JP2000197019A - Bidirectional amplifier - Google Patents

Abstract

(57) [Summary] [Problem] Regardless of the configuration of the home terminal,
A bidirectional amplifier that does not require any work to change it. When a CATV modem is installed in a home terminal, a switch RS is switched to connect a contact a and a contact b, so that an upstream signal is amplified by an upstream amplifier 16 and output. If a high-output CATV modem is installed in the home terminal, the switch RS is switched to connect the contact a to the contact c, so that the upstream signal passes through the upstream amplifier 16 and is output as it is. If a CATV modem is not installed in the home terminal, switch RS is switched to contact a.
And the contact d, the upstream signal is cut off by the upstream amplifier 16 in an inactive state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bidirectional amplifier inserted in a transmission line between a CATV center and each subscriber's house.

[0002]

2. Description of the Related Art In a conventional CATV system, CA
A transmission line is laid between the TV center and each subscriber's house. In order to compensate for transmission loss in the transmission line, a relay amplifier is inserted into the transmission line at every certain distance. As this relay amplifier, a bidirectional amplifier capable of amplifying a downlink signal and an uplink signal when an uplink signal is used is used, and the line length is equalized by the bidirectional amplifier. Line length equalization means that the transmission loss of a transmission line has an attenuation characteristic that is proportional to f ^1/2 when the frequency is f. This is an equalization method that attempts to obtain flat frequency characteristics at the receiving end.

A conventional bidirectional amplifier includes a downstream amplifier and an upstream amplifier, and the downstream amplifier has an amplifier for amplifying a downstream signal. Further, the upstream amplification unit may include an upstream amplifier that amplifies the upstream signal, a case that includes a pass circuit that allows the upstream signal to pass, and a case that includes a cutoff circuit that blocks the upstream signal. One of the configurations was adopted accordingly. For example, when the CATV modem is provided in the home terminal system, the up-amplifier has a configuration having an up-amplifier. The upstream amplifying unit has a configuration of a pass circuit that allows the upstream signal to pass through as it is so as not to cause distortion. When a CATV modem is not provided, a blocking circuit for blocking an upstream signal is provided in order to prevent ingress noise.

FIG. 7 shows an example of a circuit configuration of a conventional bidirectional amplifier. The bidirectional amplifier 100 shown in FIG. 1 includes a first terminal 101 to which a down signal is input and an up signal is output, and a second terminal 105 to which a down output signal is output and an up input signal is input. And First
Terminal 101 is connected to a first demultiplexer / mixer 102, and the first demultiplexer / mixer 102 is connected to the first terminal 10.
1 is demultiplexed to the downstream amplifier 103 and the output signal from the upstream amplifier 106 is supplied to the first terminal 1.
01. Further, the second terminal 105 is connected to a second demultiplexer / mixer 104, and the second demultiplexer / mixer 104 converts an upstream input signal input from the second terminal 105 into an upstream amplifier 106. To the downstream amplifier 10
3 is mixed with the second terminal 105.
As described above, the bidirectional amplifier 100 shown in FIG. 7 is configured when the CATV modem is provided in the home terminal system.

FIG. 8 shows another example of a circuit configuration of a conventional bidirectional amplifier. The bidirectional amplifier 100 shown in FIG.
Has a first terminal 101 to which a down signal is input and an up signal is output, and a second terminal 105 to which a down output signal is output and an up input signal is input. The first terminal 101 is connected to a first demultiplexer / mixer 102, and the first demultiplexer / mixer 102 is connected to the first demultiplexer / mixer 102.
The downstream input signal input from the terminal 101 is branched to the downstream amplifier 103, and the output selection signal from the switch 107 is mixed with the first terminal 101. Also, the second terminal 1
Reference numeral 05 is connected to a second demultiplexer / mixer 104. The second demultiplexer / mixer 104 demultiplexes the upstream input signal input from the second terminal 105 to the switch 107, The output signal from 103 is mixed with the second terminal 105.

In the bidirectional amplifier 100 shown in FIG. 8, a switch 107 has two circuits and two contacts.
The upstream signal demultiplexed by the second demultiplexer / mixer 104 is supplied to the movable contact a1 of the circuit, and the movable contact a2 of the second circuit is connected to the first demultiplexer / mixer 102. here,
When the switch 107 is switched to the state shown in FIG. 8, the movable contact a1 and the fixed contact c1 are connected, and the fixed contact c2 connected to the fixed contact c1 is connected to the movable contact a2. That is, the upstream signal from the second demultiplexer / mixer 104 is passed by the switch 107 and output to the first demultiplexer / mixer 102 as it is. This switch 1
07 indicates that the home terminal system has a high output C
This is a configuration when an ATV modem is provided.

