Control loop for data signal baseline correction

• US 6,173,019 B1
• Filed: 05/12/1998
• Issued: 01/09/2001
• Est. Priority Date: 12/10/1997
• Status: Expired due to Term

• Current Assignee: National Semiconductor Corporation (Texas Instruments, Inc.)
• Original Assignee: National Semiconductor Corporation (Texas Instruments, Inc.)
• Inventors: Phanse, Abhijit, Hee, Wong
• Primary Examiner(s): Vo, Don N.
• Assistant Examiner(s): PHU, PHUONG M
• Application Number:
  US09/076,183
• Time in Patent Office: 973 Days
• Field of Search: 375/229, 375/232, 375/316, 375/319, 375/346, 375/317, 375/371, 327/307
• US Class Current: 375/319
• CPC Class Codes: H04L 25/03885 adaptive
• CPC Class Codes: H04L 25/06 Dc level restoring means; Bias distortion correction ; Decision circuits providing symbol by symbol detection

Abstract

A closed feedback loop controls the baseline correction of a data signal. Detected signal information about the baseline and positive and negative peaks of the incoming data signal is processed to generate a baseline correction signal which identifies the difference, if any, between the present data signal baseline and that which is desired. This baseline correction signal is summed with the original data signal to bring its baseline into conformance with the desired baseline.

Claims

1. An apparatus including a control loop for controlling a baseline correction of a data signal, comprising:

a baseline correction circuit configured to receive and combine a baseline correction signal and an input data signal having a data signal baseline associated therewith and in accordance therewith provide a corrected data signal with a substantially fixed baseline;

a data signal peak detection circuit, coupled to said baseline correction circuit, configured to receive and detect said corrected data signal and in accordance therewith provide a plurality of peak parameter signals which indicates whether said corrected data signal has transcended a plurality of predetermined signal levels including predetermined minimum and maximum signal levels which are respectively below and above a mean value of said corrected data signal;

a data signal mean detection circuit, coupled to said baseline correction circuit, configured to receive and detect said corrected data signal and in accordance therewith provide a first baseline parameter signal which indicates whether said corrected data signal is within a predetermined range of values intermediate to said predetermined minimum and maximum signal levels, and provide a second baseline parameter signal which indicates a polarity of said corrected data signal relative to said mean value of said corrected data signal;

a signal processing circuit, coupled to said data signal peak detection circuit, configured to receive and process said plurality of peak parameter signals and in accordance therewith provide a third baseline parameter signal which indicates a difference between said corrected data signal and said mean value of said corrected data signal; and

a baseline control circuit, coupled to said data signal mean detection circuit, said signal processing circuit and said baseline correction circuit, configured to receive and process said first, second and third baseline parameter signals and in accordance therewith provide said baseline correction signal.

2. The apparatus of claim 1, wherein said data signal peak detection circuit comprises:

a positive peaks signal detector circuit configured to receive and detect said corrected data signal and in accordance therewith provide a portion of said plurality of peak parameter signals which indicates when said corrected data signal has transcended one or more of said plurality of predetermined signal levels which include said predetermined maximum signal level and which are more positive than said mean value of said corrected data signal; and

a negative peaks signal detector circuit configured to receive and detect said corrected data signal and in accordance therewith provide another portion of said plurality of peak parameter signals which indicates when said corrected data signal has transcended one or more of said plurality of predetermined signal levels which include said predetermined minimum signal level and which are more negative than said mean value of said corrected data signal.

3. The apparatus of claim 1, wherein said baseline control circuit comprises:

a correction loop control circuit configured to receive and process said first, second and third baseline parameter signals and in accordance therewith provide a plurality of loop control signals; and

a variable signal generator circuit, coupled to said correction loop control circuit, configured to receive and process said plurality of loop control signals and in accordance therewith provide a variably increasing and decreasing analog signal as said baseline correction signal.

4. The apparatus of claim 3, wherein said correction loop control circuit comprises:

a first pulse density modulation circuit configured to receive and process said first and second baseline parameter signals and in accordance therewith provide a first plurality of pulse density modulated signals;

a second pulse density modulation circuit configured to receive and process said third baseline parameter signal and in accordance therewith provide a second plurality of pulse density modulated signals; and

a signal selection circuit, coupled to said first and second pulse density modulation circuits, configured to receive and select among said first and second pluralities of pulse density modulated signals to be provided as said plurality of loop control signals.

