JP3950701B2 - Squelch motion control system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a squelch operation control system, and more particularly to a squelch operation control system for an intermediate relay station of a microwave communication system.
[0002]
[Prior art]
FIG. 6 is a block diagram showing the entire system of a squelch operation control system in a conventional microwave communication system. The terminal station 60 performs microwave communication with the terminal station 62 via the intermediate relay station 61. The intermediate relay station 61 is a non-regenerative intermediate relay station, and receives an intermediate relay station receiver 611 that receives a microwave signal from the terminal station 60 and an intermediate relay station transmitter 612 that transmits the microwave signal to the terminal station 62. Have
[0003]
Signal amplification in such a non-regenerative intermediate relay station generally amplifies the interference wave when there is an interference wave when the level of the signal to be received is lowered, causing unnecessary waves to be transmitted. End up. For this reason, a technique for disconnecting the communication line is required when the reception level is lowered. For example, in Japanese Patent Laid-Open No. 4-344717, a signal including an identification code is transmitted from the transmission side, and the level of the signal to be received is lowered. Thus, it is disclosed that a squelch operation is performed when an identification code included in a signal cannot be detected by a receiver.
[0004]
In these conventional squelch operation control systems in the microwave communication system, one received signal is monitored by one input circuit, and the squelch operation is determined based on whether or not a specified identification code can be detected.
[0005]
FIG. 7 is a block diagram showing a configuration of a conventional squelch operation control system. A conventional squelch operation control system shown in FIG. 7 includes a receiving antenna 1 for receiving a microwave signal, an input circuit 2 that takes in a received signal that is modulated and converts the signal from an RF band to an IF band, DEM 3 that demodulates the modulated signal, SCU 4 that converts the demodulated signal so that the CPU can capture the identification code, SQL ID 5 that serves as a signal source at the time of squelch transmission, and MOD 6 that modulates the squelch signal A computer 7 having a CPU 71 and a memory 72 incorporating software, and executing a squelch operation determination logic; an input from the computer 7 to the output circuit 9 of the squelch signal; and disconnection of the line of the received signal A switch (SW) 8 for performing transmission, an output circuit 9 for converting a signal from an IF band to an RF band and transmitting the signal, and a microwave And a transmission antenna 10 for transmission.
[0006]
Next, the operation of the conventional squelch operation control system shown in FIG. 7 will be described.
The signal received by the receiving antenna 1 is converted from the RF band to the IF band by the input circuit 2 and DEM demodulated by the DEM 3. The other signal output from the input circuit 2 is sent as it is to the output circuit 9 through the switch 8, converted again to an RF band signal, and output from the transmitting antenna 10 as a microwave signal.
[0007]
The SCU 4 receives the digitized serial data from the DEM 3, analyzes it by the computer 7, and detects the identification code to confirm whether the quality of the communication line is maintained. If the line quality is maintained, the switch 8 is set so that the switch 8 sends the data from the input circuit 2 to the output circuit 9. When it is determined that the line quality cannot be maintained, the switch 8 is set so that the signal from the SQL ID 5 is sent to the output circuit 9.
[0008]
[Problems to be solved by the invention]
In the conventional squelch operation control system described above, when the identification code cannot be detected in the actual operation state, in addition to the decrease in the level of the signal to be received and the failure of the receiver, fading in the transmission path For example, temporary noise due to the squelch operation judgment circuit timing / load data missing error, temporary troubles on the transmission side, etc. can be considered. (10 to 20 seconds), the signal must be monitored, and there is a problem of increasing the time for sending unnecessary waves and delaying switching to another system.
[0009]
The present invention has been made in view of the above problems, and the present invention is a squelch operation capable of quickly determining whether or not the line state has deteriorated and shortening the time for shifting to another line. An object is to provide a control system.
[0010]
Another object of the present invention is to improve the reliability of the system in addition to the above object.
[0011]
[Means for Solving the Problems]
According to a first aspect of the present invention, in a squelch operation control system that performs line switching by a squelch operation when a level of a received demodulated signal is lowered, a second received demodulated signal in which the received demodulated signal is lowered by a predetermined level is generated, and the received demodulated signal A squelch operation is performed when a predetermined time has elapsed after the level of the second received demodulated signal has decreased from the reference level when the signal level has decreased from the reference level.
