Digital data transmitter, transmission line encoding method, and decoding method

• US 7,190,728 B2
• Filed: 10/05/2001
• Issued: 03/13/2007
• Est. Priority Date: 10/05/2000
• Status: Expired due to Term

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Mizuguchi, Yuji, Katta, Noboru, Sakai, Takahisa, Kawada, Hirotsugu, Kurosaki, Toshihiko
• Primary Examiner(s): Bayard; Emmanuel
• Application Number:
  US10/398,447
• Publication Number:
  US 20040042555A1
• Time in Patent Office: 1,985 Days
• Field of Search: 375/261, 375/298, 375/316, 375/295, 375/346, 375/345, 375/371, 375/376, 375/231, 375/358, 375/369, 375/259, 370/84, 370/85.3, 370/110.1, 370/110.4, 370/85.11, 370/286, 370/289, 455/232.1, 455/234.1
• US Class Current: 375/259
• CPC Class Codes: H04L 25/062 Setting decision thresholds using feedforward techniques only
• CPC Class Codes: H04L 25/066 Multilevel decisions, not including self-organising maps
• CPC Class Codes: H04L 25/085 Arrangements for reducing interference in line transmission systems, e.g. by differential transmission
• CPC Class Codes: H04L 25/4919 using balanced multilevel codes H04L25/4927 takes precedence

Abstract

A digital data transmission apparatus includes a transmitting end (100) that includes: a binary/quadrary conversion unit (110) for converting a data stream; a coding unit (120) for mapping the converted data to be coded; a digital filter (130); a D/A conversion unit (140); a low-pass filter (150) for eliminating a high-band signal; a differential driver (160) for inputting an analog signal that has passed through the low-pass filter into a twisted pair cable (300), and a receiving end (200) that includes: a low-pass filter (210) for eliminating noises from both wires of the twisted pair cable; a receiver (220) for receiving the signals that have passed through the low-pass filter; an A/D conversion unit (230); a digital filter (240); an evaluation unit (250) for evaluating a signal level of a received signal; a decoding unit (260) for decoding the signal level into receipt data; and a synchronization unit (270) for generating a clock.

Claims

1. A digital data transmission apparatus comprising:

a data coding device operable to convert digital data into a signal level corresponding to a symbol that is assigned to the digital data in each symbol cycle as a prescribed unit cycle;

a first digital filter having a first sampling cycle that is shorter than a unit cycle of a signal level string that has been obtained by said data coding device, and being operable to allow only predetermined frequencies to pass;

a D/A converter operable to convert a digital data stream that has passed through said first digital filter, into an analog signal;

a low-pass filter operable to eliminate folding distortion of said first digital filter from the analog signal that has been obtained by said D/A converter, the folding distortion being determined in the first sampling cycle;

a differential driver operable to convert an output from said low-pass filter, into two signals having opposite polarities relative to a predetermined reference potential, and to input the two signals into a twisted pair cable;

a differential receiver operable to receive transmission signals transmitted through the twisted pair cable, and to convert a difference in potential between two wires of the twisted pair cable into a signal;

an A/D converter operable to convert the signal outputted from said differential receiver into a digital signal value in each second sampling cycle;

a second digital filter operable to allow only a predetermined frequency band of a digital data stream that has been obtained by sampling with said A/D converter, to pass; and

a level evaluator operable to evaluate a symbol value from a level of a signal in symbol timing, including a symbol in the signal, based on an output from said second digital filter, and to convert the symbol value into corresponding digital data,

wherein said first and second digital filters both have low-pass characteristics, and said first digital filter has frequency characteristics of cutting off at least frequency data which are higher than a frequency band in which electromagnetic waves emitted from the respective two signals that pass through the twisted pair cable cancel each other out, thereby to eliminate emission of electromagnetic waves to outside the twisted pair cable.

2. The digital data transmission apparatus of claim 1, wherein said data coding device is operable to convert data comprising two or more bits per symbol cycle, into a symbol to be transmitted.

3. The digital data transmission apparatus of claim 2, wherein said data coding device has five signal levels, and is operable to assign a symbol in a symbol transmission timing to a signal level other than a previous signal level corresponding to a signal which was transmitted in an immediately preceding symbol transmission timing, in an order of 01, 11, 00, 10, starting from a lowest signal level.

