JP2002111640A - Bidirectional signal transmission apparatus by digital system and signal transmission system using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small and low-cost bidirectional signal transmission apparatus (repeater) in which an adjustment in its installation and a readjustment after that are not required and which can obtain a sufficient amplification. SOLUTION: The bidirectional signal transmission apparatus is provided with a two-wire-to-four-wire conversion part, a digital-signal-level discrimination and restoration part, a bit-delay sorting part, a clock generation part and a direction selector part. A fundamental clock signal generated by the clock generation part is divided and supplied to each bit delay sorting part. Each bit delay sorting part outputs an input signal so as to be synchronized with the supplied clock signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital bidirectional signal transmission apparatus for amplifying bidirectional signals on a two-wire transmission line, and more particularly to synchronous classification of bidirectional signals.

[0002]

2. Description of the Related Art In order to restore a signal level transmission loss on a two-wire transmission line, a bidirectional signal transmission device (which separates and amplifies bidirectional signals on the transmission line into one-way signals, respectively). Repeater) is used. FIG. 6 shows a configuration example of a conventional repeater for a two-wire transmission line. At the connection point between the two-wire transmission line and the repeater, a hybrid coil (3-turn transformer)
Is used.

An upstream signal transmitted on the two-wire transmission line 111 from the left in the figure (the right direction in the figure is defined as upstream)
Is separated from the downstream signal by the hybrid coil 112 and transmitted only in the direction of the amplifier 113,
After being amplified at 3, the signal is relayed to the two-wire transmission line 121 via the hybrid coil 122. Similarly, a downstream signal transmitted on the two-wire transmission line 121 from the right in the figure is separated by the hybrid coil 122, amplified by the amplifier 123, and then passed through the hybrid coil 112 to the two-wire system. The data is relayed to the transmission line 111.

[0004] Such hybrid coils 112, 1
In 22, if there is an imbalance between the impedance on the transmission line side and the impedance on the repeater side, the output signal of one amplifier leaks to the input side of the other amplifier and wraparound occurs, and the round-trip gain of up and down becomes greater than 1. Oscillates and causes howling.

Accordingly, the impedance Z of the repeater
1, Z2 needs to be adjusted according to the impedance of the transmission line. However, since it is difficult to accurately predict the impedance of the transmission line, actual measurements and adjustments have been made at the site when installing the repeater.

Further, when the impedance of the transmission line changes due to the addition or change of the route, etc., it is necessary to go to the place where the repeater is installed each time and readjust the impedance of the repeater.

Further, since the impedance of the transmission line also changes due to a change in temperature or the like, it is impossible to always completely eliminate the impedance imbalance between the transmission line side and the repeater side. Therefore, in order to suppress signal wraparound and prevent howling from occurring, the amplifier 11
However, there is a problem that it is not possible to increase the gains of Nos. 3 and 123 so much that sufficient amplification cannot be obtained. In addition, the size of the hybrid coil is large, and it is difficult to reduce the size of the hybrid coil by using one chip.

That is, in the repeater for a two-wire circuit according to the prior art, the size of the entire repeater becomes large due to the large size of the hybrid coil, and a dedicated panel or the like is required. There are problems that adjustment is troublesome, re-adjustment is required every time a change occurs in the transmission line, that sufficient amplification cannot be obtained, and that a large number of repeaters must be provided.

[0009]

SUMMARY OF THE INVENTION The present invention is intended to solve such a problem, and does not require adjustment at the time of installation and subsequent readjustment, and can obtain a sufficient amplification. The purpose is to provide.

[0010]

SUMMARY OF THE INVENTION A repeater according to the present invention comprises a 2-wire to 4-wire converter, an analog / digital converter, a digital signal level discriminating / restoring unit, a bit delay discriminating unit, and a digital / analog converting unit. And a clock generator and a direction selector.

The basic clock signal generated by the clock generator is divided into an upstream clock signal and a downstream clock signal by the direction selector section, and supplied to the upstream and downstream bit delay discriminating sections. Each bit delay classification unit outputs the input signal in synchronization with the supplied clock signal.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 An embodiment of the present invention will be described with reference to FIG.

The bidirectional signal transmission device (repeater) 1 of the present invention
Numeral 0 denotes two-to-four-wire converters 11 and 21 provided at a connection point between the two-wire transmission lines 19 and 29, an analog / digital converter 12 of an up signal path (right in the figure is referred to as up),
Digital signal level discriminating / restoring section 13, bit delay sorting section 14, digital / analog converting section 15, analog / digital converting section 22 for a down signal path (left in the figure is referred to as down), digital signal level discriminating / restoring section 23,
Bit delay classification unit 24, digital / analog conversion unit 2
5, a clock generator 16 and a direction selector 17. The term "two-wire to four-wire converter" is usually used for a balanced two-wire transmission line, but here, the transmission line may be a coaxial line, an optical fiber, or another line. , The same names are used for convenience.

