JP2501191Y2 - CATV system repeater amplifier - Google Patents

Description

[Detailed description of the device] [Industrial applications]

The present invention relates to a repeater amplifier used in a CATV system having a failure recovery capability.

[Prior art]

Conventionally, the CATV system is mainly used as shown in FIG.
A head end 10 which is an information transmission end, a trunk transmission line 20 to 30 which transmits information, a relay amplifier 40 which amplifies a signal attenuated by the transmission line 20 and the like, a distributor 60 which distributes the signal and a branch which branches the signal. It is composed of a device 61 etc. and a branch line 70 etc. for branching from the main line and leading to each terminal. this house,
A coaxial cable is used for the main transmission line 20 and the like because it is easy to handle, distribute, and branch, and its transmission line network is configured in a dendritic form (the main transmission lines 20 to 30). Frequency division multiplexing (FDM) is mainly used as a signal transmission method. Therefore, signal attenuation occurs in the transmission path, and it is necessary to dispose the relay amplifier 40 and the like for amplifying the signal in various parts of the transmission path.

[Problems to be solved by the device]

As described above, the dendritic network CATV system using the coaxial cable and the relay amplifier has the following drawbacks. If a disconnection or short circuit occurs somewhere in the transmission line, or if a relay amplifier fails in any part, the information from the headend is transmitted to the subscriber terminals connected to the transmission line after the failure point. Will not be done. For example, if a cable disconnection accident occurs at point P1 of the main transmission line 21,
The information sent from the headend is not transmitted to the other main line transmission lines 24, 25, 26, 27, 28, 29, 30 connected from the P1 point to the end E1 point of the main line transmission line. Therefore, the information is not transmitted to the subscriber terminal that receives the signal from each of those transmission lines. As described above, the dendritic network system has a problem that a failure at one place greatly affects the system and the system cannot be used in a wide range. Further, in order to recover from this failure, it is necessary to find a failure point and repair the failure, which requires a lot of time. The present invention is intended to solve the above problems. That is, according to the present invention, by providing a device for switching the transmission direction of the signal in the relay amplifier, when a failure occurs in one transmission line of the CATV system, the signal transmission of the relay amplifier arranged in the failure transmission line is transmitted. It is possible to reverse the direction and connect the terminal connection device that connects the ends of multiple transmission lines to the connected state to send back the signal from another normal transmission line through the terminal connection device. The purpose is to make it quick and to minimize the area affected by obstacles.

[Means for solving problems]

The structure of the present invention is as follows. The present invention starts with
A headend, a dendritic transmission line for transmitting the frequency-multiplexed signal sent from the headend, and a state in which the dendritic transmission line is inserted between any two ends and the transmission lines are not connected to each other. , A relay amplifier to be inserted into a transmission line of a CATV system having a terminal connection device that is connected to each other so that frequency multiplexed signals can be mutually transmitted. And, the feature of the present invention is that it is generated by the head end or the terminal connector, is sent to the transmission line from the head end or the terminal connector, appears at the input terminal or the output terminal of the relay amplifier, and the amplification direction of the frequency multiplexed signal. Signal detection circuit that detects a specific signal that controls the control signal and outputs a control signal according to whether the specific signal is detected, and the input and output of the frequency multiplexed signal to be amplified according to the control signal. It has an input / output switching circuit for switching between the terminals and the other side, and the amplification direction of the frequency-multiplexed signal is inverted according to a specific signal. Here, as the embodiment, the following various types can be used. First, the specific signal is an operation signal that is generated in the terminal connector and is sent from the terminal connector to the faulty transmission line connected to the terminal connector when the transmission line fails. Only the relay amplifier inserted in the faulty transmission line among the transmission lines connected to the terminal connector is sensitive to this operation signal, and the amplification direction is inverted. Therefore,
The specific signal becomes an operation signal for inverting the amplification direction of the relay amplifier inserted in the failed transmission line. The signal detection circuit is connected to the output end of the relay amplifier, and when the operation signal is not detected by the signal detection circuit, the amplification direction of the frequency multiplexed signal is set from the head end to the terminal connector side, and the operation signal is detected. At this time, the input / output switching circuit switches between the input end and the output end. In this way, the signal transmission direction is reversed. The second is a specific signal, which is generated at the headend, is sent from the headend to the transmission line, and specifies each of the plurality of repeaters inserted in the transmission line. That is, the amplification direction is inverted in accordance with the pilot signal or the control signal using the control signal designated by. Thirdly, as the specific signal, a pilot signal of a specific frequency that is generated at the head end and is constantly sent from the head end to the transmission path is used. When the signal detection circuit is connected to the input terminal of the relay amplifier and the pilot signal is detected by the signal detection circuit, the amplification direction of the frequency multiplexed signal is set from the head end to the terminal connector side, and the pilot signal is detected. When it is no longer possible, the input end and the output end are switched so that the amplification direction of the frequency multiplexed signal is changed from the terminal connector side to the head end side.

