JP4374205B2 - Two-way CATV system booster - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an in-building booster mainly used for a bidirectional CATV system. More specifically, the present invention relates to a bidirectional CATV system using an amplifier circuit for an upstream band corresponding to a high input without degrading the quality of the upstream line. Is a booster in the building.
[0002]
[Prior art]
In the bi-directional CATV system, in order to maintain the uplink quality, it is necessary to take measures to reduce the system interference due to the upstream inflow noise. Also, special consideration is required for the uplink C / N. This is because in the bidirectional CATV system, the total number of amplifiers in the upstream direction greatly affects the C / N in the upstream direction compared to the continuous number of amplifiers in the downstream direction that affects the C / N. It is. Because of these problems, it is necessary to operate the upstream signal, which is the output signal of a device connected to the terminal side (for example, cable modem), at a high level so that the input level to the amplifier is not lowered as much as possible. .
However, when operating at such a high level, the upstream signal amplification circuit of the in-building booster, which is a distribution compensation amplifier, installed in the CATV subscriber's building may exceed the rated output level. . For this purpose, this amplifier circuit is provided with level adjusting means for gain adjustment on the input side, or with level adjusting means for gain adjustment between the stages of amplifiers connected in multiple stages constituting the amplifier circuit. In other words, the circuit configuration is such that the amplifier circuit is operated at an optimum output level. (For example, Japanese Patent Laid-Open No. 2000-151477)
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 2000-151477
[0004]
[Problems to be solved by the invention]
However, according to a conventional booster in a building, an example of an amplifier circuit provided with level adjustment means on the input side of the upstream signal amplifier circuit, for example, a high level upstream signal output from a cable modem In the circuit system in which the level adjusting means is inserted at the input of the amplifier circuit in order to operate the amplifier circuit below the rated output level when being input to the amplifier circuit, the level of the upstream signal input to the amplifier circuit As a result, the C / N of the upstream signal of the system deteriorates.
Further, when the amplifier circuit is composed of amplifiers connected in multiple stages and used in a system in which the attenuation amount of the level adjusting means is larger than the gain of the first amplifier circuit, the amplifier circuit In addition to being in a state that does not need to be provided, power that does not need to be supplied to the first amplifier circuit will continue to be supplied, resulting in extra power consumption of the amplifier circuit.
Therefore, the present invention has been made to solve the above-mentioned problems of the prior art,
The purpose is to provide an optimal in-building booster for the interactive CATV system.
Another object is to provide an in-building booster including an upstream signal amplifier circuit capable of selectively switching between a first amplifier circuit and a passage path.
Another object is to provide an in-building booster capable of adjusting an input level without deteriorating C / N.
Another object is to provide an in-building booster that saves power according to the input level.
[0005]
[Means for Solving the Problems]
The invention described in claim 1 made to achieve such an object,
In a building booster of a bidirectional CATV system, which is provided on a transmission line on the terminal side of a bidirectional CATV system and includes an amplification circuit that amplifies a downstream signal in a predetermined frequency band and an upstream signal in a frequency band different from the downstream signal. ,
  The amplifying circuit for the upstream signal is:
  A first amplifier;
  AboveFirst amplifierPlaced in parallel withA passing line,
  Select one of the first amplifier and the passing line as a path for passing the upstream signalA selection means;
  Adjust the level of the upstream signal output from the path selected by the selection meansLevel adjustment means;
  AboveSecond amplifier connected to the output of the level adjusting meansWhen,
Power supply switching means for switching whether or not to apply DC power to the first amplifier and the selection means;
And the selection means selects the first amplifier as the path of the upstream signal when the DC power is supplied via the power supply switching means, and the DC power supply is selected via the power supply switching means. When not supplied, a pass line is selected as the path of the upstream signal..
[0006]
The invention of claim 2 is configured such that the upstream signal is 10 to 55 MHz.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an example of an embodiment embodying the present invention will be described in detail with reference to the drawings. FIG. 1 shows an embodiment of a building booster 1 equipped with an amplifier circuit according to the present invention. FIG. 2 shows another embodiment.
[0008]
The in-building booster shown in the embodiment of FIG. 1 transmits a downlink signal of a predetermined frequency (for example, 70 to 770 MHz) from the center device to the terminal side, and the frequency from the terminal side to the center device side is lower than that of the downlink signal. In a bidirectional CATV system configured to transmit an upstream signal in a low predetermined frequency band (for example, 10 to 55 MHz), these signals are used when the signals are bidirectionally amplified on a transmission line.
