System for controlling signal level at both ends of a transmission link, based upon a detected value

• US 5,678,198 A
• Filed: 05/15/1995
• Issued: 10/14/1997
• Est. Priority Date: 05/22/1991
• Status: Expired due to Term

• Current Assignee: SBC Technology Resources, Inc. (AT&T, Inc.)
• Original Assignee: Southwestern Bell Technology Resources, Inc. (AT&T, Inc.)
• Inventors: Lemson, Paul H.
• Primary Examiner(s): Pham, Chi H.
• Application Number:
  US08/440,976
• Time in Patent Office: 883 Days
• Field of Search: 455/13.4, 455/14, 455/67.1, 455/67.5, 455/70, 455/72, 455/234.1, 455/234.2, 455/235.1, 455/249.1, 455/253.2, 455/254, 455/281-283, 455/289, 455/291 , 455/295, 333/17.2, 359/194, 370/7, 370/202, 375/296
• US Class Current: 455/67.11
• CPC Class Codes: H03G 3/3084 in receivers or transmitters for electromagnetic waves other than radiowaves, e.g. lightwaves H03G3/32, H03G3/34 take precedence
• CPC Class Codes: H04J 14/0298 with sub-carrier multiplexing [SCM]

Abstract

The present invention is directed to a dynamic range enhancing system for increasing the dynamic range of a transmission link, characterized as either an analog or digital link. The system includes a pre-processing unit, provided at a first location, that receives, as input, a transmit signal, and a post-processing unit, provided at a second location, remote from the first location, that receives, as input, a signal transmitted over the transmission link. The pre-processing unit includes a first signal level adjusting device for adjusting a signal level of the transmit signal to be transmitted over the transmission link and a control signal maybe provided for controlling the post-processing unit, and the post-processing unit includes a second signal level adjusting device for adjusting a signal level of the adjusted transmit signal transmitted over said transmission link. The transmit signal and the control signal maybe combined and transmitted over the transmission link together so as to eliminate synchronization problems. In this arrangement the overall system gain remains substantially constant.

Claims

1. A dynamic range enhancing system for enhancing performance of a transmission link by controlling a transmit signal to be transmitted along a communication path comprising said transmission link, said transmission link extending from a first location to a second location remote from said first location, said system comprising:

a pre-processing unit, provided at said first location, that receives, as input, said transmit signal, said pre-processing unit comprising a first signal level adjusting means for adjusting a signal level of said transmit signal to be transmitted over said transmission link, and means for transmitting said adjusted transmit signal over said transmission link; and

a post-processing unit provided at said second location that receives, as input, said adjusted transmit signal transmitted over said communication link, said post-processing unit comprising a second signal level adjusting means for adjusting a signal level of said adjusted transmit signal transmitted over said transmission link;

said pre-processing unit further comprising control means for controlling said first signal level adjusting means and said second signal level adjusting means, such that the overall system gain is substantially constant, said control means comprising means for detecting the signal level of said transmit signal at an input of said pre-processing unit, means for generating a first control signal for controlling said first signal level adjusting means based on the signal level detected by said detecting means, means for generating a second control signal for controlling said second signal level adjusting means based on the signal level detected by said detecting means, said second control signal comprising a constant amplitude signal, combining means for combining said transmit signal and said second control signal before said transmit signal has been adjusted by said first signal level adjusting means, and means for transmitting said second control signal with said adjusted transmit signal over said transmission link to said post-processing unit.

2. The dynamic range enhancing system of claim 1, said system further comprising a format converting means for converting an analog signal into digital form, wherein said transmit signal is converted before being transmitted over said transmission link.

3. The dynamic range enhancing system of claim 1, said first signal level adjusting means comprising a gain controlled amplifier, wherein a gain of said gain controlled amplifier is adjusted according to said first control signal.

4. The dynamic range enhancing system of claim 1, said transmission link comprises an analog transmission link.

5. The dynamic range enhancing system of claim 1, said transmission link comprises a digital transmission link.

6. The dynamic range enhancing system of claim 5, said digital transmission link comprising digital modulating means for modulating said transmit signal with other signals for transmission over said transmission link and digital demodulating means for removing said transmit signal from the other signals for post-processing of said transmit signal.

7. The dynamic range enhancing system of claim 1, said means for generating said second control signal comprising constant amplitude RF carrier means.

8. The dynamic range enhancing system of claim 1, said means for generating said second control signal comprising constant energy signal means.

9. The dynamic range enhancing system of claim 1, said pre-processing unit further comprises time delay means for compensating for processing time in said first signal level adjusting means.