[Action]

The signal detection circuit is connected to the input end or the output end of the relay amplifier and detects a specific signal appearing on the transmission line.
The signal detection circuit outputs a control signal to the input / output switching circuit depending on whether or not the specific signal is detected. The input / output switching circuit inputs the control signal output from the signal detection circuit and controls switching between the input end and the output end of the signal according to the signal.
In this way, the signal on the transmission path can be used to invert the direction in which the signal from the relay amplifier is amplified and transmitted.

【Example】

The present invention will be described below based on specific embodiments. The configuration of the CATV system using the relay amplifier according to the embodiment is shown in FIG. This embodiment is a two-way transmission system, and a dual pilot AGC transmission system is adopted in the downlink transmission band. And the pilot signal is
The pilot signals are sent from the pilot signal generators 11 and 12 of the headend 10, and the pilot signals are used for detecting a fault. FIG. 2 is an electric circuit diagram showing the configuration of the terminal connector 80 used in the system using the relay amplifier of this embodiment. First, the configuration of this terminal connector will be described. The terminal E1 of the transmission line 21 and the terminal E2 of the transmission line 22 are connected to the terminal connector 80. Reference numerals 81 and 82 denote power separation filters (hereinafter referred to as "PSFs") that separate the electric powers superimposed on the transmission lines 21 and 22. The separated power is supplied to the power supply unit 83, and each active element is supplied with power from the power supply unit 83. The signal detection circuit 84a detects the pilot signal on the transmission line 21 side, and the signal detection circuit 84b detects the pilot signal on the transmission line 22 side. The signal detection circuit 84a includes a directional coupler 811 that branches only a signal input from the transmission path 21, a bandpass filter (hereinafter referred to as "BPF") 801, 802, a diode D1 that forms a rectification circuit, It is composed of D2, a parallel circuit of a capacitor C1 and a resistor R7, and a comparator CP1 which inputs its output. The configuration of the signal detection circuit 84b is similar. BPF801 and 8
Reference numeral 03 separates the 450 MHz pilot signal transmitted from the pilot signal generator 11 into the transmission lines 21 and 22. or,
The BPFs 802 and 804 separate the 73 MHz pilot signal transmitted from the pilot signal generator 12. The divided reference voltage V1 by the resistors R3 and R4 and the divided reference voltage V2 by the resistors R5 and R6 are input to the inverting input terminals of the comparators CP1 and CP2, respectively. The co-collector output terminals of the comparators CP1 and CP2 are pulled up by resistors R9 and R10, respectively. The switching circuit 85 is connected to the PSFs 81 and 82, which is a transistor Tr1 that turns on when one of the outputs of the comparators CP1 and CP2 is at a low level and a relay Ry connected to its collector circuit and a relay operated by the relay. It consists of switches 851 and 852, terminating resistors R1 and R2 connected to those relay switches, and a connecting line 853. Next, the operation of this terminal connector will be described. When the system is in a normal state, pilot signals are sent from the pilot signal generators 11 and 12 to each transmission line. This pilot signal is sorted by the BPF through the directional couplers 811 and 812, and the rectifying circuit (D1, D2, C1, R7)
It is rectified by (D3, D4, C2, R8). As a result, the voltages V3 and V4 at the non-inverting input terminals of the comparators CP1 and CP2 become higher than the voltages of the reference voltages V1 and V2. Therefore, the outputs of the comparators CP1 and CP2 are both at high level, and the base voltage V5 of the transistor Tr1 is at high level. Then, the transistor Tr1 is in the OFF state, no current flows through the relay Ry, and the relay switches 851 and 852 have the contacts a1 and a2.
