JPS61263341A - Pcm communication method - Google Patents

Abstract

PURPOSE:To use a code rule violation as another one information channel and to keep a high S/N marge by using a ternary code in which a DC component is not included as a CATV transmission line code. CONSTITUTION:An inputted digital data (a) is converted to an AMI code and is modulated at a VSB modulator 13 through a roll-off filter 12 and is sent out to a CATV transmission line 15 through an RF filter 14. A signal transmitted is received at a TV tuner 17 and after AM detection, it is reproduced as the digital data of NRZ at a discriminating code converter 18 and also, the code rule violation is detected at a code rule violation detecting part 19 and is outputted as a code rule violation signal (g). Also, the digital data (f) of an NRZ code is separated to and outputted as a clock (e) and a digital data (f) by a PLL20 and a re-timing part 21.

Description

[Detailed Description of the Invention] Industrial Field of Application The present invention is applied to multipurpose information systems (MPIS: Mu).
lti-Purpose Info+nation
This invention relates to a PCM communication method suitable for use in a digital communication system using CATV lines such as a PCM system.

2. Prior Art Conventionally, this type of PCM communication method was disclosed in Japanese Unexamined Patent Application Publication No. 1986-
As described in Japanese Patent No. 15373, the transmission line code used was a digital signal with four levels or higher, a duty ratio of 100%, and a code in which violation of coding rules could not be detected.

Problems to be Solved by the Invention However, in the conventional PCM communication method described above, since the code includes a DC component, the low-frequency cutoff characteristics of the circuit and resistance to temperature fluctuations are weak, and multi-level transmission is difficult. Therefore, although the bit rate can be high, the S/H of the transmission path
The disadvantage was that the margin was small.

The present invention solves these conventional problems,
It is an object of the present invention to provide a low-cost PCM communication method that is stable against temperature fluctuations and low-frequency cutoffs, has a high S/N margin, and can use code rule violation detection as information.

Means for Solving the Problems In order to achieve the above object, the present invention uses a ternary code (for example, AM I (Alternate Mark I
(nversion) code).

Therefore, according to the present invention, since a code without a DC component is used, it is resistant to temperature fluctuations and low frequency cutoff, and
Since it is a value code, the margin of the transmission path S/H is high, and violation of the code rule can be used as another information channel, which has the effect of realizing a highly functional communication system at low cost.

Embodiment FIG. 1 shows the configuration of an embodiment of a PCM communication method using the present invention. In FIG. 1, 11 is a code converter from NRZ code to AMI code, and code converter 1
1 has digital data a1 clock b1 code rule violation (
CRV) signal C is input, and its output is input to the roll-off filter 12. The output of the roll-off filter 12 is a vestigial sideband (VSB) along with carrier d.
) is input to the modulator 13, and the output of the VSB modulator 13 is
It is input to the RF filter 14. Code converter 1
1 to RF filter 14 are elements included in the transmitter. The output of the RF filter 14 is used as the output of the transmitter,
RF filter 16 in the receiving section through CATV transmission line 15
is input. The output of the RF filter 16 is input to a TV tuner 17, and the output of the TV tuner 17 is input to an identification/code converter 18. There are two types of outputs from the identification/code converter 18; one is sent to the code rule violation detection unit 19, and the other is sent to the phase rotor group circuit (PLL').
20 and is input to the retiming section 21. P.L.
The output of L20 is outputted to the outside as a clock e and simultaneously inputted to the retiming section 21, and the output of the retiming section 21 is outputted to the outside as digital data f. Further, the output of the coding rule violation detection section 19 is outputted to the outside as a coding rule violation signal g. More than RF
The filter 16 to the retiming section 21 are elements included in the receiving section.

Next, the operation of the above embodiment will be explained. In the above embodiment, the code converter 11 converts the input digital data a into an AMI code using the clock b. still,
At this time, the code rule violation signal C can be used to cause the AMI code to violate the code rule. The digital data that became the AMI code whose conversion rule is shown in Figure 2 is
The VS is passed through a roll-off filter 12 to reduce code amount interference due to attenuation distortion and group delay distortion occurring in the transmission path 15.
The signal is modulated by the carrier d by the B modulator 13, passed through the RF filter 14, and sent to the CATV transmission line 15. CA
The TV transmission line 15 is composed of a coaxial cable, a divider, an amplifier, etc., and the end-to-end S/N, attenuation distortion, and group delay distortion are specified.

The transmitted signal passes through the RF filter 16 in the receiving section
The signal is input to the V tuner 17. The TV tuner 17 is equipped with a local oscillator corresponding to carrier d of the transmitter, and C
Of all the signals on the ATV transmission line 15, only the relevant signal is selectively received. In addition, by appropriately designing the RF filter 14.16, this PC can be used during existing CATV service.
It is possible to easily incorporate the M-bank loan method.

The received signal is subjected to AM detection in the TV tuner 17,
The identification/code converter 18 reproduces the signal into NRZ digital data, and the code rule violation detection unit 19 detects a code rule violation and outputs it as a code rule violation signal g. Also N
The RZ code digital data f is processed by the PLL 20,
The clock is extracted, and the retiming unit 21 retimes the clock based on the clock and outputs it as digital data f together with the clock e.

By using the communication method shown in the above embodiment and using ~ several channels of CATV as the transmission path, a digital communication system that is easily compatible with existing CATV systems can be constructed, and digital audio transmission, It can be used for purposes such as facsimile transmission. Also, T
The V tuner, VSB modulator, RF filter, etc. are the same as the existing TV.

Hardware for CATV systems can be used, and since AMI codes use codes without DC components, the accuracy and stability required for the hardware can be rough.
This has the advantage that the system can be configured economically. Furthermore, since code rule violation information is transmitted, by regarding this as another information channel, more sophisticated services can be realized.

FIG. 2 shows examples of various codes used in the above configuration, where 1 is an NRZ signal, 2 is a CRV signal, and 3 is an AMr signal to which the CRV signal is added. Note that the broken line A in the figure shows the AMI signal when it is desired to add the CRV signal.

Effects of the Invention As is clear from the above examples, the present invention has the following effects.

(1) Since the AMI code without DC component is used,
The accuracy and stability required for the hardware can be rough, and an economical communication system can be constructed.

(2) Since it has coding rules and can transmit violation information, the coding rule violation information can be used as another information channel, making it possible to provide more advanced services.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a device used in a PCM communication method according to an embodiment of the present invention, and FIG. 2 is an explanatory diagram of code conversion rules used in the configuration of FIG. 1. 11... Code converter, 12... Roll-off filter, I3... VSB modulator, 14...
...RF filter, 15...Transmission line, 1
6...RF filter, 17...TV tuner, 18...identification/code converter, 19...
... Code rule violation detection unit, 20 ... P L
L, 21...Retiming section.

Claims (1)

[Claims] When converting digital data into PCM and transmitting it using a CATV line as a transmission path, the digital data is converted into a ternary code that does not include a DC component, and other information data is converted into the ternary code as data that violates the coding rules of the ternary code. A PC that sends out the ternary data and separates it into the digital data and information data on the receiving side.
M communication method.