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

• US 20040042555A1
• Filed: 04/04/2003
• Published: 03/04/2004
• Est. Priority Date: 10/05/2000
• Status: Active Grant

• 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
• Granted Patent: US 7,190,728 B2
• Time in Patent Office: Days
• US Class Current: 375/257
• 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 including:

a data coding means for converting 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 means, and allowing only predetermined frequencies to pass;

a D/A conversion means for converting the digital data stream that has passed through the digital filter, into an analog signal;

a low-pass filter for eliminating folding distortion of the first digital filter from the analog signal that has been obtained by the D/A conversion means, which distortion is decided in the first sampling cycle;

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

a differential receiver for receiving transmission signals transmitted through the twisted pair cable, and converting a difference in potential between two wires of the cable into a signal;

an A/D conversion means for converting the signal outputted from the differential receiver into a digital signal value in each second sampling cycle;

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

a level evaluation means for evaluating a symbol value from a level of a signal in symbol timing, including a symbol in the signal, on the basis of an output from the second digital filter, and converting 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 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

transmission characteristics of a signal which has been passed through the first and second digital filters have roll-off characteristics.

3. The digital data transmission apparatus of claim 2 wherein

the data coding means converts data comprising two or more bits per symbol cycle, into a symbol to be transmitted.

4. The digital data transmission apparatus of claim 3 wherein

the data coding means includes signal levels which are more than the number of kinds of symbols to be transmitted per symbol cycle, and assigns a symbol in a symbol transmission timing to one of the signal levels.

5. The digital data transmission apparatus of claim 3 or 4 wherein

the data coding means has five signal levels, and assigns 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 immediately preceding symbol transmission timing, in the order of 01, 11, 00, 10, starting from a lowest signal level.

6. The digital data transmission apparatus of claim 3 or 4 wherein

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

the data coding means assigns 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 immediately preceding symbol transmission timing, in the order of 01, 11, 00, 10 starting from a lowest signal level, thereby to decide a signal level to be transmitted.

7. The digital data transmission apparatus of claim 3 or 4 wherein

the data coding means assigns a symbol in a symbol transmission timing alternately to one of signal levels which are as many as the number of kinds of symbols starting from a lowest signal level and to one of signal levels which are 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.

8. The digital data transmission apparatus of any of claims 3 to 7 wherein

the data coding means includes:

a previous signal level storage means for storing the previous signal level; and

a coding means for deciding a signal level corresponding to a symbol to be transmitted, on the basis of the previous signal level and the symbol to be transmitted.

9. The digital data transmission apparatus of claim 8 wherein

the coding means assigns 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 means.

10. The digital data transmission apparatus of any of claims 3 to 9 wherein

the data coding means is supplied with a transmission method instruction signal indicating whether or not the transmission signal has been coded by a bi-phase mark method.

11. The digital data transmission apparatus of claim 1 wherein

the level evaluation means includes:

a signal level detection means for detecting a signal level in each symbol cycle; and

a previous signal level storage means for storing a previous signal level which was received in immediately preceding symbol receipt timing, and

said level evaluation means decodes the signal level detected by the signal level detection means, into a corresponding symbol, on the basis of the previous signal level that is stored in the previous signal level storage means.

12. The digital data transmission apparatus of claim 1 or 11 wherein

the level evaluation means includes:

a threshold control means for correcting an evaluation threshold level on the basis of variation values in respective signal levels which were received during a predetermined time period;

a previous signal level storage means for storing the previous signal level; and

a threshold evaluation means for holding a threshold and performing 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.

13. The digital data transmission apparatus of claim 11 or 12 wherein

the level evaluation means includes a synchronization means for establishing synchronization with a symbol cycle of a received signal, and

the synchronization means extracts frequency components having a half cycle as long as the symbol cycle, from the received signal, and controls a symbol timing at which a symbol is detected, on the basis of a phase of the extracted signal.

14. The digital data transmission apparatus of any of claims 11 to 13 wherein

the level evaluation means is supplied with a transmission method instruction signal indicating whether or not the received signal has been coded by the bi-phase mark method.

15. The digital data transmission apparatus of any of claims 1 to 14 further including:

a scrambler for scrambling digital data to be transmitted; and

a descrambler for descrambling received scrambled digital data.

18. A data transmission/receiving apparatus including:

a transmission/receiving control means that judges the received data that is outputted from the level evaluation means of the digital data transmission apparatus of claim 1, inputs data to be retransmitted into the data coding means while outputting data that will not be retransmitted to outside as received data, and multiplexes transmission data that is inputted from outside into the retransmitted data, thereby to be inputted to the data coding means.

16. A data transmission apparatus including:

a data coding means for converting 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 the data coding means, and allowing only predetermined frequencies to pass;

a D/A conversion means for converting a digital data stream that has passed through the digital filter, into an analog signal;

a low-pass filter for eliminating folding distortion of the first digital filter from the analog signal obtained by the D/A conversion means, which distortion is decided in the first sampling cycle; and

a differential driver for converting an output of the low-pass filter, into two signals having opposite polarities relative to a predetermined reference potential, and inputting 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 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.

17. (Amended) A data receiving apparatus including:

a differential receiver for receiving transmission signals transmitted through a twisted pair cable, and converting a difference in potential between two wires of the cable into a signal;

an A/D conversion means for converting the signal outputted from the differential receiver into a digital signal value in each sampling cycle;

a digital filter that allows only lower frequency components of a digital data stream that has been obtained by sampling with the A/D conversion means, to pass; and

a level evaluation means for evaluating a symbol value from a level of a signal in symbol timing, including a symbol in the signal, on the basis of an output from the digital filter, and converting the symbol value into corresponding digital data.

19. (Amended) A transmission channel coding method including steps of:

when transmitting digital data as one symbol that is composed of an arbitrary number of bits, providing signal levels which are more than the 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 immediately preceding symbol transmission timing.

21. (Amended) The transmission channel coding method of claim 19 wherein

the signal level that represents the symbol in the transmission timing is assigned alternately to one of signal levels which are as many as the number of kinds of the symbols starting from a lowest signal level, and one of signal level which are as many as the number of kinds of the symbols starting from a highest signal level.

22. (Amended) The transmission channel coding method of claim 19 or 21 wherein

the number of kinds of the symbols is four, and two-bit data is transmitted per symbol.

23. (Amended) The transmission channel coding method of any of claims 19, 21, and 22 wherein

2-bit data are coded per one symbol by being assigned to signal levels in the order of 01, 11, 00, 10, starting from a lowest signal level.

24. (Amended) The transmission channel coding method of any of claims 19, 21, and 22 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.

25. (Amended) The transmission channel coding method of any of claims 19 and 21 to 24 wherein

the number of the signal levels is one more than the number of kinds of symbols.

26. (Amended) The transmission channel coding method of any of claims 19 and 21 to 24 wherein

the number of the signal levels is twice as many as the number of kinds of the symbols.

27. (Amended) The transmission channel coding method of any of claims 19 and 21 to 24 wherein

the number of the signal level is 1.5 times as many as the number of kinds of the symbols.

28. (Amended) The transmission channel coding method of any of claims 19 and 21 to 27 wherein

the digital data are scrambled data.

29. The transmission channel coding method of claim 28 wherein

the scrambling is self-synchronization scrambling in which transmission data is processed on the basis of data generated from the transmission data.

20. (Delete)

30. (Delete)

31. A decoding method of making a symbol correspond to a difference in signal level between a signal level in a symbol receipt timing and a signal level in immediately preceding symbol receipt timing, to decode a signal level in a symbol receipt timing into a symbol.