Connected to the side. Therefore, the transmission line 21 is non-reflectively terminated by the terminating resistor R1 and the transmission line 22 is non-reflective by the terminating resistor R2. On the other hand, when a failure occurs at the point P1 of the transmission line 21, the pilot signal is not transmitted to the terminal E1 of the transmission line 21. Therefore, the voltage V3 input to the non-inverting input terminal of the comparator CP1 becomes lower than the reference voltage V1. Therefore, its output goes low and the other comparator CP2
The voltage V5 becomes a low level regardless of the output of. Therefore,
The transistor Tr1 is turned on, a current flows through the relay Ry, and the relay switches 851 and 852 are switched to the contacts b1 and b2 side. As a result, the transmission lines 21 and 22 are directly connected by the connecting line 853, and a signal is input from the transmission line 22 having no failure,
It can be sent to the transmission line 21. At this time, the pilot signal is also sent to the transmission path 21 side at the same time, but due to the action of the directional coupler 811 this pilot signal is not input to the BPFs 801 and 802. Therefore, the voltage V5 maintains a low level, and the relay switches 851 and 852 are maintained on the contacts b1 and b2 side. When the failure of the transmission path 21 is recovered, the signal transmission direction becomes the normal direction due to the automatic recovery action of the relay amplifier described later. Therefore, the pilot signal is
Input from the transmission line 21 to the terminal connector 80 will also occur when the system is operating normally as described above, the transistor Tr1 is turned off, and the relay switches 851 and 852 have contacts a1 and a2. Connected to the side. Therefore,
The transmission lines 21 and 22 are terminated by terminating resistors R1 and R2, and are separated from each other. Next, the configuration of the relay amplifier according to this embodiment will be described with reference to FIG. Block 400 is a conventional two-way repeater amplifier. Block A is an input / output reversing device. The input / output inverting device A is connected to the PSF 401, the directional filter (hereinafter referred to as “DF”) 403, and the PSF 402 and DF 404. The signal detection circuit 51 includes a directional coupler 513 for branching the pilot signal input from the a terminal transmitted from the head end 10 to the terminal E1 side, and a BPF 51 for selecting the pilot signal.
1,512 and diode D5, D for rectifying its output
6. A rectifier circuit consisting of a capacitor C3 and a resistor R11, and a comparator CP3. The input / output switching circuit 52 includes a transistor Tr2 for driving the relay 520, a relay 520 inserted in the collector circuit of the transistor Tr2, and a relay switch 521 driven by the relay 520. Next, the operation of this relay amplifier will be described. When the system is in a normal state, the relay switch 521 is connected to the contacts a1 and a2. Therefore, the signal transmission direction is from the terminal a on the head end side to the terminal b on the terminal E1 side.
The signal is amplified in the normal direction.
At this time, the pilot signal is taken into the BPFs 511 and 512 from the input terminal a of the amplifier via the directional coupler 513, but the voltage V7 at the inverting input terminal of the comparator CP3 becomes higher than the reference voltage V8 at the non-inverting input terminal. . Therefore, the output voltage V9 becomes low level, the transistor Tr2 maintains the off state, and no current flows in the relay 520, so that the relay switch 521 maintains the initial state. On the other hand, if a failure occurs at point P1 of the transmission line 21, the pilot signal will not be input to the signal detection circuit 51. Therefore, the voltage V7 becomes lower than the reference voltage V8 and the comparator CP
The power voltage V9 of 3 becomes high level, the transistor Tr2 is turned on, and the current flows through the relay 520. Therefore, the relay switch 521 operates and is connected to the contacts b1 and b2. Therefore, the amplification direction of the signal of the amplifier is inverted, and the transmission direction of the signal is inverted from the b terminal to the a terminal. Eventually, the transmission direction of the signals of the relay amplifiers 42 to 45 between the fault point P1 and the terminal E1 of the transmission line 21 is reversed, and the signal from the headend 10 is transmitted to the transmission line 22 and the terminal connector 80 on