JP2000050228A - Relay amplifier for two-way catv - Google Patents

Abstract

PROBLEM TO BE SOLVED: To quickly and automatically suppress increase in a confluent noise for each branch of a relay amplifier. SOLUTION: This relay amplifier is provided with noise detection circuits 9, 10 that detect noise at a lower band side of an incoming signal for each branch, BSWs 7, 8 that switch-control so as to intercept the incoming signal of each branch and an SMT 4 that sends/receives a monitor control signal to/from a center side. When, e.g. the noise detection circuit 9 detects abnormal noise, the circuit 9 outputs a switching control signal 102, the BSW 7 interrupts the incoming signal in this way to suppress a confluent noise at the center side from being increased. Furthermore, when the generating source of the confluent noise is known beforehand, the center side sends a control signal to the SMT 4 which outputs a remote switching control signal 103 to the BSW 4 and it forcibly interrupts the incoming signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a repeater amplifier for a bidirectional CATV, and more particularly to a bidirectional CTV with reduced upstream ingress noise.
The present invention relates to a relay amplifier for an ATV.

[0002]

2. Description of the Related Art In general, a bidirectional CATV system is constructed in a tree topology, a main trunk is extended with a center device as a head end, and a bidirectional relay amplifier is installed at every predetermined span. A plurality of branches or branch lines extend from the relay amplifier, and a subscriber terminal device is disposed at the branch terminal. In the downstream direction from the center device, a video signal such as TV is distributed to each subscriber terminal device using a high band. At the same time, in order to perform intercommunication between the subscriber terminal device and another subscriber terminal device, an upstream band (lower band from the subscriber terminal device to the center device) and a lower high band (center device → subscriber). Bidirectional service channels are provided in both directions (lower side of the higher band to the user terminal device).

[0003] In such a bidirectional CATV system, noise entering from a subscriber's house, a drop-in line, a relay amplifier, or the like is concentrated on the center side in the upstream band, and the inflowing noise is transmitted to the bidirectional service channel. There is a problem of deteriorating communication quality.

In order to suppress this upstream inflow noise, in a conventional bidirectional CATV system, a bridge amplifier gate switch (hereinafter referred to as BSW) for opening and closing an upstream relay circuit in a relay amplifier arranged at a branch point. ) And a status monitor for controlling the BSW in accordance with a control signal from a monitoring control device in the center device. The BSW is not used for a communication path in which bidirectional communication is not performed or where noise is abnormally large. It is opened to cut off the communication path and suppress ingress noise.

[0005] For example, FIG. 4 shows a relay amplifier disclosed in Japanese Utility Model Laid-Open Publication No. Hei 3-20552. FIG. 4 is a block diagram showing a conventional example. The bidirectional signal of the center terminal 100 is branched by a bidirectional filter 41 into a high-frequency down signal and a low-frequency up signal, and the high-frequency branch amplifier 42 and the low-frequency branch amplifier 43, respectively. And is amplified by The number of branches on the terminal side is four, and the downstream signal and the upstream signal are branched into four by the distributor 45 and the coupler 47, respectively. BSWs 8a to 8d are respectively inserted in the branch circuits of the upstream signal, and the bridge signal is opened and closed by a control signal received by the status monitor 44 from the center side.

That is, in order to suppress the ingress noise on the center side, the BSW of a branch circuit that is not performing communication or a branch circuit that generates abnormally high noise is operated to open the circuit. Although not shown, the upstream signal and the downstream signal of each branch circuit are combined by a bidirectional filter on the terminal side to become a bidirectional signal, which is input / output to a trunk line or a branch line on the terminal side.