When the switch 107 is switched from the state shown in FIG. 8, the movable contact a1 and the fixed contact b1 are connected, and the fixed contact b2 is connected to the movable contact a2. Since the fixed contact b1 and the fixed contact b2 are connected to the terminating resistor R, the upstream signal from the second demultiplexing / mixing device 104 is terminated by the terminating resistor R and the first demultiplexing / mixing is performed.
The terminal on the switch 107 side of the mixer 102 is also terminated by the terminating resistor R. This state of the switch 107 indicates that the CATV modem is not provided in the home terminal system,
This is a configuration in a case where an uplink signal is not used.

[0008]

As described above, since the configuration of the bidirectional amplifier is changed depending on the configuration of the home terminal, it is verified whether or not the home terminal uses an upstream signal to determine whether the home terminal uses an upstream signal. The configuration needed to be determined. In addition, when a CATV modem is newly installed in a home terminal after installing a bidirectional amplifier, there is a problem that a change work for changing a configuration of the bidirectional amplifier must be performed.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a bidirectional amplifier that does not require any work for changing the configuration of the bidirectional amplifier regardless of the configuration of the home terminal.

[0010]

In order to achieve the above object, a bidirectional amplifier according to the present invention comprises a first terminal to which a downstream input signal is input, an upstream output signal output, and a downstream output signal. A second terminal to which an output signal is input and a second input terminal to which the input signal is input, and a downstream input signal input from the first terminal are demultiplexed to the downstream side, and the upstream output signal supplied from the upstream side is output to the second terminal. A first demultiplexer / mixer that mixes the signal with one terminal, and an upstream input signal that is input from the second terminal, is demultiplexed to the upstream side, and a downstream output signal from the downstream side is transmitted to the second terminal. A second demultiplexer / mixer that mixes the signals at a terminal; a downstream amplifier that amplifies a downstream signal is provided on the downstream side; an upstream amplifier that amplifies an upstream signal is provided on the upstream side; A pass circuit for passing the amplifier; the upstream amplifier and the pass circuit; Select one, or if a selection means for selecting a cut-off state in which the upstream signal is provided.

Further, in the bidirectional amplifier, the selecting means supplies the upstream signal split by the second splitter / mixer to one of the upstream amplifier and the pass circuit. A first selection state in which driving power is supplied to the high-frequency switch means, and a second high-frequency switch means for selecting one of the upstream signal amplified by the upstream amplifier and the upstream signal passed by the pass circuit; It may be constituted by switch means capable of selecting any one of the second selection states for supplying drive power to the upstream amplifier.

Further, in the above bidirectional amplifier,
The selection unit includes a high-frequency switch unit that selects one of an upstream signal amplified by the upstream amplifier and an upstream signal passed by the path circuit; and an upstream signal separated by the second demultiplexer / mixer. A signal is input to the upstream amplifier, and at the same time, whether to supply drive power to the upstream amplifier and the high-frequency switch means, to input the signal to the path circuit, or to terminate the upstream signal and the path circuit by a termination circuit is selected. It may be composed of switch means. Still further, the selection means includes a high frequency switch means for selecting either an upstream signal amplified by the upstream amplifier or an upstream signal passed by the pass circuit, and a demultiplexer by the second demultiplexer / mixer. Inputting the supplied upstream signal to the upstream amplifier and supplying drive power to the upstream amplifier at the same time, or inputting the same to the pass circuit and supplying drive power to the high-frequency switch means simultaneously, or terminating the upstream signal and the pass circuit. And switch means for selecting whether to terminate in a circuit.

According to the present invention, by switching the selection means, the state of the upstream side of the bidirectional amplifier is changed to the state in which the upstream signal is amplified by the upstream amplifier, the state in which the upstream signal is passed as it is, and the upstream signal is blocked. State. Therefore, even if a CATV modem is newly provided in the home terminal, the bidirectional amplifier can be dealt with only by switching the selection means, and it is not necessary to change the bidirectional amplifier. . The same applies to the case where the CATV modem is changed to a high-output modem, and a bidirectional amplifier that matches the level of the upstream signal can be provided. further,
When the CATV modem is not provided in the home terminal, the upstream side can be terminated, so that occurrence of ingress noise can be prevented.

[0014]

FIG. 1 shows a configuration example of a first embodiment of a bidirectional amplifier according to the present invention. The bidirectional amplifier 1 according to the first embodiment of the present invention shown in FIG. 1 has a first terminal 11 to which a downstream signal is input and an upstream signal is output.
And a second terminal 15 to which a downstream output signal is output and an upstream input signal is input. First terminal 1
1 is connected to a first demultiplexer / mixer 12, and the first demultiplexer / mixer 12 converts a downstream input signal input from a first terminal 11 to a downstream side provided with a downstream amplifier 13. And the upstream output signal from the upstream side is mixed with the first terminal 11. The second terminal 15 is connected to the second demultiplexer / mixer 14, and the second terminal 15 is connected to the second demultiplexer / mixer 14.
Divides the upstream input signal input from the second terminal 15 into the upstream side, and mixes the output signal from the downstream amplifier 13 with the second terminal 15.