An up signal is extracted from the two-wire transmission line 19 by the two-wire to four-wire converter 11. The extracted upstream signal is encoded by the analog / digital converter 12 and converted into a digital signal. The upstream signal converted into a digital signal is amplified by the digital signal level discriminating / restoring unit, so that the attenuation of the signal level due to the transmission loss on the transmission line can be restored to the original level.
However, since the form of the signal is a digital signal, amplification here means multiplying the numerical value of the digital signal.

By the way, as described in the prior art, the separation of the upstream signal path from the downstream signal path in the 2-wire to 4-wire conversion units 11 and 21 is not perfect, so that the downstream signal may leak in the upstream signal. is there. When the level of the output signal in the down direction in the 2-wire to 4-wire conversion unit 11 is larger than the level of the input signal in the up direction, a certain threshold value is set in the digital signal level determination / restoration unit 13 in the up signal path. By suppressing the signal having a level higher than the threshold value, it is possible to amplify the upstream signal while suppressing the leaked downstream signal. As a result, it is possible to restore the input signal attenuation due to the upstream transmission line to the original level while preventing howling more strongly.

As a method of suppressing a signal having a level higher than the threshold value, a method of replacing all signals having a level exceeding the threshold value with a threshold value, or a method of setting all signals having a level exceeding the threshold value to zero. For example, a method that can be used can be applied.

Similarly, in the down direction, the down signal taken out by the 2-wire to 4-wire conversion unit 21 is converted into an analog signal.
The data is encoded by the digital conversion unit 22 and converted into a digital signal. When the level of the output signal in the up direction in the 2-wire to 4-wire conversion unit 21 is larger than the level of the input signal in the down direction, a certain threshold value is set in the digital signal level determination and restoration unit 23 in the down signal path. By amplifying while suppressing a signal having a level higher than the threshold value, it is possible to restore the attenuation of the input signal in the downward direction to the original level while preventing howling more strongly.

That is, the attenuation of the transmission signal can be restored to the original level by a digital method without causing howling in both directions.

Further, in the bidirectional signal transmission device according to the present invention, in the four-wire transmission circuit after the two-wire to four-wire conversion,
In order to restore signal attenuation in both directions at the same time without interference between the upstream and downstream signals, the digital signals are alternately separated so that the two-way signals do not overlap with each other in time.

FIG. 2 shows the temporal arrangement of the upstream signal and the downstream signal in bit units.
As shown in (1), signal bits in the up direction and signal bits in the down direction are generated alternately so as not to overlap each other, and an interval (pause period) t is provided between each signal bit in the up direction and the down direction.

A clock generator 16 and a direction selector 17 are provided for generating the signal bits alternately at intervals so that the signal bits in the up direction and the down direction do not overlap each other. As shown in FIG.
The basic clock signal bits generated by the direction selector 17 are alternately (even and odd) by the direction selector 17.
The signals are sorted and converted into clock signal bits in the upstream and downstream directions, respectively, and supplied to the bit delay classification units 14 and 24 for the upstream and downstream, respectively. Accordingly, the phase of the clock signal supplied to the bit delay classification unit 14 in the upstream signal path and the phase of the clock signal supplied to the bit delay classification unit 24 in the downstream signal path are different from each other by 180 °. Since there is a space between them, they do not overlap each other.

The bit delay classification unit 14 delays the input upstream input signal bit and synchronizes it with the upstream clock signal bit supplied from the direction selector unit 17 to obtain an upstream output signal (see FIG. 3). Arrow). Similarly, the bit delay classification unit 24 delays the input downlink input signal bit and synchronizes it with the downlink clock signal bit supplied from the direction selector unit 17 to obtain a downlink output signal. Therefore, no down signal is output during the signal bit period of the up signal, and during the signal bit period of the down signal,
No upstream signal is output.

Further, since the signal bits based on the basic clock are distributed by the direction selector section 17, a bit delay and an idle period can be always provided between the output signal bits in the up direction and the down direction. Simultaneous operation becomes possible without interference.

The direction selector 17 and the bit delay discriminator 1
According to 4, the signal path in the up direction transmits the signal only during the signal bit period in the up direction, and interrupts the signal transmission in the down direction. Similarly, the downstream signal path transmits signals only during the downstream signal bit period. As described above, by virtue of alternately and separately separating the signal transmission time zones in the upstream and downstream signal paths, a vicious cycle of signals in the signal loop formed by the upstream and downstream signal paths can be prevented. It is possible to shut off the signal and completely prevent the signal from sneaking.