Next, another conventional example is disclosed in Japanese Patent Laid-Open No. 6-8628.
FIG. 5 shows an example described in Japanese Unexamined Patent Application Publication No. 6-2006. FIG. 5 is a block diagram showing another conventional example. In this conventional example, the switch 59 corresponding to the BSW of the upstream branch transmission line in the relay amplifier 51 can be controlled to be opened and closed from the terminal device 52, thereby preventing upstream inflow noise mixed in from the terminal device side 52. is there. The relay amplifier 51 includes a directional coupler 53 that couples the downstream trunk line and the upstream trunk line, a downstream trunk amplifier 54 that amplifies the downstream signal, and a downstream branch line from the downstream trunk line. A splitter 55 for branching, a directional coupler 62 for connecting a downstream trunk line and an upstream trunk line, a downstream branch amplifier 63 for amplifying a downstream signal, and connecting an upstream branch line and a downstream branch line. Directional coupler 64 and a distributor 65 connected to the CATV line 100 of the branch transmission line.
And a distributor 61 for distributing the upstream signal on the downstream branch transmission path.
And a switch 59 which normally opens the upstream branch transmission line so as to be connectable and blocks all upstream signals including upstream ingress noise, and a band-pass filter 60 which extracts a switch control signal.
A detector 57 for detecting a switch control signal to open and close the switch 59, a coupler 56 for coupling the upstream branch transmission line to the upstream trunk transmission line, and an upstream amplifier 57 for amplifying the upstream signal. ing.

The subscriber terminal device 2 includes a distributor 68 for distributing an uplink signal and a downlink signal, a coupler 71 for coupling a switch control signal to the uplink signal, and modulating data into an uplink signal and converting the downlink signal into data. , A oscillating circuit 72 for oscillating a switch control signal of a fixed frequency, a tuner 67 for tuning up signals, a data output control to the tuner 67, and a CATV center (not shown). And a control unit 70 that manages and controls the entire subscriber terminal device 52 such as transmission / reception control.

Next, the operation will be described. The switch 59 of the relay amplifier 51 normally opens the upstream branch transmission line in order to prevent upstream ingress noise. Subscriber terminal 52
When the control unit 70 causes the oscillation circuit 72 to transmit a switch control signal of a fixed frequency to connect the upstream branch transmission line of the relay amplifier 51, the band-pass filter 60 of the relay amplifier 51 The switch 58 is extracted and the switch control signal is detected, and the switch 59 is output to the switch 59. As a result, the switch 59 is closed to connect the up-branch transmission line, and the repeater amplifier 51
, Data transmission to the CATV center becomes possible.

[0010]

As described above, in the conventional relay amplifier, the BSW is operated by the control signal from the center side or the terminal side in order to suppress the inflow noise. B to send the signal to
It is necessary to select SW. That is, it is relatively easy to specify a BSW in a branch circuit that is not performing bidirectional communication, but it is difficult to specify a BSW in a branch circuit that generates abnormal noise. For example, when one BSW is sequentially opened for all the BSWs at the center side, the degree of reduction of the ingress noise is large.
Although the SW is selected, there is a problem that this operation takes a very long time.

In addition, there is another problem that the transmission of the control signal is disturbed in a state where abnormal noise is generated, so that the BSW cannot operate normally.

In still another conventional example, when suppressing ingress noise, a switch control signal is transmitted from the terminal device, and the common branch circuit of each terminal device on the relay amplifier side is opened by the switch. There is a problem that the bidirectional communication of another terminal device that does not transmit the switch control signal is interrupted.

[0013]

SUMMARY OF THE INVENTION Bidirectional CATV of the present invention
The relay amplifier for use includes a first directional filter that branches the bidirectional signal on the center side into a high-frequency-side down signal and a low-frequency-side up signal, and a down-converter that amplifies the branched down signal. An amplifier, an upstream amplifier for amplifying the upstream signal, and a second directional filter for combining an output signal of the downstream amplifier and an input signal of the upstream amplifier to return a bidirectional signal And a distributor for branching the bidirectional signal of the second directional filter as a branch signal on a plurality of terminals, transmitting and receiving a monitoring control signal between the center or each terminal, and monitoring each unit. A status monitor unit (SMT) for performing control,
A plurality of bridger gate switches (BSW) for blocking or passing only the upstream signal of each of the branch signals by an open / close control signal; And a plurality of noise detection circuits for transmitting the opening / closing control signal to each of the corresponding BSWs at the same time and transmitting the opening / closing control signal to the center via the SMT at the same time.

