JP2000091960A - Method for detecting noise mixed position, its device and its system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To quickly detect a noise mixed position by having only to place a noise detector for detecting a mixed noise from an outgoing signal to a relay amplifier. SOLUTION: A noise detector 6 is disposed to a transmission line 2 at an upper-stream side of each relay amplifier 4 in the system via a branching filter 7, respectively, the noise detector 6 detects a noise signal mixed in a stream of an outgoing signal from a center station side to a subscriber station side to detect a noise mixed position quickly. Thus, the noise mixed position is quickly detected and the device is made small.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and a device for detecting a noise mixing point for detecting a mixing point of ingress noise mixed in a transmission line, for example, an ingress noise of a CATV system.

[0002]

2. Description of the Related Art Conventionally, for example, in this type of detection device, a gate switch provided in a relay amplifier is turned on / off to detect whether or not ingress noise is mixed, thereby forming a tree-like structure. By partially closing the upstream transmission path, the part was separated from the CATV system to detect the mixing point of the ingress noise. However, in this system,
Since the upstream transmission line was partially closed, the subscriber station connected to the upstream transmission line had troubles such as interruption of the communication service, and could not quickly detect the location where noise was mixed. .

In order to improve such a situation, for example, Japanese Patent Application No. 8-339506 (Japanese Unexamined Patent Application Publication No.
No. 178628), a reference voltage for detecting noise is fixed beforehand when the device is installed, and based on the reference voltage, for example, a guard band which is not used for normal transmission. In some cases, the noise in the frequency band is detected to specify the noise mixing section.
In such a device, the position for introducing noise is the upstream signal input terminal.

[0004] For example, as shown in FIG. 4, a trunk branch amplifier (TBA) 4 or a branch that exists on a trunk transmission line 2 connected to a center station 1 or on a branch transmission line 3 and can perform a plurality of branches. When the noise detection device 6 is used in a system having the amplifier (BA) 5, each amplifier (hereinafter, referred to as “amplifier”)
It is necessary to connect a noise detection device 6 for detecting a noise signal from the upstream signal to the input terminals 4 and 5, respectively. In the figure, EA indicates an extension amplifier.

[0005]

However, in the case of an amplifier such as a TBA4 having a plurality of terminals of an amplifier, as shown in FIG. 7, the signal lines 8 must be connected to the status monitor 25 from each of the noise detection devices 6, respectively. Since a plurality of noise detection devices are connected, a large installation space is required. For example, when the noise detection device is installed in a narrow space such as a pole such as a telephone pole, the space occupied by the noise detection device becomes large, and the installation becomes difficult. was there. In FIG. 5, the amplifier 4 includes demultiplexing filters 20 and 21 including a high-pass filter and a low-pass filter,
An amplifier 2 connected between the demultiplexing filters 20 and 21
2, 23 and a branching device 2 connected to a transmission line for upstream transmission
4, a status monitor 25 for monitoring the state of temperature, current consumption, and noise and transmitting the information to the center station;
It comprises a demultiplexing filter 28 connected to transmission lines for downlink and uplink transmission via splitters 26 and 27, and a distributor 29 connected to the demultiplexing filter 28.

Each of the noise detectors 6 obtains power from the amplifier 4. The power consumption of the amplifier 4 is set to a predetermined amount in advance. When power is supplied from the amplifier 4 to the noise detection device 6, the power consumption used by each of the noise detection devices 6 increases, making it difficult to secure the power consumption used by the amplifier 4.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and a noise detection device for detecting noise contamination is used as a relay amplifier.
It is an object of the present invention to provide a method of detecting a noise-containing portion, which can quickly detect a noise-containing portion only by arranging a table, a device and a system thereof. Another object of the present invention is to provide a method for detecting a noise-containing portion, which can reduce the size of the device.
It is to provide the device and the system.

[0008]

In order to achieve the above object, according to the present invention, among noise signals mixed in a transmission line connecting a center station and a plurality of subscriber stations, a frequency other than a frequency band of a main signal is used. A noise-containing portion detection method for detecting a noise-containing portion based on the detection result, wherein the noise-containing portion detection device comprises: There is provided a method for detecting a noise-containing portion, which detects the noise signal mixed in a downlink signal transmitted to a station.

