JPH11355739A - Two-way amplifier for catv - Google Patents

Abstract

PROBLEM TO BE SOLVED: To set a signal sent in 2-way through a cable to a proper level, to reduce power consumption and to prevent production of noise. SOLUTION: In the case of needing amplification of an outgoing signal, an outgoing amplifier circuit 34 and a power supply 50 are turned on by switching an outgoing interlocking switch 52. In the case that amplification of the outgoing signal is not required but the outgoing signal passes as it is, an outgoing path circuit 36 is turned on to turn off the power supply 50. In the case of stopping transmission of the outgoing signal, an outgoing OFF circuit 38 is turned on to turn off the power supply 50. Conversely, in the case of needing amplification of the incoming signal, an incoming interlocking switch 54 is switched to turn on an incoming amplifier circuit 44 and the power supply 50. In the case that the amplification of the incoming signal is not required but the incoming signal passes as it is, an incoming path circuit 46 is turned on to turn off the power supply 50. In the case of stopping the transmission of the incoming signal, an incoming OFF circuit 48 is turned on to turn off the power supply 50.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CATV bidirectional amplifier, and more particularly, to a unidirectional amplifier circuit for amplifying a unidirectional signal in a cable through which a bidirectional CATV signal is transmitted, and a bidirectional amplifier circuit. The present invention relates to a CATV bi-directional amplifier including a two-way amplifier for amplifying a signal.

[0002]

2. Description of the Related Art In recent years, a CATV (Community Antenna) that distributes television broadcasting and various information to television receivers of subscriber households using a cable such as a coaxial cable or an optical fiber.
nna Television (Cable Television) service is provided. This CATV was initially performed to eliminate the difficult viewing area of television broadcasting, but recently, in particular, in order to establish uniqueness by taking advantage of being a wired media, the CATV system has a bidirectional function ( Two Way Capabi
lity) so that information can be sent from the viewer side as well. In this type of CATV system, for example, a center, which is a broadcasting station, and a terminal of a subscribing household are connected via a cable, and television broadcasting and various kinds of information can be transmitted and received in both directions. However, various signals transmitted through this cable have a large amount of attenuation due to cable loss, distribution loss, coupling loss, or the like. If the signal level is extremely reduced, signal transmission cannot be performed. For this reason, conventionally, a signal level required for transmission was maintained by inserting a bidirectional amplifier as shown in FIG. 4 in the middle of a cable and amplifying the signal. FIG. 4 is a diagram showing a circuit configuration example of a conventional bidirectional amplifier for CATV. As shown in FIG. 4, a bidirectional amplifier 60 is arranged in the middle of the cable connecting the center side and the terminal side. A signal (downstream signal) from the center side of the bidirectional amplifier 60 is input to the input / output terminal 62, divided by the duplexer 64, amplified by the amplifier circuit 66, and again sent to the terminal via the duplexer 68. The amplified downstream signal is output from the input / output terminal 70 on the side. At this time, if the signal level amplified by the amplifier circuit 66 becomes too high,
The signal level is adjusted by attaching an external attenuator (attenuator) 72 as shown in FIG. On the other hand, a signal (uplink signal) from the terminal side passes through a path reverse to the above-described downlink signal, and is input to the input / output terminal 70 and is input to the duplexer 6.
8 and amplified by the amplifier circuit 74.
The amplified upstream signal is output from the input / output terminal 62 on the center side via the terminal 4. Although not shown in FIG. 4, some conventional bidirectional amplifiers have an amplification operation on / off function capable of switching whether to amplify a downstream signal or an upstream signal. When the amplifier with the amplification operation on / off function is selected to be off, the input and the output are connected to the terminus so as to have the rated impedance.

[0003]

However, in such a conventional bidirectional amplifier for CATV, as shown in FIG. 4, when the signal level becomes too large by performing the amplifying operation, the attenuator is attenuated. Although the signal level was adjusted by lowering the signal level by adding 72, the signal level of both the downstream and upstream signals was attenuated by the added attenuator 72 in the bidirectional amplifier, so the signal level was attenuated more than necessary. There was a problem that it would. In the case where the signal level is attenuated by the built-in attenuators 76, 78, 80, and 82 shown in FIG. 4 above the gain of the amplifier circuits 66 and 74, the bidirectional amplifier 60 itself becomes unnecessary. Also, in the amplifier with the above-described amplification operation on / off function, if the amplification operation is turned off when the input signal level is sufficiently large to amplify the signal, the signal level is extremely reduced (for example, 50dB
As a result, there is a problem that signal transmission cannot be performed. Further, in the amplifier having the amplification operation on / off function, even if the amplification operation is switched from the on state to the off state, the operating power of the amplifier that has been supplied to the amplification circuit is continuously supplied. There is a problem that power is wasted unnecessarily and noise is generated from the amplifier. The present invention has been made in view of the problems of the related art, and an object of the present invention is to correct an appropriate signal level so as to compensate for transmission loss of a signal transmitted bidirectionally via a cable, CA that can eliminate wasteful power consumption and prevent generation of noise
It is to provide a bidirectional amplifier for TV.

