System for controlling signal level at both ends of a transmission link based on a detected valve

• US 5,321,849 A
• Filed: 05/22/1991
• Issued: 06/14/1994
• 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): Eisenzopf, Reinhard J.
• Assistant Examiner(s): PHAM, CHI H
• Application Number:
  US07/704,114
• Time in Patent Office: 1,119 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, 455/282, 455/283, 455/289 , 455/291, 455/295, 333/17.2, 359/194
• US Class Current: 455/67.11
• CPC Class Codes: H03G 3/3052 in bandpass amplifiers (H.F. or I.F.) or in frequency-changers used in a (super)heterodyne receiver H03G3/32, H03G3/34 take precedence
• 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, and also to a process for increasing the dynamic range of a transmission link. An instruction setting process is also provided for defining a set of instructions, for a control device of the system, which detects, at an initial position along the transmission link, the level of a transmit signal adapted to be transmitted over the transmission link. The control device controls a first signal level changing device and a second signal level changing device in response to the detected level. The first and second signal level changing devices, respectively, process the transmit signal level before and after transmission over the link.

Claims

1. A system for controlling the amount of noise introduced into a transmit signal adapted to be transmitted over a transmission link within a communication path, the 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, the level of the transmit signal, and for controlling first signal level changing means and second signal level changing means in response to the detected level;

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

said first and second signal level changing means respectively comprising first and second outputs and means for changing 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 changing 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.

2. The system of claim 1, wherein said control means comprise means for producing first and second control signals to respectively control said first and second signal level changing means.

3. The system of claim 2, wherein said control means further comprise means for transmitting information containing said second control signal over said transmission link.

4. The system of claim 2, wherein said system further comprises a modulator for modulating said second control signal to produce a modulated version of said second control signal and a demodulator for demodulating said modulated version of said second control signal to produce a demodulated version of said second control signal.

5. The system of claim 2, wherein said system further comprises means for measuring the level of said second control signal and affecting the control of said second signal level changing means.

6. The system of claim 2, wherein said second control signal which is transmitted over said transmission link comprises an FM/FSK control signal modulator.

7. The system of claim 1, wherein said first signal level changing means are positioned at an input location of said transmission link, and wherein said second level changing means are positioned at an output location of said transmission link.

8. The system of claim 1, wherein said first signal level changing means comprise a gain controlled amplifier.

9. The system of claim 1, wherein said second signal level changing means comprise a gain controlled amplifier.

10. The system of claim 1, wherein one end of said transmission link is coupled to one or more of radio channel transceivers and receivers and a second end of said transmission link is coupled to a remote antenna.

11. The system of claim 1, wherein said control means is connected directly to said first signal level changing means and is connected indirectly to said second signal level changing means via said transmission link.

12. The system of claim 1, wherein said first and second signal level changing means are controlled so that a change in the transmit signal level at the first output is equal to a change in the transmit signal level at the second output.

13. The system of claim 12, wherein said first and second signal level changing means are controlled so that a change in the transmit signal level at either of the first or second outputs is equal to the amount by which there is a change in the detected transmit signal level.

14. The system of claim 1, wherein said first and second signal level changing means each comprise an adjustable linear multiplier for multiplying the transmitted signal level by a desired instantaneous multiplicand value.

15. The system of claim 1, wherein said control means detects the level of the transmit signal before the transmit signal reaches said first signal level changing means.

17. The system of claim 1, wherein said control means comprises means for controlling said first signal level changing means and said second signal level changing means to be set at respective ends of said defined signal level changing ranges, when said detected level of said transmit signal is below a first threshold.

18. The system of claim 17, wherein said control means comprises means for controlling, when said detected level of said transmit signal is below said first threshold, said first signal level changing means to be at the most increased end of said defined signal level changing range, whereby the signal level present at said first output is at a maximum possible value.

19. The system of claim 18, wherein said control means comprises means for controlling, when said detected level of said transmit signal is below said first threshold, said second signal level changing means to be at the most decreased end of said defined signal level changing range, whereby the signal level present at said second output is at a minimum possible value.

16. A system for controlling the amount of noise introduced into a transmit signal adapted to be transmitted over a transmission link within a communication path, the 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, the level of the transmit signal, and for controlling first signal level changing means and second signal level changing means in response to the detected level;

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

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

said first and second signal level changing means each comprising means for changing the level of the transmit signal, at said first and second outputs, within defined signal level changing ranges and respective means for setting said first and second signal level changing means to be at an end of said defined signal level changing ranges, whereby each of said first and second signal level changing means increases or decreases the level of the transmit signal at respective first and second outputs by a maximum change in value when set at an end of said defined signal level changing range.