10. The dynamic range enhancing system of claim 1, said pre-processing unit comprising:

a system data device for providing system data, including ancillary system control and supervision information;

said system data, carried by said control signal, being transmitted through said transmission link.

11. The dynamic range enhancing system of claim 1, said post-processing unit comprising:

means for receiving said second control signal;

means for determining an amplitude variation of said second control signal from a constant amplitude control signal;

said second signal level adjusting means is adjusted according to the determined amplitude variation.

12. The dynamic range enhancing system of claim 1, said post-processing unit comprising:

a plurality of digital tuners for concurrently processing said adjusted transmit signal and said adjusted control signal.

13. The dynamic range enhancing system of claim 12, said digital tuners comprising specified and programmable instantaneous center frequencies and bandwidths implemented in time domain representation using digital processing.

14. The dynamic range enhancing system of claim 12, said post-processing unit comprising:

a plurality of digital tuners for concurrently processing a plurality of transmit signals and a plurality of second control signals.

15. The dynamic range enhancing system of claim 1, said post-processing unit comprising:

means responsive to said second control signal for adjusting said second signal level adjusting means.

16. The dynamic range enhancing system of claim 1, said post-processing unit comprising a band pass filter for passing said adjusted transmit signal to said second signal level adjusting means.

17. The dynamic range enhancing system of claim 1, said post-processing unit comprising time delay means for compensating for processing time in said second signal level adjusting means.

18. The dynamic range enhancing system of claim 1, said post-processing unit comprising format converting means for converting said adjusted transmit signal from a digital signal to analog form.

19. The dynamic range enhancing system of claim 1, said second signal adjusting means comprising a gain controlled amplifier, in which a gain of said gain controlled amplifier is adjusted according to said second control signal.

20. The dynamic range enhancing system of claim 1, said transmission link comprises a diversity routing switch including a plurality of digital transmission links.

21. The dynamic range enhancing system of claim 4, said analog transmission link further extending between a pair of modems, a first modem being disposed between said pre-processing unit and said analog transmission link and a second modem being disposed between said post-processing unit and said analog transmission link;

wherein said first modem converts digital signals from said pre-processing unit into analog form for transmission over said analog link and said second modem converts said transmitted analog signal into digital form for application to said post-processing unit.

22. The dynamic range enhancing system of claim 5, said digital transmission link comprising:

an analog transmission link further extending between a pair of modems;

a first modem being disposed between said pre-processing unit and said analog transmission link; and

a second modem being disposed between said post-processing unit and said analog transmission link;

wherein said first modem converts digital signals from said pre-processing unit into analog form for transmission over said analog link and said second modem converts said transmitted analog signal into digital form for application to said post-processing unit.

23. A dynamic range enhancing system for enhancing performance of a digital transmission link by controlling a transmit signal adapted to be transmitted over said digital transmission link within a communication path, said digital transmission link extending from a first location to a second location remote from the first location, said system comprising:

control means for detecting, at an initial position along the communication path, a level of the transmit signal, and for controlling first signal level adjusting means and second signal level adjusting means in response to the detected level;

said first signal level adjusting means comprising means for adjusting the signal level of said transmit signal before transmission over said digital link, and said second signal level adjusting means comprising means for adjusting the level of said transmit signal after transmission over said digital link, said control means controlling said first and second signal level adjusting means to adjust the signal level of said transmit signal in a coordinated fashion based on the detected level;

said first and second signal level adjusting means respectively comprising first and second outputs and means for adjusting the level of the transmit signal present at said first and second outputs; and

said control means comprising means for controlling said first and second signal level adjusting means so that;

the transmit signal level is decreased at the first output and increased at the second output when the detected transmit signal level increases, and

the transmit signal level is increased at the first output and decreased at the second output when the detected transmit signal level decreases.

24. The dynamic range enhancing system of claim 23, said system further comprising:

a pre-processing unit, for processing the transmit signal before transmission through said digital transmission link, comprising said control means and said first signal level adjusting means, said control means further comprising a first output for providing a first control signal and a second output for providing a second output, said first control signal controls said first signal level adjusting means and said second control signal controls said second signal level adjusting means; and

a post-processing unit, for processing said transmit signal after transmission through said digital transmission link, comprising said second signal level adjusting means.

25. The dynamic range enhancing system of claim 24, wherein said control means comprises modulation means for modulating said second control signal.

26. The dynamic range enhancing system of claim 25, wherein said modulation means modulates according to at least one of amplitude modulation, amplitude shift keying, frequency modulation, frequency shift keying, phase modulation, phase shift keying.