The upstream side provided between the upstream terminal of the first branching / mixing device 12 and the upstream terminal of the second branching / mixing device 14 is connected to a first high-frequency relay RY1. It comprises a second high-frequency relay RY2 and an upstream amplifier 16. The upstream signal branched by the second branching / mixing device 14 is supplied to the movable contact a1 of the first high-frequency relay RY1, and the fixed contact b1 of the first high-frequency relay RY1 is connected to the upstream amplifier 1
6 and the fixed contact c1 of the first high-frequency relay RY1 is connected to the fixed contact c2 of the second high-frequency relay RY2. The output of the upstream amplifier 16 is supplied to the fixed contact b2 of the second high-frequency relay RY2, and the movable contact a2 of the second high-frequency relay RY2 is connected to the first demultiplexer / mixer 12.

Further, the driving of the first high-frequency relay RY1 and the second high-frequency relay RY2,
By controlling the power supply to 6, the upstream side can be in a state of amplifying the upstream signal, passing the upstream signal, or blocking the upstream signal.
This state is switched by a switch RS having three contacts in one circuit, and the movable contact a of the switch RS is supplied with power from a power supply unit (PS). The fixed contact b of the switch RS is connected to the power supply terminal of the upstream amplifier 16, and the fixed contact c of the switch RS is connected to the drive coil RC1 of the first high-frequency relay RY1 and the drive coil RC2 of the second high-frequency relay RY2. The fixed contact d of the switch RS is not connected anywhere.

Here, when the movable contact a is connected to the fixed contact b by switching the switch RS as shown in FIG.
Power is supplied to the upstream amplifier 16. Further, power is not supplied to the drive coil RC1 of the first high-frequency relay RY1 and the second high-frequency relay RY2, and the movable contact a1 and the fixed contact b1 are connected, and the movable contact a2 and the fixed contact b2 are connected. Connected. As a result, the second demultiplexing
The upstream signal split by the mixer 14 is input to the upstream amplifier 16 via the movable contact a1 and the fixed contact b1 of the first high-frequency relay RY1, and is amplified to have a predetermined frequency characteristic. Further, the upstream output signal from the upstream amplifier 16 is
Fixed contact b2 and movable contact a2 of the second high-frequency relay RY2
To the first demultiplexer / mixer 12.

In this state, the up signal output from the CATV modem installed in the home terminal can be amplified by the bidirectional amplifier 1 and output. In addition,
In this case, the level of the upstream signal transmitted from the CATV modem is 70 to 80 dBμV. This is the CAT
In the system inside the building of V, when monitoring the state of the home terminal, a polling signal is sent in the down direction to control the up signal generator in the home terminal. Since the transmission level of the upstream signal by this upstream signal generator is set to 70 to 80 dBμV, which is the same level as that of the downstream signal, the transmission level of the CATV modem is usually 70 to 80 dBμV.
This is because it is set to ｄ80 dBμV.

When the switch RS is switched so that the movable contact a and the fixed contact c are connected, the switch R
Power is supplied to the drive coil RC1 of the first high-frequency relay RY1 and the drive coil RC2 of the second high-frequency relay RY2 via S. Further, no power is supplied to the upstream amplifier 16. In this case, the first high-frequency relay RY1
And the second high-frequency relay RY2 is driven to switch the contact, so that the movable contact a1 and the fixed contact c1 are connected, and the movable contact a2 and the fixed contact c2 are connected.
As a result, the upstream signal split by the second splitter / mixer 14 is passed through the movable contact a1 and the fixed contact c1 of the first high-frequency relay RY1, and furthermore, the fixed contact of the second high-frequency relay RY2. c2, and are supplied to the first demultiplexer / mixer 12 via the movable contact a2.

In this state, the up signal output from the high-power CATV modem installed in the home terminal can be output as it is via the pass circuit in the bidirectional amplifier 1. In general, the transmission level of a CATV modem is also set to 70 to 80 dBμV.
High-speed telephone modems for TV have been developed and are being used for CATV telephones, the Internet, and the like. This CATV modem is set to a high output in order to adjust its output level to various systems.
It has a high output level. When the output level is set to a high level as described above, an over-input upstream signal is applied to the upstream amplifier, so that it is necessary to insert an attenuator. However, if an attenuator is inserted into the line, the downstream signal will also be attenuated. Therefore, in the present invention, when a high-output CATV modem is installed in the home terminal as described above, it is necessary to pass an up-amplifier to prevent over-input and attenuate a down signal. Preventing.