20. The system of claim 16, wherein said control means comprises means for controlling said first signal level changing means to decrease the level of the transmit signal present at said first output by an amount approximately equal to the amount by which said detected level exceeds a first threshold value, when said detected level is above said first threshold value.

21. The system of claim 20, wherein said control means comprises means for concurrently controlling said second signal level changing means to increase the level of the transmit signal present at said second output by an amount approximately equal to the amount by which said detected level exceeds said first threshold value, when said detected level is above said first threshold value.

22. The system of claim 20, wherein said control means comprise means for controlling said second signal level changing means to be at the most increased end of said defined signal level changing range, whereby the signal level present at its output is at a maximum possible value, when said detected level of said transmit signal is above a second threshold which is greater than said first threshold.

23. The system of claim 21, wherein said transmission link comprises an optical link.

24. The system of claim 23, wherein said system further comprises time delay means to compensate for time delays caused by said control means.

25. The system of claim 23, wherein said system further comprises service channel transmission means for conducting maintenance communication across said transmission link.

26. The system of claim 23, wherein said control means further comprises a time division multiplexed (TDM) or frequency division multiplexed (FDM) control interface.

27. The system of claim 23, wherein said control means comprises a plurality of controllers, said first signal level changing means comprises a first set of signal level modifiers, and said second signal level changing means comprises a second set of signal level modifiers, and further wherein each of said controllers and modifiers is adapted to separately and independently provide transmission link performance enhancement for respective separate frequency bands of said transmit signal.

28. The system of claim 27, wherein said first and second sets of signal level modifiers are identical in number.

29. The system of claim 27, wherein said system comprises a respective filter for each of said separate frequency bands of said transmit signal, and further wherein the system comprises a combining network connected to the input of said transmission link and a splitting network connected to the output of said transmission link.

30. A system for controlling the amount of noise introduced into a transmit signal adapted to be transmitted over a transmission link within a communication path, the 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, the level of the transmit signal, and for controlling first signal level changing means and second signal level changing means in response to the detected level;

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

said control means comprising means for producing first and second control signals to respectively control said first and second signal level changing means;

said system further comprising a modulator for modulating said second control signal to produce a modulated version of said second control signal and a demodulator for demodulating said modulated version of said second control signal to produce a demodulated version of said second control signal, said demodulator further comprising bias control means for performing an operation on said demodulated version of said second control signal and, based on said operation, outputting a bias control signal which is proportional to said detected level of said transmit signal.

31. The system of claim 30, wherein said system further comprises a power amplifier connected to an output of said second signal level changing means, said power amplifier comprising a bias control port, and further wherein said bias control means further comprises means for connecting said bias control signal to said bias control port.

32. A system for controlling the amount of noise introduced into a transmit signal adapted to be transmitted over a transmission link within a communication path, the 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, the level of the transmit signal, and for controlling first signal level changing means and second signal level changing means in response to the detected level;

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

said control means comprising means for producing first and second control signals to respectively control said first and second signal level changing means;

said system further comprising a modulator for modulating said second control signal to produce a modulated version of said second control signal and a demodulator for demodulating said modulated version of said second control signal to produce a demodulated version of said second control signal, said demodulator further comprising bias control means for determining if said demodulated version of said second control signal is below or above a predetermined threshold value.

33. The system of claim 32, wherein said bias control means comprises means for outputting a signal having a first value when said demodulated version of said second control signal is below said predetermined threshold value and having a second value when said demodulated version of said second control signal is above said predetermined threshold value.

34. The system of claim 33, wherein said system further comprises a power amplifier connected to an output of said second signal level changing means, said power amplifier comprising a bias control port, and further wherein said bias control means further comprises means for connecting said bias control signal to said bias control port.

35. A system for controlling the amount of noise introduced into a transmit signal adapted to be transmitted over a transmission link within a communication path, the 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, the level of the transmit signal, and for controlling first signal level changing means and second signal level changing means in response to the detected level;

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

said control means comprising means for producing first and second control signals to respectively control said first and second signal level changing means;

said control means further comprising means, including a variable attenuator, for remotely verifying the proper operation of the system and determining the dynamic range of the system.