[0012]
According to a second aspect of the present invention, there is provided input means for receiving an RF band received signal including an identification code for identifying a line and converting the received signal into an IF band signal, and demodulating the IF band signal to obtain a first demodulated signal. A first demodulating means for outputting; an attenuating means for attenuating the IF band signal to a level lower than that of the first demodulating means; and a signal demodulated from the attenuating means for demodulating and outputting a second demodulated signal And when a predetermined time has elapsed since the identification signal included in the second demodulated signal cannot be detected when the identification signal included in the first demodulated signal cannot be detected. And a control means for performing a squelch operation.
[0013]
According to a third aspect of the present invention, in the second aspect of the invention, there is provided switching means for switching an IF band signal output from the input means to the attenuation means to be output to the second demodulation means. And
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing a configuration of an embodiment relating to a squelch operation control system of the present invention. In addition to the configuration of the conventional squelch operation control system shown in FIG. 7, the squelch operation control system according to the present embodiment includes an ATT (attenuator) 11 that lowers the level of the IF band signal output from the input circuit 2, and an ATT. The second DEM 12 that demodulates the signal output from the (attenuator) 11 and the second SCU 13 that converts the signal demodulated by the second DEM 12 so that the CPU can capture the identification code from the demodulated signal. Prepare.
[0015]
Next, the operation of this embodiment will be described in detail with reference to the drawings. In FIG. 1, the signal received by the receiving antenna 1 is converted from the RF band to the IF band by the input circuit 2, and the IF signal is branched and one is directly input to the DEM 3, and the other is input to the DEM 12 through the ATT 11. Becomes lower by that amount. Each of these signals is DEM demodulated, and one of the signals from the input circuit 2 is sent as it is to the output circuit 9 through the switch 8, converted again to a signal in the RF band, and output from the transmitting antenna 10 as a microwave signal. Is done.
[0016]
The SCUs 4 and 13 receive the digitized serial data from the DEMs 3 and 12, analyze them with the computer 7, and detect whether the communication line quality is maintained by detecting the identification code. If the quality is maintained, the switch 8 is set so that the switch 8 sends the data from the input circuit 2 to the output circuit 9. When it is determined that the line quality cannot be maintained, the switch 8 is set so that the signal from the SQL ID 5 is sent to the output circuit 9.
[0017]
FIG. 2 is a flowchart showing a squelch operation control procedure in the squelch operation control system of the present embodiment. The computer 7 periodically fetches the communication data transmitted from the DEMs 3 and 12 (steps 201 and 202), and in a normal state in which there is no data error and the identification code included in the communication data from the DEM 3 can be recognized. (Step 203 YES), the next data to be transmitted is received and the same processing is repeated.
[0018]
When a situation occurs in which the identification code included in the communication data from the DEM 3 cannot be recognized (NO in step 203), the previous line state on the lower sensitivity DEM 12 side is analyzed and the past history is examined (step 204). As a result, if a sufficient time (about 10 seconds) has elapsed since the identification code could no longer be recognized so far, it can be determined that the reception level has gradually decreased (step 205), and the squelch The operation process is activated and the switch 8 is switched.
[0019]
In the cases other than the above in Steps 204 and 205, it is impossible to determine whether the squelch operation should be activated due to a permanent failure of the device that should activate the squelch operation or a temporary deterioration of the line quality due to other causes. Similarly, the same loop (steps 201 to 205) is repeated several times over a sufficient time, and then the squelch operation is determined to be performed.
[0020]
FIG. 3 is a waveform diagram showing a change in the reception level when the reception level gradually decreases due to long-period fading, worsening weather, and the like. This is a case where the identification code cannot be detected from the signal from the DEM 12 having the lower reception level at t1, and the identification code cannot be detected even by the DEM 3 at the original reception level at t2.
[0021]
In the conventional example, the squelch operation is activated after monitoring that this state (10 to 20 seconds) continues for a while from the state of t2. In this embodiment, if a sufficient time has elapsed from t1 at the time t2, the reception level gradually decreases, and it is unlikely that the reception level will suddenly recover, so the squelch operation is activated. To do.