4. The digital data transmission apparatus of claim 2,

wherein digital data to be transmitted have been coded by a bi-phase mark method, and

wherein said data coding device is operable to assign a symbol in a symbol transmission timing to a signal level other than a previous signal level corresponding to a signal which was transmitted in an immediately preceding symbol transmission timing, in an order of 01, 11, 00, 10, starting from a lowest signal level, thereby to decide a signal level to be transmitted.

5. The digital data transmission apparatus of claim 2, wherein said data coding device is operable to assign a symbol in a symbol transmission timing alternately to one of a number of signal levels which is as many as a number of kinds of symbols starting from a lowest signal level and to one of the number of signal levels which is as many as the number of kinds of the symbols starting from a highest signal level, thereby to decide a signal level to be transmitted.

6. The digital data transmission apparatus of any of claim 2, wherein said data coding device includes:

a previous signal level storage device operable to store a previous signal level; and

a coding device operable to decide a signal level corresponding to a symbol to be transmitted, based on the previous signal level and the symbol to be transmitted.

7. The digital data transmission apparatus of claim 6, wherein said coding device is operable to assign a symbol in a symbol transmission timing to a signal level having a predetermined difference from the previous signal level that is stored in the previous signal level storage device.

8. The digital data transmission apparatus of claim 2, wherein said data coding device is supplied with a transmission method instruction signal indicating whether the transmission signal has been coded by a bi-phase mark method.

9. The digital data transmission apparatus of claim 1, wherein transmission characteristics of a signal which has been passed through said first and second digital filters have roll-off characteristics.

10. The digital data transmission apparatus of claim 1,

wherein said level evaluator includes:

a signal level detector operable to detect a signal level in each symbol cycle; and

a previous signal level storage device operable to store a previous signal level which was received in an immediately preceding symbol receipt timing, and

wherein said level evaluator is operable to decode the signal level detected by said signal level detector, into a corresponding symbol, based on the previous signal level that is stored in said previous signal level storage device.

11. The digital data transmission apparatus of claim 10, wherein said level evaluator further includes:

a threshold controller operable to correct an evaluation threshold level based on variation values in respective signal levels which were received during a predetermined time period; and

a threshold evaluator operable to hold a threshold and to perform threshold evaluation to a difference in signal level between a signal level that is detected in symbol timing and the previous signal level, thereby to decode a symbol value.

12. The digital data transmission apparatus of claim 10, wherein said level evaluator further includes a synchronization device operable to establish synchronization with a symbol cycle of a received signal, and

wherein said synchronization device is operable to extract frequency components having a half cycle as long as the symbol cycle, from the received signal, and to control a symbol timing at which a symbol is detected, based on a phase of the extracted signal.

13. The digital data transmission apparatus of claim 10, wherein said level evaluator is supplied with a transmission method instruction signal indicating whether the received signal has been coded by the bi-phase mark method.

14. The digital data transmission apparatus of claim 1, wherein said level evaluator includes:

a threshold controller operable to correct an evaluation threshold level based on variation values in respective signal levels which were received during a predetermined time period;

a previous signal level storage device operable to store a previous signal level; and

a threshold evaluator operable to hold a threshold and to perform threshold evaluation to a difference in signal level between a signal level that is detected in symbol timing and the previous signal level, thereby to decode a symbol value.

15. The digital data transmission apparatus of claim 1, further comprising:

a scrambler operable to scramble digital data to be transmitted; and

a descrambler operable to descramble received scrambled digital data.

16. The digital data transmission apparatus of claim 1, wherein said data coding device includes a number of signal levels which is greater than a number of kinds of symbols to be transmitted per symbol cycle, and is operable to assign a symbol in a symbol transmission timing to one of the signal levels.

17. The digital data transmission apparatus of claim 16, wherein said data coding device has five signal levels, and is operable to assign a symbol in a symbol transmission timing to a signal level other than a previous signal level corresponding to a signal which was transmitted in an immediately preceding symbol transmission timing, in an order of 01, 11, 00, 10, starting from a lowest signal level.

