JPS60204128A - Reception switching system - Google Patents

Abstract

PURPOSE:To switch a faulty existing machine to a spare machine even when an electric field of the spare machine is lowered by providing a means for generating separate squelch signals with respect to two detecting points apart by a prescribed level to allow a reception switching control means to combine the four squelch signals. CONSTITUTION:A reception signal from an antenna 3 is inputted to an existing receiver 1 via a selection switch 4 and also a reception signal lower by a predetermined level is fed to a spare receiver 2 at the same time. A signal from an IF amplifier circuit 14 of the receiver 1 is fed to a changeover switch 16 and also fed to a squelch circuit 18. Two squelch signals A1, A2 part by a prescribed level are fed to an electric field alarm detection circuit 19 from the circuit 18. Further, two squelch signals B1, B2 from the receiver 2 are fed to the circuit 19 and the signals A1, A2, B1, B2 are combined and the result is fed to selection and changeover switches 4, 16 via a device control section 20. Even if the electric field of the spare machine 2 is lowered, the faulty existing machine 1 is switched to the spare machine 2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a reception switching system for a receiver configured as a working type and a standby type.

[Prior art]

In a communication system that performs reception switching as described above, for example, in a communication system that constantly sends and receives signals, the receiver generally monitors the state of the line by detecting the input electric field. Reception switching is performed based on the signal. However, in such a receiver, it is very difficult to distinguish between a case where one line is disconnected and a case where the receiver itself is broken. This is because electric field detection becomes impossible in either case. In such a receiver, reception switching may occur other than when the receiver itself fails. This occurs when the opposing transmitter is disconnected, or when some long fading occurs and the electric field detection level decreases. The reception switching that occurs in such a case is not only unnecessary because it is not caused by a failure of the receiver, but is also inconvenient because it impairs the reliability and usability of the system.

To prevent the above situation, input the input signal with some leakage to the backup receiver.

There is a method in which the backup receiver is operated with an input electric field that is several dB lower than that of the active receiver.

Figure 31 is a diagram to explain the operation of a conventional system that performs such an operation, and since the input level of the active machine and the input level of the standby machine are different, squelch occurs in response to input fluctuations. The squelch on the active side is turned on later than the standby side (ON) at 9 degrees with different times.

It turns off quickly. In addition, for the sake of the following explanation, ON is indicated by the symbol "o", and OFF is indicated by the symbol "°".
'1''. Therefore, by using this time relationship, it is possible to quickly determine whether the input signal is cut off due to a failure of the receiver. In other words, if the squelch on the standby side turns on earlier than the squelch on the working side, It is possible to prevent switching by assuming a drop in the input electric field or a loss of the input signal.However, this method has a major drawback: the backup side operates at a lower input electric field than the active side. 1. For example, the standard input electric field is low due to long distances.

This is because even if reception is possible on the active side, if the squelch is ON in the backup mode, reception switching will not occur if the active side fails. This kind of thing also occurs when the input acupuncture field decreases due to phasing for a long time. The fact that switching is not performed even though the standby side is normal is a serious drawback that impairs the reliability of the system.

[Purpose of the invention]

Therefore, an object of the present invention is to provide a communication system as described above, in which even if the active equipment fails while the backup/backup receiver is generating an alarm due to a drop in the input electric field, the backup receiver can It is an object of the present invention to provide a reception switching method in which switching is performed at a receiver.

[Structure of the Invention] According to the present invention, there are two types of receivers that detect the input level of a received signal and emit a squelch signal: a working type and a backup type.
The standby receiver is operated in parallel at an input level that is a predetermined level lower than the input level of the active receiver.
In the communication device configured to control reception switching using the squelch signal, each means for emitting the squelch signal includes squelch circuit means for emitting mode-specific squelch signals for two detection points separated by the predetermined level. Deaυ,
The means for controlling reception switching uses a combination of two squelch signals, a total of four, on the working side and the standby side, and when the working receiver fails, the standby receiver emits the squelch signal from before. There is obtained a reception switching system characterized in that the reception switching is performed even when the reception switching is performed.

〔Example〕

Next, the present invention will be explained.

FIG. 2 is a diagram showing an embodiment of the present invention, in which 1 is a working receiver and 2 is a backup receiver. However, since both receivers are exactly the same, the internal details will only be described for the current receiver 1.

The received signal from the antenna 3 passes through the selection switch 4 and enters the working receiver 1. The selection switch 4 also simultaneously leaks the received signal to the backup receiver 2 at a predetermined level. Therefore, the backup receiver 2 operates at a level lower than the working receiver 1 by the predetermined level.

The received signal that has entered the working receiver 1 is sent to the high frequency amplification circuit 11.
The signal is amplified by the intermediate frequency (IF
) signal is extracted. This IF multiplied signal IF filter 1
3, the signal is amplified by an intermediate frequency (IF) amplification circuit 14, and provisionally modulated by a demodulator 15.

It passes through the changeover switch 16 and exits to the device output end 17.

At this time, the output signal from the standby receiver 2 is
6 is blocked. Further, an electric field detection signal is taken out from the IF amplification circuit 14 and enters the squelch circuit 18. Here, the detection signal is compared with two predetermined 7 bells, and 2
Row squelch ON.

Oh squelch OFF! A 1 and A 2 are sent to the electric field alarm detection circuit 19. Electric field alarm detection circuit] 9 also receives two lines of signals B1 from the standby receiver 2.

B2 is received, and based on these four signals, an alarm signal AaeB3 is obtained and sent to the device control section 20 through an operation that will be described later. Note that the input terminal 21 is used to input into the open side 1 part which receiver is selected as the active device, and in this case, it is assumed that 111 # is input. The device control section 20 controls the selection switch 4 and the changeover switch 16 using the output signals A, , B3 of the four-field alarm detection circuit 19.

