JP2616389B2 - Bidirectional CATV system and bidirectional CATV repeater / amplifier used therefor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bidirectional CATV system and a bidirectional CATV repeater / amplifier provided in the system.

[0002]

2. Description of the Related Art Conventionally, in a CATV transmission line, a transmission level in a downlink direction of a relay amplifier is set to be constant.
A pilot signal for AGC is transmitted from the head end equipment of the center to control the gain of the relay amplifier.

FIG. 3 is a block diagram showing an example of a conventional CATV transmission line.

The AGC pilot signal generator 4 sends out a signal for the relay amplifying device to perform an AGC operation. The head-end equipment 5 sends out various signals including the AGC pilot signal to the transmission path. The relay amplifiers 21 and 22 are bidirectional CATV relay amplifiers, and the first input / output terminal 8 is a downstream input terminal and an upstream output terminal of the relay amplifier 22. The second input / output terminal 20 is connected to a relay amplifier 22
Are the downstream output terminal and the upstream input terminal.

The directional filters 9 and 19 branch and couple transmission signals in both the up and down bands. The downstream variable amplifier 10 increases the downstream signal level to a desired level. The downstream AGC unit 11 adjusts the gain of the variable downstream amplifier 10 according to the pilot signal level. The upstream variable amplifier 17 receives the pilot signal level from the downstream of the transmission path or the like.
The gain is adjusted by the C unit 18.

Next, the operation will be described. The CATV transmission line is not transmitted according to the transmission level diagram mainly due to the change in the attenuation due to the temperature of the cable. In order to compensate for this, it is necessary to adjust the transmission level of each relay amplifier to a predetermined value.

Therefore, a pilot signal generator 4 for AGC is provided in the head end equipment 5 so that the level fluctuation can be detected and adjusted. A pilot signal is input to the relay amplification device 22, passes through the first input / output terminal 8, the directional coupler 9, and the downlink variable amplifier 10.
Reach 1 The downlink AGC unit 11 detects a pilot signal level and adjusts the gain of the variable downlink amplifier 10 so that the pilot signal level becomes a specified level.

[0008]

SUMMARY OF THE INVENTION The above-mentioned conventional CAT
In the V transmission line, the gain of the repeater amplifier is controlled by the AGC function, and even if an unnecessary wave signal is generated due to external unnecessary radiation or oscillation due to equipment failure or construction failure, it cannot be detected. Since the signal is transmitted with the gain, the image degradation continues, and there is no unit for outputting the alarm, and the subscriber has to respond to the complaint.

[0009]

The gist of the bidirectional CATV repeater amplifying apparatus provided by the present invention in order to solve the above-mentioned problems lies in the following two items.

[1] In a bidirectional CATV system including a center station as a CATV signal source, a bidirectional CATV relay amplifying device, and a transmitting / receiving device on the viewer side, the center station includes a monitoring device, a headend facility, an automatic gain control. The monitoring device comprises a pilot signal generator (hereinafter referred to as AGC), wherein the monitoring device receives a monitoring signal transmitted from a bidirectional CATV repeater amplification device using an upstream band, and the head-end facility transmits an AGC pilot signal. And the AGC pilot signal generator sends out a pilot signal for the bidirectional CATV repeater / amplifier to perform an AGC operation.
The bidirectional CATV repeater / amplifier comprises a level detector, a supervisory controller, an alarm data transmitter, a switch, and a CATV signal output variable amplifier.
The signal level of the unnecessary wave signal generated on the V transmission path is detected, and a detection level signal corresponding to the detection level is output. The monitoring control unit sets the level of the detection level signal of the level detection unit in advance. If the detected level is determined to be equal to or greater than the allowable level, a gain control signal and a monitor signal are output, and the alarm data transmitting unit outputs the monitor signal. If you receive
The switch transmits alarm data to the center station, and when the gain control signal is received, the switch switches the CATV signal output variable amplifier to the normal AGC gain control based on the level of the pilot signal. And supplying the gain control signal, wherein the CATV signal output variable amplifier comprises:
When the gain control signal is received, the normal AGC
A bidirectional CATV system comprising amplifying the CATV signal with a gain lower than a gain obtained by gain control.