5. The apparatus of claim 3, wherein said variable signal generator circuit comprises:

an up/down counter circuit configured to receive said plurality of loop control signals and in accordance therewith provide a variably increasing and decreasing digital count signal; and

a digital-to-analog conversion circuit, coupled to said up/down counter circuit, configured to receive and convert said variably increasing and decreasing digital count signal to said variably increasing and decreasing analog signal.

6. The apparatus of claim 3, wherein:

said signal processing circuit further provides a fourth baseline parameter signal which indicates whether said corrected data signal is substantially centered about said mean value of said corrected data signal; and

said baseline control circuit is further configured to receive and process said fourth baseline parameter signal with said first, second and third baseline parameter signals and in accordance therewith provide said baseline correction signal.

7. The apparatus of claim 6, wherein said baseline control circuit comprises:

a correction loop control circuit configured to receive and process said first, second, third and fourth baseline parameter signals and in accordance therewith provide a plurality of loop control signals; and

a variable signal generator circuit, coupled to said correction loop control circuit, configured to receive said plurality of loop control signals and in accordance therewith provide a variably increasing and decreasing analog signal as said baseline correction signal.

8. The apparatus of claim 7, wherein said correction loop control circuit comprises:

a first pulse density modulation circuit configured to receive and process said first and second baseline parameter signals and in accordance therewith provide a first plurality of pulse density modulated signals;

a second pulse density modulation circuit configured to receive and process said third baseline parameter signal and in accordance therewith provide a second plurality of pulse density modulated signals; and

a signal selection circuit, coupled to said first and second pulse density modulation circuits, configured to receive said fourth baseline parameter signal and in accordance therewith receive and select among said first and second pluralities of pulse density modulated signals to be provided as said plurality of loop control signals.

9. The apparatus of claim 7, wherein said variable signal generator circuit comprises:

an up/down counter circuit configured to receive said plurality of loop control signals and in accordance therewith provide a variably increasing and decreasing digital count signal; and

a digital-to-analog conversion circuit, coupled to said up/down counter circuit, configured to receive and convert said variably increasing and decreasing digital count signal to said variably increasing and decreasing analog signal.

10. An apparatus including a control loop for controlling a baseline correction of a data signal, comprising:

a baseline correction circuit configured to receive and combine a baseline correction signal and an input data signal having a data signal baseline associated therewith and in accordance therewith provide a corrected data signal with a substantially fixed baseline;

a data signal peak detection circuit, coupled to said baseline correction circuit, configured to receive and detect said corrected data signal and in accordance therewith provide a plurality of peak parameter signals which indicates whether said corrected data signal has transcended a plurality of predetermined signal levels including predetermined minimum and maximum signal levels which are respectively below and above a mean value of said corrected data signal;

a signal processing circuit, coupled to said data signal peak detection circuit, configured to receive and process said plurality of peak parameter signals and in accordance therewith provide a first baseline parameter signal which indicates a difference between said corrected data signal and said mean value of said corrected data signal; and

a baseline control circuit, coupled to said signal processing circuit and said baseline correction circuit, configured to receive and process said first baseline parameter signal and in accordance therewith provide said baseline correction signal.

11. The apparatus of claim 10, wherein said data signal peak detection circuit comprises:

a positive peaks signal detector circuit configured to receive and detect said corrected data signal and in accordance therewith provide a portion of said plurality of peak parameter signals which indicates when said corrected data signal has transcended one or more of said plurality of predetermined signal levels which include said predetermined maximum signal level and which are more positive than said mean value of said corrected data signal; and

a negative peaks signal detector circuit configured to receive and detect said corrected data signal and in accordance therewith provide another portion of said plurality of peak parameter signals which indicates when said corrected data signal has transcended one or more of said plurality of predetermined signal levels which include said predetermined minimum signal level and which are more negative than said mean value of said corrected data signal.

12. The apparatus of claim 10, wherein said baseline control circuit comprises:

a correction loop control circuit configured to receive and process said first baseline parameter signal and in accordance therewith provide a plurality of loop control signals; and

a variable signal generator circuit, coupled to said correction loop control circuit, configured to receive and process said plurality of loop control signals and in accordance therewith provide a variably increasing and decreasing analog signal as said baseline correction signal.

13. The apparatus of claim 12, wherein said correction loop control circuit comprises a pulse density modulation circuit configured to receive and process said first baseline parameter signal and in accordance therewith provide a plurality of pulse density modulated signals as said plurality of loop control signals.

14. The apparatus of claim 12, wherein said variable signal generator circuit comprises:

an up/down counter circuit configured to receive said plurality of loop control signals and in accordance therewith provide a variably increasing and decreasing digital count signal; and

a digital-to-analog conversion circuit, coupled to said up/down counter circuit, configured to receive and convert said variably increasing and decreasing digital count signal to said variably increasing and decreasing analog signal.

