JPH06164764A - Modem - Google Patents

Abstract

PURPOSE:To adopt a low voltage power supply for the MODEM and to improve data transmission reception quality. CONSTITUTION:An interface 1 sends and receives serial data with a terminal equipment. A transmission reception controller 2 applies speed adjustment to transmission data from the interface 1 and speed adjustment or the like to data fed to the interface 1. A data pump circuit 4 modulates/demodulates the data. The data pump circuit 4 and the transmission reception controller 2 are isolated by photocouplers 3, 10. Modulation data outputted from the data pump circuit 4 are sent to a telephone line 8 via a transmission filter 5 and a mixing/ distribution circuit 6. An analog reception signal received from the telephone line 8 is fed to the data pump circuit 4 via the mixing/distribution circuit 6 and a reception filter 9. A low voltage power supply is adopted and the data transmission quality is improved by employing the photocouplers 3, 10 as means to isolate the line side and the terminal equipment side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a modulation / demodulation device for modulating / demodulating a signal transmitted / received between a communication line and a terminal device at the end of a communication line such as an analog telephone line, and particularly to the communication line and the terminal device. Regarding the insulation demarcation method between and.

[0002]

2. Description of the Related Art Conventionally, a device connected to a telephone line is required to meet various electrical conditions so as not to disturb the function of the network or to disturb other users or exchanges. It is said that this condition is specified by the Ordinance of the Ministry of Posts and Telecommunications. For this reason, in a modulation / demodulation device (modem) connected between the analog line and the data terminal device, it is necessary to somehow perform insulation demarcation between the line and the terminal.

In a conventional modulator / demodulator, a transformer having a simple structure and a low cost is used as a means for insulating and disassembling the line and the terminal. That is, the data output from the data terminal device is, for example, PSK modulated by the modulator / demodulator,
2 of the transformer through the transmission filter and mixing / distribution circuit
It is supplied to the secondary side and transmitted to the telephone line via the primary side of the transformer. Further, the analog reception signal received from the telephone line is transmitted from the primary side to the secondary side of the transformer, further PSK demodulated through the mixing / distribution circuit and the reception filter, and supplied to the data terminal device. In this way, the electrical condition described above can be satisfied by achieving insulation from the line via the transformer.

[0004]

However, in the above conventional modulator / demodulator, the primary side (line side) of the transformer is used.
To obtain sufficient amplitude characteristics, the secondary side (terminal side)
Therefore, the drive power commensurate with that is required, and the power for that must be supplied from the outside. In recent years, there is an increasing demand for lower power supply voltage in this type of device as well, but in the conventional device, it becomes impossible to drive the transformer with a sufficient amplitude when the power supply voltage is lowered. There is a problem that it is difficult to achieve. Also,
In the conventional device, there is a problem that the phase rotation of the modulation signal and the increase of the harmonic distortion cannot be avoided due to the analog transfer characteristic of the transformer, and the data error easily occurs.

The present invention has been made in order to solve such a problem, and aims at lowering the power supply voltage of the device while improving the insulation demarcation between the line and the terminal and improving the quality of data transmission / reception. It is an object of the present invention to provide a modulation device and a demodulation device that can perform the above.

[0006]

A modulation / demodulation device according to the present invention is provided in a modulation / demodulation device provided between a terminal device and a communication line, for modulating / demodulating a signal transmitted / received between the terminal device and the communication line. A digital transmission / reception means for performing a predetermined transmission / reception process on the serial transmission data from the terminal device and the serial reception data to the terminal device,
Modulation / demodulation means for modulating transmission data output from the digital transmission / reception means and demodulation processing for supplying demodulation data to the digital transmission / reception means, and a modulation signal output from the modulation / demodulation means are sent to the communication line. At the same time, the analog transmission / reception means for supplying the reception signal received from the communication line to the modulation / demodulation means, and the serial transmission / reception data path in the digital transmission / reception means are provided to optically couple the terminal device side and the communication line side. And an optical coupling means that electrically insulates.