[0022]
FIG. 4 is a waveform showing a change in the reception level when the reception level is temporarily lowered, such as a data missing error or a momentary trouble on the transmission side, and when the reception level is suddenly lowered due to a failure of the receiver. FIG.
[0023]
When the reception level temporarily decreases, the identification code cannot be detected from the signal from the DEM 12 having a low reception level at t3, and the identification code cannot be detected even by the DEM3 at the original reception level at t4. The time difference between is small and the squelch action is not activated.
[0024]
Similarly, when the reception level is lowered due to a failure of the transceiver, the time difference between t5 and t6 is reduced, and after the line state is monitored for a while as in the conventional example, the squelch operation is activated at t7.
[0025]
As another embodiment of the present invention, the basic configuration is as described above. However, as shown in FIG. 5, by using the switch 14 for switching the output destination from the input circuit 2 to the ATT 11, the use described above is performed. In addition to the form, the following functions can be added. If the identification code cannot be detected by the DEM 3 at the original reception level while the identification code can be detected from the signal from the DEM 12 having a low reception level, it can be determined that the DEM 3 or the SCU 4 has failed. Therefore, the ATT11 is disconnected, the output to the ATT11 of the input circuit 2 can be directly connected to the DEM12, and the conventional squelch control operation system can be maintained. Can be improved.
[0026]
【The invention's effect】
As described above, according to the present invention, the time until the squelch operation when the reception level is reduced can be set earlier than in the prior art, and the determination of erroneous line disconnection due to a trouble in the input circuit can be made more accurately. There is an effect that can be judged.
[0027]
In addition, according to the present invention, the time until the squelch operation when the reception level is reduced can be set earlier than in the past, and the determination of erroneous line disconnection due to a trouble in the input circuit can be more accurately determined. , The reliability of the system can be improved.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a squelch operation control system of the present invention.
FIG. 2 is a flowchart showing a squelch operation control procedure of the present embodiment.
FIG. 3 is a waveform diagram showing a change in reception level when the reception level gradually decreases in the present embodiment.
FIG. 4 is a waveform diagram showing a change in reception level when the reception level temporarily decreases and when the reception level rapidly decreases;
FIG. 5 is a block diagram showing a configuration of another embodiment of the present invention.
FIG. 6 is a block diagram showing an entire system of a squelch operation control system in a conventional microwave communication system.
FIG. 7 is a block diagram showing a configuration of a conventional squelch operation control system.
[Explanation of symbols]
1 receiving antenna 2 input circuit 3 DEM
4 SCU
5 SQL ID
6 MOD
7 Computer 8 Switch 9 Output Circuit 10 Transmitting Antenna 11 ATT (Attenuator)
12 DEM
13 SCU
14 switch 60 terminal station 61 intermediate relay station 62 terminal station 71 CPU
72 Memory 611 Relay intermediate station receiver 612 Relay intermediate station transmitter

Claims (3)

In a squelch operation control system that performs line switching by a squelch operation when a level of a received demodulated signal is lowered, a second received demodulated signal in which the received demodulated signal is lowered by a predetermined level is generated, and the level of the received demodulated signal is lowered from a reference level In this case, the squelch operation control system performs a squelch operation when a predetermined time has elapsed since the level of the second received demodulated signal decreased from the reference level. Input means for receiving an RF band received signal including an identification code for identifying a line and converting it into an IF band signal; first demodulating means for demodulating the IF band signal and outputting a first demodulated signal; Attenuating means for attenuating the IF band signal to a level lower than that of the first demodulating means; a second demodulating means for demodulating the signal output from the attenuating means and outputting a second demodulated signal; Control means for performing a squelch operation when a predetermined time has passed since the identification signal included in the second demodulated signal cannot be detected when the identification signal included in the first demodulated signal cannot be detected. A squelch motion control system comprising: 3. The squelch operation control system according to claim 2, further comprising switching means for switching an IF band signal output from the input means to the attenuation means to be output to the second demodulation means.

Images