When the switch RS is switched so that the movable contact a and the fixed contact d are connected, the switch R
No power is supplied through S. Therefore, the first
The high-frequency relay RY1 is not driven, the movable contact a1 and the fixed contact b1 are connected, and the second high-frequency relay R
The movable contact a2 and the fixed contact b2 are also connected without Y2 being driven. Further, since power is not supplied to the upstream amplifier 16, the upstream signal split by the second splitter / mixer 14 is inactive via the movable contact a1 and the fixed contact b1 of the first high-frequency relay RY1. The state is input to the up-amplifier 16 and the state is cut off. That is, if no CATV modem is installed in the home terminal,
In the bidirectional amplifier 1, the upstream signal is cut off, and the occurrence of ingress noise can be prevented.

Next, in the bidirectional amplifier of the present invention, the second
FIG. 2 shows a configuration example of this embodiment. The bidirectional amplifier 1 according to the second embodiment of the present invention shown in FIG. 2 is designed to cut off the upstream signal on the upstream side of the bidirectional amplifier 1 according to the first embodiment of the present invention. The impedance matching can be achieved. The description of the configuration common to the bidirectional amplifier 1 according to the first embodiment is omitted. In the bidirectional amplifier 1 according to the second embodiment of the present invention, between the upstream terminal of the first demultiplexer / mixer 12 and the upstream terminal of the second demultiplexer / mixer 14. The provided up side is the first high-frequency relay RY1
And a switch RS having two circuits and three contacts, and an upstream amplifier 16.

An up signal split by the second splitter / mixer 14 is supplied to the movable contact a of the first circuit of the switch RS.
The fixed contact b of the switch RS is connected to the input of the upstream amplifier 16, the fixed contact c of the switch RS is connected to the fixed contact g of the second circuit of the switch RS, and supplied via the DC cut capacitor C3. RS fixed contact d
Are connected to ground via a terminating resistor R1. The movable contact e of the second circuit of the switch RS is connected to the first high-frequency relay RY via a DC cut capacitor C1.
One fixed contact c1 is connected to form a pass circuit. Power is supplied to this path circuit from a power supply (PS) via a choke coil CH1. In addition,
A bypass capacitor C2 is connected between the other end of the choke coil CH1 and the ground.

Further, the fixed contact f of the second circuit of the switch RS is connected to the power supply terminal of the upstream amplifier 16 and the drive coil RC1 of the first high frequency relay RY1, and the fixed contact g of the second circuit is connected to the first contact of the switch RS. The fixed contact c of the second circuit is connected to the fixed contact c of the circuit, and the fixed contact h of the second circuit is connected to the ground via a series circuit of the capacitor C4 and the terminating resistor R.
Further, the output of the upstream amplifier 16 is applied to the fixed contact b1 of the first high-frequency relay RY1, and the movable contact a1 of the first high-frequency relay RY1 is connected to the first demultiplexer / mixer 12.

Here, when the switch RS is switched to connect the movable contact a and the fixed contact b as shown in FIG. 2 and the movable contact e and the fixed contact f are connected, the movable contact e and the fixed contact f are connected. Power is supplied to the upstream amplifier 16 and the drive coil RC1 of the first high-frequency relay RY1 via f. For this reason, the up amplifier 16 becomes active, the first high-frequency relay RY1 is switched, and the movable contact a1 is connected to the fixed contact b1. Further, an upstream signal is input to the upstream amplifier 16 via the movable contact a and the fixed contact b of the switch RS. Thus, the upstream signal demultiplexed by the second demultiplexer / mixer 14 is input to the upstream amplifier 16 and amplified to have a predetermined frequency characteristic. Further, the upstream output signal from the upstream amplifier 16 is applied to the first demultiplexer / mixer 12 via the fixed contact b1 and the movable contact a1 of the first high-frequency relay RY1. In this state, the up signal output from the CATV modem installed in the home terminal can be amplified by the bidirectional amplifier 1 and output.

Further, the switch RS for simultaneously switching the movable contact a and the movable contact e is switched so that the movable contact a
When the fixed contact c and the movable contact e and the fixed contact g are connected, the power via the switch RS is not supplied to the first high-frequency relay RY1 and the upstream amplifier 16. Therefore, the first high-frequency relay RY1 is not driven, the movable contact a1 and the fixed contact c1 are connected, and the up-amplifier 16 is deactivated. As a result, the connection of the inactive upstream amplifier 16 is disconnected, and the upstream signal split by the second splitter / mixer 14 is connected to the movable contact a-fixed contact c-fixed contact of the switch RS. The voltage is applied to the path circuit via the g-movable contact e, and further applied to the first demultiplexer / mixer 12 via the capacitor C1 and the fixed contact c1 and the movable contact a1 of the first high-frequency relay RY1. In this state, the upstream signal output from the high-output CATV modem installed in the home terminal can be output as it is from the bidirectional amplifier 1 via the pass circuit.