[0007]

According to the modulation / demodulation apparatus of the present invention, by arranging the optical coupling means in the serial transmission data path from the serial interface portion of the digital transmission / reception means arranged on the terminal device side to the subsequent stage portion, a small amount of light is transmitted. The number of coupling elements makes it possible to demarcate the data path between the terminal side and the line side. In general, an optical coupling means such as a photocoupler has an insulation characteristic higher than that of a transformer, so that it is possible to sufficiently satisfy the electrical conditions required for the modulator / demodulator. Furthermore, since the optical coupling means is smaller than the transformer, the device can be downsized. And
According to the present invention, the optical coupling means is used instead of the conventional transformer, so that the drive power on the secondary side can be significantly reduced as compared with the conventional case. Further, in the present invention,
Since insulation is provided at the portion close to the terminal side, more circuit elements can be arranged on the primary side (line side) than in the past. Then, the electric power required on the primary side can effectively utilize the direct current for forming the reception monitoring signal of the line. Therefore, according to the present invention, it is possible to significantly reduce the power supply voltage of the device.

Further, according to the present invention, since the insulating demarcation unit transmits information as a digital signal, it is not affected by analog effects such as phase rotation and harmonic distortion. Therefore, the data transmission quality is also greatly improved.

[0009]

Embodiments of the present invention will be described below with reference to the accompanying drawings. 1 is a block diagram showing the configuration of a modulation / demodulation device according to a first embodiment of the present invention. Transmission data Ds output from a terminal device such as a computer (not shown) is supplied to the transmission / reception controller 2 via the interface 1. The transmission / reception controller 2 adjusts the speed of the transmission data Ds by an internal buffer (not shown), and performs processing such as data compression by Hoffman code and addition of error check code. The serial data output from the transmission / reception controller 2 drives the photodiode 3a on the input side of the photocoupler 3. Photo coupler 3
The serial data transmitted to the output-side phototransistor 3b is supplied to the data pump circuit 4. The data pump circuit 4 performs PSK (Phase Shift Keying) modulation on the input data by digital processing, and then D /
A convert. The obtained PSK modulation signal is supplied to the telephone line 8 via the transmission filter 5, the mixing / distribution circuit 6 and the DP (dial pulse) relay 7.

On the other hand, the analog reception signal received from the telephone line 8 via the DP relay 7 is supplied to the data pump circuit 4 after passing through the reception filter 9. The data pump circuit 4 A / D-converts the input analog modulation signal and then performs PSK demodulation. The demodulated data is output in the form of serial data. This serial demodulated data is input to the photodiode 10 on the input side of the photocoupler 10.
Drive a. The serial data transmitted to the output-side phototransistor 10b of the photocoupler 10 is supplied to the transmission / reception controller 2. The transmission / reception controller 2 performs processing such as error checking and data decompression on the received demodulated data, and outputs an retransmission request and the like to the telephone line 8 side when an error occurs, and also adjusts the data rate with an internal buffer to make the interface 1 The reception data Dr is supplied to the terminal device via the.

The sequence controller 11 controls the operations of the transmission / reception controller 2 and the data pump circuit 4 and exchanges control data with the terminal device via the interface 1 to drive the tone dialer 12 and the pulse dialer 13. . Tone dialer 12 is DTMF
A circuit for transmitting a (Dual Tone Multi Frequency) signal through the mixing / distribution circuit 6, a pulse dialer 13
Is a circuit for generating a dial pulse to drive the DP relay 7. The sequence controller 1
1 is arranged on the primary side, the photo couplers 3, 10 are provided between the sequence controller 11 and the interface circuit 1 and the transmission / reception controller 2 (portions shown in the figure).
When the sequence controller 11 and the data pump circuit 4 are insulated by a photo coupler similar to the above, and the sequence controller 11 is arranged on the secondary side, the same as the photo couplers 3 and 10 is provided between the sequence controller 11 and the data pump circuit 4 (the portion shown in the drawing). Insulate with a photo coupler.

FIG. 2 is a block diagram showing details of the data pump circuit 4. The serial transmission data supplied from the transmission / reception controller 2 via the photocoupler 3 is rearranged by the scrambler 21 to change the data position,
Burst errors are distributed. The modulation circuit 22 performs PSK modulation on the output of the scrambler 21, for example. The obtained digital modulation data is converted to an analog P by the D / A converter 23.
It is converted into SK modulated data and output. On the other hand, the analog reception data is converted into digital data having a predetermined number of bits by the A / D converter 24, then demodulated by the demodulation circuit 25, for example, by PSK demodulation, and the order of the data is changed by the descrambler 26. This serial reception data is supplied to the photocoupler 10.