That is, by detecting a guard band signal that is not used for normal transmission by the noise mixing point detecting device, the center station can quickly reduce noise mixed in the downstream signal without interrupting communication service in each section. Detect the signal mixing section. Further, in claim 2, the center station and the plurality of subscriber stations are connected via a transmission line and a plurality of relay amplifiers existing on the transmission line, and among the noise signals mixed in the transmission line, the main signal A noise-mixed point detection device that detects a noise signal having a frequency other than the frequency band,
A noise mixing unit that is provided in the relay amplifier and that includes a branching unit that branches a downstream signal on the transmission path and a noise detection unit that includes a noise detection device that detects the noise signal from the downstream signal branched by the branching unit; A location detection device is provided.

That is, one noise detection device is disposed upstream of the relay amplifier, and the noise detection device detects a noise signal mixed in a downstream signal transmitted from the center station to the subscriber station. , Where noise is mixed. Claim 3
Then, the branching means, the noise detection means and the relay amplifier,
The unit is provided in the same unit, and the branching of the signal on the transmission line, noise detection, and relay amplification are performed by the unit, so that the size of the device is reduced.

According to a fourth aspect of the present invention, the center station and the plurality of subscriber stations are connected via a transmission line and a plurality of relay amplifiers existing on the transmission line, and among the noise signals mixed in the transmission line, A noise mixing point detection device that detects a noise signal having a frequency other than the frequency band of the main signal, the connector including a connector, connected to at least the relay amplifier via the connector, and a signal on the transmission path. By providing a branching means for branching and a noise detecting means for detecting the noise signal mixed with the downstream signal branched from the branching means, only one noise detecting device for detecting noise mixing is arranged in the relay amplifier. To quickly detect noise-mixed points.

According to a fifth aspect of the present invention, of the noise signals mixed in the transmission line connecting the center station and the plurality of subscriber stations,
A noise signal having a frequency other than the frequency band of the main signal,
A noise-contaminated point detection system that detects a noise-contaminated point based on the detection result by the noise-contaminated point detection device, wherein the noise-contaminated point detection device includes a downlink transmitted from the center station to a subscriber station. By detecting the noise signal mixed in the signal, the center station quickly detects the mixed section of the noise signal mixed in the downstream signal without interrupting the communication service in each section.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for detecting a noise-containing portion, its device and its system according to the present invention will be described with reference to FIGS. In the following drawings, the same components as those in FIGS. 4 and 5 are denoted by the same reference numerals for convenience of explanation.

FIG. 1 is a configuration diagram showing the configuration of a CATV system according to the present invention. In the figure, bidirectional CATV
The system includes, for example, a trunk transmission line 2 configured in a tree shape.
And a center station 1 and a plurality of subscriber stations 8 through a branch transmission line 3.
Are connected, and the center station 1 and the subscriber station 8 communicate with each other. Such a bidirectional CATV system distributes a broadcast wave received from the antenna 30 to each subscriber station 8 via a downlink and converts a signal transmitted from each subscriber station 8 via an uplink, Compensates for the attenuation of signals transmitted via the center station 1 for transmitting to the down-link and the like, and the transmission lines (for example, coaxial cables or optical fibers) 2 and 3 connecting each subscriber station 8 and the center station 1. And a tap-off 9 for distributing a signal to each subscriber station 8, a protector 10 for electrically protecting each subscriber station 8, and the like. 8a is a two-way home terminal of the subscriber station 8.

For example, the transmission frequency band used for the uplink of the 750 MHz CATV system is 10 to 50 MHz.
z, transmission frequency band used for downlink is 70-75
0 MHz. For example, when information is transmitted from a certain subscriber station 8 to another subscriber station such as inter-subscriber communication, a signal transmitted from the certain subscriber station 8 using an uplink is transmitted to, for example, the center station 1 by a downlink. And then retransmitted to other subscriber stations.

