JPS63156434A - Switching circuit - Google Patents

Abstract

PURPOSE:To send a main signal via a spare system when a fault is generated at the time of extending a system in current use, by connecting the base on one side of m-number of a pair of transistors whose emitter is connected to a common constant current source via a corresponding switching means, to a distribution means in one to one. CONSTITUTION:A control device applies a high voltage V2 on the base of a transistor Q10, and sets the ON states of transistors Q6 and Q7, and sends a test signal to a reception side via the transmitter 6 of the spare system. Next, when the fault is generated in the system in current use which transmits the main signal 1, by adding the voltage V2 on the base of a transistor Q8, and a voltage V1 on the transistor Q10, transistors Q2 and Q3 are turned ON, and the transistors Q6 and Q7 are turned OFF. Then, the transmission of the test signal is interrupted, and the main signal 1 is added on the base of the transistor Q3 passing through a hybrid 201, and is sent to the reception side via the collector and the transmitter 6.

Description

[Detailed Description of the Invention] [Summary] In a switching circuit, the emitters of n transistor pairs whose emitters are connected to each other are connected to a common constant current source through corresponding switches. This makes it possible to extract any main signal among the n series of main signals even when the system is expanded, and to prevent deterioration of the transmission waveform.

[Industrial application field]

The present invention relates to an improvement in the switching circuit 5 used in, for example, a microwave digital multiplex radio device.

In general, it is used to monitor the deterioration of transmission quality and line quality caused by fading in the propagation path and failure of equipment that makes up the transmission path, or to prevent service interruptions when testing and repairing equipment or lines. It is normal to have a reserve.

One of the methods for providing this reserve is the system reserve method. In this method, a backup system that uses a different radio frequency is provided in addition to the current system, and the system is switched to the backup system when a failure occurs in the current system.

Note that the system includes an I-route modulator, transmitter, receiver, and demodulator.

FIG. 3 is an explanatory diagram of line switching operation when the system backup method is used, and the line switching operation will be explained using this diagram.

First, when the current system is normal, the input main signal passes through the switching circuit 1 and undergoes various processing at the transmitter 2.
The carrier wave is digitally modulated and sent to the receiving side. On the receiving side, the receiving device 3 receives the signal, extracts the original main signal, and sends it out via the switching circuit 4.

On the other hand, in the backup system, the test signal from the test signal generator 5 is transmitted to the switching circuit 1. Transmitting device 6. The receiving device 7 is applied to the test signal detector 8 through the switching circuit 4 to monitor the operating status of the backup system.

Now, when the receiving side detects that a fault has occurred in the working line, this information is added to the control device 10.

Therefore, the control device confirms that the standby system is normal and not in use, and sends out a sending end parallel signal to the sending side via the control line.

On the transmitting side, the switching circuit 1 is driven to apply the main signal to the backup system. On the receiving side, after confirming that the main signal can be received even in the backup system, the switching circuit 4 is driven to take out the signal from the receiving device 7, and the switching to the backup system is completed.

Here, there is a need for a switching circuit that can add any one of the zero main signals to the standby system even when the current system is expanded, and that does not degrade the transmission waveform.

[Conventional technology]

FIG. 4 shows a block diagram of a conventional example.

In the figure, a bipolar main signal -1 input from a carrier terminal device (not shown) is distributed by a hybrid 111 in a switching circuit 11 and applied to a transmitter 2 and a switch 112. is off, so it is sent to the receiving side via the transmitting device 2. However, if a failure occurs in the active system that transmits the main signal-1, the switch 112 is driven as shown by the dotted line, so the main signal-1 is also applied to the transmitting device 6, and sent to the receiving side via the backup system. Sent.

In the case of the switching circuit 12 for the main signal 2, the switching circuit 11
It is similar to

FIG. 5 is a block diagram of another conventional example, and 15.16 indicates a switching circuit.

In the figure, when a failure occurs in the current system that transmits the main signal-1, the main signal-1 is transferred to the hybrid circuit 151.
Since it is also applied to the transmitting device 6 via the resistor RI5 and the transistor, it is sent to the receiving side via the backup system.

[Problem that the invention seeks to solve]

In the case of Fig. 4, when adding another working system between the two working systems transmitting main signal-1 and main signal-2, or between the last working system and the T-PG, In this case, it is necessary to disconnect the wiring 13' or 13 and reconnect or add cables. Furthermore, if a failure occurs in the switching circuit 12 that transmits the main signal-2, there is a problem that the backup system cannot be used because the test signal cannot be transmitted.

Furthermore, in the case of Fig. 5, it is ideal that the emitter impedance of transistor Q1 is 0Ω, but in reality the emitter impedance of a transistor takes a finite value from several Ω to several tens of Ω. When the number of main signals connected to the emitter of transistor Q changes due to the addition of transistors to There is a problem that changes.