27. The dynamic range enhancing system of claim 24, said system further comprising:

combining means, coupled to said first signal adjusting means, for combining said transmit signal and said second control signal,

wherein said transmit signal is adjusted by said first signal adjusting means before said combining means combines said transmit signal and said control signal.

28. The dynamic range enhancing system of claim 23, said system further comprising a format converting means for converting an analog signal into digital form, wherein said transmit signal is converted before being transmitted over said transmission link.

29. The dynamic range enhancing system of claim 24, said first signal level adjusting means comprising a gain controlled amplifier, wherein a gain of said gain controlled amplifier is adjusted according to said first control signal.

30. The dynamic range enhancing system of claim 23, said digital transmission link comprising digital modulating means for modulating said transmit signal with other signals for transmission over said transmission link and digital demodulating means for removing said transmit signal from the other signals for post-processing of said transmit signal.

31. The dynamic range enhancing system of claim 23, said pre-processing unit further comprises time delay means for compensating for processing time in said first signal level adjusting means.

32. The dynamic range enhancing system of claim 24, said pre-processing unit comprising:

a system data device for providing system data, including ancillary system control and supervision information;

said system data, carried by said control signal, being transmitted through said transmission link.

33. The dynamic range enhancing system of claim 24, said system further comprising:

a plurality of pre-processing units for processing a plurality of transmit signals;

frequency converting means for converting a frequency of said transmit signal to be within a predetermined range;

format converting means for converting an analog signal to a digital form for transmission over said transmission link.

34. The dynamic range enhancing system of claim 33, said system further comprising combining means for combining each of the plurality of frequency converted transmit signals, such that a single signal is format converted before transmission over said transmission link.

35. The dynamic range enhancing system of claim 33, wherein said format converting means comprises a plurality of format converting means, such that each of the plurality of frequency converted transmit signal is individually format converted before transmission over said transmission link.

36. The dynamic range enhancing system of claim 24, said post-processing unit comprising:

means for receiving said second control signal; and

means responsive to said received second control signal for adjusting said second signal adjusting means.

37. The dynamic range enhancing system of claim 36, said means for receiving comprising a signal demodulator.

38. The dynamic range enhancing system of claim 24, said post-processing unit comprising:

a plurality of digital tuners for concurrently processing said transmit signal and said control signal.

39. The dynamic range enhancing system of claim 38, said digital tuners comprising specified and programmable instantaneous center frequencies and bandwidths implemented in time domain representation using digital processing.

40. The dynamic range enhancing system of claim 38, said post-processing unit comprising:

a plurality of digital tuners for concurrently processing a plurality of transmit signals and a plurality of second control signals.

41. The dynamic range enhancing system of claim 24, said post-processing unit comprising:

means responsive to said second control signal for adjusting said second signal level adjusting means.

42. The dynamic range enhancing system of claim 24, said post-processing unit comprising a band pass filter for passing said transmit signal to said second signal level adjusting means.

43. The dynamic range enhancing system of claim 24, said post-processing unit comprising time delay means for compensating for processing time in said second signal level adjusting means.

44. The dynamic range enhancing system of claim 24, said post-processing unit comprising format converting means for converting said transmit signal from a digital signal to analog form.

45. The dynamic range enhancing system of claim 34, said post-processing unit further comprising means for splitting an analog signal and filter means for passing predetermined portions of the split signal.

46. The dynamic range enhancing system of claim 24, said second signal adjusting means comprising a gain controlled amplifier, in which a gain of said gain controlled amplifier is adjusted according to said second control signal.

47. The dynamic range enhancing system of claim 35, said post-processing unit comprising a plurality of format converting means for converting a digital signal into analog form, and a plurality of post-processing units for processing each of the plurality of format converted signals.

48. The dynamic range enhancing system of claim 34, said post-processing unit comprising:

a plurality of digital tuners for concurrently processing the combined transmit signals, said digital tuners comprising specified and programmable instantaneous center frequencies and bandwidths implemented in time domain representation using digital processing.

49. The dynamic range enhancing system of claim 35, said post-processing unit comprising:

a plurality of digital tuners for concurrently processing each individually format converted signals, said digital tuners comprising specified and programmable instantaneous center frequencies and bandwidths implemented in time domain representation using digital processing.

