JPH07298246A - Signal transmission method for two-way catv system and two-way amplifier used for the method - Google Patents

Abstract

PURPOSE:To provide a signal transmission method securing lots of incoming lines without disturbing re-transmission of a TV broadcast and to provide a two-way amplifier required to realize the two-way CATV system. CONSTITUTION:In the signal transmission method for the two-way CATV system having a signal band in which an incoming band 1 used to send an incoming signal is set to a low frequency band and an outgoing band 2 used to send an outgoing signal is set to a high frequency band, a band 3 being part of the outgoing band 2 is blocked and the blocked band 3 is used for a 3nd incoming band 3 through which the incoming signal is sent. In the claim 2, the incoming band 1 is set as a subsplit band for 10-50MHz band and the outgoing band 2 is set as a subsplit band for 70MHz or over.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal transmission method for a bidirectional CATV system and a bidirectional amplifier used for the method, which is effective when it is desired to secure a large number of channels (ch) for upstream signals. is there.

[0002]

2. Description of the Related Art Two-way CATV of single-coaxial cable system
In the system, as shown in FIG. 4, an upstream signal to the center and a downstream signal sent from the center are divided into two bands, an upstream band A on the low frequency side and a downstream band B on the high frequency side, and transmitted. . Of these, in the sub-split system, 10 to 50 MHz are used for the upstream band and 70 to 4 MHz for the downstream band.
50 MHz is used, and in the mid-split system, 10 to 108 MHz is used for the upstream band and 174-45 is used for the downstream band.
0 MHz is used.

A bidirectional amplifier used in such a bidirectional CATV system, as shown in FIG. 5, processes an up signal of an up band A and a down signal of a down band B by a high pass filter (HPF) and a low pass filter (HPF). LPF), and the upstream signal is input to the upstream amplifier circuit C and the downstream signal is input to the downstream amplifier circuit D to amplify the respective signals.

[0004]

The above-mentioned sub-split system and mid-split system have the following problems, respectively. ． In the sub-split system, 10 to 50 MHz can be used as the upstream band, but 10 to 30 MHz in the same band
Is difficult to use due to short wave broadcasting and CB radio,
The band available for V broadcasting is only 30 to 42 MHz.
This is only for two channels (ch) in TV broadcasting, and it is difficult to increase the number of channels.

.. The mid-split system can secure a larger number of channels in the upstream band than the sub-split system, but the 90 to 108 MHz band of the upstream band is the same as the 1 to 3 channel TV broadcast using 90 to 108 MHz. 1-3 because they overlap
The TV broadcast of the channel cannot be transmitted to the CATV subscriber.

It is an object of the present invention to provide a signal transmission method of a bidirectional CATV system which can secure a larger number of uplinks without hindering the retransmission of TV broadcasting, and the bidirectional required for realizing the system. To provide an amplifier.

[0007]

According to the signal transmission method of the bidirectional CATV system according to claim 1 of the present invention, as shown in FIG. 1, the upstream band 1 for transmitting the upstream signal transmits the downstream signal to the low frequency side and the downstream signal to the downstream side. In a signal transmission method in a bidirectional CATV system in which a downstream band 2 to be transmitted is distributed to a high frequency side, a second band for blocking a part of the band 3 of the downstream band 2 and transmitting an upstream signal to the blocked band 3 is used. It is characterized in that it is used as the upstream band 3.

The signal transmission method of the bidirectional CATV system according to claim 2 of the present invention is the signal transmission method of the bidirectional CATV system according to claim 1, wherein the frequency arrangement is such that the upstream band 1 is 10 to 50 MHz and the downstream band 2 is It is characterized by being a sub-split of 70 MHz or more.

In the bidirectional amplifier according to claim 3 of the present invention, as shown in FIG. 2, the input side high pass filter 5a is provided on the input side of the downstream signal amplification circuit 4, and the output side high pass filter 5b is provided on the output side. And an upstream transmission line 9 having an input side low-pass filter 8a on the input side and an output side low-pass filter 8b on the output side of the upstream signal amplification circuit 7. In the bidirectional amplifier, a band stop filter 10 for blocking a part of the downlink band 3 is provided on the input / output sides of the downlink signal amplification circuit 4 of the downlink transmission line 6, and the input side of the uplink signal amplification circuit 7 and the band stop filter 10 are provided. Of the upstream signal between the output side high-pass filter 5b of the
The input side band pass filter 11a for passing the band 3 blocked by the above is provided, and the band stop filter of the upstream signal between the output side of the upstream signal amplification circuit 7 and the input side high pass filter 5a is provided. An input-side bandpass filter 11b that passes the band 3 blocked by 10 is provided, and the upstream signal amplification circuit 7 can amplify both the upstream band 1 on the low frequency side and the band 3 that has passed through the bandpass filter 11a. It is characterized by that.