the transmission line between them. Will be transmitted around. Therefore, the information is transmitted to the user terminal connected during this period as before the failure. Note that the pilot signal is also sent back through the transmission line 21 between the fault point P1 and the terminal point E1 at the same time, but because it is not input to the BPFs 511 and 512 due to the action of the directional coupler 513, the relay 520 does not operate. Next, the recovery action at the time of failure recovery will be described. When the failure at the point P1 is repaired, the pilot signal is transmitted from the head end 10 toward the terminal end E1. For this reason,
Since the pilot signal is input from the a terminal of the relay amplifier 42 immediately after the failure point P1 and the pilot signal is detected by the detection circuit 51, the voltage V7 becomes higher than the reference voltage V8 and the output voltage V9 of the comparator CP3. Will be low level. Therefore, the transistor Tr2 is turned off, the current flowing in the relay 520 is cut off, and the relay switch 5
21 is in the initial state (connected to the contacts a1, a2 side). Therefore, the signal transmission direction of the relay amplifier 42 is the normal direction toward the terminal E1 side. Then, the pilot signal is also input to the next relay amplifier 43 from the terminal on the head end side, and due to the same action, the transmission direction of the signal of the relay amplifier becomes the normal direction. In this way, the transmission direction of the signal to the relay amplifier 45 is sequentially inverted to the normal direction, and the terminal connector 80 also receives the pilot signal from the direction of the terminal E1. Therefore, the terminal connector switches the contacts of the relay switches 851 and 852 to the terminating resistance side by the above-mentioned operation, and the transmission lines 21 and 22 are separated into the normal state. In this way, the direction of signal transmission on the transmission line is
Automatically reverses when a failure occurs, and automatically recovers when the failure is restored. Next, another embodiment will be described. In this embodiment, the operation signal for inverting the signal transmission direction of the relay amplifier is output from the terminal connector 80. FIG. 4 shows the configuration of the terminal connector 80 used in the system using the relay amplifier according to this embodiment, and the parts having the same functions as those of the parts described in the previous embodiment are the same. Numbers are attached. The signal detection circuit 86a detects a pilot signal input from the transmission path 21 side, and the signal detection circuit 86b detects a pilot signal input from the transmission path 22 side. Its operation is similar to that described in the previous embodiment. Occurrence of motion signal
87a is a transistor Tr3 driven by the output of the comparator CP1, a relay Ry3 driven by it, a relay switch 871 operated by it, a signal generator 875 generating an operation signal, and a relay Ry4.
It consists of a normally closed relay contact 877 that stops the oscillation of 875. The other operation signal generating circuit 87b has the same configuration. However, the signal generators 875 and 876 have different oscillation frequencies, and it is specified which of the transmission lines 21 and 22 the input / output of the relay amplifier is inverted. The constitution of the relay amplifier is as shown in FIG.
The operation signal detection circuit 53 is configured similarly to the signal detection circuit 51 of FIG. 3, and only the operation signal is input from the terminal b on the terminal side of the transmission path and selected. However, the frequency of the operation signal detected by the relay amplifier is different between the transmission line 21 and the transmission line 22. The switching circuit 54 has the same structure as the input / output switching circuit 52 shown in FIG. That is, the relay switch 521 is switched to operate. The relay switch 521 corresponds to that of FIG. Next, the operation of the CATV system using the relay amplifier according to this embodiment will be described. In FIG. 4, when the system is in a normal state, the relay switches 871 and 872 are connected to the contacts a1, a2, a3, a4 side. Therefore, the transmission line 21 is terminated by the resistor R1 and the transmission line 22 is terminated by the resistor R2. Further, since the pilot signal is input from both transmission lines, the voltages V3 and V4 are higher than the reference voltages V1 and V2, and the outputs of the comparators CP1 and CP2 are low level. Therefore, the transistors Tr3 and Tr4 are in the off state, and no current flows through the relays Ry3 and Ry4. Therefore, the relay switches 871 and 872 continue to be connected to the terminating resistor side. By the way, when a failure occurs at point P1 of the transmission line 21, the pilot signal is not input from the side of the transmission line 21.