18. The digital data transmission apparatus of claim 16,

wherein digital data to be transmitted have been coded by a bi-phase mark method, and

wherein said data coding device is operable to assign a symbol in a symbol transmission timing to a signal level other than a previous signal level corresponding to a signal which was transmitted in an immediately preceding symbol transmission timing, in an order of 01, 11, 00, 10 starting from a lowest signal level, thereby to decide a signal level to be transmitted.

19. The digital data transmission apparatus of claim 16, wherein said data coding device is operable to assign a symbol in a symbol transmission timing alternately to one of a number of signal levels which is as many as a number of kinds of symbols starting from a lowest signal level and to one of the number of signal levels which is as many as the number of kinds of the symbols starting from a highest signal level, thereby to decide a signal level to be transmitted.

20. The digital data transmission apparatus of claim 16, wherein said data coding device further includes:

a previous signal level storage device operable to store a previous signal level; and

a coding device operable to decide a signal level corresponding to a symbol to be transmitted, based on the previous signal level and the symbol to be transmitted.

21. The digital data transmission apparatus of claim 20, wherein said coding device is operable to assign a symbol in a symbol transmission timing to a signal level having a predetermined difference from the previous signal level that is stored in the previous signal level storage device.

22. The digital data transmission apparatus of claim 16, wherein said data coding device is supplied with a transmission method instruction signal indicating whether the transmission signal has been coded by a bi-phase mark method.

23. A transmission channel coding method comprising:

when transmitting digital data as one symbol having of an arbitrary number of bits, providing a number of signal levels which is greater than a number of kinds of symbols; and

assigning a signal level that represents a symbol in a symbol transmission timing to one of the signal levels other than a previous signal level in an immediately preceding symbol transmission timing.

24. The transmission channel coding method of claim 23, wherein the number of kinds of the symbols is four, and two-bit data is transmitted per symbol.

25. The transmission channel coding method of claim 23, wherein 2-bit data are coded per one symbol by being assigned to signal levels in an order of 01, 11, 00, 10, starting from a lowest signal level.

26. The transmission channel coding method of claim 23, wherein the signal level that represents the symbol in the symbol transmission timing is assigned to a signal level having a predetermined difference from the previous signal level.

27. The transmission channel coding method of claim 23, wherein the number of the signal levels is one more than the number of kinds of symbols.

28. The transmission channel coding method of claim 23, wherein the number of the signal levels is twice as many as the number of kinds of the symbols.

29. The transmission channel coding method of claim 23, wherein the signal level that represents the symbol in the transmission timing is assigned alternately to one of the number of signal levels which is as many as the number of kinds of the symbols starting from a lowest signal level, and one of the number of signal levels which is as many as the number of kinds of the symbols starting from a highest signal level.

30. The transmission channel coding method of claim 29, wherein the number of kinds of the symbols is four, and two-bit data is transmitted per symbol.

31. The transmission channel coding method of claim 29, wherein 2-bit data are coded per one symbol by being assigned to signal levels in an order of 01, 11, 00, 10, starting from a lowest signal level.

32. The transmission channel coding method of claim 29, wherein the signal level that represents the symbol in the symbol transmission timing is assigned to a signal level having a predetermined difference from the previous signal level.

33. The transmission channel coding method of claim 29, wherein the number of the signal levels is one more than the number of kinds of symbols.

34. The transmission channel coding method of claim 29, wherein the number of the signal levels is twice as many as the number of kinds of the symbols.

35. The transmission channel coding method of claim 29, wherein the number of the signal level is 1.5 times as many as the number of kinds of the symbols.

36. The transmission channel coding method of claims 23, wherein the number of the signal level is 1.5 times as many as the number of kinds of the symbols.