[0010]

In the signal transmission method of the bidirectional CATV system of the present invention, a part of the band 3 of the downlink band 2 is blocked, and the blocked band 3 is used as the second upstream band 3 for transmitting the upstream signal. The number of downlink channels decreases, but the number of uplink channels can be increased. In particular, in a sub-split bidirectional CATV in which the frequency arrangement is 10 to 50 MHz in the upstream band 1 and 70 MHz or more in the downstream band 2, the number of channels in the uplink is significantly smaller than the number of channels in the downlink (only 2 channels can be secured). ), This method is effective. In this case, if the second upstream band 3 is secured within the mid band (108 to 170 MHz) that is not used for general TV broadcasting, the upstream line can be secured without hindering the transmission of TV broadcasting.

In the bidirectional amplifier of the present invention, as shown in FIG. 2, a band stop filter 10 for stopping a part of the band 3 of the down band is provided on the input and output sides of the down signal amplification circuit 4 of the down transmission line 6, An input side band pass filter 11a is provided between the input side of the upstream signal amplifying circuit 7 and the output side high pass filter 5b to pass the band 3 of the upstream signal blocked by the band stop filter 10. An input side band pass filter 11b for passing the band 3 blocked by the band stop filter 10 of the upstream signal between the output side of the upstream signal amplifying circuit 7 and the input side high pass filter 5a.
And the upstream signal amplifier circuit 7 has an upstream band 1 on the low frequency side.
Since it is possible to amplify both the band 3 and the band 3 that has passed through the band pass filter 11a, the upstream and downstream signals of FIG. 1, which is the signal transmission method of the present invention, are amplified by the upstream signal amplification circuit 4 and the downstream signal amplification circuit 7, respectively. Can be output.

[0012]

First Embodiment FIG. 1 is an explanatory diagram showing the states of upper and lower signal transmission bands in a signal transmission method for a bidirectional CATV system according to the present invention. In this system, as the frequency band of the upstream signal sent from the subscriber side toward the center,
Two bands, 10 to 50 MHz (upstream band 1), which is generally used in the sub-split, and 120 to 156 MHz (second upstream band 3), which is used as the down band in the sub-split, are used from the center to the subscriber side. As the frequency band of the downlink signal to be sent, 70
The remaining part (downstream band 2) obtained by excluding the second upstream band 3 from ˜450 MHz is used.

The upstream band 1 can be used in the range of 30 to 42 MHz except for the part which is difficult to use for short wave broadcasting and CB radio. In this 12 MHz region, two TV broadcasting signals that require a frequency of 6 MHz per channel can be transmitted. That is, two channels can be secured for TV broadcasting.

36 MHz can be used for the second upstream band 3, and 6 M per channel can be used for this 36 MHz.
Five TV broadcasting signals requiring a frequency of Hz can be transmitted. That is, 6 channels can be secured for TV broadcasting.

As the downlink band 2, the remaining part (downlink band 2) excluding the second uplink band 3 from 70 to 450 MHz can be used, but the second uplink band 3 is separated from the downlink band 2. Considering the guard band of the filter for the two channels (12 MHz) on the upper and lower sides, 70 to 108 MHz and 170 to 450 MHz can be actually used. Therefore, TV channels 1 to 70 are 70
It is possible to transmit to the subscriber using a band of ˜108 MHz, and to transmit to the subscriber using 170 to 450 MHz from 4 channels.

In the embodiment described above, the downlink signal bands are 70 to 108 MHz and 170 to 450 MHz, and the uplink signal bands are 10 to 50 MHz and 120 to 156 MHz.
Although the second upstream band 3 is used, the numerical value is not limited to this.

[0017]

[Embodiment 2] FIG. 2 is a block diagram showing an embodiment of a bidirectional amplifier which can be used in the signal transmission method of the bidirectional CATV system of the present invention. 20 in the figure is a downlink signal from the center (70 to 108 MHz, 170 to 450 M).
Hz) is input and the upstream signal from the terminal (10-5)
0 MHz, 120 to 156 MHz) is output on the center side, 21 is an input terminal for an up signal from the terminal, and 7 is a terminal terminal for outputting a down signal from the center.
Down signal amplification circuit covering 0 to 450 MHz,
Reference numeral 7 is an upstream signal amplifier circuit that covers up to 10 to 156 MHz.

