and

shifting the phase of the at least one subsequent frame respectively according to the at least one drop clock signal while holding the phase and frequency of the first frame constant.

42. The method of claim 41, wherein the step of generating the at least one drop clock signal comprises the step of providing a predetermined phase shift for the at least one subsequent frame.

43. The method of claim 40, wherein the at least one subsequent frame comprises a plurality of subsequent frames, and the step of setting the phase of the at least one subsequent frame comprises the step of setting the phases of the plurality of subsequent frames.

44. The method of claim 43, wherein the step of setting the phases of the plurality of subsequent frames comprises the steps of:

generating a plurality of drop clock signals respectively for the plurality of subsequent frames; and

shifting the phases of the plurality of subsequent frames respectively according to the drop clock signals while holding the phase and frequency of the first frame constant.

45. The method of claim 44, wherein the step of generating the plurality of drop clock signals comprises the step of providing a predetermined phase shift for each of the subsequent frames.

46. The method of claim 45, wherein the predetermined phase shift is 0°

.

47. The method of claim 45, wherein the step of providing the predetermined phase shift comprises the step of providing a fixed phase shift between immediately adjacent frames in the plurality of frames.

48. The method of claim 40, further comprising the step of providing a reference clock frequency adapted to provide the first and second reference frequencies.

49. The method of claim 48, wherein the step of providing the first reference frequency includes the step of dividing the reference clock frequency by a first divisor, and the step of providing the second reference frequency includes the step of dividing the reference clock frequency by a second divisor.

50. The method of claim 49, wherein the first divisor is less than the second divisor.

51. A method of frequency and phase locking in a plurality of synchronous frames including a first frame and at least one subsequent frame, each frame characterized by a frequency and a phase, the phase of the first frame referenced by a first reference frequency and the frequency of the first frame referenced by a second reference frequency, the method comprising the steps of:

(a) adjusting the second reference frequency to obtain a frequency lock in the first frame;

(b) adjusting the first reference frequency to obtain a phase lock in the first frame;

(c) generating at least one drop clock signal corresponding to the at least one subsequent frame;

(d) setting the phase of the at least one subsequent frame in coherence with the phase of the first frame respectively according to the at least one drop clock signal while holding the phase and frequency of the first frame constant;

(e) tracking the phase and frequency of the first frame;

(f) determining whether the phase lock of the first frame is lost; and

(g) repeating steps (b) through (d) if the phase lock of the first frame is lost.

52. The method of claim 51, further comprising the steps of:

(h) determining whether the phase lock of the first frame is lost for more than a predetermined time; and

(i) repeating steps (a) through (d) if the phase lock of the first frame is lost for more than the predetermined time.

53. The method of claim 51, wherein the step of generating the at least one drop clock signal comprises the step of providing a predetermined phase shift for the at least one subsequent frame.

54. The method of claim 53, wherein the predetermined phase shift is 0°

.

55. The method of claim 53, wherein the at least one subsequent frame comprises a plurality of subsequent frames.

56. The method of claim 55, further comprising the steps of:

(h) determining whether the phase lock of the first frame is lost for more than a predetermined time; and

(i) repeating steps (a) through (d) if the phase lock of the first frame is lost for more than the predetermined time.

57. The method of claim 55, wherein the step of generating the at least one drop clock signal comprises the step of generating a plurality of drop clock signals respectively for the plurality of subsequent frames, and the step of setting the phase of the at least one subsequent frame comprises the step of shifting the phases of the plurality of subsequent frames respectively according to the drop clock signals while holding the phase and frequency of the first frame constant.

58. The method of claim 57, wherein the step of generating the plurality of drop clock signals comprises the step of providing a predetermined phase shift for each of the subsequent frames.

59. The method of claim 58, wherein the predetermined phase shift is 0°

.

60. The method of claim 58, wherein the step of providing the predetermined phase shift comprises the step of providing a fixed phase shift between immediately adjacent frames in the plurality of frames.

61. The method of claim 51, further comprising the step of providing a reference clock frequency adapted to provide the first and second reference frequencies.

62. The method of claim 61, further comprising the steps of:

dividing the reference clock frequency by a first divisor to obtain the first reference frequency; and

dividing the reference clock frequency by a second divisor to obtain the second reference frequency.

