JPS605100B2 - Digital regenerative repeater with signal return circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a digital regenerative repeater that can return up and down signals on a digital signal relay transmission path.

In this type of digital signal relay transmission system, a large number of intermediate repeaters are installed along the transmission line in a manhole, on a pole, or the like.

In such a relay system, if a failure occurs in the relay transmission line, a means is usually provided to locate the point of failure in order to find out which repeater (or section) caused the failure at the station building. It is being For example, if the error rate of a digital code deteriorates during relay, it is necessary to accurately locate the deteriorated repeater. A method for locating degraded repeaters or their sections by sending a command signal from the station between stations, returning the signal at an arbitrary relay point, and measuring code errors in the digital signal returned to the station. is being explored. Conventionally, as a repeater capable of returning the above-mentioned signals, switch circuits 5 and 6 are connected between uplink and downlink repeaters 1 and 2, as shown in the block diagram of FIG. When the control circuit 3 receives a command signal from the station, the control signal switches the switch circuits 5 and 6 so that the output signal from the repeater 1 on one side is returned to the input side of the repeater 2 on the opposite side. It has become. According to this method, in order to provide mutual compensation with the transmission line characteristic compensation circuit inserted in advance on the input side of the repeater, a pseudo line network 4 that approximates the transmission line characteristics is connected to the return circuit. There is a need to. Therefore, the input signal of the repeater that is looped back is a signal that has passed through the pseudo-line circuit 4, but since this signal is not a signal that has passed through the actual line, the input waveform of the repeater that is looped back is Compared to the input waveform during actual operation, there is an error or imperfection. In addition, since it is practically difficult to prepare many types of pseudo line network 4, it is inconvenient that if a deteriorated repeater deteriorates in a manner related to the relay distance of the section, the point of failure cannot be found. will occur. In addition, since a changeover switch circuit is connected to the input and output of the repeater, the characteristics as a pseudo line are further distorted, causing an error when compared with the original transmission characteristics, which can distort the judgment of deterioration. There was a drawback. The purpose of the present invention is to eliminate such drawbacks of conventional signal folding circuits, and to locate fault points using a simple folding circuit such as a logic circuit under the same conditions as the signal transmission state in the normal transmission direction. The object of the present invention is to provide a digital regenerative repeater with a signal folding circuit that can perform the following functions.

According to the present invention, an identification circuit that determines the presence or absence of a pulse;
In a digital regenerative repeater that accommodates uplink and downlink repeaters each including a regeneration circuit that converts the output of the identification circuit into a transmission signal, at least one of the uplink and downlink repeaters A switch circuit is inserted between the identification circuit and the regeneration circuit, and by switching the switch circuit, the output of the identification circuit of the other repeater is given as an input to the regeneration circuit of the one repeater. A digital regenerative repeater with a characteristic signal folding circuit is obtained.

Next, embodiments of the digital regenerative repeater according to the present invention will be described in detail with reference to the drawings.

FIG. 2 is a block diagram showing the configuration of an embodiment according to the present invention.

In this figure, 10a is a one-way transmission repeater, and 10b is a transmission repeater for the opposite direction. These digital repeaters 10a and 10b include equalization amplifier circuits 11a and 11b, identification circuits 12a and 12b,
Timing extraction circuits 13a and 13b, regeneration circuit 15
It consists of circuits such as a and 15b. Here, the reproducing circuits 15a and 15b are used to receive the pulse signal determined by the preceding stage identification circuit and regenerate a bipolar signal for transmission to the transmission path from the pulse signal. In such a digital repeater, among the signals appearing in these circuits, the output waveforms of the equalization amplifier circuits 11a and 11b are transformed into analog signals due to distortion. However, the identification circuits 12a and 12 that determine the presence or absence of pulses
The output waveform of the identification circuit 12a, 12b is a completely digital signal of ``nl'' or ``0''. This is an attempt to realize folding back of signals between the two lines with a simple circuit.
The switch circuits indicated by 14b and 14b are circuits added as features according to the present invention. In the above configuration, when performing normal signal transmission, the switch circuits 14a and 14
b is connected so that the outputs of the identification circuits 12a and 12b of the repeaters in the respective directions are added to the input sides of the reproducing circuits 15a and 15b, respectively, as shown by the solid line in the figure, and the respective normal It is sent to the next repeater in the direction of the transmission path.

In addition, when the signal is looped back, when the control circuit 10c receives a command signal from the station side, the switch circuits 14a and 14b are respectively switched to the broken line side in the figure by the control signal C obtained at its output. With this connection, repeater 1
The identification signal a on the 0a side is the regeneration circuit 15b on the repeater 10b side.
In addition, the identification signal b on the repeater 10b side drives the regeneration circuit 15a on the repeater 10a side, so that the signals transmitted from the respective opposing sides are returned from this relay point in the respective sending directions. be done. Then, by receiving the returned signals at the stations on both sides and measuring their code errors, it is possible to determine whether there is a failure on each side up to the relay point. As mentioned earlier, the identification circuit of a digital repeater is a circuit that determines the presence or absence of a pulse sent out from the previous repeater, and the output signal identified here will be recognized even if there is a code error. ,
It is completely a digital signal of either "1" or "0".