Further, the SMT receives a remote opening / closing control signal transmitted from the center side and receives it from the BSW.
And when the BSW receives the remote open / close control signal, the BSW may operate prior to the open / close signal.

Further, the noise detection circuit converts the detected noise level into a data signal and transmits the data signal to the SMT.
The MT may transmit this data signal to the center side.

More specifically, the noise detection circuit inputs a part of the branch signal and amplifies the input signal, and an up signal band of the branch signal, that is, a low band from the output signal of the buffer amplifier. A band-pass filter (BPF) for extracting noise in a vacant band, an A / D converter for converting an output signal of the BFF into a digital signal,
The output signal of the converter is output as the data signal, and the switching control signal is output when the level of the noise processed and extracted exceeds the first reference value and the duration exceeds the second reference value. An arithmetic circuit may be provided.

More specifically, the BSW includes a high-pass filter (HPF) for blocking the upstream signal and passing the downstream signal, and a branch path for transmitting the branch signal when the switching control signal is received. A switch that removes the HPF when the HPF is inserted and does not receive the open / close control signal, and a priority circuit that operates the switch in a similar manner to the open / close control signal when the remote open / close control signal is received. May be provided.

Further, the arithmetic circuit may be capable of changing the first reference value and the second reference value.

Further, the PBF may include a plurality of BPFs having different extraction bands.

[0020]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a block diagram showing a configuration of a noise detection circuit in FIG. 1, and FIG. 3 is a block diagram showing a configuration of a BSW in FIG.

Referring to FIG. 1, first, the configuration of the relay amplifier of the present invention will be described. A transmission line (not shown) from a center device or a relay amplifier on the center side is connected to the center-side input / output terminal 13, and terminal-side branch terminals 14 and 15 are connected to a terminal device or a terminal-side relay amplifier. Are connected (not shown). In this embodiment, the number of branches on the terminal side is two.
Two cases are shown.

A directional filter 1 for branching a center-side bidirectional signal input / output to / from a center-side input / output terminal 13 into a high-frequency down signal and a low-frequency up signal; A directional filter 5 that combines the output signal of the down-amplifier 2 and the input signal of the up-amplifier 3 and returns a bidirectional signal; And a distributor 6 for branching the bidirectional signal of the directional filter 5 into two and outputting a branch signal to the terminal side branch terminals 14 and 15, and transmitting and receiving a supervisory control signal between the center side or each terminal side. A status monitor unit (SMT) 4 for monitoring and controlling, and two bridger gate switches (BSW) 7 and 8 for blocking or passing only the upstream signal of each branch signal by opening / closing control signals 102 and 105.
And splitters 11 and 12 for splitting the upstream signal of each split signal
When the noise in the band of the upstream signal branched by the branching units 11 and 12, ie, the low band, is detected and the noise equal to or more than the reference value is detected, the switching control signals 102 and 105 are sent to the corresponding BSWs 7 and 8.
Is transmitted to the SMT 4 at the same time as the opening / closing control signals 102, 1
And the noise detection circuits 9 and 10 for transmitting the signal 05.

The SMT 4 receives the remote opening / closing control signals 103 and 105 transmitted from the center side and sends them to the BSWs 7 and 8. The BSWs 7 and 8 open / close when the remote opening / closing control signals 103 and 104 are received. Control signal 10
It operates prior to 2,105.

The noise detection circuit 9 converts the detected noise into data signals 101 and 106 and transmits the data signals to the SMT 4,
The SMT 4 transmits the data signals 101 and 106 to the center.