37. A data transmission apparatus comprising:

a data coding device operable to convert digital data into a signal level corresponding to a symbol that is assigned to the digital data in each symbol cycle as a prescribed unit cycle;

a first digital filter having a first sampling cycle that is shorter than a unit cycle of a signal level string which has been coded by said data coding device, and being operable to allow only predetermined frequencies to pass;

a D/A converter operable to convert a digital data stream that has passed through said first digital filter, into an analog signal;

a low-pass filter operable to eliminate folding distortion of said first digital filter from the analog signal that has been obtained by said D/A converter, the folding distortion being determined in the first sampling cycle; and

a differential driver operable to convert an output of said low-pass filter, into two signals having opposite polarities relative to a predetermined reference potential, and to input the two signals into a twisted pair cable,

wherein said first digital filter has frequency characteristics of cutting off at least frequency data which are higher than a frequency band in which electromagnetic waves emitted from the respective two signals that pass through the twisted pair cable cancel each other out, thereby to eliminate emission of electromagnetic waves to outside the twisted pair cable.

38. A data receiving apparatus for receiving transmission signals that are transmitted from a data transmission apparatus including:

a data coding device operable to convert digital data into a signal level corresponding to a symbol that is assigned to the digital data in each symbol cycle as a prescribed unit cycle;

a first digital filter having a first sampling cycle that is shorter than a unit cycle of a signal level string that has been obtained by the data coding device, and being operable to allow only predetermined frequencies to pass;

a D/A converter operable to convert a digital data stream that has passed through the first digital filter, into an analog signal;

a low-pass filter operable to eliminate folding distortion of the first digital filter from the analog signal that has been obtained by the D/A converter, the folding distortion being determined in the first sampling cycle;

a differential driver operable to convert an output from the low-pass filter, into two signals having opposite polarities relative to a predetermined reference potential, and to input the two signals into a twisted pair cable, wherein the first digital filter has low-pass characteristics of cutting off at least frequency data which are higher than a frequency band in which electromagnetic waves emitted from the respective two signals that pass through the twisted pair cable cancel each other out, thereby to eliminate emission of electromagnetic waves to outside the twisted pair cable, the data receiving apparatus comprising;

a differential receiver operable to receive transmission signals transmitted through the twisted pair cable, and to convert a difference in potential between two wires of the twisted pair cable into a signal;

an A/D converter operable to convert the signal outputted from said differential receiver into a digital signal value in each sampling cycle;

a second digital filter operable to allow only lower frequency components of a digital data stream that has been obtained by sampling with said A/D converter, to pass; and

a level evaluator operable to evaluate a symbol value from a level of a signal in symbol timing, including a symbol in the signal, based on an output from said second digital filter, and to convert the symbol value into corresponding digital data.

39. A data transmission/receiving apparatus for receiving data outputted from a data transmission apparatus including:

a data coding device operable to convert digital data into a signal level corresponding to a symbol that is assigned to the digital data in each symbol cycle as a prescribed unit cycle;

a first digital filter having a first sampling cycle that is shorter than a unit cycle of a signal level string that has been obtained by the data coding device, and being operable to allow only predetermined frequencies to pass;

a D/A converter operable to convert a digital data stream that has passed through the first digital filter, into an analog signal;

a low-pass filter operable to eliminate folding distortion of the first digital filter from the analog signal that has been obtained by the D/A converter, the folding distortion being determined in the first sampling cycle;

a differential driver operable to convert an output from the low-pass filter, into two signals having opposite polarities relative to a predetermined reference potential, and to input the two signals into a twisted pair cable;

a differential receiver operable to receive transmission signals transmitted through the twisted pair cable, and to convert a difference in potential between two wires of the twisted pair cable into a signal;

an A/D converter operable to convert the signal outputted from the differential receiver into a digital signal value in each second sampling cycle;

a second digital filter operable to allow only a predetermined frequency band of a digital data stream that has been obtained by sampling with the A/D converter, to pass; and

a level evaluator operable to evaluate a symbol value from a level of a signal in symbol timing, including a symbol in the signal, based on an output from the second digital filter, and to convert the symbol value into corresponding digital data, wherein the first and second digital filters both have low-pass characteristics, and the first digital filter has frequency characteristics of cutting off at least frequency data which are higher than a frequency band in which electromagnetic waves emitted from the respective two signals that pass through the twisted pair cable cancel each other out, thereby to eliminate emission of electromagnetic waves to outside the twisted pair cable, the data transmission/receiving apparatus comprising;

a transmission/receiving controller operable to judge whether the digital data outputted from the level evaluator of the data transmission apparatus is to be retransmitted, output the digital data that is not to be retransmitted as received data, and multiplex transmission data inputted from outside with the digital data that is to be retransmitted, thereby to be inputted to the data coding device.