Further, 5a and 5b are input side high pass filters (HPFs) and output side high pass filters (HPFs) that allow signals of 70 MHz or more to pass, and 8a and 8b are 50M.
Input side low-pass filter (LPF), output side low-pass filter (LPF) that allows signals of Hz or less to pass, 1
0 is a band elimination filter (BEF) for blocking signals of 108 to 170 MHz as shown in FIG.
a and 11b are 120 to 156M as shown in FIG.
They are an input side band pass filter (BPF) and an output side band pass filter (BPF) that allow passage of a Hz signal.

In this amplifier, the downlink signal (70 to 108 MHz, 170 to 450) input to the center side terminal 20 is used.
(MHz) passes through the HPF 5a and the BEF 10 and is amplified by the downlink signal amplifier circuit 4, and is sent out to the terminal side terminal 21 through the BEF 10 and the HPF 5b (downlink transmission line 6). In addition, the upstream signal (10
10 to 50 MHz, 120 to 156 MHz)
The 50 MHz signal passes through the LPF 8a on the terminal 21 side, is amplified by the upstream signal amplifying circuit 7, and is sent out to the center side terminal 20 through the LPF 8b (upstream transmission line 9), 1
The signal of 20-156MHz is the HPF 5b on the terminal 21 side,
After passing through the BPF 10, the signal is amplified by the upstream signal amplifying circuit 7, passes through the BPF 11b and the HPF 5a, and the center side terminal 2
Sent to 0.

[0020]

By using the signal transmission method of the bidirectional CATV system of the present invention, it is possible to increase the number of channels of the upstream line, and moreover, to obtain the frequency of the second upstream band in the mid band which is not used in TV broadcasting. For example, it is possible to secure the uplink without hindering the retransmission of TV broadcast.

By using the bidirectional amplifier of the present invention, the signal transmission method of the bidirectional CATV system can be realized.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an embodiment of a signal transmission method of a bidirectional CATV system of the present invention.

FIG. 2 is a block diagram showing an embodiment of a bidirectional amplifier used in the signal transmission method of the bidirectional CATV system of the present invention.

3 (a) is a BE used in the bidirectional amplifier of FIG.
Explanatory drawing which showed the characteristic of F, (b) is explanatory drawing which showed the characteristic of BPF used for the bidirectional amplifier of FIG.

FIG. 4 is an explanatory diagram showing an example of a signal transmission method of a conventional bidirectional CATV system.

FIG. 5 is a block diagram showing an example of a bidirectional amplifier used in a signal transmission method of a conventional bidirectional CATV system.

[Explanation of symbols]

 1 upstream band 2 downstream band 3 second upstream band 4 downstream signal amplification circuit 5a input side high-pass filter 5b output side high-pass filter 6 downstream transmission line 7 upstream signal amplification circuit 8a input side low-pass filter 8b output side Low pass filter 9 Upstream transmission line 10 Band stop filter 11a Input side band pass filter 11b Output side band pass filter

Claims (3)

[Claims] 1. A signal transmission method in a bidirectional CATV system in which an upstream band (1) for transmitting an upstream signal is distributed to a low frequency side and a downstream band (2) for transmitting a downstream signal is distributed to a high frequency side. A two-way CATV system characterized by blocking a part of the band (3) of the band (2) and using the blocked band (3) as a second upstream band (3) for transmitting upstream signals. Signal transmission method. 2. The signal transmission method for a bidirectional CATV system according to claim 1, wherein the frequency array has an upstream band (1) of 1
A signal transmission method of a bidirectional CATV system, characterized in that the sub-split is 0 to 50 MHz and the downstream band (2) is 70 MHz or more. 3. A downlink transmission line (6) having an input side high-pass filter (5a) on the input side and an output side high-pass filter (5b) on the output side of the downlink signal amplification circuit (4). ,
The input side low pass filter (8a) is provided on the input side of the upstream signal amplification circuit (7), and the output side low pass filter (8a) is provided on the output side.
In the bidirectional amplifier including the upstream transmission line (9) provided with b), a part of the downstream band (3) is provided on the input / output side of the downstream signal amplification circuit (4) of the downstream transmission line (6). ) Is provided to block the band stop filter (10) of the upstream signal between the input side of the upstream signal amplifier circuit (7) and the output side high-pass filter (5b). ), An input side band pass filter (11a) for passing the band (3) blocked by the above) is provided, and the output side of the upstream signal amplification circuit (7) and the input side high pass filter (5) are provided.
An input side band pass filter (11b) for passing the band (3) blocked by the band stop filter (10) of the upstream signal is provided between the upstream signal amplification circuit (a) and the upstream signal amplification circuit (7). A bidirectional amplifier characterized in that both the upstream band (1) on the frequency side and the band (3) that has passed through the band pass filter (11a) can be amplified.