[2] Both the CATV signal and the pilot signal are transmitted from the center station to the transmission line, the transmission / reception device of the viewer is connected to the transmission line, and two-way communication is performed between the center station and the transmission / reception device. A relay amplification device inserted into the transmission line in a directional CATV system, comprising: a first input / output terminal, a first directional filter, a downstream variable amplifier, a downstream AGC unit, an unnecessary signal extraction unit, and a level detection. Unit, a monitoring control unit, a switch, an alarm data transmitting unit, an upstream variable amplifier, an upstream AGC unit, a second directional filter, and a second input / output terminal. , A downstream input terminal and an upstream output terminal, wherein the second input / output terminal is
A downstream output terminal and an upstream input terminal, wherein the first directional filter filters a signal of a band (hereinafter, referred to as a downstream signal) received from the transmission path to the first input / output terminal, by the downstream variable Branching to an amplifier, and coupling a signal in a band (hereinafter, referred to as an upstream signal) transmitted from the first input / output terminal to the transmission line to the first input / output terminal; Amplifying the signal level of the downlink signal from the directional filter to a desired level, wherein the downlink AGC unit controls the gain of the variable downlink amplifier based on the level of the pilot signal. And the unnecessary signal extracting section selectively passes only the unnecessary signal included in the downlink signal, and the level detecting section includes the unnecessary signal passing through the unnecessary signal extracting section. Down signal The monitor control unit detects the signal level of the unnecessary wave signal included, and the monitoring control unit compares the detection level signal of the unnecessary wave signal from the level detection unit with an allowable level, and determines the magnitude of the detection level. Output the gain control signal to the switching device and the monitoring signal to the alarm data transmitting unit when the gain control signal is equal to or higher than the permissible level. Receiving the signal, prioritizes the gain control signal of the monitoring control unit over the AGC signal of the downstream AGC unit, and controls the gain of the variable downstream amplifier by the gain control signal of the monitoring control unit; The alarm data sending unit, upon receiving the monitoring signal,
Using the upstream transmission band of the transmission line to send alarm data to a center monitoring device provided in the center station, the variable upstream amplifier includes a signal of the upstream signal from the directional filter. Amplifying the level to a desired level, wherein the uplink AGC section receives the pilot signal level from the downstream of the transmission path or the like, adjusts the gain of the uplink variable amplifier, and The directional filter branches an upstream signal received from the transmission line to the second input / output terminal to the upstream variable amplifier, and converts a downstream signal transmitted from the second input / output terminal to the transmission line. A bidirectional CATV repeater / amplifier coupled to the second input / output terminal.

[0012]

Next, the present invention will be described with reference to the drawings.

FIG. 1 shows a bidirectional CATV provided by the present invention.
FIG. 1 is a system diagram illustrating a first embodiment of a system.

In FIG. 1, relay amplifiers 1 to 3 are bidirectional CATV relay amplifiers. The AGC pilot signal generator 4 sends out pilot signals for the relay amplifiers 1 to 3 to perform AGC operation.

The head-end equipment 5 sends out various signals including the AGC pilot signal to the transmission line. Center station 7
Is provided with a head-end facility 5 and a monitoring device 6. The monitoring device 6 receives a monitoring signal using the upstream band.

FIG. 2 shows a bidirectional CATV used in the present invention.
FIG. 2 is a block diagram illustrating a first embodiment of the relay amplifier.

In FIG. 2, a first input / output terminal 8 is a downstream input terminal and an upstream output terminal of the relay amplifiers 1 to 3.

The second input / output terminal 20 is connected to the relay amplifier 1
3 and 4 are downstream output terminals and upstream input terminals. The directional filter 9 branches and couples transmission signals in both the upstream and downstream bands.
The downstream variable amplifier 10 increases the downstream signal level to a desired level. The downstream AGC unit 11 controls the gain of the variable downstream amplifier 10 according to the pilot signal level.