According to the modulator / demodulator thus configured, the transmission / reception controller 2 and the data pump circuit 4 are insulated and demarcated by the photocouplers 3 and 10. Can be significantly downsized. Further, the power supply of the circuit on the primary side can use the reception monitoring signal (DC current of about 20 mA to 120 mA) from the exchange that flows through the telephone line 8 when off hook. Therefore, as the secondary power, only the interface 1, the transmission / reception controller 2, the sequence controller, and the power for driving the photodiode 3a are required, so that the power supply voltage of the device can be lowered. Further, according to this apparatus, since the insulation demarcation point is transmitted as information by serial digital data, there is no analog loss such as phase rotation or generation of harmonic distortion, which occurs when a transformer is used. Therefore, the data transmission / reception quality can be improved.

FIG. 3 is a block diagram of a modulator / demodulator according to another embodiment of the present invention. That is, in the above-described embodiment, the transmission / reception controller 2 and the data pump circuit 4 are insulated by the photocouplers 3 and 10. However, in this embodiment, the interface 1 and the transmission / reception controller 2 are isolated from each other. I'm trying to insulate. Further, the interface 1 and the sequence controller 11 (white circles in the figure) are also insulated by a photo coupler similar to the photo couplers 3 and 10. Even in this case, since the data exchanged between the interface 1 and the transmission / reception controller 2 is serial digital data, the photocouplers 3 and 10 can easily transmit information. Further, according to this embodiment, the number of circuit elements arranged on the secondary side can be further reduced, so that the electric power from the line on the primary side can be used more effectively and the electric power required for the device can be further reduced. can do.

In each of the above embodiments, the photocoupler is used as the optical coupling means, but other optical coupling means using an optical integrated circuit or the like may be used. Further, the modulation / demodulation system is not limited to the PSK system, but may be FSK (Frequency Shrink).
ift Keying), QAM (Quadrature Amplitude Modurat)
The present invention can also be applied to devices using other modulation / demodulation methods such as ion). The modulation / demodulation device of the present invention may be incorporated in the terminal device as in the case of a facsimile or the like.

[0016]

As described above, according to the present invention,
Since the optical coupling means is used instead of the conventional transformer as the insulation demarcation means for the line and the terminal, it is possible to significantly reduce the power supply voltage of the device. According to the invention,
Since the insulating demarcation unit transmits information by serial digital data, it is not affected by analog effects such as phase rotation and harmonic distortion, and the data transmission quality is significantly improved.

[Brief description of drawings]

FIG. 1 is a block diagram of a modulation / demodulation device according to an embodiment of the present invention.

FIG. 2 is a block diagram of a data pump circuit in the device.

FIG. 3 is a block diagram of a modulation / demodulation device according to another embodiment of the present invention.

[Explanation of symbols]

1 ... Interface, 2 ... Transmission / reception controller, 3, 1
0 photo coupler, 4 ... Data pump circuit, 5 ... Transmission filter, 6 ... Mixing / distribution circuit, 7 ... DP relay, 8 ... Telephone line, 9 ... Reception filter, 11 ... Sequence controller, 12 ... Tone dialer, 13 ... Pulse Dialer, 2
DESCRIPTION OF SYMBOLS 1 ... Scrambler, 22 ... Modulation circuit, 23 ... D / A converter, 24 ... A / D converter, 25 ... Demodulation circuit, 26 ... Descrambler.

Claims (1)

[Claims] 1. A device provided between a terminal device and a communication line,
A modulator / demodulator for modulating / demodulating a signal transmitted / received between the terminal device and the communication line, wherein digital transmission / reception for performing a predetermined transmission / reception process on serial transmission data from the terminal device and serial reception data to the terminal device. Means, modulation / demodulation means for modulating the transmission data output from the digital transmission / reception means and performing demodulation processing to supply demodulation data to the digital transmission / reception means, and the modulation signal output from the modulation / demodulation means for the communication line. And an analog transmission / reception means for supplying the reception signal received from the communication line to the modulation / demodulation means, and a serial transmission / reception data path in the digital transmission / reception means for connecting the terminal device side and the communication line side. Optical coupling means for optically coupling and electrically insulating A modulator / demodulator characterized by.