When the switch RS for simultaneously switching the movable contact a and the movable contact e is switched and the movable contact a and the fixed contact d and the movable contact e and the fixed contact h are connected, the switch RS is switched. No power is supplied anywhere, and the movable contact a1 and the fixed contact c1 of the first high-frequency relay RY1 are connected, and the upstream amplifier is inactive. As a result, the connection of the inactive amplifier 16 is disconnected, and the second demultiplexer
The upstream signal demultiplexed by the mixer 14 is terminated by the terminating resistor R1 via the movable contact a and the fixed contact d of the switch RS, and the path circuit also has the movable contact e and the fixed contact h of the switch RS.
And is terminated by a terminating resistor R2. Note that the capacitor C4 is a DC cut capacitor that cuts off the power supply. In this state, when the CATV modem is not installed in the home terminal, the terminating resistors R1 and R2 in which the upstream signal is impedance-matched in the bidirectional amplifier 1.
, And is cut off by being terminated, whereby the occurrence of ingress noise can be efficiently prevented.

Next, the third bidirectional amplifier of the present invention will be described.
FIG. 3 shows a configuration example of this embodiment. The bidirectional amplifier 1 according to the third embodiment of the present invention shown in FIG. 3 reduces the peak value of power consumption on the upstream side of the bidirectional amplifier 1 according to the second embodiment of the present invention. It is something to do. The description of the configuration common to the bidirectional amplifier 1 according to the first embodiment is omitted. In the bidirectional amplifier 1 according to the third embodiment of the present invention, between the upstream terminal of the first demultiplexer / mixer 12 and the upstream terminal of the second demultiplexer / mixer 14. The provided upstream side includes a first high-frequency relay RY1, a switch RS having three contacts of two circuits, and an upstream amplifier 16.

An up signal split by the second splitter / mixer 14 is supplied to the movable contact a of the first circuit of the switch RS.
The fixed contact b of the switch RS is connected to the input of the upstream amplifier 16, the fixed contact c of the switch RS is connected to the fixed contact g of the second circuit of the switch RS, and supplied via the DC cut capacitor C3. RS fixed contact d
Are connected to ground via a terminating resistor R1. The movable contact e of the second circuit of the switch RS is connected to the first high-frequency relay RY via a DC cut capacitor C1.
One fixed contact c1 is connected to form a pass circuit. Power is supplied to this path circuit from a power supply (PS) via a choke coil CH1. In addition,
A bypass capacitor C2 is connected between the other end of the choke coil CH1 and the ground.

Further, the fixed contact f of the second circuit of the switch RS is connected to the power supply terminal of the upstream amplifier 16, the fixed contact g of the second circuit is connected to the fixed contact c of the first circuit of the switch RS, and The fixed contact h of the second circuit is connected to the drive coil RC1 of the first high-frequency relay RY1 via the choke coil CH2, and is connected to the drive coil RC1 of the first high-frequency relay RY1 via the choke coil CH3. It is connected to ground via a series circuit of a capacitor C4 and a terminating resistor R2. Further, the output of the upstream amplifier 16 is applied to the fixed contact b1 of the first high-frequency relay RY1, and the movable contact a1 of the first high-frequency relay RY1 is connected to the first demultiplexer / mixer 12.

Here, when the switch RS is switched to connect the movable contact a and the fixed contact b as shown in FIG. 3 and the movable contact e and the fixed contact f are connected, the movable contact e and the fixed contact f are connected. Power is supplied to the upstream amplifier 16 via f. In this case, power is not supplied to the drive coil RC1 of the first high-frequency relay RY1 and the drive coil RC1 is not driven.
When the upstream amplifier 16 becomes active, the movable contact a1 of the first high-frequency relay RY1 is connected to the fixed contact b1. As a result, the upstream signal is input to the upstream amplifier 16 through the movable contact a and the fixed contact b of the switch RS, so that the upstream signal split by the second splitter / mixer 14 is
The signal is input to the upstream amplifier 16 and amplified so as to have a predetermined frequency characteristic. Further, the upstream output signal from the upstream amplifier 16 is applied to the first demultiplexer / mixer 12 via the fixed contact b1 and the movable contact a1 of the first high-frequency relay RY1. In this state, the CA installed at the home terminal
The upstream signal output from the TV modem can be amplified and output by the bidirectional amplifier 1.

