JP2000175173A - Bidirectional amplifier with monitor terminal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To monitor a down amplifier and an up amplifier in a bidirectional amplifier without reconnecting a cable of a measuring instrument. SOLUTION: A downstream output signal outputted from a downstream amplifier 13 is branched by a first branching device 14 and guided to a second fixed contact c of a switch means 19. The upstream output signal output from the upstream amplifier 17 is branched by the second branching device 18 and guided to the first fixed contact a of the switch means 19. Switch means 19
By connecting the cable of the measuring instrument to the monitor terminal 20 to which the fixed contact b is connected and switching the switch means 19, the downstream amplifier 13 and the upstream amplifier 17 can be monitored without reconnecting the cable of the measuring instrument. Can be.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art In a conventional bidirectional CATV system, a transmission line is laid between a CATV center and each subscriber's house. , A relay amplifier is inserted every certain distance. As the relay amplifier, a bidirectional amplifier capable of amplifying a downlink signal and an uplink signal 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.
For this reason, in the bidirectional amplifier, the output level with the frequency on the horizontal axis can be measured, and the frequency characteristic of the bidirectional amplifier is monitored and adjusted while observing the measured value.

FIG. 5 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 106 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 109 is supplied to the first terminal 1.
01. Further, the second terminal 106 is connected to a second demultiplexer / mixer 105, and the second demultiplexer / mixer sends the upstream input signal input from the second terminal 106 to the upstream amplifier 109. The signal is demultiplexed, and the output signal from the downstream amplifier 103 is mixed with the second terminal 106. Further, in order to monitor the output level of the downstream amplifier 103, the downstream output signal branched by the first branching device 104 connected to the output side of the downstream amplifier 103 is monitored.
Is led to. Further, in order to monitor the output level of the upstream amplifier 109, the upstream signal branched by the second branching unit 110 connected to the output side of the upstream amplifier 109 is guided to the monitor terminal 108.

In such a bidirectional amplifier 100,
When monitoring whether the output level of the downstream amplifier 103 or the upstream amplifier 109 is an output level having a predetermined frequency characteristic, a measuring instrument such as a spectrum analyzer is connected to the downstream output monitor terminal 107 or the upstream output monitor terminal 108. Connect the cable and monitor the measuring instrument. At this time, in order to obtain a predetermined frequency characteristic,
The level adjusting means (not shown) of the downstream amplifier 103 or the upstream amplifier 109 can be adjusted. However, the output levels of the downstream amplifier 103 and the upstream amplifier 109 cannot be monitored at the same time.
07, the output level of the downstream amplifier 103 is monitored by connecting a cable of the measuring instrument, or this cable is connected again to the monitor terminal 108 of the upstream output to monitor the output level of the upstream amplifier 109. Absent.

Next, another example of the circuit configuration of a conventional bidirectional amplifier is shown in FIG. 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 106 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 signal from the upstream amplifier 109 is mixed to the first terminal 101. Also, the second terminal 10
6 is connected to a second demultiplexer / mixer 105, which demultiplexes the upstream input signal input from the second terminal 106 to the upstream amplifier 109, The output signal from 103 is mixed with the second terminal 106. Further, in order to monitor the levels of the downstream input signal and the upstream output signal, the first terminal 101 and the first demultiplexer / mixer 102 are connected to the monitor terminal 107 via a resistor R, and the downstream output signal is monitored. The second demultiplexer / mixer 105 and the second terminal 10
6 and the monitor terminal 108 are connected via a resistor R.

As described above, the bidirectional amplifier 10 shown in FIG.
At 0, the level of the downstream input signal or the upstream input signal input to the first terminal 101 or the second terminal 106 can be monitored and monitored. In the bidirectional amplifier 100 shown in FIG. 6, when monitoring the levels of the downstream input signal and the upstream output signal by monitoring, the monitor terminal 107 may be connected to a cable of a measuring instrument such as a spectrum analyzer. When monitoring and monitoring the levels of the downstream output signal and the upstream input signal, the cable of the measuring instrument may be connected to the monitor terminal 108 again.