Since the wiring forms of the transmission lines 2 and 3 are tree-shaped, noise that has entered the end of the transmission line or into the middle of the transmission line is at the branch point of the transmission line (the branch point of the amplifiers 4 and 5 and the tap-off 9). As the noise merges and further approaches the center station 1, the addition of noise in the transmission band used in the uplink at each branch point is repeated, and all the noise that has entered the uplink and the thermal noise of the amplifiers 4 and 5 are reduced. They will gather at the center station 1. This noise is generally called ingress noise. As described above, there are various types of noise mixed into the transmission line from the outside, and when noise of a certain frequency jumps through a crack generated in a cable or a loose connector, noise radio waves present at other frequencies also It will jump not only to the above-mentioned up-link but also to the down-link.

Therefore, the present invention uses another frequency band other than the transmission frequency actually used for communication, detects the presence or absence of noise jumping into the downlink, and notifies the center station 1 or the like of a predetermined point. A noise detection device 6 for detecting such noise is connected to each of the relay amplifiers 4 and 5. Since the noise detection device 6 of this embodiment has the same configuration as that of the noise detection device 6 connected to the relay amplifiers 4 and 5, only the device connected to the relay amplifier 4 that is a TBA will be described here.

As shown in the first embodiment of FIG. 2, the noise detecting device 6 constituting the noise detecting means of the present invention is the same as the first embodiment shown in FIG. The band-pass filter circuit 11, the amplifier circuit 12, and the detection circuit 13 connected to the branching unit 7 constituting the branching unit compare the voltage level of the reference voltage, which is a preset reference level, with the voltage level of the input voltage. It comprises a voltage comparison circuit 14 and a voltage holding circuit 15 connected to a status monitor 25 described later, and outputs information on the detected noise to the status monitor 25. It should be noted that the relay amplifier 4 includes the demultiplexing filters 20, 21, and 28 and the amplifier 2 as in FIG.
2, 23, branching units 24, 26, 27, a status monitor 25, and a distributor 29. The noise detection device 6 and the splitter 7 can be built in or external to the same unit of the relay amplifier 4 as shown in FIG.

Normally, in this CATV system, a guard band (50 to 50) which is a frequency between upstream transmission and downstream transmission is used.
The signal within 70 MHz is removed by the operation of the demultiplexing filters 20 and 21 and is not transmitted. Therefore, in this embodiment, a signal (noise) of a guard band of 50 to 70 MHz is used.
Is detected by the band-pass filter circuit 11 of the noise detection device 6, thereby enabling the center station 1 to specify the noise mixing section.

As shown in FIG. 1, the center station 1 has a head-end device 31 connected to the main transmission line 2 and a control device 32 for monitoring and controlling noise.
Reference numeral 2 denotes a host computer, a polling machine, and a transceiver (not shown). The center station 1 calls the status monitor 25 of each of the relay amplifiers 4 and 5 at time intervals set by the polling method as in the related art, and The information of various states including is taken in. Center station 1
Can determine the location where noise is mixed based on this information.

That is, as shown in FIG. 2, the guard band signal jumped onto the trunk transmission line 2 for downstream transmission is branched by the branching unit 7, passes through the band-pass filter circuit 11, and passes through the amplification circuit. Input to 12. The signal is amplified by the amplifier circuit 12 and further detected by the detection circuit 13 to be applied as a DC voltage to the voltage comparison circuit 14.

This DC voltage is compared with a reference voltage set in advance by a voltage comparison circuit 14. Here, when the DC voltage is higher than the reference voltage, that is, when the level of noise to be detected is strong, the output voltage level of the voltage comparison circuit 14 changes from a low level to a high level and is output to the voltage holding circuit 15. . Since the noise is not always present, the voltage holding circuit 15 holds the output voltage level from the voltage comparison circuit 14 for a certain time. The status monitor 25 detects the presence or absence of noise contamination by monitoring the output state from the connected voltage holding circuit 15,
The center station 1 detects a noise mixing section from the information of the status monitor 25 (output state and identification information of each relay amplifier).