50. A dynamic range enhancing system for enhancing performance of a transmission link by controlling a transmit signal to be transmitted along a communication path comprising said transmission link, said transmission link extending from a first location to a second location remote from said first location, said system comprising:

a pre-processing unit, provided at said first location, that receives, as input, said transmit signal, said pre-processing unit comprising a first signal level changing device which changes a signal level of said transmit signal to be transmitted over said transmission link, and a transmitter which transmits said adjusted transmit signal over said transmission link; and

a post-processing unit provided at said second location that receives, as input, said adjusted transmit signal transmitted over said communication link, said post-processing unit comprising a second signal level changing device which changes a signal level of said adjusted transmit signal transmitted over said transmission link, and a controller which controls said first signal level changing device and said second signal level changing device, such that the overall system gain is substantially constant, said controller comprising;

a detector which detects the signal level of said transmit signal at an input of said pre-processing unit;

a first generating device which generates a first control signal for controlling said first signal level changing device based on the signal level detected by said detector;

a second generating device which generates a second control signal which controls said second signal level changing device based on the signal level detected by said detector, said second control signal comprising a constant amplitude signal;

a signal combiner which combines said transmit signal and said second control signal before said transmit signal has been adjusted by said first signal level changing device, wherein said transmitter transmits said second control signal with said adjusted transmit signal over said transmission link to said post-processing unit.

51. The dynamic range enhancing system of claim 50, said system further comprising an A/D converter which converts an analog signal into a digital form, wherein said transmit signal is converted before being transmitted over said transmission link.

52. The dynamic range enhancing system of claim 50, said first signal level changing device comprising a gain controlled amplifier, wherein a gain of said gain controlled amplifier is adjusted according to said first control signal.

53. The dynamic range enhancing system of claim 50, wherein said transmission link comprises an analog transmission link.

54. The dynamic range enhancing system of claim 50, wherein said transmission link comprises a digital transmission link.

55. The dynamic range enhancing system of claim 54, said digital transmission link comprising a digital modulator which modulates said transmit signal with other signals for transmission over said transmission link and a digital demodulator which demodulates said transmit signal from the other signals for post-processing of said transmit signal.

56. The dynamic range enhancing system of claim 50, wherein said second generating device generates a constant amplitude RF carrier.

57. The dynamic range enhancing system of claim 50, said second generating device generating a constant energy signal.

58. The dynamic range enhancing system of claim 50, said pre-processing unit further comprises a time delay which compensates for processing time in said first signal level changing device.

59. The dynamic range enhancing system of claim 50, said pre-processing unit comprising a system data device which provides system data, including ancillary system control and supervision information, wherein said system data, carried by said control signal, is transmitted through said transmission link.

60. The dynamic range enhancing system of claim 50, said post-processing unit comprising:

a receiver which receives said second control signal;

a power detector/controller which detects an amplitude variation of said second control signal from a constant amplitude control signal, wherein said second signal level changing device is adjusted according to the determined amplitude variation.

61. The dynamic range enhancing system of claim 50, said post-processing unit further comprising a plurality of digital tuners for concurrently processing said adjusted transmit signal and said adjusted control signal.

62. The dynamic range enhancing system of claim 61, said digital tuners comprising specified and programmable instantaneous center frequencies and bandwidths implemented in time domain representation using digital processing.

63. The dynamic range enhancing system of claim 61, wherein said plurality of digital tuners concurrently process a plurality of transmit signals and a plurality of second control signals.

64. The dynamic range enhancing system of claim 50, wherein said post-processing is responsive to said second control signal and adjusts said second signal level changing device.

65. The dynamic range enhancing system of claim 50, said post-processing unit comprising a band pass filter for passing said adjusted transmit signal to said second signal level changing device.

66. The dynamic range enhancing system of claim 50, said post-processing unit comprising a time delay which compensates for a processing time in said second signal level changing device.

67. The dynamic range enhancing system of claim 50, said post-processing unit comprising a D/A converter which converts said adjusted transmit signal from a digital signal to analog form.

68. The dynamic range enhancing system of claim 50, said second signal level changing device comprising a gain controlled amplifier, in which a gain of said gain controlled amplifier is adjusted according to said second control signal.

69. The dynamic range enhancing system of claim 50, said transmission link comprises a diversity routing switch including a plurality of digital transmission links.

70. The dynamic range enhancing system of claim 53, said analog transmission link further extending between a pair of modems, a first modem being disposed between said pre-processing unit and said analog transmission link and a second modem being disposed between said post-processing unit and said analog transmission link,

wherein said first modem converts digital signals from said pre-processing unit into analog form for transmission over said analog link and said second modem converts said transmitted analog signal into digital form for application to said post-processing unit.

71. The dynamic range enhancing system of claim 54, said digital transmission link comprising:

an analog transmission link further extending between a pair of modems;

a first modem being disposed between said pre-processing unit and said analog transmission link; and

a second modem being disposed between said post-processing unit and said analog transmission link;

wherein said first modem converts digital signals from said pre-processing unit into analog form for transmission over said analog link and said second modem converts said transmitted analog signal into digital form for application to said post-processing unit.