[0007]

As described above, when monitoring the downstream amplifier and the upstream amplifier in the bidirectional amplifier, it is necessary to monitor the output signal, but since the monitor terminals are provided separately, However, there is a problem that it is impossible to monitor both the upstream and downstream amplifiers without reconnecting the cable of the measuring instrument.

Accordingly, an object of the present invention is to provide a bidirectional amplifier having a monitor terminal capable of monitoring a downstream amplifier and an upstream amplifier in a bidirectional amplifier without reconnecting a cable of a measuring instrument.

[0009]

In order to achieve the above object, a bidirectional amplifier having a first monitor terminal according to the present invention comprises:
A first terminal to which a downstream input signal is input and to which an upstream output signal is output; a second terminal to which a downstream output signal is output and to which an upstream input signal is input; , Inserted between the input side of the downstream amplifier and the output side of the upstream amplifier, splits the downstream input signal input from the first terminal to the downstream amplifier, and outputs the upstream output signal from the upstream amplifier. A first demultiplexer / mixer for mixing with the first terminal, the second terminal, an output side of the downstream amplifier, and an input side between the input side of the upstream amplifier;
A second demultiplexer / mixer that splits an upstream input signal input from the second terminal into the upstream amplifier and mixes a downstream output signal from the downstream amplifier with the second terminal; A monitor terminal is provided for outputting one of the branched output signal of the amplifier and the branched output signal of the upstream amplifier as a monitor signal by a switch means.

Further, a bidirectional amplifier having a second monitor terminal according to the present invention capable of achieving the above object has 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 to which an upstream input signal is input;
Terminal, an input side of the down-amplifier, and an output side of the up-amplifier, and separates the down-input signal input from the first terminal to the down-amplifier, and A first demultiplexer / mixer for mixing an output signal with the first terminal, the second terminal, an output side of the downstream amplifier, and an input side between the input side of the upstream amplifier; A second demultiplexer / mixer for demultiplexing an upstream input signal input from a second terminal to the upstream amplifier and mixing a downstream output signal from the downstream amplifier with the second terminal; And a monitor terminal to which the upstream output signal branched from the upstream amplifier is directly connected.

Further, the bidirectional amplifier having the third monitor terminal according to the present invention, which can achieve the above object, has 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 to which an upstream input signal is input, the first terminal, an input side of a downstream amplifier, and an output side of an upstream amplifier; A first demultiplexer / mixer that demultiplexes a downstream input signal input from a first terminal to the downstream amplifier, and mixes an upstream output signal from the upstream amplifier with the first terminal; Terminal, the output side of the downstream amplifier, and inserted between the input side of the upstream amplifier, splits the upstream input signal input from the second terminal to the upstream amplifier, from the downstream amplifier, The downstream output signal of the second terminal A second branching and mixer for mixing,
At least one of the branched down output signal of the down amplifier and the branched up output signal of the up amplifier is led to switch means via filter means capable of blocking the other output signal, and the switch means And a monitor terminal for outputting any one of the selected output signals as a monitor signal.

Still further, in the bidirectional amplifier having the fourth monitor terminal according to the present invention which can achieve the above object, a first downstream input signal and a second downstream input signal having different frequency bands are input. And a first terminal from which an uplink output signal is output, a second terminal from which a first downlink output signal and a second downlink output signal having different frequency bands are output, and an uplink input signal is input. , The first terminal inserted between the first terminal, the second demultiplexer / mixer, and the input side of the second downstream amplifier, and the first terminal input from the first terminal.
And the second input signal from the first terminal is split into the second downstream amplifier, and the second input signal is split into the second output amplifier. Demultiplexing of
A first demultiplexer / mixer for mixing the upstream output signal output from the mixer to the first terminal, the first demultiplexer / mixer, an input side of a first downstream amplifier, and an upstream A first downstream input signal inserted from the first branching / mixing device, which is inserted between the output side of the amplifier and the first downstream branching / mixing device, is branched to the first downstream amplifier, and an upstream output signal from the upstream amplifier is output. To the first demultiplexer / mixer, a fourth demultiplexer / mixer, an output of the first down-amplifier, and an input of the up-amplifier. , The upstream input signal input from the fourth demultiplexer / mixer is split into the upstream amplifier, and the first downstream output signal output from the first downstream amplifier is A third demultiplexer / mixer for mixing with the fourth demultiplexer / mixer, the second terminal, the third demultiplexer / mixer, Inserted between the output side of the second downlink amplifier demultiplexes the upstream input signal input from the second terminal to the third branching and mixer, the third branching and
A first downstream output signal output from the mixer;
A fourth demultiplexer / mixer for mixing a second downstream output signal from the downstream amplifier into the second terminal, the first downstream output signal branched from the second terminal, and the second And the output signal of the upstream amplifier and the output signal branched by the upstream amplifier are guided to switch means via filter means capable of blocking the other output signal, and any one of the outputs selected by the switch means is output. A monitor terminal for outputting a signal as a monitor signal.