[0009]
This in-building booster 1 is connected to the center device via a downstream signal input path including an input terminal 5 connected to the transmission line on the center device side and a high-pass filter 10 (hereinafter referred to as HPF) having a cutoff frequency of 70 MHz. The downstream signal transmitted from the side is taken in, the signal level of the captured downstream signal is amplified by the downstream signal amplification circuit 14, and the downstream signal after the amplification is transmitted to the HPF 18 having a cutoff frequency of 70 MHz and the terminal side transmission It is configured to output on the terminal side transmission line via a downlink signal output path composed of an output terminal 7 connected to the line.
In the embodiment of the present invention, the downstream signal amplifier circuit 14 is provided between the front and rear amplifier circuits 14a and 14b and the downstream signal level so that the downstream signal amplifier circuit 14 has a predetermined output level. It is comprised with the level adjustment means 14c to adjust.
[0010]
Next, the in-building booster 1 is provided with an upstream signal amplifier circuit 3 having a predetermined amplification characteristic for amplifying the upstream signal.
The upstream signal transmitted from the terminal side is input to the upstream signal amplifying circuit 3 via an upstream signal input path including the output terminal 7 and a low-pass filter 24 (hereinafter referred to as LPF) having a cutoff frequency of 55 MHz. Is done. The input signal is amplified by the upstream signal amplifying circuit 3, and the amplified upstream signal is transmitted on the center apparatus side via the upstream signal output path composed of the LPF 46 having a cutoff frequency of 55 MHz and the input terminal 5. Output on the line.
[0011]
The upstream signal amplifier circuit 3 includes a first amplifier circuit 30, a pass line 31 connected in parallel to the first amplifier circuit, and the first signal connected in parallel to the upstream signal in the CATV system. Selection means 32 (32a, 32b) for selecting and outputting via either the amplifier circuit 30 or the passage line 31, a level adjusting means 33 connected to the output of the selection means 32, and the level The second amplifier 34 is connected to the output of the adjusting means 33.
[0012]
Reference numeral 36 denotes power supply switching means provided between the DC power output from the power supply circuit 38 and the first amplifier circuit 30 and the selection means 32 (32a, 32b). For example, when the power supply switching means 36 is turned on, the first amplifier circuit 30 and the selection means 32 (32a, 32b) are configured to selectively apply a DC voltage to the selection means 32 (32a, 32b). ), The path of the first amplifier circuit 30 is selected for the upstream signal. When the power supply switching means 36 is turned off, the path of the passing line 31 is selected for the upstream signal by stopping the power supply to the first amplifier circuit 30 and the selection means 32 (32a, 32b).
The level adjusting means 33 includes a fixed attenuator 33b, a switching means 33a for switching the fixed attenuator 33b into and out of the signal line, and a variable attenuator 33c. Reference numeral 39 denotes an AC plug for obtaining an AC power supply from a commercial power supply.
[0013]
The in-building booster 1 configured as described above will be described in more detail.
An information terminal such as a cable modem is connected to the terminal side transmission line connected to the output terminal 7. The upstream signal output from the cable modem is input from the output terminal 7. At this time, if the level of the upstream signal does not exceed the rated output level of the upstream signal amplification circuit 3, the output level is adjusted by the level adjustment means 33 of the upstream signal amplification circuit 3 according to the design of the CATV system. Adjust to a predetermined level.
When the level of the upstream signal exceeds the rated output level of the upstream signal amplification circuit 3, the selection means (for example, a high frequency relay) 32 (32a) is provided on the side of the pass line 31 connected in parallel to the first amplification circuit 30. , 32b).
[0014]
The selection of the line is performed by turning on / off the power supply switching means 36. As described above, the DC power output from the power supply circuit 38 is supplied or not supplied to the selection means 32 (32a, 32b) and the first amplifier circuit 30 via the power supply switching means 36. Do. That is, if the upstream signal level is within the appropriate input level range, the power supply switching means 36 (for example, a switch) is turned on. As a result, power is supplied to the first amplifier circuit 30 and the selection means 32 (32a, 32b), whereby the path on the first amplifier circuit 30 side is selected, and the upstream signal is amplified by the first amplifier circuit 30. After that, it is connected to the circuit after the level adjusting means 33.
When the upstream signal is at a high level, the switch 36 is turned off to stop the power supply to the first amplifier circuit 30 and the selection means 32 (32a, 32b). As a result, the path on the passing line 31 side is selected, and the upstream signal passes through the passing line 31 and is then connected to the circuit after the level adjusting means 33.