Next, the internal configuration of the noise detection circuit 9 will be described with reference to FIG. A buffer amplifier 91 which receives and amplifies a part of the branch signal from the branching unit 11 and an upstream signal band of the branch signal, that is, a free band of a low band (for example, an upstream signal band of 10 to 50 M
A band-pass filter (BPF) 92 for extracting noise in the vicinity of 42 MHz in the case of Hz, an A / D converter 93 for converting an output signal of the BFF 92 into a digital signal,
The output signal of the A / D converter 93 is output as the data signal 101, and at the same time, when the level of the noise processed and extracted exceeds the first reference value and its duration exceeds the second reference value, the switching control signal Arithmetic circuit 94 that outputs 102
It consists of:

Referring to FIG. 3, the internal configuration of the BSW 7 will be described. A high-pass filter (HPF) 71 for blocking an upstream signal of the branch signal and passing a downstream signal;
When the switch control signal 102 is received, the HPF 71 is inserted into the branch path for transmitting the branch signal, and when the switch control signal 102 is not received, the switch 72 that removes the HPF 71,
When a remote opening / closing control signal 102 is received, a priority circuit 73 is provided to prioritize the opening / closing control signal 102 and operate the switch 72 similarly.

Next, the operation of FIG. 1 will be described. The high-frequency downstream signal of the bidirectional signal applied to the center-side input / output terminal 13 is branched by the directional filter 1 and the downstream amplifier 2
, And is combined with the upstream signal again by the bidirectional filter 5 to become a bidirectional signal. , 15 and transmitted to a terminal device or a downstream relay amplifier.

On the other hand, the low-frequency upstream signal of the bidirectional signal applied to the terminal-side branch terminals 14 and 15 respectively
At 1 and 12, a part is branched for noise detection and input to BSWs 7 and 8. Here, after the upstream signal is subjected to the switch control of blocking or passing, the two upstream signals (each having a different carrier frequency) become one upstream signal in the distributor 6 in the distributor 6, and then the directional filter 5. The signal is branched and amplified by the upstream amplifier. The signal is again converted into a bidirectional signal by the bidirectional filter 1, and is output to the center side input / output terminal 13 and transmitted to the center side.

The upstream signals branched by the distributors 11 and 12 are subjected to noise detection by noise detection circuits 9 and 10. The noise detection circuits 9 and 10 are 42 MHz when the free band on the high frequency side of the upstream signal, for example, the band of the upstream signal is 10 to 50 MHz.
When the nearby noise is extracted by a BPF and converted into a digital signal, the extracted noise level exceeds a predetermined first reference value and the duration exceeds a predetermined second reference value. Processing for outputting 102 and 105 is performed. Since the first and second reference values are set to the upper limit of the normal noise amount, the open / close control signals 102 and 105 are output when the noise amount of the branch path becomes abnormally large.

Data signals 101 and 10 indicating the amount of noise
6 is output. These data signals 101 and 106 are STM
The signal is transmitted to the center side via the line 4, and the center side can monitor this to monitor the noise state of the branch path in each relay amplifier in a concentrated manner.

The BSWs 7 and 8 normally maintain the passing state with respect to the bidirectional signal on the branch path.
The PF is inserted and the upstream signal is cut off. That is, when the noise of the branch becomes abnormally large, the upstream signal of the branch is cut off, this abnormal noise is prevented from being transmitted to the center side, and the ingress noise is automatically increased. Restrained. This opening / closing control signal is also transmitted to the center side via the STM4 at the same time.
It is possible to collectively grasp the operation state of W.

Also, when the center does not perform bidirectional communication, or when the cause of the increase in ingress noise is known in advance,
When the BSW of the branch road is to be shut off in advance, for example, when the BSW 7 is to be shut off, the remote control signal is transmitted to the SMT 4, and the SMT 4 sends the remote open / close control signal 103 to the BSW 7. BSW7
Is forcibly brought into the shut-off state prior to the opening / closing control signal 102. As a result, ingress noise can be reduced.

The remote opening / closing control signals 103, 1
04 and the data signal 10 indicating the amount of noise described above.
If the functions relating to 1 and 106 are unnecessary, they may be deleted in advance.

Further, the first reference value and the second reference value of the noise detection circuits 9 and 10 may be variably set, so that the allowable ingress noise amount that differs depending on the system may be set. It can be easily handled.

Further, the BPF of the noise detection circuits 9 and 10 is
A plurality of BPFs having different extraction bands may be used, and in this case, the noise detection accuracy can be further improved.