[0004]

According to a first aspect of the present invention, there is provided a one-way cable which is provided in the middle of a cable through which a CATV signal is transmitted bidirectionally and amplifies a one-way signal attenuated during signal transmission. In a CATV bidirectional amplifier having an amplifying circuit and a bidirectional amplifier circuit for amplifying a bidirectional signal attenuated during signal transmission, a unidirectional path for passing the unidirectional signal when amplification of the unidirectional signal is unnecessary. A circuit, a one-way interlocking switch for switching on and off a power supply for amplification supplied to the one-way amplifier circuit while switching and connecting the one-way amplifier circuit and the one-way path circuit; When the amplification is unnecessary, the other-direction path circuit that passes the other-direction signal, the other-direction amplification circuit and the other-direction path circuit are switched and connected, and an additional signal supplied to the other-direction amplification circuit is provided. And a switch for turning on / off the power supply for the other direction. When signal amplification in one direction or the other direction is required, the signal is switched to the amplifier circuit in that direction and the power supply for amplification is turned on. If
The switching to the path circuit in this direction is performed, and the power supply for amplification is turned off. According to this, in addition to the one-way amplification circuit and the other-direction amplification circuit for amplifying the signal transmitted in both directions via the cable, a one-way path circuit for passing each signal as it is when signal amplification is unnecessary. And an other direction path circuit. And
If one-way signal amplification is required, switch to the one-way amplifier circuit using a one-way interlock switch and turn on the power supply for amplification.If one-way signal amplification is not required, switch to a one-way path circuit. Turn off the power supply for amplification. If amplification of the other direction signal is necessary, switch to the other direction amplification circuit using the other direction interlocking switch and turn on the power supply for amplification.If amplification of the other direction signal is not necessary, connect to the other direction path circuit. Switch and turn off the power supply for amplification. For this reason, it is possible to select whether to amplify or pass the signal as it is in accordance with the necessity of amplifying the signal transmitted in one direction and the other direction, and to turn off the amplifying power supply when the signal amplification is not necessary, thereby consuming the amplifier. Power and noise generation can be reduced.

[0005] Further, the invention according to claim 2 is based on claim 1.
In the CATV bidirectional amplifier according to the above, a one-way OFF circuit that stops signal transmission of the one-way signal when not using the one-way signal, and performs signal transmission of the other-direction signal when not using the other-way signal When the signal transmission in one direction or the other direction is stopped, the circuit is switched to the OFF circuit in the direction using a link switch in the direction, and the power supply for amplification is turned off. It is like that. According to this, a one-way OFF circuit for stopping signal transmission of one-way signals and a other-direction OFF circuit for stopping signal transmission of other-direction signals are further provided. The one-way interlocking switch can be used to arbitrarily select from a one-way amplifier circuit, a one-way path circuit, and a one-way OFF circuit, and the power supply for amplification is turned off except when the one-way amplifier circuit is selected. To do it. In addition, by using the other direction interlocking switch, it is possible to arbitrarily select from the other direction amplifier circuit, the other direction path circuit and the other direction OFF circuit, and to turn off the amplification power supply except when the other direction amplifier circuit is selected. To do it. For this reason, there is a distinction between a case in which a signal can be passed as it is without amplification and a case where signal transmission is stopped (when an OFF circuit is selected), as well as a case where amplification is necessary, and a case where amplification is not required. In addition, since the power supply for amplification is always turned off when amplification is unnecessary, power consumption of the amplifier and generation of noise can be reduced.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to FIGS. FIG. 1 shows an overall configuration diagram of a CATV system 10 according to the present embodiment. In FIG. 1, a CATV system 10
Is a center 12 for performing television broadcasting and the like, a cable 14 for transmitting bidirectional signals such as television broadcasting and various information, and a cable loss, coupling loss or distribution during transmission of the bidirectional signals via the cable 14. Bidirectional amplifiers 16a, 16b, 1
6c, a distributor 18 for distributing signals to a plurality of subscribing households, a home terminal 20 provided in each house for converting a CATV signal, etc., and a television receiver 2 for monitoring a received image
2 and the like. Here, a signal transmitted from the center 12 of FIG. 1 to the home terminal 20 of each house via the cable 14 is referred to as a down signal (right arrow on the paper), and conversely, a signal transmitted from the home terminal 20 to the center 12 Is referred to as an up signal (left arrow in the drawing).