40. A signal processing method for processing transmission signals that are transmitted from a data transmission apparatus including:

a data coding device operable to convert digital data into a signal level corresponding to a symbol that is assigned to the digital data in each symbol cycle as a prescribed unit cycle;

a first digital filter having a first sampling cycle that is shorter than a unit cycle of a signal level string that has been obtained by the data coding device, and being operable to allow only predetermined frequencies to pass;

a D/A converter operable to convert a digital data stream that has passed through the first digital filter, into an analog signal;

a low-pass filter operable to eliminate folding distortion of the first digital filter from the analog signal that has been obtained by the D/A converter, the folding distortion being determined in the first sampling cycle;

a differential driver operable to convert an output from the low-pass filter, into two signals having opposite polarities relative to a predetermined reference potential, and to input the two signals into a twisted pair cable, wherein the first digital filter has frequency characteristics of cutting off at least frequency data which are higher than a frequency band in which electromagnetic waves emitted from the respective two signals that pass through the twisted pair cable cancel each other out, thereby to eliminate emission of electromagnetic waves to outside the twisted pair cable, the data coding device is operable to convert data comprising two or more bits per symbol cycle, into a symbol to be transmitted, the data coding device includes;

a previous signal level storage device operable to store a previous signal level; and

a coding device operable to decide a signal level corresponding to a symbol to be transmitted, based on the previous signal level and the symbol to be transmitted, the coding device is operable to assign a symbol in a symbol transmission timing to a signal level having a predetermined difference from the previous signal level that is stored in the previous signal level storage device, the signal processing method comprising;

obtaining a difference between a signal level in a first symbol receipt timing and a signal level in a second symbol receipt timing; and

establishing a symbol to correspond to the difference to decode a signal level in the first symbol receipt timing.

41. The signal processing method of claim 40, wherein the second symbol receipt timing corresponds to a symbol that is received prior to a symbol of the first symbol receipt timing.

42. A signal processing method for processing transmission signals that are transmitted from a data transmission apparatus including:

a data coding device operable to convert digital data into a signal level corresponding to a symbol that is assigned to the digital data in each symbol cycle as a prescribed unit cycle;

a first digital filter having a first sampling cycle that is shorter than a unit cycle of a signal level string that has been obtained by the data coding device, and being operable to allow only predetermined frequencies to pass;

a D/A converter operable to convert a digital data stream that has passed through the first digital filter, into an analog signal;

a low-pass filter operable to eliminate folding distortion of the first digital filter from the analog signal that has been obtained by the D/A converter, the folding distortion being determined in the first sampling cycle;

a differential driver operable to convert an output from the low-pass filter, into two signals having opposite polarities relative to a predetermined reference potential, and to input the two signals into a twisted pair cable, wherein the first digital filter has low-pass characteristics of cutting off at least frequency data which are higher than a frequency band in which electromagnetic waves emitted from the respective two signals that pass through the twisted pair cable cancel each other out, thereby to eliminate emission of electromagnetic waves to outside the twisted pair cable, the data coding device includes a number of signal levels which is greater than a number of kinds of symbols to be transmitted per symbol cycle, the data coding device is operable to assign a symbol in a symbol transmission timing to one of the signal levels, the data coding device includes;

a previous signal level storage device operable to store a previous signal level; and

a coding device operable to decide a signal level corresponding to a symbol to be transmitted, based on the previous signal level and the symbol to be transmitted, the coding device is operable to assign a symbol in a symbol transmission timing to a signal level having a predetermined difference from the previous signal level that is stored in the previous signal level storage device, the signal processing method comprising;

obtaining a difference between a signal level in a first symbol receipt timing and a signal level in a second symbol receipt timing; and

establishing a symbol to correspond to the difference to decode a signal level in the first symbol receipt timing.

43. The signal processing method of claim 42, wherein the second symbol receipt timing corresponds to a symbol that is received prior to a symbol of the first symbol receipt timing.