15. The apparatus of claim 10, wherein:

said signal processing circuit further provides a second baseline parameter signal which indicates whether said corrected data signal is substantially centered about said mean value of said corrected data signal; and

said baseline control circuit is further configured to receive and process said second baseline parameter signal with said first baseline parameter signal and in accordance therewith provide said baseline correction signal.

16. The apparatus of claim 15, wherein said baseline control circuit comprises:

a correction loop control circuit configured to receive and process said first and second baseline parameter signals and in accordance therewith provide a plurality of loop control signals; and

a variable signal generator circuit, coupled to said correction loop control circuit, configured to receive said plurality of loop control signals and in accordance therewith provide a variably increasing and decreasing analog signal as said baseline correction signal.

17. The apparatus of claim 16, wherein said correction loop control circuit comprises a pulse density modulation circuit configured to receive and process said first baseline parameter signal and in accordance therewith provide a plurality of pulse density modulated signals as said plurality of loop control signals.

18. The apparatus of claim 16, wherein said variable signal generator circuit comprises:

an up/down counter circuit configured to receive said plurality of loop control signals and in accordance therewith provide a variably increasing and decreasing digital count signal; and

a digital-to-analog conversion circuit, coupled to said up/down counter circuit, configured to receive and convert said variably increasing and decreasing digital count signal to said variably increasing and decreasing analog signal.

19. An apparatus including a control loop for controlling a baseline correction of a data signal, comprising:

a baseline correction circuit configured to receive and combine a baseline correction signal and an input data signal having a data signal baseline associated therewith and in accordance therewith provide a corrected data signal with a substantially fixed baseline;

a data signal mean detection circuit, coupled to said baseline correction circuit, configured to receive and detect said corrected data signal and in accordance therewith provide a first baseline parameter signal which indicates whether said corrected data signal is within a predetermined range of values intermediate to said predetermined minimum and maximum signal levels, and provide a second baseline parameter signal which indicates a polarity of said corrected data signal relative to a mean value of said corrected data signal; and

a baseline control circuit, coupled to said data signal mean detection circuit and said baseline correction circuit, configured to receive and process said first and second baseline parameter signals and in accordance therewith provide said baseline correction signal.

20. The apparatus of claim 19, wherein said baseline control circuit comprises:

a correction loop control circuit configured to receive and process said first and second baseline parameter signals and in accordance therewith provide a plurality of loop control signals; and

a variable signal generator circuit, coupled to said correction loop control circuit, configured to receive and process said plurality of loop control signals and in accordance therewith provide a variably increasing and decreasing analog signal as said baseline correction signal.

21. The apparatus of claim 20, wherein said correction loop control circuit comprises a pulse density modulation circuit configured to receive and process said first and second baseline parameter signals and in accordance therewith provide a plurality of pulse density modulated signals as said plurality of loop control signals.

22. The apparatus of claim 20, wherein said variable signal generator circuit comprises:

an up/down counter circuit configured to receive said plurality of loop control signals and in accordance therewith provide a variably increasing and decreasing digital count signal; and

a digital-to-analog conversion circuit, coupled to said up/down counter circuit, configured to receive and convert said variably increasing and decreasing digital count signal to said variably increasing and decreasing analog signal.

23. A method of controlling a baseline correction of a data signal with a control loop, comprising the steps of:

receiving and combining a baseline correction signal and an input data signal having a data signal baseline associated therewith and in accordance therewith generating a corrected data signal with a substantially fixed baseline;

detecting said corrected data signal and in accordance therewith generating a plurality of peak parameter signals which indicates whether said corrected data signal has transcended a plurality of predetermined signal levels including predetermined minimum and maximum signal levels which are respectively below and above a mean value of said corrected data signal;

detecting said corrected data signal and in accordance therewith generating a first baseline parameter signal which indicates whether said corrected data signal is within a predetermined range of values intermediate to said predetermined minimum and maximum signal levels, and generating a second baseline parameter signal which indicates a polarity of said corrected data signal relative to said mean value of said corrected data signal;

processing said plurality of peak parameter signals and in accordance therewith generating a third baseline parameter signal which indicates a difference between said corrected data signal and said mean value of said corrected data signal; and

processing said first, second and third baseline parameter signals and in accordance therewith generating said baseline correction signal.