FIG. 2 is a circuit diagram of the bidirectional amplifier 16 according to the present embodiment. In FIG. 2, the bidirectional amplifier 16 is provided with a signal input / output terminal 30 provided on the center 12 side and a duplexer 32 that separates a downstream signal from an upstream signal, and the downstream of the duplexer 32. Downstream amplifier circuit 34 having an amplifier 35 for amplifying a signal
And a downstream path circuit 36 for passing the downstream signal as it is.
And a downstream OFF circuit 38 having terminations at input and output ends of the downstream signal so as to have a rated impedance.
Two circuits are arranged in parallel so that they can be selectively selected by the switch SW1 and the switch SW2. The downstream signal selected by the switch SW2 is output from the input / output terminal 42 provided on the home terminal 20 side via the duplexer 40.

Conversely, when the upstream signal sent from the home terminal 20 is input from the input / output terminal 42 of the home terminal 20, the splitter 40 separates the upstream signal into a downstream signal and an upstream signal. Has an upstream amplifier circuit 44 having an amplifier 45 for amplifying the upstream signal, an upstream path circuit 46 for passing the upstream signal as it is, and a terminal arranged at each of an input terminal and an output terminal of the upstream signal to have a rated impedance. The three circuits of the raised up OFF circuit 48 are switches S
They are arranged in parallel so that they can be alternatively selected by W4 and switch SW5. The upstream signal selected by the switch SW4 is output from the input / output terminal 30 provided on the center 12 side via the duplexer 32. Further, the bidirectional amplifier 16 is provided with a power supply 50 from which power for amplification is supplied to the amplifier 35 of the downstream amplifier circuit 34 and the amplifier 45 of the upstream amplifier circuit 44. The ON / OFF control of the power supply to the amplifier 35 is performed by switching the switch SW3, and the ON / OFF control of the power supply to the amplifier 45 is performed by switching the switch SW6. Then, the switches SW1, SW
2 and SW3 are interlocked and switched by the down link switch 52, and the switches SW4, SW5 and S
W6 is switched by the up-link switch 54 in an interlocked manner.

[0009] CATV system 10 according to the present embodiment
The bidirectional amplifier 16 used therein is configured as described above, and its operation will be described below with reference to FIGS. As shown in FIG. 1, the cable 14 of the CATV system 10 is provided with a cable for correcting a cable loss and a distribution loss of a downlink signal transmitted from the center 12 via the cable 14 and a home terminal 20 on the terminal side. A bidirectional amplifier 16 is arranged to correct cable loss and coupling loss of an upstream signal transmitted from the GW. In particular, as shown in FIG. 1, when the cable length is long or the distribution is large, the bidirectional amplifiers 16a and 16
This is dealt with by inserting b and 16c. At this time, in the bidirectional amplifier of the present embodiment, if the signal level of the downstream signal or the upstream signal becomes excessive or the signal level is out of balance, either one of the downstream signal or the upstream signal is used depending on the situation. , Or both, can be selected to be amplified or passed through without amplification. The selection according to such a situation is shown in FIG.
The down link switch 52 and the up link switch 54 shown in FIG.
And is switched by each of them.

FIG. 3 shows a flowchart of the switching process of the interlock switch. First, in the switching process of the downlink interlock switch 52, it is determined in step S100 whether the downlink signal needs to be amplified. Excluding the case where signal transmission is stopped, the necessity of signal amplification
The determination is made based on the signal level of the downstream signal according to the signal attenuation. That is, when the signal level is low, it is necessary to amplify the signal, so that the switches SW1 to SW3
To turn on the downstream amplifier circuit 34 and the power supply 50 (step S102). As a result, amplification power is supplied to the amplifier 35, and amplification processing of the downstream signal is performed.
Further, in step S100, when the amount of attenuation of the downlink signal is small and the signal level is sufficiently large, or when transmission of the signal is stopped, it is not necessary to amplify the signal, so the process proceeds to step S104. In step S104, when the signal level of the downstream signal is sufficiently high and it is better to pass the signal as it is, the switches SW1 to SW3
To turn on the downstream path circuit 36, but the power supply 50 is turned off (step S106). In particular, in the bidirectional amplifier 16 of the present embodiment, since no external attenuator or the like is provided, the downstream signal can be passed with almost no attenuation. In addition, in this case, the power supply 50 for amplification is turned off, so that power consumption can be reduced and noise generated from the amplifier can be eliminated.