The unnecessary wave signal extracting section 12 allows the unnecessary wave signal to pass. The level detector 13 detects the level of the signal that has passed through the unnecessary signal extractor 12. The monitoring control unit 14
The detection level signal received from the level detection unit 13 is determined,
When the magnitude of the detection level is equal to or higher than the allowable level, the gain control signal is output to the switch 15 and the monitoring signal is output to the alarm data transmission unit 16.

Upon receiving the gain control signal, the switch 15 gives priority to the gain control signal of the monitor control section 14 over the AGC signal of the downstream AGC section 11, and controls the gain of the variable downstream amplifier 10 using the gain control signal. Alarm data sending unit 16
Sends the alarm data to the center monitoring device 6 using the upstream transmission band when receiving the monitoring signal. The gain of the uplink variable amplifier 17 is adjusted by an uplink AGC unit 18 which receives a pilot signal level from the downstream of the transmission path or the like.

Next, the operation will be described.

The pilot signal transmitted from the AGC pilot signal generator 4 is input from the first input / output terminal 8 of each of the relay amplifiers 1 to 3 and passes through the down variable amplifier 10 to perform AGC.
The level is detected by the control unit 11. Repeater amplifiers 1-3
Operates normally and there is no high output unnecessary wave signal, the switch 15 outputs the AGC signal of the downstream AGC unit 11 to the downstream variable amplifier 10 and adjusts the gain. However, the operation when an unnecessary wave signal is generated is as follows. The generated unnecessary wave signal is output from a part of the output signal of the down variable amplifier 10 to the unnecessary wave signal
2, the level is detected by the level detection unit 13, and a detection level signal is output to the monitoring control unit 14.

The monitoring controller 14 determines whether the detection level signal is higher than the allowable level. If the detection level signal is higher than the allowable level, the monitoring controller 14 sends the gain control signal to the switch 15
The monitoring signal is output to the alarm data transmitting unit 16. Upon receiving the gain control signal, the switch 15 switches the AGC
The gain control signal of the monitor control unit 14 is prioritized over the GC signal, and the gain of the variable down amplifier 10 is controlled by the gain control signal.

When the variable gain amplifier 10 receives the gain control signal, it lowers the entire signal level within a range that does not affect the image. When receiving the monitoring signal, the alarm data transmitting unit 16 transmits the alarm data to the center monitoring device 6 through the first input / output terminal 8 using the upstream transmission.

[0025]

As described above, the bidirectional CATV repeater amplifying apparatus according to the present invention detects the level of an unnecessary wave signal, and when the magnitude of the detected level is judged to be equal to or larger than the allowable level, the gain of the amplifier is increased. Because it is configured to reduce to the extent that does not affect the image, even if unnecessary wave signals are generated due to external unnecessary radiation dive or oscillation due to functional failure or construction failure, the occurrence of distortion is suppressed and the signal is not cut off Image degradation can be prevented to a minimum, and alarm data is sent to the center monitoring device, so that the system can be quickly restored before responding to a complaint from a subscriber or within a minimum image degradation state. Has the effect that it becomes possible.

[Brief description of the drawings]

FIG. 1 is a system diagram showing a first embodiment of a bidirectional CATV system of the present invention.

FIG. 2 is a block diagram showing a first embodiment of a bidirectional CATV repeater / amplifier used in the present invention.

FIG. 3 is a block diagram showing an example of a conventional CATV transmission line.