According to the present invention, since only one monitor terminal for monitoring the upstream output signal and the downstream output signal can be used, the monitoring of the upstream output signal without reconnecting the cable of the measuring instrument, Monitoring of the downstream output signal can be performed. In addition, when the up output signal and the down output signal are switched by the switch means and output from the monitor terminal,
By guiding the monitor signal from one amplifier to the switch means via the filter means capable of blocking the output signal of the other, the stop band attenuation of the demultiplexer / mixer can be complemented, and the monitor terminal is only used. However, it is possible to prevent the occurrence of the oscillation phenomenon and the frequency characteristic failure caused by the bidirectional amplifier.

[0014]

FIG. 1 shows a configuration example of a first embodiment of a bidirectional amplifier having a monitor terminal according to the present invention. A bidirectional amplifier 1 having a monitor terminal according to the first embodiment of the present invention shown in FIG. 1 has a first terminal 11 to which a down signal is input and an up signal is output, and a down output signal which is output. And a second terminal 16 to which an upstream input signal is input. The first terminal 11 is connected to a first demultiplexer / mixer 12, and the first demultiplexer / mixer 12 splits a downstream input signal input from the first terminal 11 into a downstream amplifier 13. The output signal from the upstream amplifier 17 is mixed with the first terminal 11. Further, the second terminal 16 is connected to a second demultiplexer / mixer 15, and the second demultiplexer / mixer 15 converts the upstream input signal input from the second terminal 16 into an upstream amplifier 17. And the output signal from the downstream amplifier 13 is mixed with the second terminal 16.
Further, in order to monitor the output level of the downstream amplifier 13, the downstream output signal branched by the first branch unit 14 connected to the output side of the downstream amplifier 13 is guided to the second fixed contact c of the switch means 19. ing. Further, in order to monitor the output level of the upstream amplifier 17, the upstream output signal branched by the second branching device 18 connected to the output side of the upstream amplifier 17 is guided to the first fixed contact a of the switch means 19. ing. The movable contact b of the switch means 19 is guided to the monitor terminal 20.

In such a bidirectional amplifier 1, when monitoring whether the output level of the downstream amplifier 13 or the upstream amplifier 17 is an output level having predetermined frequency characteristics, a monitor terminal 20 is connected to the monitor terminal 20. Connect the measuring instrument cable. Then, the movable contact b of the switch means 19 is connected to one of the fixed contacts a and b. Here, if the movable contact b is connected to the second fixed contact c, the output level of the downstream amplifier 13 is measured by a measuring instrument. Can be monitored. If the movable contact b is connected to the first fixed contact a, the output level of the up-amplifier 17 can be monitored by a measuring instrument. At this time, a level adjusting means (not shown) of the downstream amplifier 13 or the upstream amplifier 17 can be adjusted so as to obtain a predetermined frequency characteristic. As described above, in the bidirectional amplifier having the monitor terminal according to the first embodiment of the present invention, the output level of the downstream amplifier 13 or the output level of the upstream amplifier 17 is changed by switching the switch means 19, and the measuring instrument is connected to the monitor terminal 20 and can be monitored.