Further, when the transmission of the signal is stopped in step S104, the process proceeds to step S108 in order not to pass the signal. Here, the case where the signal transmission is stopped means, for example, that the current CATV is in a one-way service, but in the future, a facility that performs a two-way service uses an upstream (or downstream) band. If not, there is a case where the signal transmission of the band is stopped for operation. When the two-way service is started, the operation can be performed by setting the amplification circuit to ON in step S102 or setting the path circuit to ON in step S106. In step S108, by switching the switches SW1 to SW3, the downstream OFF circuit 38 is turned on but the power supply 50 is turned off.
For this reason, signal transmission can be stopped, and in this case, the power supply 50 for amplification is turned off, so that power consumption can be reduced and generation of noise from the amplifier can be prevented. The switching process of the interlocking switch described above relates to the down linking switch 52.
The same applies to the case of the uplink interlocking switch 54, and the downstream amplifier circuit 34, the downstream path circuit 36,
The down-off circuit 38 is changed to an up-amplifier circuit 44, an up-pass circuit 46, and an up-off circuit 48, and the switches SW1, S
Since W2 and SW3 are changed to switches SW5, SW4 and SW6, the description of the switching process of the interlock switch 54 is omitted.

As described above, according to the present embodiment, the signal level can be adjusted to an appropriate level according to the state of each signal transmitted bidirectionally through the CATV cable. Reliability can be improved. In addition, since the power supply for amplification is turned off when signal amplification is not required, power consumption can be reduced and generation of noise from the amplifier can be prevented.
In the above embodiment, a case has been described as an example in which signals are transmitted bidirectionally between the center side and the terminal side for television broadcasting and various information using a cable for CATV. The present invention is not limited to this, and can be applied to all bidirectional amplifiers used for transmitting signals bidirectionally using a cable. Also,
In the bidirectional amplifier of the above-described embodiment, the amplifying circuit, the pass circuit, and the OFF circuit are arranged so as to be selectable in each of the down direction and the up direction of the signal, but are not necessarily limited to this configuration. Although at least the amplifier circuit and the pass circuit are necessary, the OFF circuit may not be provided or may be provided only in one direction depending on the application.

[0013]

As described above, according to the first aspect of the present invention, a signal is amplified or passed as it is in accordance with the state of a signal transmitted bidirectionally through a cable in each direction. In addition to this, the power supply for amplification can be turned off when signal amplification is not required, and power consumption of the amplifier and generation of noise can be reduced. According to the second aspect of the present invention, it is possible to select whether to amplify the signal, pass the signal as it is, or stop the signal transmission according to the signal state in each direction transmitted bidirectionally via the cable. When the signal amplification is not required, the power supply for amplification is turned off, so that the power consumption of the amplifier and the generation of noise can be reduced.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a CATV system according to the present embodiment.

FIG. 2 is a circuit configuration diagram of a bidirectional amplifier according to the present embodiment.

FIG. 3 is a flowchart of a switching process of an interlock switch.

FIG. 4 is a diagram illustrating a circuit configuration example of a conventional bidirectional amplifier for CATV.

[Explanation of symbols]

10 CATV systems, 12 centers, 14
Cable, 16 bidirectional amplifier, 16a, 16b,
16c bidirectional amplifier, 18 distributor, 20 home terminal, 22 television receiver, 30, 42
I / O terminal, 32, 40 demultiplexer, 34 downstream amplifier circuit, 35 amplifier, 36 downstream path circuit, 38
Down OFF circuit, 44 Up amplifier circuit, 45 Amplifier, 46 Up path circuit, 48 Up OFF circuit, 50 Power supply, 52 Down link switch, 54 Up link switch

Claims (2)

[Claims] 1. A one-way amplifier circuit is provided in a cable through which a CATV signal is bidirectionally transmitted and amplifies a one-way signal attenuated during signal transmission, and a two-way signal attenuated during signal transmission. Having a multi-directional amplifier circuit for amplifying the signal
In the ATV bidirectional amplifier, a one-way path circuit that allows a one-way signal to pass when amplification of the one-way signal is unnecessary, and switches and connects the one-way amplifier circuit and the one-way path circuit, A one-way interlock switch for turning on / off an amplifying power supply supplied to the one-way amplifier circuit; a other-direction path circuit for passing the other-directional signal when amplification of the other-directional signal is unnecessary; and the other-directional amplifier circuit And an other-way interlocking switch for switching on and off the power supply for amplification supplied to the other-direction amplifier circuit while switching and connecting the other-direction path circuit, and signal amplification in one direction or the other direction is required. In this case, switch to the amplification circuit in the direction and turn on the amplification power supply. If signal amplification is not required, switch to the path circuit in the direction and turn on the amplification power supply. For CATV bi-directional amplifier, characterized by. 2. A one-way OFF circuit for stopping signal transmission of a one-way signal when the one-way signal is not used, and a other-direction OFF circuit for stopping signal transmission of a one-way signal when the one-way signal is not used. And, when stopping signal transmission in one direction or the other direction, switching to an OFF circuit in the direction using an interlocking switch in the direction, and turning off the power supply for amplification. The bidirectional amplifier for CATV according to claim 1.