For example, if it is assumed that a cable crack is present at point g between a and b of the transmission line 2 and a noise signal over a wide band including around 60 MHz is mixed therefrom, the downstream side of FIG. In the noise detector 6 (middle, right of point g),
The noise can be detected. That is, this noise is blocked by the demultiplexing filters 20 and 21 in the relay amplifier 4 to which the noise detection device 6 is connected, and does not exist in the next-stage relay amplifier, but is present on the downstream side of the point g. 6 is detected, and the output state is held in the voltage holding circuit 15.

The output state is stored in the voltage holding circuit 15.
Monitoring and collecting by the status monitor 25 connected to
The data is transmitted to the center station 1. Based on the transmitted information, the control device 32 of the center station 1 can detect that the noise mixing section is between a and b in the section in the CATV system. As described above, in this embodiment, the guard band signal not used for normal transmission is detected, the detection result is collected by the status monitor, and the polling performed between the center station and the relay amplifier is performed similarly to the related art. Since the above information is transmitted by using the method, the center station can quickly detect a mixed section of a noise signal mixed in a downstream signal flow without interrupting communication service in each section.

Further, in the present embodiment, since noise contamination is detected from the flow of the downstream signal, it is possible to realize a configuration in which one noise detection device is arranged in the relay amplifier, thereby reducing the size of the device and simplifying the internal configuration of the device. Can be planned. In this embodiment, the guard band (50 to 70 MHz) is used as the frequency of noise detection. However, in this frequency band, there are few signals to be noise, and it is considered that versatility in practical use is poor. Has proposed a system in which a guard band is set to 70 to 90 MHz. In this case, it is possible to monitor FM radio broadcasting existing in the guard band as a noise monitoring target.

Further, in this embodiment, frequencies not used for normal transmission, that is, neither for uplink transmission nor for downlink transmission, include frequency bands other than the guard band. For example, a frequency band of 750 MHz or more in a 750 MHz CATV system and a frequency band of 450 MHz or more in a 450 MHz CATV system correspond to the frequency. In the former, a UHF television broadcast signal can be set as a target, and in the latter, a mobile communication signal can be set as a target of the noise monitoring. . Furthermore, the frequency bands of 10 MHz or less in these systems are also included in frequencies not used for normal transmission, and short-wave broadcasting, amateur radio, medium-wave broadcasting, and the like can be targets for noise monitoring.

Further, in this embodiment, the case where noise is mixed in the main line has been described. However, the present invention is not limited to this, and a device comprising a noise detection device, a demultiplexing filter and a status monitor is connected to the branch transmission line 3. Only one relay amplifier (BA) 5, extension amplifier (EA), tap-off of a drop-in line, or a protector can be built in or externally attached to the same unit. In this case, it is possible to detect a further subdivided noise mixing section.

In addition, the existing relay amplifier generally does not include an element (branch) that branches from the transmission line therein. The arrangement on the road 2 is almost impossible in consideration of the place where the relay amplifier is installed. Therefore, when the noise detection device is installed in an existing relay amplifier, for example, as shown in FIG. 3, the branching device 37 that forms the branching means of the present invention having the connectors 35 and 36 that form the connector portion of the present invention. Is coupled between the relay amplifier 4 and the trunk transmission line 2, and the branch line (coaxial cable or optical fiber) 38 branched from the trunk transmission line 2 is connected to the noise detection device 6 built in the relay amplifier 4. It is desirable to configure as follows.

Thus, in the configuration shown in FIG. 3, the trunk line and the branching device, and the branching device and the relay amplifier can be easily connected through the respective connectors, and the noise detection device arranged in the relay amplifier can be easily connected. Since the branched down signal can be supplied, also in the present embodiment, the mixed section of the noise signal mixed in the flow of the down signal can be detected quickly. Also,
Also in the configuration shown in FIG. 3, since one noise detection device for detecting noise contamination from the flow of the downstream signal is arranged in the relay amplifier, the size of the device can be reduced.

Although the apparatus of this embodiment has been described with respect to a case where a noise detection device is built in a relay amplifier of a main transmission line, the present invention is not limited to this, and it is possible to attach an external device. It can be built in or externally attached to the same unit such as a relay amplifier (BA), an extension amplifier (EA), a tap-off of a drop-in line, and a protector in a branch transmission line.