In the current explanation, receivers 1 and 2 receive input electric field f x (dB
m). Further, the difference between the input electric field level of the working receiver l and the input electric field level of the backup receiver 2 is defined as y (dB). Therefore, in backup receiver 2, Y(
dB) low level signal will be input.

Next, in the squelch circuits 18 and 19, when the input electric field level becomes X (dBm) and X+Y (dBm)
The squelch is configured to turn ON-OFF when this occurs.

That is, two detection points are provided for the input electric field. And squelch 8 signal A for these two detection points
1 and A2 and Bl and B2 are sent to the electric field alarm detection circuit 19.

FIG. 3 is a diagram for explaining the operation of the reception switching system according to the present invention, and the upper half shows the input electric field of both receivers at time t.
The lower half shows the squelch 0N-OFF state for the two detection points and this state as time passes. FIG. 4 is a diagram showing waveforms of four signals output in ON-OFF. Output signal A1 as in Figure 1
~B2 indicates PaO''' when the squelch is ON, and indicates II II II when the squelch is OFF. In FIG.

In region (1), the squelch is OFF and all the signals remain "operational", and when the squelch for the detection point n) passes in that state, and in the same way, in region a) starting from time t2, signals B and A2 become II OII in addition to the above-mentioned signal B2, and in region (IV) starting from time t3, signals A and A are also “0”
becomes.

Here, the electric field alarm detection circuit 1 of FIG.
To explain the operation of 9, receiver selection signal input terminal 2
Since 1 is °゛1n, the output of the inverter 22 is II
Since the NAND gate 23 is a prohibited gate, the signal B2 cannot be applied to the output of the NAND gate 23. That is, the boundary detection signal of the receiver 2 on the standby side has no influence on the receiver 1 on the active side. In this electric field alarm detection circuit, 25 to 28 are inverters, and 29 and 30 are inverters.
is a NAND circuit.

Returning to FIG. 3, in region (1), signal A 1
+A2 y Bl #B2 are all II I II, so the outputs A3 + B3 are all "1" like the signals A, , B1. Under this situation, when the working receiver 1 becomes a failure, switching to the backup receiver is normally performed.

In area QI), signal B2 is P0'' (squelch).
However, as mentioned above, this is prohibited by the NAND)l''-to 23 and is not transmitted to the output, and has no effect on the output signal A3. Therefore, as in the case of area (1), the current receiver 1 When a failure occurs, switching is performed normally.

Region (e) is the main focus of the present invention. In the conventional technology, the signal B3 becomes an alarm signal due to a drop in the input electric field, so even if the active device 1 fails in this state and the output signal corresponding to A3 becomes an alarm, switching to the backup receiver 2 is not performed. . However, in the present invention, the signal A2 becomes II O# in the current device 1, and the NAND key is
-) 29 becomes '0'' and the NAND gate 30 becomes inhibit dart. Therefore, the output signal B3 becomes i of °'1''.
It does not change at t, and the alarm signal does not occur. Therefore, if the active machine 1 breaks down at this time, switching to the standby machine 2 is performed without any problem. Note that in this area, even if the standby machine 2 is out of order, it will be in a normal signal state, but in this case, if the active machine is out of order, switching will still be performed. However, in any case, since both receivers are out of order, no particular problem occurs even if switching occurs.

Since both receivers in the area are unable to receive data due to a drop in the input electric field, there is no particular problem even if switching from the active unit to the standby unit occurs at this time.

〔Effect of the invention〕

As described above, in the receiver switching method according to the present invention, even if the level of the input electric field is so low that the backup receiver would issue an alarm signal and switching would be impossible in the conventional method, the current receiver Switching between the receiver and the backup receiver can be performed normally. Therefore, the defects in the switching system mentioned in the explanation of the prior art are eliminated, and the reliability of the device and system is improved, which has a great effect.

In the explanation so far, for convenience, the receiver 1 and the working machine have been described, but it goes without saying that even if the receiver 2 is selected as the working machine, the operation is exactly the same.

[Brief explanation of the drawings] Figure 1 is a diagram explaining the operation of the conventional reception switching system, and Figure 2 is a diagram explaining the operation of the conventional reception switching system.
The figure is a block diagram showing the configuration of an embodiment of the present invention, and FIG. 3 is a diagram for explaining the operation of the reception switching system in the present invention. Explanation of symbols: 1 is the current receiver, 2 is the preliminary ◇11'' receiver. 4 is a selection switch, 11 is a high frequency amplifier circuit, 12 is a frequency conversion section, 13 is an IF filter, 14 is an IF amplifier circuit,
15 is a demodulation section, 16 is a changeover switch, 17 is a device signal output terminal, 18 is a squelch circuit, 19 is an electric field alarm detection circuit, and 20 is a device control section. Reference numerals 21 denote receiver selection signal input terminals, respectively.

Claims (1)

[Claims] 1. Equipped with two receivers, a working type and a backup type, that detect the input level of the received signal and emit a squelch signal, and the backup receiver has an input level that is lower than the input level of the active receiver by a predetermined level. In the communication device, the squelch signal is operated in parallel at different levels and the reception switching is controlled using the squelch signal, wherein each means for emitting the squelch signal generates separate squelch signals for two detection points separated by the predetermined level. The means for controlling the reception switching uses a total of four squelch signals in combination on the working side and the standby side, and when the working receiver fails, the squelch circuit means controls the reception switching. 1. A reception switching system characterized in that the reception switching is performed even if the squelch signal has been emitted from before.