63. The method of claim 62, wherein the first divisor is less than the second divisor.

64. A method of frequency and phase locking in a plurality of synchronous frames including a first frame and a plurality of subsequent frames, each frame characterized by a frequency and a phase, the method comprising the steps of:

(a) providing a first reference frequency adapted to reference the phase of the first frame;

(b) providing a second reference frequency adapted to reference the frequency of the first frame;

(c) adjusting the second reference frequency to obtain a frequency lock in the first frame;

(d) adjusting the first reference frequency to obtain a phase lock in the first frame;

(e) generating a plurality of drop clock signals respectively for the plurality of subsequent frames;

(f) setting the phases of the subsequent frames in coherence with the phase of the first frame respectively according to the drop clock signals while holding the phase and frequency of the first frame constant;

(g) tracking the phase and frequency of the first frame;

(h) determining whether the phase lock of the first frame is lost; and

(i) repeating steps (d) through (f) if the phase lock of the first frame is lost.

65. The method of claim 64, further comprising the steps of:

(j) determining whether the phase lock of the first frame is lost for more than a predetermined time; and

(k) repeating steps (c) through (f) if the phase lock of the first frame is lost for more than the predetermined time.

66. The method of claim 64, wherein the step of setting the phases of the subsequent frames comprises the step of shifting the phases of the subsequent frames respectively according to the drop clock signals while holding the phase and frequency of the first frame constant.

67. The method of claim 64, wherein the step of generating the plurality of drop clock signals comprises the step of providing a predetermined phase shift for each of the subsequent frames.

68. The method of claim 67, wherein the predetermined phase shift is 0°

.

69. The method of claim 67, wherein the step of providing the predetermined phase shift comprises the step of providing a fixed phase shift between immediately adjacent frames in the plurality of frames.

70. The method of claim 64, further comprising the step of providing a reference clock frequency adapted to provide the first and second reference frequencies.

71. The method of claim 70, wherein the step of providing the first reference frequency comprises the step of dividing the reference clock frequency by a first divisor, and the step of providing the second reference frequency comprises the step of dividing the reference clock frequency by a second divisor.

72. The method of claim 71, wherein the first divisor is less than the second divisor.

73. A method of frequency and phase locking in a plurality of synchronous frames including a first frame and a plurality of subsequent frames, each frame characterized by a frequency and a phase, the method comprising the steps of:

(a) providing a first reference frequency adapted to reference the phase of the first frame;

(b) providing a second reference frequency adapted to reference the frequency of the first frame;

(c) adjusting the second reference frequency to obtain a frequency lock in the first frame;

(d) adjusting the first reference frequency to obtain a phase lock in the first frame;

(e) generating a plurality of drop clock signals respectively for the plurality of subsequent frames;

(f) setting the phases of the subsequent frames in coherence with the phase of the first frame respectively according to the drop clock signals while holding the phase and frequency of the first frame constant;

(g) tracking the phase and frequency of the first frame;

(h) determining whether the phase lock of the first frame is lost;

(i) repeating steps (d) through (f) if the phase lock of the fir s t frame is lost;

(j) determining whether the phase lock of the first frame is lost for more than a predetermined time; and

(k) repeating steps (c) through (f) if the phase lock of the first frame is lost for more than the predetermined time.

74. The method of claim 73, wherein the step of setting the phases of the subsequent frames comprises the step of shifting the phases of the subsequent frames respectively according to the drop clock signals while holding the phase and frequency of the first frame constant.

75. The method of claim 73, wherein the step of generating the plurality of drop clock signals comprises the step of providing a predetermined phase shift for each of the subsequent frames.

76. The method of claim 75, wherein the predetermined phase shift is 0°

.

77. The method of claim 75, wherein the step of providing the predetermined phase shift comprises the step of providing a fixed phase shift between immediately adjacent frames in the plurality of frames.

78. The method of claim 73, further comprising the step of providing a reference clock frequency adapted to provide the first and second reference frequencies.

79. The method of claim 78, wherein the step of providing the first reference frequency comprises the step of dividing the reference clock frequency by a first divisor, and the step of providing the second reference frequency comprises the step of dividing the reference clock frequency by a second divisor that is greater than the first divisor.