Further, the switch RS for simultaneously switching the movable contact a and the movable contact e is switched so that the movable contact a
And the fixed contact c and the movable contact e and the fixed contact g are connected, the power supply via the switch RS is applied to drive the drive coil RC1 of the first high-frequency relay RY1 via the choke coil CH3. , But is not supplied to the upstream amplifier 16. Therefore, the first high-frequency relay RY1 switches, the movable contact a1 and the fixed contact c1 are connected, and the up-amplifier 16 is deactivated. As a result, the inactive amplifier 16 becomes inactive.
Is disconnected and the second demultiplexer / mixer 14
The upward signal split by the switch RS is connected to the movable contact a- of the switch RS.
The voltage is applied to the path circuit via the fixed contact c, the fixed contact g, and the movable contact e, and is further applied to the first demultiplexer / mixer 12 via the fixed contact c1 and the movable contact a1 of the capacitor C1 and the first high frequency relay RY1. Is applied to In this state, the upstream signal output from the high-output CATV modem installed in the home terminal can be output as it is from the bidirectional amplifier 1 via the pass circuit.

When the switch RS for simultaneously switching the movable contact a and the movable contact e is switched to connect the movable contact a to the fixed contact d and the movable contact e to the fixed contact h, the switch RS is switched. The power supply is applied to drive the drive coil RC1 of the first high-frequency relay RY1 via the choke coil CH2.
6 is not supplied. Therefore, the first high-frequency relay RY1 switches, the movable contact a1 and the fixed contact c1 are connected, and the up-amplifier 16 is deactivated. Thereby, the connection of the inactive up amplifier 16 is disconnected, and the up signal split by the second splitter / mixer 14 is passed through the movable contact a and the fixed contact d of the switch RS. The path circuit is terminated by the terminating resistor R1, and the path circuit is also terminated by the terminating resistor R2 via the movable contact e and the fixed contact h of the switch RS. Note that the capacitor C4 is a DC cut capacitor for cutting off the power supply, and the capacitor C5 connected in parallel to the drive coil RC1 is a bypass capacitor.

In this state, the CAT is connected to the home terminal.
When no V modem is installed, the upstream signal is cut off in the bidirectional amplifier 1 and the occurrence of ingress noise can be prevented. As described above, in the third embodiment of the bidirectional amplifier of the present invention, power is not supplied to the up-amplifier 16 and the first high-frequency relay RY1 at the same time. Therefore, the peak value of the power consumption is set to the second value in the bidirectional amplifier of the present invention.
Can be reduced as compared with the embodiment.

Next, the first high-frequency relay RY1 in the bidirectional amplifier according to the second embodiment of the present invention shown in FIG.
FIG. 4 shows a first modification in which is replaced by a switch means using a diode. Bidirectional amplifier 1 of the present invention shown in FIG.
When the switch RS is switched to connect the movable contact a and the fixed contact b as shown in FIG. 4 and the movable contact e and the fixed contact f are connected as shown in FIG. Power is supplied to the second amplifier D2 via the upstream amplifier 16 and the choke coil CH5 via f. For this reason, the up-amplifier 16 becomes active, and the second diode D2 is forward-biased and conducts. Further, an upstream signal is input to the upstream amplifier 16 via the movable contact a and the fixed contact b of the switch RS. Thus, the upstream signal demultiplexed by the second demultiplexer / mixer 14 is input to the upstream amplifier 16 and amplified to have a predetermined frequency characteristic. Further, the upstream output signal from the upstream amplifier 16 is applied to the first demultiplexer / mixer 12 via the DC cut capacitor C6 and the conductive second diode D2, and further via the capacitor C5. In this state, the CA installed at the home terminal
The upstream signal output from the TV modem can be amplified and output by the bidirectional amplifier 1. It is preferable to use PIN diodes having excellent high-frequency characteristics as the diodes D1 and D2. The resistor R3 is a limiting resistor for limiting the current flowing through the diodes D1 and D2, and the capacitors C7 and C8 are bypass capacitors.

Further, the switch RS for simultaneously switching the movable contact a and the movable contact e is switched, and the movable contact a
When the fixed contact c and the movable contact e and the fixed contact g are connected, the power via the switch RS is supplied to the first diode D1 via the choke coils CH3 and CH4. It is not supplied to the upstream amplifier 16. Therefore, the first diode D1 is forward-biased and conducts, but the up-amplifier 16 is inactive. As a result, the inactive upstream amplifier 1
6 is disconnected and the second demultiplexer / mixer 1
The upward signal demultiplexed at 4 is the movable contact a of the switch RS.
-Fixed contact c-fixed contact g-applied to the path circuit via the movable contact e, and furthermore, the first demultiplexer / mixer 12 via the capacitor C1 and the conducting first diode D1, and further via the capacitor C5. Is applied to In this state, the upstream signal output from the high-output CATV modem installed in the home terminal can be output as it is from the bidirectional amplifier 1 via the pass circuit.