Therefore, the voltage V3 becomes lower than the reference voltage V1 and the output of the comparator CP1 becomes high level, so that the transistor Tr3 is turned on. Therefore, a current flows through the relay Ry3, and the contacts of the relay switch 871 are switched to the b1 and b2 sides.
Therefore, the transmission lines 21 and 22 are directly connected, and the operation signal is sent from the signal generator 875 to the transmission line 21 side via the directional coupler 873. The operation signal is sent from the terminal b of the relay amplifier to the directional coupler 51.
Input to the operation signal detection circuit 53 via 3. The operation signal detection circuit 53 outputs the detection signal S1 to the switching circuit 54, and the switching circuit 54 contacts the contacts of the relay switch 521 from the terminals a1 and a2.
Switch to the b1 and b2 terminal side. By this operation, the signal transmission direction is switched from the b terminal to the a terminal.
By this action, the transmission direction of the signal of the relay amplifier between the fault point P1 and the terminal end E1 of the transmission line 21 can be reversed, and the signal can be diverted from the terminal connector 80 side to the transmission line 21 side. Next, the case where the failure is recovered will be described. When the fault is restored, the output of the pilot signal is suspended. Then, the comparator C of the signal detection circuit 86b of the terminal connector 80.
The output of P2 becomes high level, transistor Tr4 turns on, and current flows through relay Ry4. As a result, the relay contact 877, which is a normally closed contact, is opened, and the signal generator 875
Output stops. Then, the operation signal detection circuit 53 of the relay amplifier 45 no longer detects the operation signal, so that the switching circuit 54
Resets the relay switch 521 to the original state. In this way, the relay amplifier sequentially switches the signal transmission direction from 45 to 42 to the normal direction. When the transmission direction of the signals of all the relay amplifiers has completely returned to the normal direction,
Even if the pilot signal is sent, the terminal connector 80
Inputs a pilot signal from both its input terminals,
The initial state, that is, the transmission lines 21 and 22 are separated by the terminating resistors. As described above, the relay amplifier of the present embodiment can invert the signal amplification, that is, the transmission direction, or restore it depending on the presence or absence of the operation signal from the terminal connector. In the above embodiment, the output of the operation signal is stopped by disconnecting the pilot signal when the failure is restored. However, the switch of the signal generator may be manually opened. The switching control of the terminal connector and the input / output inversion control of the relay amplifier are performed by selecting each terminal connector and the relay amplifier to be inverted by the address designation from the head end side and outputting the control signal. May be. The pilot signal described above may be a pilot signal dedicated to this system or a pilot signal for AGC of a relay amplifier used in a conventional system. As the connection transmission line from the trunk transmission lines 21 and 22 to the terminal connector 80, an optical fiber transmission line, a spatial optical transmission line, a wireless transmission line and the like can be used in addition to the coaxial cable transmission line. If the distance between the trunk transmission lines that should be connected by the terminal connection device is long, the coaxial cable transmission line requires a relay amplifier for the lead-in line to the terminal connection device. It has the advantage of not needing it.