The present invention is not limited to these embodiments, and various modifications can be made without departing from the gist of the present invention. For example, since the noise signal also exists in a bus-like or star-like transmission line, the present invention is applied to a system using the bus-like or star-like transmission line, for example, a LAN system. It is possible.

[0032]

As described above, according to the present invention, a noise signal mixed in a transmission line between a center station and a plurality of subscriber stations is detected. A branching means for branching the signal; and noise detecting means for detecting a noise signal having a frequency other than the frequency band of the main signal mixed into the downstream signal branched by the branching means. The noise signal is transmitted from the center station to the subscriber station. Since the noise signal mixed with the downstream signal is detected, the noise mixing portion can be quickly detected and the device can be miniaturized simply by arranging one noise detection device for detecting the noise mixing in the relay amplifier. Can be.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a configuration of a CATV system according to the present invention.

FIG. 2 is a diagram illustrating a first example of the relay amplifier and the noise detection device illustrated in FIG. 1;
FIG. 3 is a block diagram illustrating a configuration of an example.

FIG. 3 is a block diagram showing a schematic configuration of the second embodiment.

FIG. 4 is a configuration diagram showing a configuration of a conventional CATV system.

5 is a block diagram showing a configuration of the relay amplifier and the noise detection device shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Center station 2 Trunk transmission line 3 Branch transmission line 4,5 Relay amplifier 6 Noise detection device 7,24,26,27,37 Branch device 8 Subscriber station 8a Subscriber station bidirectional home terminal 9 Tap-off 10 Security device 11 band Pass filter circuit 12 Amplifier circuit 13 Detection circuit 14 Voltage comparison circuit 15 Voltage holding circuit 20, 21, 28 Demultiplexing filter 22, 23 Amplifier 25 Status monitor 29 Distributor 30 Antenna 31 Head end device 32 Control device 35, 36 Connector 38 Branch line

Claims (5)

[Claims] 1. A noise signal having a frequency other than the frequency band of a main signal among noise signals mixed in a transmission line connecting a center station and a plurality of subscriber stations is detected by a noise mixing point detecting device. A method for detecting a noise-containing portion based on the detection result, wherein the noise-containing portion detection device detects the noise signal mixed in a downlink signal transmitted from the center station to a subscriber station. A method for detecting a noise-containing part. 2. A center station and a plurality of subscriber stations are connected via a transmission line and a plurality of relay amplifiers existing on the transmission line, and a frequency band of a main signal among noise signals mixed in the transmission line. A noise mixing point detecting device that detects a noise signal having a frequency other than the above, which is disposed in the relay amplifier, a branching unit that branches a downlink signal on the transmission path, and a branch signal that is branched by the branching unit. An apparatus for detecting a noise-containing portion, comprising: a noise detection unit configured to detect the noise signal. 3. The apparatus according to claim 2, wherein the branching unit, the noise detecting unit, and the relay amplifier are disposed in the same unit, and the unit performs the branching, noise detection, and relay amplification of the signal on the transmission line. Item 3. The noise-mixed point detecting device according to Item 2. 4. A center station and a plurality of subscriber stations are connected via a transmission line and a plurality of relay amplifiers existing on the transmission line, and a frequency band of a main signal among noise signals mixed in the transmission line. A noise mixing point detecting device for detecting a noise signal having a frequency other than the above, comprising a connector portion, connected to at least the relay amplifier via the connector portion, and branching means for branching the signal on the transmission line. And a noise detecting means for detecting the noise signal mixed into the downstream signal branched from the branching means. 5. A noise signal having a frequency other than the frequency band of a main signal among noise signals mixed in a transmission line connecting a center station and a plurality of subscriber stations is detected by a noise mixing point detecting device, A noise contamination point detection system that detects a noise contamination point based on the detection result, wherein the noise contamination point detection device detects the noise signal mixed in a downlink signal transmitted from the center station to a subscriber station. And a noise detection part detection system.