[Means for solving problems]

The above problem is solved by the switching circuit shown in FIG. 20 is n distribution means for distributing n series of main signals; 22 is n transistor pairs 17 whose emitters are connected to each other; switching means connected to the source 19;

The problem is solved by the switching circuit of the present invention, which uses these signals to control the transistor 19 and output any desired output from the n series of main signals.

[Effect]

In the present invention, there are n transistors whose emitters are connected to each other, and the base of one of the transistor pairs is connected to the distribution means 20 on a one-to-one basis.

Therefore, even when the active system is expanded, the main signal is added to the backup system, and since each input is independent, there is no need to disconnect part of the main signal line or the backup line even when expanding. Even if the number of connected wires changes, the waveform does not deteriorate.

〔Example〕

FIG. 2 shows a circuit diagram of an embodiment of the invention. Note that the same reference numerals indicate the same objects throughout the figures. Also, transistor Q
t '''-Q ?... is a component of the transistor pair 17, transistors Q8+ Q9+ ql... is a component of the switch 18, hybrid 201.202
. . . indicates constituent parts of n distribution means 20.

Hereinafter, the operation of the embodiment of the present invention will be explained with reference to FIG. 2, with two active system systems and one backup system system.

First, during normal operation of the current system, a controller (not shown) applies a low voltage vI to the base of transistor Qll+09.
is added to turn off transistors 02-Q.

Therefore, the main signal -1 is sent through the hybrid 201 and sent to the transmitter 2, and the main signal -2 is sent to the receiving side via the hybrid 202 and the transmitter 4.

On the other hand, the control device is a transistor Q. By applying high voltage v2 to the base of transistor G6+ Q? is turned on and the test signal is sent to the receiving side via the transmitting device 6 of the backup system.

Next, when a failure occurs in the current system that transmits the main signal -1, if voltage ν2 is applied to the base of transistor Q, and voltage v1 is applied to transistor Q1, then transistor Q
2+ Qi turned on +06+ Q? is turned off.

Thereupon, the transmission of the test signal is cut off, and the main signal -1 passes through the hybrid 201 and is also applied to the base of the transistor Q, and is sent out to the receiving side via the collector and the transmitting device 6.

Note that RI7 to R23 represent resistors, and the constant current source 19 is used to keep the current flowing through the transistor pair constant even when the transistor pair is switched, thereby reducing level changes applied to the transmitting device 6.

In other words, even if a failure occurs in the current system when the current system is expanded, the main signal can be sent via the backup system, and originally (in the case of a differential configuration) the transistor has a current flowing through the emitter at 1/β. is thought to flow to the base, so the base impedance is β times the impedance looking out from the emitter, and the base impedance can be considered high.

Also, since each main signal is connected to one base, the resistor (
If R181R2゜+R2□) in the figure is selected appropriately, the signal branched by the hybrid will be terminated correctly regardless of whether the transistor pair is selected, and the impedance due to expansion will change. No waveform deterioration occurs.

Furthermore, the reason for using transistor pairs is as follows.

■ When switching lines, in order to prevent errors as much as possible, it is necessary to wait 10 meters from line failure detection until the end of line switching.
Since only about 5 switching times are given, a high-speed switching circuit is required.

■ Relays can be used for switching, but normal relays have chattering and impedance etc. are not fixed.

■ Coaxial mercury relays can be used for this purpose, but the structure is large and difficult to implement in multi-systems.

(2) Bipolar signals may be unbalanced as in the embodiment, but at low speeds, they may be balanced.

By taking these into consideration and using transistors, it is easy to integrate these switch sections into LSIs, which allows extremely high speed and miniaturization of the system.

The impedance does not change even during expansion, so no waveform deterioration occurs.

〔Effect of the invention〕

As explained in detail above, if a failure occurs in the active system 1 or another active system during expansion, the main signal can be sent via the backup system, and the effect is that the waveform does not deteriorate. be.

[Brief explanation of the drawing]

Fig. 1 is a principle block diagram of the present invention, Fig. 2 is a circuit diagram of an embodiment of the present invention, Fig. 3 is an explanatory diagram of line switching operation, Fig. 4 is a block diagram of a conventional example, and Fig. 5 is a different circuit diagram. In the block diagram of the conventional example, 17 is n transistor pairs, and 18 is n switches. 19 is a constant current source, 20 is n distribution means, 77) Katana Aohko Fuparock 5 pieces 1st
Figure 3 - Game L long row file A7 page 4 Figure 3

Claims (1)

[Claims] n distribution means (20) for distributing n series (n is a positive integer) of main signals, and n distribution means (20) for controlling transmission of the main signals output from the n distribution means. A transistor pair (17), n switch means (18) for controlling the operation of the n transistor pairs, and a constant current source that supplies a constant current through the switch means corresponding to the transistor pair in operation. (19) A switching circuit comprising: