JPH05236441A - Repeating amplifier for catv network - Google Patents

Abstract

PURPOSE:To obtain the repeating amplifier for more developing a bidirectional tree shaped CATV network by effectively removing noise from upward signals to be transmitted from a customer terminal side to a head end side. CONSTITUTION:A repeating amplifier 17 is provided with a terminal 17a connected to an upward side transmission line and terminals 17b and 17c connected to a downward side transmission line. The upward side contact of a synthesizer/ distributor 18 is connected to the terminal 17a, and a first noise removal filter 19 is connected between one downward side contact of the synthesizer/distributor 18 and the terminal 17b. On the other hand, a second noise removal filter 20 is connected between the other contact and the terminal 17c. These filters 19 and 20 is provided with variable functions to set plural attenuation amounts for blocking the passage of signals for each arbitrary frequency and can set a through state or a filter characteristic combining one or two passage block hands or more.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a relay amplifier provided in a CATV network, and more particularly to a relay amplifier having a noise eliminating filter built therein.

[0002]

2. Description of the Related Art A CATV network is a wired communication network that connects a data center and a customer terminal with a coaxial cable and a relay amplifier to enable bidirectional communication. A wiring type (tree type) network configuration is known. Since the star type connects the information center and the customer terminal individually, it is suitable for the communication form based on the individual request of the terminal, and is suitable for the expansion of the network and the development to the two-way communication, the end-to-end communication, etc. The tree type is suitable for one-way communication from the information center to the customer terminal, for example, broadcast communication.

The latter tree-type CATV network is, for example,
As shown in FIG. 5, a head end 1 (a part that retransmits broadcasts or broadcasts independently) provided in an information center or the like is connected to a main line 3 composed of a low-loss coaxial cable via a main line amplifier 2 to form a main line 3. A plurality of branch lines 5 extend in a dendritic manner via the main line branch amplifier 4 provided, and further, a plurality of distribution lines 7 are provided via a main line distribution amplifier 6 provided on the branch line 5.
Extend in a dendritic form, and further, a plurality of distribution lines 9 extend in a dendritic form via a distribution amplifier 8 provided in the distribution line 7,
Lead-in wire 11 connected to tap-off 10 provided in
The customer terminal 12 is connected to. Then, from the head end 1 to the customer terminal 12 side, approximately 70 MHz to 550 MH
A downlink signal in the z frequency band is transmitted, and an upstream signal in the frequency band of approximately 10 MHz to 50 MHz is transmitted from the customer terminal 12 to the headend 1 side, whereby bidirectional transmission is performed.

Here, these relay amplifiers such as the trunk line branch amplifier 4, the trunk line distribution amplifier 6 and the distribution amplifier 8 are all connected to the head end 1 side (hereinafter referred to as the upstream side) as shown in FIG. A first circuit unit 14 having a filter 13 for removing noise, and a branched line side (hereinafter,
The second circuit unit 16 has a multiplexer / distributor 15 connected to the downstream side), and the respective circuit units 14 and 16 are mutually connected at predetermined connection terminals 13b and 16a as shown in the drawing. Connected to the connection terminal 1
3a to connect to the upstream transmission line, and the connection terminal 16
It is designed to be connected to two downstream transmission lines via b and 16c.

Then, the downstream signal in the frequency band of about 70 MHz to 550 MHz input from the upstream side to the connection terminal 13a passes through the filter 13 and then is multiplexed by the multiplexer / divider 15 into the two downstream side connection terminals 16b, 16b. 16c is distributed and transmitted, while the connection terminals 16b, 1
The two upstream signals in the frequency band of about 10 MHz to 50 MHz input via 6c are merged by the multiplexer / divider 15 and then passed through the filter 13 to be connected to the connection terminal 13
It is transmitted from a to the upstream transmission line.

Here, the noise removing filter 13 merges the noise included in the upstream signal transmitted from the transmission line connected to the downstream side of the multiplexer / distributor 15 and the plurality of customer terminals 12 into the merging / distributor. It is provided in order to prevent the occurrence of a transmission error or the like by transmitting only the upstream signal to the upstream side by removing the signals collectively after joining at 15. For example,
A low-pass filter that blocks passage of low-frequency components in consideration of relatively low-frequency noise generated from the power supply of each customer terminal 12 and jump-in noise in the 35 MHz band used in wireless mobile phone networks. Has been applied.

That is, in the tree type CATV network, the number of transmission lines and customer terminals 12 increases as it goes to the end system through the relay amplifiers such as the main branch amplifier 4, the main distribution amplifier 6 and the extension amplifier 8. From that,
On the contrary, when a plurality of upstream signals output from the plurality of customer terminals 12 on the end side are gradually transmitted to the upstream transmission line while being merged by each multiplexing / distributor 15 in the relay amplifier, Since the noise superimposed on the upstream signal is gradually added and increases, these noises (referred to as inflow noise) are collectively collected by the filters 13 connected to the upstream side of the respective multiplexer / distributor 15. I try to remove it.

[0008]

By the way, the tree-type CATV network is used exclusively for unidirectional communication from the information center to the customer terminal, although it has bidirectionality as described above. Therefore, the communication from the customer terminal to the information center side is sufficiently utilized as it is applied to so-called polling processing for detecting the occurrence of failure or defect of each relay amplifier or customer terminal in the CATV network. I didn't.

The reason why the bidirectional communication cannot be effectively used in this way is that the relay amplifiers such as the trunk line branch amplifier 4 and the trunk line distribution amplifier 6 shown in FIG. This is because the ingress noise in the upstream signal transmitted to the side cannot be effectively removed.

That is, a large number of customer terminals connected to the CATV network have their own causes of noise generation, and the frequency distributions of these noises are diverse, so that the upstream side of the multiplexer / distributor has a large number of customers. Even if an ingress noise is to be removed collectively by a low-frequency blocking type filter having a fixed cutoff frequency f _C , a filter having an extremely complicated frequency characteristic is required or the frequency band of the upstream signal is increased. This is because it is extremely difficult to effectively remove the ingress noise that exists over almost the entire range.

A more specific problem example will be described with reference to FIG. 7. The frequency band of the upstream signal output from each customer terminal is about 10 MHz to 50 MHz as shown in FIG. 7A. As shown in FIG. 7 (B), noise in a frequency band lower than a certain frequency f _N is superposed on the upstream signal from the first customer terminal, and the upstream signal from the second customer terminal is higher than the frequency f _N. When noise of a high frequency band is superimposed, when these upstream signals are input to the connection contacts 16b and 16c of the merging distributor 16 of FIG. 6, respectively, the merging distributor 1
The frequency band of the ingress noise appearing at the connection contact 16a of No. 5 is about 10 MHz to 50 MHz, which is the same as the upstream signal. Therefore, in order to remove this ingress noise with the filter 13, the pass-blocking frequency band is about 10 MHz to 50 MHz.
Since it has to be set to, and not only the ingress noise but also the upstream signal is removed, communication cannot be substantially performed.

The present invention has been made in view of the above problems to be solved in the related art, and it is possible to effectively remove noise from an upstream signal transmitted from a customer terminal side to a head end side to obtain bidirectionality. It is an object of the present invention to provide a relay amplifier capable of further developing a tree-type CATV network having the above.

[0013]

In order to achieve such an object, the present invention distributes a downlink signal to a plurality of transmission systems in a relay amplifier provided in a CATV network, and
At least one merge distributor for merging a plurality of upstream signals and transmitting them to the upstream transmission system, and a noise removal filter provided for each transmission system between the merge distributor and the downstream transmission system The noise elimination filter has one or more pass-stop frequency bands, and one or two or more pass-stop frequency bands are selected so that no pass-stop frequency band is set. The frequency band for blocking the passage of noise is set. The merge distributor and the noise blocking filter are incorporated into one unit.

[0014]

According to this structure, in the final stage of the CATV network, the respective upstream signals transmitted from the plurality of customer terminals subordinately connected to the downstream side of the relay amplifier are
After passing through a specific noise elimination filter set according to the noise characteristics peculiar to each customer terminal, after being merged by the multiplexing distributor in the relay amplifier, it is transmitted to the upstream transmission line, It is possible to reliably remove the noise for each customer terminal, as compared with the case where the conventional relay amplifier removes the noise from the upstream signal that merges in the multiplexer / distributor all together. On the other hand, in the middle part of the CATV network, noise mixed in the upstream signal can be individually removed by each transmission line, so that the transmission accuracy can be improved.

By selecting a plurality of stop bands set in the noise removing filter, noise can be removed according to the noise characteristic in the upstream signal.
Optimal adjustment and reliable maintenance can be performed easily. or,
By incorporating the noise removal filter and the confluence distributor in the same unit, the mountability to the CATV network is improved and the maintenance of the CATV network is facilitated.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a relay amplifier according to the present invention will be described below with reference to the drawings. Incidentally, the relay amplifier of this embodiment is
As shown in FIG. 5, the present invention is applied to a trunk line branch amplifier, a trunk line distributor, etc. for realizing a tree type CATV network.