In other words, since this signal has no analog elements that depend on the waveform, even if it passes through a logic circuit such as a gate circuit, as long as the "1" or "0" does not change, the transmission characteristics of the repeater will not be affected in any way. There is nothing I can do. Therefore, if the switch circuit for loopback is configured with a gate circuit and this gate circuit is inserted between the identification circuit and the regeneration circuit of the repeater, switching control becomes easier. If the switch circuits 14a and 14b in the embodiment of FIG. 2 are constituted by gate circuits, a simple example as shown in FIG. 3 can be obtained. In this figure, 14 is a switch circuit composed of a plurality of gate circuits, and is connected between the capture U circuits 12a, 12b and the reproducing circuits 15a, 15b. Let us briefly explain the operation of this circuit.

In the discrimination circuit 12a, the equalized waveform signal to be discriminated is inputted to the terminal A, and the clock signal giving the discrimination time point is inputted to the terminal A2, and the presence or absence of a pulse is discriminated and an output signal a is obtained. Now, when a high level "1" is applied to the control terminal Co of the switch circuit 14 as the control signal c, the switch circuit 14
Suppose that input signals a and b appear at the input sides of reproduction circuits 15a and 15b as output signals d and e, respectively. As a result, the output a of the identification circuit 12a is given to the input side of the regeneration circuit 15a, and the output b of the identification circuit 12b of the repeater transmitting in the opposite direction is given to the input side of the regeneration circuit 15b. be done. Conversely, control terminal C
When o is given a low level "0", the input a of the switch circuit 14 appears as the output e and the input b as the output d at the input sides of the reproducing circuits 15b and 15a, respectively. That is,
The identification signal a is regenerated and outputted to the output terminal B3, the identification signal b is regenerated and outputted to the output terminal A3, and the transmission signal is looped back. This switch circuit 14 may be a commercially available general-purpose IC called a selector. It goes without saying that it can be easily realized with such a general IC, but it is also possible to use any other switching element such as a transistor or relay. For simplicity, the case where one identification circuit is used in each direction is shown, but the same can be achieved in the case of multi-plant transmission with multiple identification circuits by increasing the number of switch circuits accordingly. can be easily understood.

Furthermore, in the above embodiment, an example was described in which signals in each direction are returned in each direction at the same time, but even if a signal on one side is only returned in the opposite direction, one of the connection lines can be This can be easily carried out by removing it. In addition, in the embodiment described above, a case has been described in which a timing signal is not supplied to the reproducing circuits 15a and 15b, but when a timing signal is required for the operation of the reproducing circuits 15a and 15b, an identification signal return circuit is provided. It is easy to understand that by providing a timing signal folding circuit separately from the timing signal and switching these two folding circuits at the same time, exactly the same signal folding as explained above will occur. As is clear, according to the present invention, by providing a loopback circuit between the identification circuit and the regeneration circuit of the repeater, it is possible to omit the use of a conventional artificial line network, etc. At this time, the signal at the relay point can be faithfully sent back from the output side of the repeater, regardless of whether there is a code error or the like.

Therefore, under normal transmission conditions, if a code error occurs at any repeater or in that section,
By changing the turning point as appropriate and investigating, it is possible to accurately locate the point of failure that has occurred in either direction. Of course, even if the deterioration of a repeater is related to its relay distance, there is no fear that the point of failure will become unclear due to the difference between the actual transmission line length and the pseudo line due to loopbacks as in the past. Since the signal loopback circuit of the present invention can accurately locate the point of failure with a simple configuration, it has a great effect on maintaining the digital signal relay transmission line efficiently and economically. .

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a conventional digital regenerative repeater with a signal return circuit, FIG. 2 is a block diagram showing the configuration of an embodiment according to the present invention, and FIG. FIG. 2 is a circuit diagram showing a specific example of a circuit configuration. In the figure, 10a, 10b are repeaters, 11a, 11b
is an equalization amplifier circuit, 12a and 12b are identification circuits, 13a,
13b is a timing extraction circuit, 14, 14a, 14b are switch circuits, and 15a, 15b are regeneration circuits. 1st
Figure 2 Figure 3

Claims (1)

[Claims] 1. In a digital regenerative repeater that accommodates uplink and downlink repeaters each including an identification circuit that determines the presence or absence of a pulse and a regeneration circuit that converts the output of the identification circuit into a transmission signal, the uplink and downlink A switch circuit is inserted between the identification circuit and the regeneration circuit of at least one of the repeaters, and by switching the switch circuit, the output of the identification circuit of the other repeater changes to the output of the identification circuit of the other repeater. A digital regenerative repeater with a signal return circuit, characterized in that the signal is supplied as an input to a regenerative circuit.