[0036]

As described above, the bidirectional CA according to the present invention is used.
The TV relay amplifier detects abnormal noise in the upstream signal band for each branch, and cuts off the upstream signal of the corresponding branch by this detection signal. Has the effect of suppressing. Further, since the abnormal noise of each branch is detected and immediately shut off, there is an effect that the occurrence of the abnormal noise in one branch can prevent the entire system from being disrupted. Furthermore, since the upstream signal is blocked for each branch, there is an effect that the other branches are not affected.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a block diagram of a noise detection circuit in FIG. 1;

FIG. 3 is a block diagram of a BSW in FIG. 1;

FIG. 4 is a block diagram showing a configuration of a conventional example.

FIG. 5 is a block diagram showing a configuration of another conventional example.

[Explanation of symbols]

 1,5 Directional filter 2 Down-amplifier 3 Up-amplifier 4 Status monitor unit (SMT) 6 Distributor 7 BSW (BSW) 9,10 Noise detection circuit 91 Buffer amplifier 92 BPF 93 A / D converter 94 Operation circuit 71 HPF 72 Switch 73 priority circuit

Continued on the front page F term (reference) 5C064 BA01 BB05 BC12 BC13 BC14 BD01 BD07 5J069 AA01 AA54 AA55 AC01 BC04 CA41 CA51 CA89 FA17 FA18 HA38 KA34 KA42 KA44 KA46 KA55 KA68 KC06 KC07 MA10 MA11 MA14 MA20 SA08 TA01K03

Claims (7)

[Claims] 1. A first directional filter for branching a bidirectional signal on a center side into a high-frequency-side down signal and a low-frequency-side up signal, and a downstream increase signal for amplifying the branched down signal. An amplifier, an amplifier for amplifying the upstream signal, and a second directional filter for combining an output signal of the downstream amplifier and an input signal of the upstream amplifier to return to a bidirectional signal And the second
And a status monitor for transmitting and receiving a supervisory control signal between the center side or each terminal side and supervising and controlling each unit. A unit (SMT), a plurality of bridger gate switches (BSW) for blocking or passing only the upstream signal of each of the branch signals by an open / close control signal, and detecting an upstream signal band of each of the branch signals, that is, a noise in a low band. And a plurality of noise detection circuits for transmitting the open / close control signal to each of the corresponding BSWs when the noise equal to or more than the reference value is detected, and for simultaneously transmitting the open / close control signal to the center via the SMT. A relay amplifier for bidirectional CATV, characterized by the following. 2. The SMT receives a remote opening / closing control signal transmitted from the center side and sends it to the BSW. When the BSW receives the remote opening / closing control signal, the BSW takes precedence over the opening / closing signal. 2. The relay amplifier for bidirectional CATV according to claim 1, which performs opening and closing operations. 3. The noise detection circuit converts the detected noise level into a data signal and transmits the data signal to the SMT.
3. The relay amplifier for bidirectional CATV according to claim 1, wherein said data signal is transmitted to said center side. 4. The noise detection circuit according to claim 1, further comprising: a buffer amplifier for inputting a part of the branch signal and amplifying the input signal; A band-pass filter (BPF) for extracting noise, an A / D converter for converting an output signal of the BFF into a digital signal, and performing data processing simultaneously with outputting the output signal of the A / D converter as the data signal. 4. An operation circuit for outputting the switching control signal when the level of the extracted noise exceeds a first reference value and its duration exceeds a second reference value. Bidirectional CATV relay amplifier. 5. A high-pass filter (HPF) for blocking the upstream signal and passing the downstream signal.
When the switch control signal is received, the HPF is inserted into a branch path for transmitting the branch signal, and when the switch control signal is not received, the switch that removes the HPF and the remote switch control signal are received. 5. A relay amplifier for a bidirectional CATV according to claim 2, further comprising: a priority circuit which gives priority to said opening / closing control signal and operates said switch in a similar manner. 6. The relay amplifier for bidirectional CATV according to claim 4, wherein said arithmetic circuit is capable of changing said first reference value and said second reference value. 7. The PBF includes a plurality of Bs having different extraction bands.
7. The method according to claim 4, which is made of PF.
The relay amplifier for two-way CATV as described.