[0015]
When the upstream signal amplifier circuit 3 is operated at a high level as described above, a conventional method for providing an attenuator or the like on the input side of the first amplifier circuit 30 and adjusting the upstream signal to an appropriate level is a cable modem. Therefore, the signal amplified by the upstream signal amplifying circuit 3 is output with the C / N deteriorated. Further, when an attenuator for attenuating the upstream signal is required more than the gain of the first amplifier circuit 30, the first amplifier circuit 30 is not necessary, and in addition, power is supplied to the first amplifier circuit 30. There was no need for power supply.
[0016]
In contrast to this, in the present invention, when the upstream signal amplifier circuit 3 is operated at a high level, the path is selected as the pass line 31 by the power source switching means 36, so that the second amplifier circuit 33 is selected. Thus, a signal of an appropriate level is input, and the cable modem can be operated within the rated output range without deteriorating the C / N of the output signal of the cable modem. In addition, since the power supply to the first amplifier circuit 30 is stopped, the power consumption can be reduced when the upstream signal is operated at a high level.
[0017]
Next, a second embodiment of the present invention will be described with reference to FIG. In the following description, the same components as those in the first embodiment are given the same reference numerals, and detailed description thereof is omitted. In this embodiment, a 10-55 MHz band (hereinafter referred to as uplink L signal) and 650-770 MHz (hereinafter referred to as uplink H signal) are used as the uplink signal band.
[0018]
The in-building booster 1 transmits from the center device side via a downstream signal input path composed of an input terminal 5 connected to the transmission line on the center device side, an HPF 10 with a cut-off frequency of 70 MHz, and an LPF 12 with a cut-off frequency of 600 MHz. The received downstream signal is captured, the signal level of the captured downstream signal is amplified by the downstream signal amplifier circuit 14, and the downstream signal after the amplification is converted into an LPF 16 having a cutoff frequency of 600 MHz and an HPF 18 having a cutoff frequency of 70 MHz. And a downlink signal output path composed of an output terminal 7 connected to the terminal-side transmission line, and output to the terminal-side transmission line. The HPF 10 and LPF 12 constituting the downlink signal input path, and the LPF 16 and HPF 18 constituting the downlink signal output path are band-pass filters that regulate signals passing through them to signal components in the frequency band (70 to 600 MHz) of the downlink signal. Configure.
[0019]
Next, the in-building booster 1 is provided with an upstream signal amplification circuit 3 having a predetermined amplification characteristic for amplifying the upstream H signal from the upstream L signal.
The upstream H signal transmitted from the terminal side is transmitted through an upstream H signal input path including the output terminal 7, the HPF 18 having a cutoff frequency of 70 MHz, the HPF 20 having a cutoff frequency of 650 MHz, and the HPF 22 having a cutoff frequency of 650 MHz. The signal is input to the upstream signal amplifier circuit 3.
Further, the upstream L signal transmitted from the terminal side passes through the upstream L signal input path including the output terminal 7, the LPF 24 having a cutoff frequency of 55 MHz, and the LPF 26 having the cutoff frequency of 55 MHz. 3 is input.
As a result, an upstream signal obtained by mixing the upstream H signal and the upstream L signal is input to the upstream signal amplifying circuit 3 via the HPF 22 and the LPF 26, and these input signals are received by the upstream signal amplifying circuit 3. It amplifies to a predetermined level.
[0020]
Among the upstream signals after the amplification, the upstream H signal includes an HPF 40 having a cutoff frequency of 650 MHz, an HPF 42 having a cutoff frequency of 650 MHz, an HPF 10 having a cutoff frequency of 70 MHz, and the input terminal 5. The signal is output on the transmission line on the center apparatus side via the upstream H signal output path.
The upstream L signal is output to the transmission line on the center apparatus side via an upstream L signal output circuit comprising an LPF 44 having a cutoff frequency of 55 MHz, an LPF 46 having a cutoff frequency of 55 MHz, and an input terminal 5. Is done.
[0021]
The in-building booster 1 of the present application is a booster for compensating distribution loss in the building on the terminal device side in the bidirectional CATV system, and outputs the downstream signal from the center device to an optimum level for each terminal. At the same time, as an upstream signal, a signal from an information terminal such as a cable modem is amplified and output to the center device.
[0022]
In this bidirectional CATV system, it is necessary to reduce the upstream inflow noise and maintain the uplink C / N in a good state. As a method for this purpose, a method of operating the output of a cable modem or the like at a high level and reducing the input level of the upstream signal amplifier circuit as much as possible can be considered. As described above, when the upstream signal is operated at a high level, the first amplifier circuit 30 is used as a problem that the rated output of the upstream signal amplifier circuit 3 of the in-building booster 1 exceeds the rated output, or as a means corresponding to this problem. When the attenuator is inserted at the input, the C / N of the output signal of the upstream signal amplifying circuit is deteriorated. Further, when the attenuator on the input side is required to exceed the first stage gain, There is a problem that the first stage amplifier circuit 30 is not necessary, and in addition, there is no need to supply power to the first stage amplifier circuit 30.