36. A system for controlling the amount of noise introduced into a transmit signal adapted to be transmitted over a transmission link within a communication path, the 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, the level of the transmit signal, and for controlling first signal level changing means and second signal level changing means in response to the detected level;

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

said control means comprising means for producing first and second control signals to respectively control said first and second signal level changing means;

said second control signal which is transmitted over said transmission link comprising a PM/PSK modulated control signal.

37. A system for controlling the amount of noise introduced into a transmit signal adapted to be transmitted over a transmission link within a communication path, the 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, the level of the transmit signal, and for controlling first signal level changing means and second signal level changing means in response to the detected level;

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

said control means comprising means for producing first and second control signals to respectively control said first and second signal level changing means, said second control signal which is transmitted over said transmission link comprising an AM/ASK modulated control signal.

38. A system for controlling the amount of noise introduced into a transmit signal adapted to be transmitted over a transmission link within a communication path, the 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, the level of the transmit signal, and for controlling first signal level changing means and second signal level changing means in response to the detected level;

said first signal level changing means comprising means for changing the level of said transmit signal before transmission over said link, and said second signal level changing means comprising means for changing the level of said transmit signal after transmission over said link, said control means controlling said first and second signal level changing means to change the level of said transmit signal in a coordinated fashion based on the detected level, said transmit signal being an RF signal and comprising a variable number of input signals.

39. A system for controlling the amount of noise introduced into a transmit signal adapted to be transmitted over a transmission link within a communication path, the 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, the level of the transmit signal, and for controlling first signal level changing means and second signal level changing means in response to the detected level;

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

said control means comprising means for controlling said first and second signal level changing means in order to enhance a usable RF input signal level range of the transmission link.

40. A system for controlling the amount of noise introduced into a transmit signal adapted to be transmitted over a transmission link within a communication path, the 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, the level of the transmit signal, and for controlling first signal level changing means and second signal level changing means in response to the detected level;

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

said control means comprising means for measuring the instantaneous composite power level of said transmit signal before transmission over said transmission link.

41. The system of claim 40, wherein said control means comprise means for monitoring the power level of said transmit signal before pre-transmission processing by said first signal level changing means.

42. A system for controlling the amount of noise introduced into a transmit signal adapted to be transmitted over a transmission link within a communication path, the 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, the level of the transmit signal, and for controlling first signal level changing means and second signal level changing means in response to the detected level;

said first signal level changing means comprising means for changing the level of said transmit signal before transmission over said link, and said second signal level changing means comprising means for changing the level of said transmit signal after transmission over said link, said control means controlling said first and second signal level changing means to change the level of said transmit signal in a coordinated fashion based on the detected level, said control means comprising means for measuring the total average RF signal level of said transmit signal before transmission over said transmission link.

43. A system for controlling the amount of noise introduced into a transmit signal adapted to be transmitted over a transmission link within a communication path, the 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, the level of the transmit signal, and for controlling first signal level changing means and second signal level changing means in response to the detected level;

said first signal level changing means comprising means for changing the level of said transmit signal before transmission over said link, and said second signal level changing means comprising means for changing the level of said transmit signal after transmission over said link, said control means controlling said first and second signal level changing means to change the level of said transmit signal in a coordinated fashion based on the detected level, said control means comprising means for approximating the number of high level signals present in said transmit signal and measuring the resulting second-order intermodulating products.

44. A system for controlling the amount of noise introduced into a transmit signal adapted to be transmitted over a transmission link within a communication path, the 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, the level of the transmit signal, and for controlling first signal level changing means and second signal level changing means in response to the detected level;

said first signal level changing means comprising means for changing the level of said transmit signal before transmission over said link, and said second signal level changing means comprising means for changing the level of said transmit signal after transmission over said link, said control means controlling said first and second signal level changing means to change the level of said transmit signal in a coordinated fashion based on the detected level, said first signal level changing means comprising a variable attenuator.

45. A system for controlling the amount of noise introduced into a transmit signal adapted to be transmitted over a transmission link within a communication path, the 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, the level of the transmit signal, and for controlling first signal level changing means and second signal level changing means in response to the detected level;

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

said second signal level changing means comprising a variable attenuator.

46. A system for controlling the amount of noise introduced into a transmit signal adapted to be transmitted over a transmission link within a communication path, the 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, the level of the transmit signal, and for controlling first signal level changing means and second signal level changing means in response to the detected level;

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

said system further comprising a tandem combination of at least one amplifier and at least one attenuator coupled to a first input location of said transmission link, said tandem combination comprising said first signal level changing means.