24. The method of claim 23, wherein said step of detecting said corrected data signal and in accordance therewith generating a plurality of peak parameter signals which indicates whether said corrected data signal has transcended a plurality of predetermined signal levels including predetermined minimum and maximum signal levels which are respectively below and above a mean value of said corrected data signal comprises:

detecting said corrected data signal and in accordance therewith generating a portion of said plurality of peak parameter signals which indicates when said corrected data signal has transcended one or more of said plurality of predetermined signal levels which include said predetermined maximum signal level and which are more positive than said mean value of said corrected data signal; and

detecting said corrected data signal and in accordance therewith generating another portion of said plurality of peak parameter signals which indicates when said corrected data signal has transcended one or more of said plurality of predetermined signal levels which include said predetermined minimum signal level and which are more negative than said mean value of said corrected data signal.

25. The method of claim 23, wherein said step of processing said first, second and third baseline parameter signals and in accordance therewith generating said baseline correction signal comprises:

processing said first, second and third baseline parameter signals and in accordance therewith generating a plurality of loop control signals; and

processing said plurality of loop control signals and in accordance therewith generating a variably increasing and decreasing analog signal as said baseline correction signal.

26. The method of claim 25, wherein said step of processing said first, second and third baseline parameter signals and in accordance therewith generating a plurality of loop control signals comprises:

processing said first and second baseline parameter signals and in accordance therewith generating a first plurality of pulse density modulated signals;

processing said third baseline parameter signal and in accordance therewith generating a second plurality of pulse density modulated signals; and

selecting among said first and second pluralities of pulse density modulated signals to be provided as said plurality of loop control signals.

27. The method of claim 25, wherein said step of processing said plurality of loop control signals and in accordance therewith generating a variably increasing and decreasing analog signal as said baseline correction signal comprises:

receiving said plurality of loop control signals and in accordance therewith generating a variably increasing and decreasing digital count signal; and

converting said variably increasing and decreasing digital count signal to said variably increasing and decreasing analog signal.

28. The method of claim 23, wherein:

said method further comprises the step of processing said plurality of peak parameter signals and in accordance therewith generating a fourth baseline parameter signal which indicates whether said corrected data signal is substantially centered about said mean value of said corrected data signal; and

said step of processing said first, second and third baseline parameter signals and in accordance therewith generating said baseline correction signal comprises processing said fourth baseline parameter signal with said first, second and third baseline parameter signals and in accordance therewith generating said baseline correction signal.

29. The method of claim 28, wherein said step of processing said fourth baseline parameter signal with said first, second and third baseline parameter signals and in accordance therewith generating said baseline correction signal comprises:

processing said first, second, third and fourth baseline parameter signals and in accordance therewith generating a plurality of loop control signals; and

receiving said plurality of loop control signals and in accordance therewith generating a variably increasing and decreasing analog signal as said baseline correction signal.

30. The method of claim 29, wherein said step of processing said first, second, third and fourth baseline parameter signals and in accordance therewith generating a plurality of loop control signals comprises:

processing said first and second baseline parameter signals and in accordance therewith generating a first plurality of pulse density modulated signals;

processing said third baseline parameter signal and in accordance therewith generating a second plurality of pulse density modulated signals; and

receiving said fourth baseline parameter signal and in accordance therewith receiving and selecting among said first and second pluralities of pulse density modulated signals to be outputted as said plurality of loop control signals.

31. The method of claim 29, wherein said step of receiving said plurality of loop control signals and in accordance therewith generating a variably increasing and decreasing analog signal as said baseline correction signal comprises:

receiving said plurality of loop control signals and in accordance therewith generating a variably increasing and decreasing digital count signal; and

converting said variably increasing and decreasing digital count signal to said variably increasing and decreasing analog signal.

32. A method of controlling a baseline correction of a data signal with a control loop, comprising the steps of:

receiving and combining a baseline correction signal and an input data signal having a data signal baseline associated therewith and in accordance therewith generating a corrected data signal with a substantially fixed baseline;

detecting said corrected data signal and in accordance therewith generating a plurality of peak parameter signals which indicates whether said corrected data signal has transcended a plurality of predetermined signal levels including predetermined minimum and maximum signal levels which are respectively below and above a mean value of said corrected data signal;

processing said plurality of peak parameter signals and in accordance therewith generating a first baseline parameter signal which indicates a difference between said corrected data signal and said mean value of said corrected data signal; and

processing said first baseline parameter signal and in accordance therewith generating said baseline correction signal.