When the switch RS for simultaneously switching the movable contact a and the movable contact e is switched to connect the movable contact a to the fixed contact d and the movable contact e to the fixed contact h, the switch RS is switched. The power via the choke coil CH2 and the choke coil CH4 is supplied so as to conduct the first diode D1. This allows
The upstream signal demultiplexed by the second demultiplexer / mixer 14 is supplied to the terminating resistor R via the movable contact a and the fixed contact d of the switch RS.
1 and the path circuit also has a movable contact e of the switch RS,
It is terminated by a terminating resistor R2 via a fixed contact h. In addition,
The capacitor C4 is a DC cut capacitor for cutting off the power supply. In this state, CA
If no TV modem is installed, the bidirectional amplifier 1
In this case, the upstream signal is terminated by terminating resistors R1 and R2 whose impedance has been matched, whereby the upstream signal is cut off, so that the occurrence of ingress noise can be efficiently prevented.

Next, FIG. 5 shows a second modification in which the first high-frequency relay RY1 in the bidirectional amplifier 1 of the present invention shown in FIG. 2 is changed to a semiconductor switch. The operation of the bidirectional amplifier 1 of the present invention shown in FIG.
And the movable contact a and the fixed contact b as shown in FIG.
When the movable contact e and the fixed contact f are connected together, power is applied to the drive terminal A of the up amplifier 16 and the semiconductor switch 17 via the movable contact e and the fixed contact f. As a result, the upstream amplifier 16 becomes active, and the semiconductor switch 17 receives the input IN-A and the output OUT.
Only the gap is conductive. Further, the movable contact a of the switch RS
And the upstream signal is input to the upstream amplifier 16 via the fixed contact b. Thus, the upstream signal demultiplexed by the second demultiplexer / mixer 14 is input to the upstream amplifier 16 and amplified to have a predetermined frequency characteristic. Further, the upstream amplifier 1
6 is a DC cut capacitor C6.
Via the semiconductor switch 17 and the capacitor C
5 is applied to the first demultiplexer / mixer 12. In this state, the up signal output from the CATV modem installed in the home terminal can be amplified by the bidirectional amplifier 1 and output.

Further, the switch RS for simultaneously switching the movable contact a and the movable contact e is switched so that the movable contact a
When the movable contact e and the fixed contact g are connected to each other, the power supply via the switch RS is connected to the drive terminal B of the semiconductor switch 17 via the choke coil CH3.
And is not supplied to the upstream amplifier 16. Therefore, the upstream amplifier 16 is inactivated, and only the input IN-B and the output OUT of the semiconductor switch 17 conduct. As a result, the connection of the inactive upstream amplifier 16 is disconnected, and the upstream signal split by the second splitter / mixer 14 is connected to the movable contact a-fixed contact c-fixed contact of the switch RS. g—applied to the pass circuit via the movable contact e, further applied from the input IN-B of the capacitor C1 and the semiconductor switch 17 to the output OUT, and further applied to the first demultiplexer / mixer 12 via the capacitor C5. .
In this state, the upstream signal output from the high-output CATV modem installed in the home terminal can be output as it is from the bidirectional amplifier 1 via the pass circuit.

When the switch RS for simultaneously switching the movable contact a and the movable contact e is switched to connect the movable contact a to the fixed contact d and the movable contact e to the fixed contact h, the switch RS is switched. The power passed through is supplied to the drive terminal B of the semiconductor switch 17 via the choke coil CH2. Therefore, the input I of the semiconductor switch 17 is
Only the NB and the output OUT conduct. As a result, the upstream signal split by the second splitter / mixer 14 is supplied to the terminating resistor R1 via the movable contact a and the fixed contact d of the switch RS.
And the path circuit is also terminated by the terminating resistor R2 via the movable contact e and the fixed contact h of the switch RS. Note that the capacitor C4 is a DC cut capacitor that cuts off the power supply. In this state, the CAT is
When no V modem is installed, the terminating resistor R whose impedance is matched to the upstream signal in the bidirectional amplifier 1
1 and R2, it is cut off, and the occurrence of ingress noise can be efficiently prevented.

FIG. 6 shows an example of the configuration of the semiconductor switch 17. In the semiconductor switch 17 shown in FIG.
Is supplied with a positive voltage, the transistors TR2, TR1
Are connected, the input IN-A and the output OUT are conducted, and the input IN-B is connected to the ground GND. Also, terminal B
Are supplied with a positive voltage, the transistors TR3, TR4
Are connected, the input IN-B and the output OUT are conducted, and the input IN-A is connected to the ground GND. The transistors TR1 to TR4 are preferably MES (metal semiconductor) type field effect transistors using gallium arsenide as a substrate material, and can be a semiconductor switch 17 having excellent high frequency characteristics.