47. The system of claim 46, wherein said tandem combination comprises a first preamplifier, a first attenuator, a second pre-amplifier, and a second attenuator, connected in cascade.

48. The system of claim 47, wherein said control means comprises a directional coupler, monitor means, a DC processor, an AC processor, combining means for processing and combining signals output by said DC processor and said AC processor, and attenuator control means for controlling attenuation values of at least one of the attenuators in said system, wherein:

said directional coupler is connected to an output of said first preamplifier, and is adapted to feed an amplified sample of said transmit signal to said monitor means;

said monitor means is adapted to receive said amplifier sample and provides a rectified version of said amplified sample in the form of a video signal, having a bandwidth typically greater than 1 MHz;

said DC processor comprises means for providing a DC measurement signal of said video signal, wherein said DC measurement signal is proportional to the instantaneous composite RF level at the output of said first preamplifier; and

said AC processor comprises means for providing an AC measurement signal based on an AC analysis of said video signal, wherein said AC measurement signal is indicative of the instantaneous second order intermodulation products generated by said monitor means.

49. A system for controlling the amount of noise introduced into a transmit signal adapted to be transmitted over a transmission link within a communication path, the 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, the level of the transmit signal, and for controlling first signal level changing means and second signal level changing means in response to the detected level;

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

said system further comprising a downward frequency converter for converting said transmit signal to a lower frequency before transmission over said link.

50. The system of claim 49, wherein said system further comprises an upward frequency converter for converting said transmit signal to a higher frequency after transmission over said link.

51. The system of claim 49, wherein said downward frequency converter comprises means for acting on said transmit signal before processing by said first signal level changing means.

52. The system of claim 49, wherein said transmit signal is transmitted over said transmission link from a side of said transmission link which is connected to a remote antenna.

53. The system of claim 50, wherein said transmit signal is transmitted over said transmission link to a side of said transmission link which is connected to a remote antenna.

54. The system of claim 49, wherein said downward frequency converter comprises means for acting on said transmit signal before processing by said first signal level changing means, and said upward frequency converter comprises means for acting on said transmit signal after processing by said second signal level changing means.

55. A system for controlling the amount of noise introduced into a transmit signal adapted to be transmitted over a transmission link within a communication path, the 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, the level of the transmit signal, and for controlling first signal level changing means and second signal level changing means in response to the detected level;

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

said control means being connected directly to said first and second signal level changing means.

56. A process for increasing the dynamic range of a transmission link extending from a first location to a second location remote from the first location, said process comprising:

detecting the level of a transmit signal adapted to be transmitted over said transmission link;

based on said detected level of said transmit signal and within parameters set forth by a set of control instructions, modifying said transmit signal at the first and second locations;

creating a table of values having a plurality of signal level codes representing the detected level of said transmit signal, said table also having a plurality of signal level modification codes, respectively corresponding to said signal level codes; and

defining said set of control instructions to set forth certain parameters, said set of control instructions being established as a function of said detected level of said transmit signal.

57. The process according to claim 56, further comprising:

approximating the number of high level input signals that are in said transmit signal, and determining whether said approximated number of signals are within a first range of values or a second range;

separately modifying said transmit signal at the first and second locations according to a first configuration when said approximated number of signals are within said first range; and

separately modifying said transmit signal at the first and second locations according to a second configuration when said approximated number of signals are within said second range.

58. The process according to claim 57, wherein said first location is adjacent to an input of said transmission link and said second location is adjacent to an output of said transmission link.

59. A process for increasing the dynamic range of a transmission link extending from a first location to a second location remote from the first location, said process comprising:

monitoring, at an initial position along said transmission link, the level of a transmit signal which is adapted to be transmitted over said transmission link, and based upon said monitored level, independently controlling the level of said transmit signal at a first location before the transmission link and at a second location after the transmission link; and

decreasing the level of the transmit signal at said first location by an amount approximately equal to the amount by which said monitored level exceeds a threshold value, when said monitored level is above said threshold vale.

60. The process of claim 59, wherein said process, during controlling, carries out a pre-transmission processing of said transmit signal at said first location, and caries out a post-transmission processing of said transmit signal at said second location.

61. The process of claim 59, wherein independently controlling said level includes transmitting information over said transmission link to control the level of said transmit signal at said second location.

62. The process of claim 59, further comprising concurrently increasing the level of the transmit signal at said second location by an amount approximately equal to the amount by which said monitored level exceeds said threshold value, when said detected level is above said threshold value.