[0023]
On the other hand, the upstream signal amplification circuit 3 is connected in parallel with the first amplifier 30, the pass line 31 connected in parallel with the first amplifier 30, and the upstream signal in the CATV system. Selection means 32 (32a, 32b) for selective output via the path of either the first amplifying device 30 or the passage line 31, and level adjustment means 33 connected to the output of the selection means 32 And a second amplifier 34 connected to the output of the level adjusting means 33, and by applying a direct current voltage to the first amplifier 30 and the selecting means 32 (32a, 32b) in parallel, When the upstream signal is operated at a high level in the bidirectional CATV system, it is possible to select the rated output without deterioration of C / N. The level can be obtained, and further, the path of the first amplifying device 30 is switched to the passage line, and power supply to the amplifying device 30 is stopped, so that power saving can be achieved. The in-building booster 1 can be provided.
[0024]
The present invention is not limited to the above-described embodiment, and may be implemented by appropriately changing the configuration of each amplifier circuit, the filter circuit, the predetermined frequency band, etc. without departing from the spirit of the present invention. Is possible.
[0025]
【The invention's effect】
  As detailed above,According to the in-building booster of the first aspect, when the power source switching means is switched to the side where the DC power source is applied to the first amplifier and the selection means, the first amplifier is selected as a path through which the upstream signal passes. At the same time, the first amplifier operates to amplify the upstream signal. Then, the amplified upstream signal is amplified to a desired level via the level adjusting means and the second amplifier. Further, when the power source switching means is switched to the side where the DC power source is not applied to the first amplifier and the selection means, the upstream signal is input to the second amplifier via the passage path and the level adjusting means, Is amplified to a predetermined level.
For this reason,When operating upstream signals at a high levelIn this case, by switching the path of the upstream signal from the first amplifier to the pass line, a high level upstream signal can be input to the second amplifier without passing through the first amplifier. , The upstream signal can be amplified without degrading C / N. In addition, as described above, when the upstream signal path is switched to the pass line, the power supply to the selection means and the first amplifier is stopped, so that it is possible to save power in the building booster. it can.
[0026]
The invention of claim 2 is constructed so that the upstream signal is 10 to 55 MHz. Therefore, it is provided with an information terminal such as a cable modem and is useful for a CATV Internet system that transmits and receives information to and from the center apparatus side. An internal booster can be provided.
[Brief description of the drawings]
FIG. 1 shows an embodiment of an in-building booster of a bidirectional CATV system according to the present invention.
FIG. 2 shows another embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Booster in a building, 3 ... Up signal amplification circuit, 5 ... Input terminal, 7 ... Output terminal, 10, 18, 20, 22, 40, 42 ... HPF (high pass filter), 12, 16, 24, 26, 44 , 46... LPF (low pass filter), 14... Downstream signal amplifier circuit, 14 a, 14 b... Amplifier circuit, 14 c... Level adjustment means, 30. Means 33, level adjusting means 33a, switching means 33b, attenuator 33c, variable resistor, 34 second amplifier, 36 power supply switching means 38 power circuit, 39 AC plug,

Claims (2)

In a building booster of a bidirectional CATV system, which is provided on a transmission line on the terminal side of a bidirectional CATV system and includes an amplification circuit that amplifies a downstream signal in a predetermined frequency band and an upstream signal in a frequency band different from the downstream signal. ,
The amplifying circuit for the upstream signal is:
A first amplifier;
The passing line to said first amplifier are arranged in parallel,
A selection means for selecting one of the first amplifier and the passing line as a path through which the upstream signal passes ;
Level adjusting means for adjusting the level of the upstream signal output from the path selected by the selecting means ;
A second amplifier connected to the output of the level adjusting means ;
Power supply switching means for switching whether or not to apply DC power to the first amplifier and the selection means;
And the selection means selects the first amplifier as the path of the upstream signal when the DC power is supplied via the power supply switching means, and the DC power supply is selected via the power supply switching means. A booster in a building of a bidirectional CATV system , wherein when it is not supplied, a pass line is selected as the path of the upstream signal . The in-building booster of a bidirectional CATV system according to claim 1, wherein the upstream signal is 10 to 55 MHz.

Images