The bidirectional amplifier 1 having a monitor terminal according to the present invention is inserted in a transmission line connecting a CATV center and each subscriber's house, and is provided in the bidirectional amplifier so that the line length can be equalized. Up amplifier 13 and down amplifier 1
7, the frequency characteristics of the output level are adjusted. Also,
The downlink signal is a signal of a plurality of channels of FM broadcast, television broadcast, and still image broadcast transmitted from the CATV center, and has a frequency band of, for example, 70 to 450 MHz. The uplink signal is various information transmitted from the user via a CATV terminal installed at each subscriber's house, and has a frequency band of, for example, 10 to 48 MHz. As described above, since the frequency band of the upstream signal is relatively different from the frequency band of the downstream signal, the isolation between the upstream signal and the downstream signal in the demultiplexers / mixers 12 and 15 shown in FIG. Is kept. Therefore, the signals output to the input sides of the downstream amplifier 13 and the upstream amplifier 17 do not return, and it is possible to prevent occurrence of phenomena such as oscillation and poor frequency characteristics even if the signal leaks in the switch unit 19.

Next, FIG. 2 shows a configuration example of a second embodiment of a bidirectional amplifier having a monitor terminal according to the present invention. The bidirectional amplifier 1 having the monitor terminal according to the second embodiment of the present invention shown in FIG. 2 is different from the switch means 19 in the bidirectional amplifier 1 having the monitor terminal according to the first embodiment of the present invention described above. Is omitted. The description of the configuration common to the bidirectional amplifier 1 according to the first embodiment is omitted. Bidirectional amplifier 1 having a monitor terminal according to a second embodiment of the present invention
Then, the monitor signal from the first branch unit 14 that branches the output signal of the downstream amplifier 13 and the monitor signal from the second branch unit 18 that branches the output signal of the upstream amplifier 17 are directly combined at point A. It is output from the monitor terminal 30. In this case, for example, in the downstream amplifier 13, the first branching device 14-A
A loop is formed by the point, the second branching device 18, the first demultiplexing / mixing device 12, and the downstream amplifier 13. A loop is similarly formed in the upstream amplifier 17. For this reason, the output signal returns to the input side of the amplifier due to this loop, and phenomena such as oscillation and poor frequency characteristics are likely to occur. To prevent this, the first splitter 14 and the second splitter are used. 18, the first demultiplexer / mixer 12, the second
The sum with the stop band attenuation of the demultiplexer / mixer 15 is set to be sufficiently larger than the amplification of the downstream amplifier 13 or the amplification of the upstream amplifier 17. The term “stopband attenuation” refers to the amount of attenuation at which the upstream signal is attenuated at the terminal that separates the downstream signal, and the amount of attenuation at which the downstream signal is attenuated at the terminal that separates the upstream signal.

In such a bidirectional amplifier 1, when monitoring whether the output level of the downstream amplifier 13 or the upstream amplifier 17 is an output level having a predetermined frequency characteristic, a monitor terminal 30 is connected to the monitor terminal 30. Connect the measuring instrument cable. By monitoring the level of the up output signal and the level of the down output signal simultaneously displayed on the measuring instrument, the output level of the down amplifier 13 and the output level of the up amplifier 17 can be monitored simultaneously.

Next, FIG. 3 shows a configuration example of a third embodiment of a bidirectional amplifier having a monitor terminal according to the present invention. In the bidirectional amplifier 1 having the monitor terminal according to the third embodiment of the present invention shown in FIG. 3, the switch means in the bidirectional amplifier 1 having the monitor terminal according to the first embodiment of the present invention described above. 19 between the first fixed contact a and the second branch 18.
PF) 21 is inserted. The description of the configuration common to the bidirectional amplifier 1 according to the first embodiment is omitted. In the bidirectional amplifier 1 having the monitor terminal according to the third embodiment of the present invention, the stopband attenuation in the demultiplexer / mixer 12 and the demultiplexer / mixer 15 is reduced by the amplification of the downstream amplifier 13 and the upstream amplifier 17. It may be smaller than the degree. In this case, since the degree of isolation between the contacts in the switch means 19 deteriorates with a high-frequency down signal, the down signal output from the down amplifier 13 may return to the input side and cause phenomena such as oscillation and poor frequency characteristics. is there. Therefore, as shown in FIG.
The LPF 21 that allows only the upstream signal to pass is inserted between the branching device 18 and the first fixed contact a. This allows
Even if a down signal leaks from the second fixed contact c to the first fixed contact a in the switch means 19, the leaked down signal is attenuated by the LPF 21 and does not return to the input side of the down amplifier 13; And a phenomenon such as poor frequency characteristics does not occur.