33. The method of claim 32, wherein said step of detecting said corrected data signal and in accordance therewith generating a plurality of peak parameter signals which indicates whether said corrected data signal has transcended a plurality of predetermined signal levels including predetermined minimum and maximum signal levels which are respectively below and above a mean value of said corrected data signal comprises:

detecting said corrected data signal and in accordance therewith generating a portion of said plurality of peak parameter signals which indicates when said corrected data signal has transcended one or more of said plurality of predetermined signal levels which include said predetermined maximum signal level and which are more positive than said mean value of said corrected data signal; and

detecting said corrected data signal and in accordance therewith generating another portion of said plurality of peak parameter signals which indicates when said corrected data signal has transcended one or more of said plurality of predetermined signal levels which include said predetermined minimum signal level and which are more negative than said mean value of said corrected data signal.

34. The method of claim 32, wherein said step of processing said first baseline parameter signal and in accordance therewith generating said baseline correction signal comprises:

processing said first baseline parameter signal and in accordance therewith generating a plurality of loop control signals; and

processing said plurality of loop control signals and in accordance therewith generating a variably increasing and decreasing analog signal as said baseline correction signal.

35. The method of claim 34, wherein said step of processing said first baseline parameter signal and in accordance therewith generating a plurality of loop control signals comprises processing said first baseline parameter signal and in accordance therewith generating a plurality of pulse density modulated signals as said plurality of loop control signals.

36. The method of claim 34, wherein said step of processing said plurality of loop control signals and in accordance therewith generating a variably increasing and decreasing analog signal as said baseline correction signal comprises:

receiving said plurality of loop control signals and in accordance therewith generating a variably increasing and decreasing digital count signal; and

converting said variably increasing and decreasing digital count signal to said variably increasing and decreasing analog signal.

37. The method of claim 32, wherein:

said method further comprises the step of processing said plurality of peak parameter signals and in accordance therewith generating a second baseline parameter signal which indicates whether said corrected data signal is substantially centered about said mean value of said corrected data signal; and

said step of processing said first baseline parameter signal and in accordance therewith generating said baseline correction signal comprises processing said second baseline parameter signal with said first baseline parameter signal and in accordance therewith generating said baseline correction signal.

38. The method of claim 37, wherein said step of processing said second baseline parameter signal with said first baseline parameter signal and in accordance therewith generating said baseline correction signal comprises:

processing said first and second baseline parameter signals and in accordance therewith generating a plurality of loop control signals; and

receiving said plurality of loop control signals and in accordance therewith generating a variably increasing and decreasing analog signal as said baseline correction signal.

39. The method of claim 38, wherein said step of processing said first and second baseline parameter signals and in accordance therewith generating a plurality of loop control signals comprises processing said first baseline parameter signal and in accordance therewith generating a plurality of pulse density modulated signals as said plurality of loop control signals.

40. The method of claim 38, wherein said step of receiving said plurality of loop control signals and in accordance therewith generating a variably increasing and decreasing analog signal as said baseline correction signal comprises:

receiving said plurality of loop control signals and in accordance therewith generating a variably increasing and decreasing digital count signal; and

converting said variably increasing and decreasing digital count signal to said variably increasing and decreasing analog signal.

41. A method of controlling a baseline correction of a data signal with a control loop, comprising the steps of:

receiving and combining a baseline correction signal and an input data signal having a data signal baseline associated therewith and in accordance therewith generating a corrected data signal with a substantially fixed baseline;

detecting said corrected data signal and in accordance therewith generating a first baseline parameter signal which indicates whether said corrected data signal is within a predetermined range of values intermediate to said predetermined minimum and maximum signal levels, and generating a second baseline parameter signal which indicates a polarity of said corrected data signal relative to a mean value of said corrected data signal; and

processing said first and second baseline parameter signals and in accordance therewith generating said baseline correction signal.

42. The method of claim 41 wherein said step of processing said first and second baseline parameter signals and in accordance therewith generating said baseline correction signal comprises:

processing said first and second baseline parameter signals and in accordance therewith generating a plurality of loop control signals; and

processing said plurality of loop control signals and in accordance therewith generating a variably increasing and decreasing analog signal as said baseline correction signal.

43. The method of claim 42, wherein said step of processing said first and second baseline parameter signals and in accordance therewith generating a plurality of loop control signals comprises processing said first and second baseline parameter signals and in accordance therewith generating a first plurality of pulse density modulated signals as said plurality of loop control signals.

44. The method of claim 42, wherein said step of processing said plurality of loop control signals and in accordance therewith generating a variably increasing and decreasing analog signal as said baseline correction signal comprises:

receiving said plurality of loop control signals and in accordance therewith generating a variably increasing and decreasing digital count signal; and

converting said variably increasing and decreasing digital count signal to said variably increasing and decreasing analog signal.