The switch driving voltage supplied to the terminals A and B may be a negative voltage. In this case, the transistors TR1 to TR4 may be of a negative voltage driving type. Also, an example was described in which the high-frequency relay in the bidirectional amplifier of the present invention shown in FIG. 2 was changed to a switch using a semiconductor, but the high-frequency relay in the bidirectional amplifier of the present invention shown in FIG. 1 or FIG. A switch using a semiconductor may be used. In this case, a switch shown in FIG. 4 or FIGS. 5 and 6 can be used as a switch using a semiconductor.

[0043]

According to the present invention, as described above, the state of the bidirectional amplifier on the upstream side is changed by switching the selection means comprising a switch, the state where the upstream signal is amplified by the upstream amplifier, the state where the upstream signal is passed as it is, Any of the states of blocking the upstream signal can be set. Therefore, even if a CATV modem is newly provided in the home terminal, the bidirectional amplifier can be dealt with only by switching the selection means, and it is not necessary to change the bidirectional amplifier. . The same applies when the CATV modem is changed to a high-output modem.
A bidirectional amplifier that matches the level of the upstream signal can be provided. Further, when the CATV modem is not provided in the home terminal, the upstream side can be terminated, so that occurrence of ingress noise can be prevented.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of a first embodiment in a bidirectional amplifier of the present invention.

FIG. 2 is a circuit diagram showing a configuration of a second embodiment of the bidirectional amplifier of the present invention.

FIG. 3 is a circuit diagram showing a configuration of a third embodiment of the bidirectional amplifier of the present invention.

FIG. 4 is a circuit diagram showing a first modification of the configuration of the second embodiment in the bidirectional amplifier of the present invention.

FIG. 5 is a circuit diagram illustrating a second modification of the configuration of the bidirectional amplifier according to the second embodiment of the present invention;

FIG. 6 is a circuit diagram illustrating an example of a configuration of a semiconductor switch.

FIG. 7 is a circuit diagram showing a configuration of a bidirectional amplifier in a conventional bidirectional CATV system.

FIG. 8 is a circuit diagram showing another configuration of a bidirectional amplifier in a conventional bidirectional CATV system.

[Explanation of symbols]

 1,100 Bidirectional amplifier 11,101 First terminal 12,102 First demultiplexer / mixer 13,103 Downstream amplifier 14,104 Second demultiplexer / mixer 15,105 Second terminal 16,106 Up amplifier 17 Semiconductor switch 107 Switch C1 to C8 Capacitor CH1 to CH5 Choke coil D1, D2 Diode R1, R2 Termination resistor RC1, RC2 Drive coil RS switch RY1, RY2 High frequency relay

Claims (4)

[Claims] A first terminal to which a downstream input signal is input and an upstream output signal is output; a second terminal to which a downstream output signal is output and an upstream input signal is input; The downstream input signal input from the first terminal is branched to the downstream side, and the upstream output signal supplied from the upstream side is converted to the first output signal.
A first demultiplexer / mixer that mixes the signals with the first and second terminals; and an upstream input signal that is input from the second terminal, and is demultiplexed to the upstream side.
A second demultiplexer / mixer that mixes the signals at the terminals of the first and second terminals; a downstream amplifier that amplifies the downstream signal is provided on the downstream side; an upstream amplifier that amplifies the upstream signal is provided on the upstream side; Both of which are provided with a path circuit for passing the upstream amplifier and a selection means for selecting either the upstream amplifier or the path circuit or a cutoff state for blocking the upstream signal. Amplifier. 2. The first high frequency switch means for supplying an upstream signal demultiplexed by the second demultiplexer / mixer to one of the upstream amplifier and the pass circuit, A first selection state in which drive power is supplied to an upstream signal amplified by an upstream amplifier and second high-frequency switch means for selecting one of the upstream signal passed in the pass circuit; and a drive power supply to the upstream amplifier. 2. The bidirectional amplifier according to claim 1, further comprising switch means for selecting one of the second selection states to be given. 3. The high-frequency switching means for selecting either the upstream signal amplified by the upstream amplifier or the upstream signal passed by the path circuit, and the second branching / mixing unit. The split upstream signal is input to the upstream amplifier, and at the same time, drive power is supplied to the upstream amplifier and the high-frequency switch means, or input to the pass circuit, or the upstream signal and the pass circuit are terminated by a termination circuit. 2. The bidirectional amplifier according to claim 1, further comprising switch means for selecting whether to perform the operation. 4. The high-frequency switching means for selecting either an upstream signal amplified by the upstream amplifier or an upstream signal passed by the path circuit, and a second branching / mixing unit. Whether the separated upstream signal is supplied to the upstream amplifier and drive power is supplied to the upstream amplifier at the same time, or is supplied to the pass circuit and drive power is supplied to the high-frequency switch means at the same time. 2. A bidirectional amplifier according to claim 1, further comprising: switch means for selecting whether or not the signal is terminated by a terminating circuit.