In such a bidirectional amplifier 1 according to the third embodiment of the present invention, when monitoring whether the output level of the downstream amplifier 13 or the upstream amplifier 17 is an output level having a predetermined frequency characteristic. , A cable of a measuring instrument such as a spectrum analyzer is connected to the monitor terminal 40. Then, the movable contact b of the switch means 19 is connected to one of the fixed contacts a and b.
Assuming that the movable contact b is connected to the fixed contact c, the output level of the downstream amplifier 13 can be monitored by a measuring instrument. If the movable contact b is connected to the first fixed contact a, the output level of the up-amplifier 17 can be monitored by a measuring instrument. At this time, a level adjusting means (not shown) of the downstream amplifier 13 or the upstream amplifier 17 can be adjusted so as to obtain a predetermined frequency characteristic. Thus, by switching the switch means 19, the output level of the downstream amplifier 13 or the output level of the upstream amplifier 17 can be monitored while the measuring instrument is connected to the monitor terminal 40.

When the upstream signal output from the upstream amplifier 17 returns to its input side, a high-pass filter for passing only the downstream signal is inserted between the first branch 14 and the second fixed contact c. I just need. Also, by using a low-pass filter that passes only the above-described up signal or a high-pass filter that passes only the down signal,
The technique of preventing the phenomenon of oscillation and frequency characteristic failure even with one monitor terminal may be applied to the bidirectional amplifier 1 according to the second embodiment shown in FIG.

Next, FIG. 4 shows a configuration example of a fourth embodiment of a bidirectional amplifier having a monitor terminal according to the present invention. The bidirectional amplifier 1 having the monitor terminal according to the fourth embodiment of the present invention shown in FIG. 4 is different from the bidirectional amplifier 1 having the monitor terminal according to the first embodiment of the present invention described above. The configuration is such that a second downstream amplifier 23 for amplifying a high downstream signal is added. Less than,
The explanation will be given. The bidirectional amplifier 1 according to the fourth embodiment includes a first terminal 11 to which a downstream signal is input and an upstream signal is output, and a first terminal 11 to which a downstream output signal is output and an upstream input signal is input. 2 terminals 16. The first terminal 11 is connected to a third demultiplexer / mixer 22. The third demultiplexer / mixer 22 demultiplexes a downstream input signal in a high frequency band and outputs a second downstream amplifier 23. , And separates the downstream input signal in the low frequency band and supplies it to the first demultiplexer / mixer 12.

The first demultiplexer / mixer 12 demultiplexes the downstream input signal demultiplexed by the third demultiplexer / mixer 22 to the first downstream amplifier 13 and outputs the output signal from the upstream amplifier 17. It is mixed with the third demultiplexer / mixer 22. This upstream output signal is mixed into the first terminal 11 in the third demultiplexer / mixer 22. The second terminal 16 is connected to a fourth demultiplexer / mixer 24, and the fourth demultiplexer / mixer 24
Mixes the downstream output signal of the high frequency band output from the second downstream amplifier 23 with the second terminal 16 and converts the downstream output signal of the low frequency band from the second demultiplexer / mixer 15 into the second terminal 16. Mixed with the terminals. Further, the upstream input signal input from the second terminal 16 is split by the fourth splitter / mixer 24 and supplied to the second splitter / mixer 15. The second demultiplexer / mixer 15 demultiplexes the upstream input signal supplied from the fourth demultiplexer / mixer 24 to the upstream amplifier 17 and outputs the output signal from the downstream amplifier 13 to the fourth demultiplexer.・
It is mixed in the mixer 24.

Further, in order to monitor the output level of the first downstream amplifier 13 and the output level of the second downstream amplifier 23, a first demultiplexer / mixer 24 and a second terminal 16 are connected. Of the first branching device 25
Is output to the second fixed contact c of the switch means 19. Further, in order to monitor the output level of the upstream amplifier 17, the upstream signal branched by the second branching unit 18 connected to the output side of the upstream amplifier 17 is
Low-pass filter (LPF) that passes only the upstream signal
It is led to the first fixed contact a of the switch means 19 via 21. The movable contact b of the switch means 19 is led to the monitor terminal 50.

