JPH01154647A - Channel switching equipment for digital communication system - Google Patents

Abstract

PURPOSE:To reduce a switching time by providing a pseudo signal output circuit in cooperation with a sending end side switching circuit of each active system so as to eliminate undesired reply of an equalizer even if any interruption takes place in a bipolar signal at the changeover to a standby system. CONSTITUTION:When a channel switching signal CH-EXCH is produced, the sending end side switching circuit 11 switches a bipolar signal from the active system into the standby system, but in this case, momentary interruption of an output signal S11 takes place. On the other hand, a pseudo signal output circuit 12 generates a pseudo signal PSD-SIG to compensate the momentary interruption of the output signal S11 as soon as the channel switching signal CH-EXCH is produced and sends it to the standby system. As a result, since the pseudo signal PSD-SIG is outputted to the standby system during the momentary interruption of the output signal S11, no hit in the standby system is occurred. Thus, the equalizer in a bipolar/unipolar converter does not give any unnecessary reply and the switching time is reduced.

Description

[Detailed Description of the Invention] [Summary] Regarding a line switching device for a digital communication system configured to be able to mutually switch between a working system and a standby system, transmission signal disconnection based on the operation of a changeover switch circuit occurs when switching lines. This system has a working system and a backup system, with the aim of preventing unnecessary responses of the equalizer in the backup system and substantially shortening the line switching time.
A digital communication system configured to mutually switch between the working system and the protection system, wherein each sending end of the working system sends a transmission signal to the protection system in response to a line switching signal. a switching circuit on the transmitting end side, which generates a predetermined pseudo signal in order to compensate for the transmission signal interruption caused by switching of the changeover switch circuit, and a switching period of the line switching signal from the working system to the protection system, and and a pseudo signal output circuit for sending out a pseudo signal to the auxiliary flower vase, and is configured to operate the standby system vase based on the pseudo signal during the switching period.

[Industrial application field]

The present invention relates to a digital communication system that has a plurality of working systems and one protection system and is capable of mutually switching lines, and more specifically, the present invention relates to a digital communication system that has a plurality of working systems and one protection system and is capable of mutually switching lines. The present invention relates to a line switching device that eliminates the prolongation of line switching time caused by unnecessary responses caused by instantaneous signal loss.

FIG. 4 shows a configuration diagram of a digital communication system to which the line switching device of the present invention is applied. One backup system 100 and a plurality of active systems, however, only one active system 200 is shown in the figure, are provided in parallel. The active system 200 includes a hybrid circuit 2011 changeover switch 202, a bipolar/unipolar conversion device 203, on the transmission side (sending end side),
It has a modulator 204 and an antenna 205. Current system 2
00 also has an antenna 251, a demodulator 252, a unipolar/bipolar converter 253, and a changeover switch 254 on the receiving side (receiving end side) connected to the transmitting end side via an air line. Other active systems (not shown) also have the same configuration as above. The protection system 100 has a bipolar/unipolar conversion device 103, a modulation device 104, and an antenna 105 on the sending end side. In addition, the backup system 100 has an antenna 151, a demodulator 152, and a unipolar/bipolar converter 153 on the receiving end side connected to the sending end side via an air line.
has.

The plurality of active systems and the backup system 100 are connected via a line 911 on the sending end side, and one of the active systems and the backup system can be switched by a changeover switch, for example 202. Hybrid 201 and selector switch 202
The transmitting end side switching circuit TSW is configured by the above. A test pattern signal generator 901 is connected to line 911 .

The transmitting end is switched depending on the signal reception state of the receiving end, for example, when the quality of the received signal deteriorates due to fading. That is, for example, when the receiving end detects a decline in the quality of the received signal due to fading, it instructs the transmitting end to switch the line to the protection system. At the same time, the changeover switch 254 on the own receiving end side is also switched to the standby system. When the received signal recovers to a predetermined quality or higher, the protection system is switched back to the working system.