[Effect of device]

The present invention relates to a relay amplifier of a CATV system, which is connected to an input terminal or an output terminal of the relay amplifier, detects a specific signal appearing at those terminals, and detects whether or not the specific signal is detected. An input / output switching circuit for switching between the input end and the output end is provided. Therefore, due to the operation of the input / output reversing device, when a failure occurs, the signal transmission direction can be reversed.
Therefore, in a CATV system using this relay amplifier, from a normal transmission line to a faulty transmission line via a terminal connector that can switch between connection and disconnection of terminations of multiple dendritic transmission lines. The signal can be sent back. Therefore, in the conventional system, the failure section greatly expanded toward the terminal side, but in the CATV system using the relay amplifier of the present invention,
This failure section can be made as narrow as possible. Further, since the signal transmission direction of the relay amplifier can be switched quickly, the failure time due to a failure can be reduced to the switching time of the transmission path.

[Brief description of drawings]

FIG. 1 shows a CA using a relay amplifier according to an embodiment of the present invention.
A system diagram showing the entire configuration of the TV system, FIG. 2 is an electric circuit diagram showing the configuration of a terminal connector used in the system, and FIG. 3 is an example used in the system. FIG. 4 is an electric circuit diagram showing the configuration of a relay amplifier, FIG. 4 is an electric circuit diagram showing the configuration of a terminal connector used in a CATV system using a relay amplifier according to another embodiment, and FIG.
FIG. 6 is a block diagram showing the configuration of the relay amplifier according to the embodiment used in the system, and FIG. 6 is a system diagram showing the overall configuration of the conventional CATV system. 10 ... Headend, 20-30 ... Trunk transmission line 11, 12 ... Pilot signal generator 41-45 ... Relay amplifier, 51 ... Signal detection circuit 52 ... Input / output switching circuit 84a, b, 86a, b …… Signal detection circuit 85 …… Switching circuit 87a, b …… Operation signal generation circuit 851,852,521 …… Relay switch

Claims (4)

(57) [Scope of utility model registration request] 1. A headend for frequency-multiplexing analog signals for transmission, a dendritic transmission line for transmitting the frequency-multiplexed signals transmitted from the headend and laid in a dendritic path, and the dendritic transmission line. Between the two arbitrary terminations, the terminations of which are not connected to each other, and the terminations are connected to each other so that the frequency-multiplexed signals can be transmitted to each other. A relay amplifier for amplifying the frequency-multiplexed signal, which is inserted into the transmission path of a CATV system having a terminal connector, which is generated by the headend or the terminal connector, and which is generated from the headend or the terminal connector. A specific signal that is sent to the transmission line and appears at the input terminal or the output terminal of the relay amplifier and controls the amplification direction of the frequency multiplexed signal is detected, and the specific signal is detected. Signal detection circuit for outputting a control signal according to the presence or absence of the control signal, and an input for switching the input and output of the frequency multiplexed signal to be amplified according to the control signal between the input end and the output end. A relay amplifier for a CATV system, comprising: an output switching circuit, and inverting the amplification direction of the frequency multiplexed signal according to the specific signal. 2. The specific signal is generated in the terminal connector, and is transmitted from the terminal connector to a faulty transmission line connected to the terminal connector when the transmission line is in a faulty state, and is amplified by a relay amplifier. An operation signal for inverting the direction, the signal detection circuit is connected to the output end of the relay amplifier, when the operation signal is not detected by the signal detection circuit, the amplification direction of the frequency multiplexed signal From the head end to the terminal connector side, and when the operation signal is detected, the input / output switching circuit switches between the input end and the output end to set the amplification direction of the frequency multiplexed signal to the terminal. The relay amplifier for a CATV system according to claim 1, characterized in that the connection side is the head end side. 3. The specific signal is generated at the head end, is sent from the head end to the transmission path, and has a specific frequency that is unique to each of the plurality of repeaters inserted in the transmission path. A repeater amplifier for a CATV system according to claim 1, which is a pilot signal or a control signal in which a unique address is designated. 4. The specific signal is a pilot signal of a specific frequency that is generated in the head end and is constantly sent from the head end to the transmission path, and the signal detection circuit is connected to the input end of the relay amplifier. Connected, when the pilot signal is detected by the signal detection circuit, the amplification direction of the frequency multiplexed signal is from the head end to the terminal connector side, and when the pilot signal is no longer detected, the The CATV system according to claim 1, characterized in that the amplification end of the frequency-multiplexed signal is switched from the terminal connector side to the headend side by switching between the input end and the output end. Relay amplifier.