As described above, each bit in the up direction and the down direction can be transmitted simultaneously in the reverse direction without interfering with each other.

The input signal level attenuated by the communication transmission distance is determined by the digital signal level discriminating / restoring units 13 and 23.
Thus, the signal is digitally restored (amplified) to the original specified level on the transmission side and output.

Since the effect of preventing the signal from being wrapped around is enhanced, the necessity of adjusting the impedance of the repeater at the time of installation and after the installation is drastically reduced, and labor and cost for maintenance are hardly generated, and labor costs are greatly reduced. Can be reduced.

Second Embodiment In the first embodiment, the two-way signal is configured not to overlap each other in a bit unit. However, in a byte unit composed of a plurality of bits or a format composed of the same plurality of bits. Even in units, the bidirectional signal transmission device can be configured in the same manner.

Further, the repeater according to the present invention can be applied to both analog and digital two-wire transmission lines, and it is possible to restore the attenuation of the bidirectional signal level while suppressing the loop. Can do it. When the two-wire transmission line is of a digital type, it is not necessary to provide an analog / digital converter and a digital / analog converter.

Therefore, the two-way signal transmission device of the present invention can be applied to any line including a telephone line, a communication line in a company or a premises, and various network lines such as the Internet and an intranet.

Embodiment 3 A two-wire transmission system is provided by connecting the output of various transmission, communication, and control devices to I and the input to O in the bidirectional signal transmission device 10 of the present invention described in FIG. The above-mentioned various devices can be controlled and operated from a line, and it is of course possible to use the device as a conversion device from a two-wire transmission line to a four-wire transmission circuit. Regarding the connection of the analog type device, the connection may be made to O 'and I' in FIG.

As shown in FIG. 4, when one or a plurality of bidirectional signal transmission devices 10 of the present invention are arranged in the middle of a long communication transmission line, an address is assigned to the bidirectional signal transmission device 10 of the present invention. By adding a branch control unit 30 for detecting various separation / selection symbols such as, for example, branch transmission of various data between various devices 40, control of various devices 40, response control by answer signals from various devices 40, etc. A signal transmission system can be configured.
The input of the branch control unit 30 is connected to O or O 'which is the output side of the bit delay classification unit 14 of the upstream circuit of the bidirectional signal transmission device 10 shown in FIG. Is done. The outputs of the various devices 40 are connected to I or I ', which is the input side of the bit delay classification unit 24 of the downstream circuit of the bidirectional signal transmission device 10.

Embodiment 4 The two-wire / four-wire converters 11 and 21 can be configured using a semiconductor circuit that defines the signal transmission direction. FIG.
Shows an example in which the 2-wire to 4-wire conversion units 11 and 21 are configured by semiconductor circuits. Using the differential amplifier 51, an upstream signal is extracted from the bidirectional signal on the two-wire transmission line 19. On the other hand, the downstream signal is transmitted through the differential amplifier 52 to 2
It is sent out on a wire transmission line 19. A capacitor 53 is provided to block the DC voltage supplied to the transmission line.

In order to prevent the downstream signal from leaking to the upstream signal, the resistors R1, R2 and R3 are set in accordance with the impedance of the transmission line, and the differential amplifier 51 is connected via the resistor R1.
And the downstream signal appearing at the inverting input terminal via the resistor R2 are offset each other. 2 using this differential amplifier
Although the line-to-wire converter cannot completely prevent one signal from leaking to the other, the repeater of the present invention further includes an analog / digital converter and a digital signal level discriminator.
Since the restoration section and the bit delay separation section are provided, it is possible to digitally restore or amplify the attenuation of the transmission signal to the original level, while completely preventing the signal from wrapping around.

As described above, the two-to-four-wire converter is constituted by a semiconductor circuit, so that an analog / digital converter, a digital signal level discriminating / restoring unit, a bit delay discriminator, a digital / analog converter, and a clock generator are provided. Since the entire repeater including the direction selector unit and the like can be constituted only by semiconductors, it is possible to realize a single chip by implementing any other integrated circuit such as DSP or ASIC. Therefore, since a heavy and large hybrid coil is not required, the size can be significantly reduced as compared with the conventional repeater, and an installation place is hardly required.
There is no need to provide a dedicated panel or other installation space, and it can be attached to wiring or wiring equipment, for example, by installing it in a connector on the transmission line,
There is no need to choose an installation location.

[0036]

According to the present invention, it is possible to prevent one of an upstream signal and a downstream signal from leaking to the other while preventing sneak.
It is possible to restore the level attenuation of both signals.

Further, since the effect of preventing the signal from being wrapped around is enhanced, the necessity of adjusting the impedance of the repeater at the time of installation and after installation is drastically reduced. It can be significantly reduced.