Figure 4 describes the case where data is transmitted in one direction, with one side being the sending end and the other being the receiving end, but normally bidirectional data transmission is possible, and both the backup system and the active system A transmitting/receiving system is provided on one side, and a transmitting/receiving system is also provided on the other side.

It is desirable that line switching from the active line to the protection line and vice versa be performed without momentary interruption. For this reason, measures have been taken to increase the speed of the changeover switch, and to adjust the phase shift and data pattern shift during switching. Although these various measures are taken on both the sending end side and the receiving end side, the present invention mainly provides switching from the sending end side that causes instantaneous interruptions or less influence on the receiving end side.

[Conventional technology]

Bipolar/unipolar conversion device 103 or 2 on the sending end side
03, as shown in FIG. 5, the flower vase 1 having the same line length, an amplitude detector 31, an amplifier 32, a clock regeneration circuit 4a, and a bipolar/unipolar converter 5 are constructed as shown. The line length equalizer 1 inputs the transmission bipolar signal SBI via the changeover switch 202 or the hybrid 201, forms an AGC loop with the amplitude detector 31 and the amplifier 32, and equalizes the input bipolar signal SBI. become The clock regeneration circuit 4a outputs the output S of the flower vase 1a.
A clock CLK is extracted from 1 and applied to the bipolar/unipolar converter 5a. Bipolar/unipolar converter 5 converts the equalized bipolar signal S
1 into unipolar signals and modulating devices 104 and 20
4 and antennas 105 and 205.

[Problem that the invention seeks to solve]

The selector switch 202 is made faster in order to achieve faster switching, but bipolar signals can be switched using a mercury relay, etc.
A switching time of several milliseconds or so is used. Therefore, switching from the active system to the protection system requires a switching time τ, as shown in FIG. 6(a), during which time the bipolar signal SBI is lost.

On the other hand, since the equivase l itself has a delay element,
Even if the input bipolar signal SBI is disconnected, an unnecessary response is generated depending on the time constant of the delay element, and its output fluctuates as shown in FIG. 6(b). Furthermore, the time τ' required to reach stability is considerably longer than the signal interruption time. Since the fluctuating signal that has made an unnecessary response is sent out accordingly, a problem arises in that the receiving end also makes an unnecessary response. Furthermore, there is a problem in that the unnecessary response time τ' is longer than the switching time τ, making the actual switching time considerably longer.

From the above, by the switching operation of the changeover switch 202, even if the bipolar signal to the standby system is interrupted, the input signal to the vases will not be interrupted, and unnecessary responses of the vases can be prevented, and the switching time can be shortened. It is requested that it be possible.

[Means for solving problems]

FIG. 1 shows a principle block diagram of a line switching device for a digital communication system according to the present invention.

The line switching device is a transmitting end switching circuit (TS) of each working system.
N) was set up to cooperate with 11.

A pseudo signal output circuit 12 is provided. Sending end side switching circuit 11
itself may be composed of a hybrid 201 and a changeover switch 202 as shown in FIG.

[For production]

The operation of the line switching device shown in FIG. 1 will be described with reference to FIGS. 2(a) to 2(d).

When the line switching signal CI-EXCH is generated (Fig. 2 (
a)) The sending end side switching circuit 11 switches the bipolar signal from the active system to the standby system, causing a momentary interruption of the output signal Sll (FIG. 2(b)). One line switching signal CI
- Simultaneously with the generation of EXCH, the pseudo signal output circuit 12 outputs a pseudo signal PSD -SI to fill the momentary interruption of the output signal Sll.
G is generated and sent to the backup system (Fig. 2 (C)). As a result, during the instantaneous interruption period of the output signal 311, the pseudo signal PSD
-SIG is output to the protection system (FIG. 2(d)), and there is no momentary interruption of the signal to the protection system.

The pseudo signal PSD-SIG is a random signal having the same hierarchical band as the bipolar signal in order to prevent unnecessary responses to the equal parts in the standby bipolar/unipolar conversion device.

〔Example〕

A line switching device according to an embodiment of the present invention will be described with reference to FIG.