In the bidirectional amplifier 1 having the monitor terminal according to the fourth embodiment of the present invention, the second downstream amplifier 2
Since the frequency band of the downstream signal amplified in step 3 is made higher, the degree of separation between the contacts in the switch means 19 deteriorates for the downstream signal. In order to prevent the down signal output from the second down amplifier 23 from returning to the input side thereof and causing phenomena such as oscillation and poor frequency characteristics,
An LPF 21 that allows only an upstream signal to pass is inserted between the second branch 18 and the first fixed contact a. Thereby, even if a downstream signal having a high frequency band leaks from the second fixed contact c to the first fixed contact a in the switch means 19, the leaked downstream signal is attenuated by the LPF 21 and is input to the input side of the downstream amplifier 13. Since it does not return, the above-mentioned phenomena such as oscillation and poor frequency characteristics do not occur.

In the bidirectional amplifier 1 according to the fourth embodiment of the present invention, the output level of the first down amplifier 13, the second down amplifier 23 or the up amplifier 17 has a predetermined frequency characteristic. When monitoring whether or not the output level has been adjusted, a cable of a measuring instrument such as a spectrum analyzer is connected to the monitor terminal 50. Then, the movable contact b of the switch means 19 is replaced with one of the fixed contacts a,
b, but here the movable contact b is connected to the second fixed contact c.
Are connected, the first downlink amplifier 13 and the second
The output level of the downstream amplifier 23 can be monitored by a measuring instrument. If the movable contact b is connected to the first fixed contact a, the output level of the up-amplifier 17 can be monitored by a measuring instrument. At this time, the level adjusting means (not shown) of the first down amplifier 13, the second down amplifier 23 or the up amplifier 17 can be adjusted so as to obtain a predetermined frequency characteristic. As described above, by switching the switch means 19, the first downstream amplifier 1 is switched.
3. The output level of the second downstream amplifier 23 or the output level of the upstream amplifier 17 can be monitored while the measuring instrument is connected to the monitor terminal 50.

[0027]

As described above, according to the present invention, since only the monitor terminal for monitoring the upstream output signal and the downstream output signal can be used, the monitoring of the upstream output signal can be performed without reconnecting the cable of the measuring instrument. In addition, it is possible to monitor a downstream output signal. When the up output signal and the down output signal are switched by the switch means and output from the monitor terminal, the monitor signal is guided from one amplifier to the switch means through the filter means capable of blocking the other output signal. As a result, the stop band attenuation of the demultiplexer / mixer can be complemented, and the occurrence of oscillation phenomena, poor frequency characteristics, and the like due to the bidirectional amplifier can be prevented even if only the monitor terminal is used.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of a first embodiment of a bidirectional amplifier having a monitor terminal according to the present invention.

FIG. 2 is a circuit diagram showing a configuration of a second embodiment of a bidirectional amplifier having a monitor terminal according to the present invention.

FIG. 3 is a circuit diagram showing a configuration of a third embodiment of a bidirectional amplifier having a monitor terminal according to the present invention.

FIG. 4 is a circuit diagram showing a configuration of a fourth embodiment of a bidirectional amplifier having a monitor terminal according to the present invention.

FIG. 5 is a circuit diagram showing a configuration of a bidirectional amplifier in a conventional bidirectional CATV system.