Also, without the need for additional equipment or parts,
It is possible to connect both digital and analog 4-wire devices.

Further, by providing a branch control unit for performing address discrimination, it is possible to perform branch transmission of various data or control and operation of various devices and response control such as answer.

Further, all of the circuits can be constituted by semiconductors, and the entire bidirectional signal transmission device (repeater) can be constituted by one chip, so that ultra miniaturization and significant cost reduction can be achieved. Can be measured.

Further, it is hardly necessary to particularly prepare an installation place due to the drastic size reduction, and it can be easily applied by attaching it to a wiring or wiring equipment.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a repeater according to the present invention.

FIG. 2 is a diagram illustrating that an uplink signal and a downlink signal have an interval and do not overlap with each other;

FIG. 3 is a diagram for explaining a method of preventing an uplink signal and a downlink signal from being overlapped by using a control bit.

FIG. 4 is a diagram illustrating an example in which a branch control unit is provided to perform branch transmission of data.

FIG. 5 is a diagram illustrating a 2-wire to 4-wire conversion unit using a differential amplifier.

FIG. 6 is a diagram illustrating a configuration of a conventional repeater.

[Explanation of symbols]

 Reference Signs List 10 bidirectional signal transmission device (repeater) 11, 21 2-wire to 4-wire converter 12, 22 analog / digital converter 13, 23 digital signal level discriminating / restoring unit 14, 24-bit delay discriminating unit 15, 25 digital / Analog converter 16 Clock generator 17 Direction selector 19, 29 2-wire transmission line 30 Branch controller 40 Equipment 51, 52 Differential amplifier 111, 121 2-wire transmission line 112, 122 Hybrid coil 113, 123 Amplifier

Claims (7)

[Claims] 1. A transmission line inserted in a bidirectional signal transmission line, which separates a bidirectional transmission signal into an upstream transmission signal and a downstream transmission signal and amplifies each of them to restore line transmission loss of the transmission signal. A two-wire to four-wire converter, a clock generator for generating a basic clock signal, and distributing the basic clock signal into an even-numbered signal and an odd-numbered signal in an upstream direction. A direction selector unit for converting a clock signal and a downstream clock signal, an upstream bit delay classification unit for outputting an upstream input signal in synchronization with the upstream clock signal, and a downstream input signal for the downstream input signal. A bidirectional signal transmission device, comprising: a bit delay discriminating unit for a downlink signal that is output in synchronization with the clock signal. 2. A transmission line inserted in a bidirectional signal transmission line, which separates a bidirectional transmission signal into an upstream transmission signal and a downstream transmission signal and amplifies each of them, thereby restoring the line transmission loss of the transmission signal. A two-wire-to-four-wire conversion unit, and an output signal of the two-wire-to-wire conversion unit is determined by a threshold value, and a signal having a higher level than the threshold value is suppressed. Bidirectional signal transmission device, comprising: a digital signal level determination / restoration unit for amplifying and amplifying. 3. A transmission line inserted in a bidirectional signal transmission line, which separates a bidirectional transmission signal into an upstream transmission signal and a downstream transmission signal and amplifies each of them to restore line transmission loss of the transmission signal. A two-wire-to-four-wire conversion unit, and an output signal of the two-wire-to-wire conversion unit is determined by a threshold value, and a signal having a higher level than the threshold value is suppressed. A digital signal level discriminating / restoring unit for amplifying the clock signal; a clock generating unit for generating a basic clock signal; A direction selector unit that converts the signal into a signal, and an upstream bit delay classification unit that outputs an upstream input signal from the digital signal level determination / restoration unit in synchronization with the upstream clock signal. Bidirectional signal transmission device and a bit delay fractional portion of the downstream signal and outputs the downlink input signal from the digital signal level determination and restoration module in synchronization with the clock signal of the downlink. 4. An output signal from a four-wire transmission circuit to a user is taken from an output side of a bit delay classification unit of the upstream circuit, and an input signal from the user to the four-wire transmission circuit is 4. The bidirectional signal transmission device according to claim 1, wherein the signal is injected into an input side of a bit delay classification unit of the downstream circuit. 5. The semiconductor device according to claim 1, wherein the separation of the bidirectional signal into an upstream signal and a downstream signal is performed by a semiconductor circuit using an amplifier for defining a signal transmission direction. 5. The bidirectional signal transmission device according to 4. 6. A signal transmission system that uses the bidirectional signal transmission device according to claim 1 or 2 and includes a branch control unit on an output side of the bit delay classification unit to perform branch transmission of data. 7. The signal transmission system according to claim 6, wherein the separation of the bidirectional signal into an upstream signal and a downstream signal is performed by a semiconductor circuit using an amplifier that defines a signal transmission direction. .