[Explanation of symbols]

 1-3 Relay amplifying device 4 AGC pilot signal generator 5 Head-end equipment 6 Monitoring device 7 Center station 8 First input / output terminal 9, 19 Directional filter 10 Down variable amplifier 11 Down AGC unit 12 Unwanted signal Extraction unit 13 Level detection unit 14 Monitoring and control unit 15 Switching unit 16 Alarm data transmission unit 17 Uplink variable amplifier 18 Uplink AGC unit 20 Second input / output terminal 21, 22 Conventional relay amplification device

Claims (2)

(57) [Claims] 1. A bidirectional CATV system comprising a center station serving as a CATV signal source, a bidirectional CATV repeater / amplifier, and a transmission / reception apparatus on the viewer side. The monitoring device receives a monitoring signal transmitted from a bidirectional CATV repeater amplifying device using an upstream band, and the head-end equipment transmits an AGC pilot signal. The AGC pilot signal generator sends out the various signals including
The bidirectional CATV repeater amplifies a level detector, a supervisory controller, an alarm data transmitter, a switch, a CATV, and the like.
A signal output variable amplifier, wherein the level detector detects a signal level of an unnecessary wave signal generated on the CATV transmission line, and outputs a detection level signal corresponding to the detection level. The magnitude of the detection level signal of the level detection unit is compared with a preset allowable level, and when it is determined that the magnitude of the detection level is equal to or higher than the allowable level, the gain control signal and the monitoring signal are compared. The alarm data sending unit sends the alarm data to the center station when receiving the monitor signal, and the switch outputs the CATV signal when receiving the gain control signal. For a variable amplifier, instead of the normal AGC gain control based on the level of the pilot signal,
The gain control signal is supplied, and the variable CATV signal output amplifier, when receiving the gain control signal, amplifies the CATV signal with a lower gain than the gain by the normal AGC gain control. Bidirectional CATV system. 2. A bidirectional system for transmitting a CATV signal and a pilot signal from a center station to a transmission line, connecting a transmission / reception device of a viewer to the transmission line, and performing bidirectional communication between the center station and the transmission / reception device. A relay amplification device inserted into the transmission line in a CATV system, comprising: a first input / output terminal, a first directional filter, a variable downstream amplifier, a downstream AGC section, an unnecessary signal extraction section, and a level detection section. A monitoring control unit, a switch, an alarm data transmission unit, an upstream variable amplifier, an upstream AGC unit, a second directional filter, and a second input / output terminal. A downstream input terminal and an upstream output terminal; the second input / output terminal is a downstream output terminal and an upstream input terminal; and the first directional filter is configured to perform the first input / output from the transmission line. Signal of the band received by the terminal ( Below, the) that downlink signal branch to the downlink variable amplifier, the first band of the signal transmitted from the output terminal to the transmission line (hereinafter,
An upstream signal) to the first input / output terminal, and the variable downstream amplifier amplifies a signal level of the downstream signal from the directional filter to a desired level; The downlink AGC section controls the gain of the downlink variable amplifier based on the level of the pilot signal, and the unnecessary signal extraction section selects only the unnecessary signal contained in the downlink signal. The level detector detects a signal level of the unnecessary wave signal included in the downlink signal that has passed through the unnecessary wave signal extraction unit, and the monitoring control unit includes: Comparing the detection level signal of the unnecessary wave signal from the level detection unit with an allowable level, and switching the gain control signal to the switch when the magnitude of the detection level is equal to or higher than the allowable level; The switching unit outputs the monitoring signal to the alarm data transmitting unit, and the switch receives the gain control signal from the monitoring control unit, and outputs the monitoring control unit more than the AGC signal of the downlink AGC unit. And the gain control signal of the monitor control unit controls the gain of the downlink variable amplifier according to the gain control signal. It sends alarm data to a center monitoring device provided in the center station using an upstream transmission band, and the variable upstream amplifier controls a signal level of the upstream signal from the directional filter to a desired level. The uplink AGC unit receives the pilot signal level from the downstream of the transmission path or the like, and adjusts the gain of the uplink variable amplifier. Wherein the second directional filter branches an upstream signal received from the transmission line to the second input / output terminal to the upstream variable amplifier, from the second input / output terminal A bidirectional CATV repeater / amplifier, wherein a downstream signal transmitted to the transmission path is coupled to the second input / output terminal.