Pulse or digital communications – Repeaters – Testing
Patent
1984-03-08
1987-10-27
Olms, Douglas W.
Pulse or digital communications
Repeaters
Testing
375113, H04L 2534, H04L 2549, H04L 706
Patent
active
047034947
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a transmission system of PCM signals resulting from sampling and quantizing of analog signals.
BACKGROUND ART
In the field of signal transmission, there are generally two methods of transmission: one being that transfer clock signals and clock signals of a sampling interval are transmitted as well as data to be transmitted; and the other being that data are modulated and transmitted over a single data line. Especially, the latter is further classified into two methods: (A) a synchronizing pattern as shown in FIG. 1 is added to every data block prior to modulation and (B) a synchronizing interval which is a violation of the modulation rule as indicated in FIG. 2 is provided for every data block. The modulation rule used herein is the Bi-phase method, for example. The method (A) requires a pattern matching circuit on the demodulator side for detecting the synchronizing pattern and incurs the risk of causing an error in detection of a sampling interval in the event that a data block happens to bear the same pattern as the synchronizing patterns. In addition, the method (B) has problems of expansion of a frequency band necessary for transmission and decline of the capacity of data transmission, because of the violation of the modulation rule.
DISCLOSURE OF THE INVENTION
An object of the present invention is to provide a data transmission technique by which a synchronizing interval violating a rule of modulation is provided for each predetermined interval and a level reversal interval following each synchronizing interval is provided for every data block (or interval).
More particularly, according to the present invention, the synchronizing interval which is a violation of the modulation rule is provided for synchronizing reasons and is always followed by a level reversal interval of a desired bit length. This enables PCM signal, PCM signal transfer block signals and sampling interval clock signals to be carried over a single data line, thus assuring PCM signal transmission over a longer transmission distance without requiring a complicated and large-sized circuit structure.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagram illustrating a conventional waveform of transmitted PCM signals to which a synchronizing pattern is provided for every data block as a representation of a sampling interval;
FIG. 2 is an illustration of another conventional waveform of transmitted PCM signals to which a synchronizing interval violating a rule of modulation is provided as a representation of a sampling interval;
FIG. 3 is an illustration of an example of a waveform of transmitted PCM signals according to the present invention;
FIGS. 4 (a) and 4(b) are illustrations of waveforms of transmitted PCM signals and the demodulated signals thereof according to the present invention;
FIGS. 5(a) and 5(b) are illustrations of transmitted PCM signals and the demodulated signals thereof according to the conventional technique;
FIG. 6 is a circuit diagram of a transmitter according to the present invention;
FIG. 7 is a time chart for the transmitter;
FIG. 8 is a circuit diagram of a receiver according to the present invention;
FIG. 9 is a time chart for the receiver;
FIG. 10 is an illustration of a typical transmission signal waveform in application of the present invention to PE modulation; and
FIG. 11 is an illustration of a typical transmission signal waveform in application of the present invention to MFM modulation.
THE BEST MODE FOR CARRYING OUT THE INVENTION
In FIG. 3, there is shown a waveform of a signal transmitted according to an embodiment of the present invention. FIG. 3(a) depicts pre-modulated data in which "0" is always placed at the leading data bit position immediately following a synchronizing interval. FIG. 3(b) shows a waveform of transmitted PCM signals in which data are modulated in the Bi-phase method and the synchronizing interval (an interval where no transition occurs for 4 bit times) is set up. As is apparent from FIG. 3(b), the interval where no transit
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"A Digital Interface for the Interconnection of Professional Digital Audio Equipment", Dr. R. Lagadec, et al., 71st Convention, Mar. 2-5, 1982 Montreux, Audio Engineering Society.
Ozaki Minoru
Tanaka Kunimaro
Chin Wellington
Mitsubishi Denki & Kabushiki Kaisha
Olms Douglas W.
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