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Digital data transmitter

  • US 20040028145A1
  • Filed: 04/04/2003
  • Published: 02/12/2004
  • Est. Priority Date: 10/05/2000
  • Status: Active Grant
First Claim
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1. A digital data transmission apparatus comprising:

  • 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 obtained by the data coding means, and allows 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 first 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;

    a differential driver for converting an output of the first low-pass filter, into two signals having opposite polarities relative to a predetermined reference potential, and differentially outputting the obtained signals;

    a second low-pass filter for eliminating a predetermined frequency band from each of the signals which are outputted from the differential driver, and outputting obtained signals to a twisted pair cable;

    a differential receiver for receiving transmission signals transmitted through the twisted pair cable, and converting a difference in potentials 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, and combination of the first low-pass filter and the second low-pass filter has low band cut-off characteristics of eliminating folding distortion of the first digital filter, which is decided in the first sampling cycle.

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