The pseudo signal output circuit 12 outputs line switching signals C11-EXC.
When ll is switching from the working system to the protection system, it consists of a pseudo signal generation circuit 121 and a hybrid circuit 122 that generate a random signal having the same hierarchical band as the bipolar transmission signal. The sending end side switching circuit 11 and others are the same as those shown in FIG.

In the hybrid 122, when the changeover switch 202 performs a switching operation and data to the standby system is lost, the hybrid 122 sends out the pseudo signal PSD-SIG of the pseudo signal generating circuit 121 to the standby system. As a result, the spare vase 1 (Fig. 5) does not perform any unnecessary operation, and its output S1 is as shown by the broken line in Fig. 6 (b) (the period τ is kept almost constant, and after the switching period τ elapses) , the normal operation is resumed as well, as shown by the broken line.

From the above, there is virtually no signal interruption to the isoka vase, and a constant output is output from the iso vase regardless of the switching time τ.

Therefore, unnecessary operations do not occur on the receiving end side either.

Note that a switch circuit 123 is inserted between the pseudo signal generation circuit 121 and the hybrid 122, and while the pseudo signal generation circuit 121 is constantly operated to continue generating pseudo signals,
Normally, the switch circuit 123 is terminated in the state shown by the solid line in the figure so that the signal from the sending end switching circuit 11 is output to the protection system, and the line switching signal CH-EXCll is switched from the working system to the protection system for a certain period of time. Only the switch circuit 123 can be set to the state shown by the broken line so that the pseudo signal is applied to the hybrid 122. According to this circuit configuration, the delay in the rise response of the pseudo signal generation circuit 121 can be covered.

〔Effect of the invention〕

As described above, according to the present invention, even if the input signal is actually disconnected due to the operation of the changeover switch, the present invention can effectively prevent other crimes such as actually disconnecting the input signal due to the operation of the changeover switch. A line switching device that does not cause unnecessary operations is provided. As a result, unnecessary operations associated with line switching and disconnection do not occur on the receiving end side.

[Brief explanation of the drawing]

Fig. 1 is a principle block diagram of the line switching device of the digital communication system of the present invention, Fig. 2 (a) to (d) are signal waveform diagrams showing the operation of the line switching device of Fig. 1, and Fig. 3 is the present invention. FIG. 4 is a circuit diagram of a digital communication system to which the line switching device of the present invention is applied. FIG. 5 is a circuit diagram of a bipolar/unipolar conversion device. (a) and (b) are operation timing diagrams of the device in Figure 5;
It is. (Explanation of symbols) 11... Sending end side switching circuit, 12... Pseudo signal output circuit, 121... Pseudo signal generation circuit, 122... Hybrid, 123... Switch circuit, 201... Hybrid, 202... selector switch. Figure 4 is a configuration diagram of a digital communication system to which the line switching device of the present invention is applied.

Claims (1)

[Scope of Claims] 1. A digital communication system having a working system and a protection system, and configured to be able to switch between the working system and the protection system, wherein each transmission of the working system On the end side, a transmission end side switching circuit (11) that sends a transmission signal to either the working system or the protection system in response to a line switching signal (CH-EXCH); Switching period to standby system,
a pseudo signal output circuit (12) that generates a predetermined pseudo signal to compensate for a transmission signal interruption caused by switching of the changeover switch circuit and sends it to the backup system; A line switching device for a digital communication system configured to operate the standby equalizer. 2. The pseudo signal output circuit includes a pseudo signal generation circuit (121
), a switch circuit (123) that outputs the pseudo signal only during the switching period of the line switching signal from the working system to the protection system;
The line switching device according to claim 1, comprising a hybrid circuit (122) connected at a subsequent stage of the changeover switch circuit so as to output the output of the pseudo signal generation circuit to the standby system. 3. The line switching according to claim 1 or 2, wherein the predetermined pseudo signal is a random signal having the same hierarchical band as the transmission signal, which prevents unnecessary responses of the equalizer. Device.