FIG. 6 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 12,15,22,24,102,105 demultiplexer / mixer 13,23,103 downstream amplifier 14,18,25,104,110 brancher 16,106 Second terminal 17, 109 Up-amplifier 19 Switch means 20, 30, 40, 50, 107, 108 Monitor terminal 21 Low-pass filter

Continued on the front page F-term (reference) 5C064 BA01 BA02 BB05 BC12 BC27 BD01 BD07 5J069 AA01 AA21 AA51 AA55 BC00 CA54 CA92 CA97 CA98 FA14 FA18 HA25 HA38 KA42 SA13 TA01

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; A first terminal, which is inserted between the input side of the downstream amplifier and the output side of the upstream amplifier, branches the downstream input signal input from the first terminal to the downstream amplifier, A first demultiplexer / mixer that mixes the upstream output signal with the first terminal, and is inserted between the second terminal, the output side of the downstream amplifier, and the input side of the upstream amplifier. Demultiplexing the upstream input signal input from the second terminal to the upstream amplifier,
A second demultiplexer / mixer that mixes a downstream output signal from the downstream amplifier with the second terminal, a downstream output signal branched from the downstream amplifier, and a upstream output signal branched from the upstream amplifier. And a monitor terminal for outputting any one of the above as a monitor signal by a switch means. 2. 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; A first terminal, which is inserted between the input side of the downstream amplifier and the output side of the upstream amplifier, branches the downstream input signal input from the first terminal to the downstream amplifier, A first demultiplexer / mixer that mixes the upstream output signal with the first terminal, and is inserted between the second terminal, the output side of the downstream amplifier, and the input side of the upstream amplifier. Demultiplexing the upstream input signal input from the second terminal to the upstream amplifier,
A second demultiplexer / mixer that mixes a downstream output signal from the downstream amplifier with the second terminal, a downstream output signal branched from the downstream amplifier, and a upstream output signal branched from the upstream amplifier. And a monitor terminal directly connected to the bidirectional amplifier. 3. 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; A first terminal, which is inserted between the input side of the downstream amplifier and the output side of the upstream amplifier, branches the downstream input signal input from the first terminal to the downstream amplifier, A first demultiplexer / mixer that mixes the upstream output signal with the first terminal, and is inserted between the second terminal, the output side of the downstream amplifier, and the input side of the upstream amplifier. Demultiplexing the upstream input signal input from the second terminal to the upstream amplifier,
A second demultiplexer / mixer that mixes the downstream output signal from the downstream amplifier with the second terminal, a downstream output signal branched from the downstream amplifier, and a upstream output signal branched from the upstream amplifier. A monitor terminal for guiding at least one of the output signals to the switch means via a filter means capable of blocking the other output signal, and outputting any one of the output signals selected by the switch means as a monitor signal. A bidirectional amplifier having a monitor terminal. 4. A first terminal to which a first downstream input signal and a second downstream input signal having different frequency bands are input, and a first terminal from which an upstream output signal is output, and a first downstream output having a different frequency band. A second terminal to which a signal and a second downstream output signal are output and to which an upstream input signal is input; the first terminal; a second demultiplexer / mixer; A first downstream input signal inserted between the first input terminal and the first input terminal is split into the second demultiplexer / mixer, and the second input signal is input from the first terminal. A first demultiplexer / mixer for demultiplexing the second downstream input signal to the second downstream amplifier and mixing the upstream output signal output from the second demultiplexer / mixer with the first terminal. Between the first demultiplexer / mixer, the input side of the first downstream amplifier, and the output side of the upstream amplifier. And splits a first downstream input signal input from the first demultiplexer / mixer to the first downstream amplifier, and outputs an upstream output signal from the upstream amplifier to the first demultiplexer. A second demultiplexer / mixer that mixes with the mixer, a fourth demultiplexer / mixer, and inserted between the output side of the first downstream amplifier and the input side of the upstream amplifier; The upstream input signal input from the fourth demultiplexer / mixer is split into the upstream amplifier, and the first downstream output signal output from the first downstream amplifier is converted into the fourth splitter / multiplexer. A third demultiplexer / mixer that mixes with the mixer, inserted between the second terminal, the third demultiplexer / mixer, and an output side of the second downstream amplifier; The upstream input signal input from the second terminal is split into the third demultiplexer / mixer and output from the third demultiplexer / mixer. 1, a fourth demultiplexer / mixer that mixes the second downstream output signal from the second downstream amplifier with the second terminal, and the fourth branching / mixing device, which is branched from the second terminal. Leading the first downstream output signal and the second downstream output signal, and the upstream output signal branched from the upstream amplifier to switch means via filter means capable of blocking the other output signal;
A monitor terminal for outputting any output signal selected by the switch means as a monitor signal.