First, the circuit configuration will be described with reference to FIG. 1. This relay amplifier 17 has a connection terminal 17a connected to an upstream transmission line and two connection terminals connected to a downstream transmission line. 17b and 17c, and the connecting terminal 17a is connected to the upstream side contact of the multiplexer / distributor 18.
The first noise removing filter 19 is connected between the one contact on the down side of 8 and the connection terminal 17b, and the second noise is connected between the other contact on the down side of the multiplexer / distributor 18 and the connection terminal 17c. The removal filter 20 is connected.

As shown in FIG. 2, both of these noise removing filters 19 and 20 are at least DC to 50 MHz.
It has a variable function that can set a plurality of attenuation amounts to block the passage of signals for each arbitrary frequency within the frequency range of, and these pass-stop bands are external terminals (not shown). When selectively designated from the above, the through state having no pass stop band can be set, and the filter characteristic in which one or more pass stop bands are combined can be set.

Further, the multiplexer / distributor 18 and the first and second noise blocking filters 19 and 20 are incorporated in the same unit. The relay amplifier 17 having such a configuration is shown in FIG.
The following functions are exerted by being applied to the trunk line branch amplifier, trunk line distributor, etc. of the tree type CATV network shown in FIG.

First, when connecting the two customer terminals at the ends to the connection terminals 17b and 17c shown in FIG. 1, respectively, a builder or the like superimposes on the upstream signal of the customer terminal connected to the connection terminal 17b. First according to the frequency band f _W1 of the noise component
While setting the pass-stop frequency band of the noise removal filter 19 of No. 2, the second noise removal filter is adjusted in accordance with the frequency band f _W2 of the noise component superimposed on the upstream signal of the customer terminal connected to the connection terminal 17c. 20 pass stop frequency bands are set.

Therefore, the noises of different frequencies which are superimposed on the upstream signal output from each customer terminal are individually removed by the first and second noise removing filters 19 and 20,
A noise-free upstream signal is input to the merge distributor 18.
Then, the ingress noise is not transmitted from the connection terminal 17a to the upstream transmission system.

The point to be noted here is, for example, in FIG.
As shown in (B), the noise superimposed on one upstream signal and the noise superimposed on the other upstream signal have different frequency bands, but when ingress noise is used, the same frequency band as the frequency band of the upstream signal is used. In such a case, the communication itself is conventionally impossible, but according to this embodiment, the communication shown in FIG.
As shown in (B), each noise removal filter 19,
If the pass stop bands of 20 are set separately, before the two upstream signals are merged by the merge distributor 18, the noises having their own characteristics are individually filtered in advance by the individual noise elimination filters 19,
Since it is removed at 20, the remaining upstream signals can be merged and transmitted to the upstream transmission system.

Further, when the CATV network is connected to the middle stage, the noise mixed in the upstream signal on each transmission line can be removed individually, so that the transmission accuracy can be improved.

Further, no matter where it is provided in the CATV network, a noise removing filter is provided for each transmission system, so that adjustments for removing noise superimposed on the upstream signal are individually performed. Therefore, it is possible to realize accurate adjustment and facilitate maintenance work and the like for the builder.

FIG. 4 shows the configuration of another embodiment. In this embodiment, while the embodiment shown in FIG. 1 has a two-way multiplexing / distributing function, it has a four-way multiplexing / distributing function.
It is adapted to be applied to a complicated tree type CATV network.

That is, the relay amplifier 21 has a connection terminal 21a connected to an upstream transmission line and four connection terminals 21b to 21e connected to four downstream transmission lines.
Is provided, and the connection terminal 21a is provided with
The two upstream contacts are connected, and the two downstream contacts are connected to the upstream contacts of the second and third merge distributors 23 and 24, respectively. Then, the second and third merge distributors 23, 2
A total of four down-side contacts 4 are connected to the connection terminals 21b to 21e via the separate noise removal filters 25 to 28, so that a merging and distributing function of four systems is obtained.

Also in this embodiment, since the noise elimination filters 25 to 28 can individually adjust the respective pass-stop frequency bands, the noise superimposed on the upstream signal is eliminated and the four upstream signals are removed. It becomes possible to merge and transmit to the upstream transmission line.

Further, in each of the embodiments shown in FIGS. 1 and 4, the merge distributor and the filter group are integrally incorporated into the same substrate, package and the like to form a unit, so that the operator or the like can easily construct the CATV network. Can be maintained and inspected.

In the above embodiment, the relay amplification of two lines and four lines is shown, but the present invention can be applied to the relay amplification of more lines, and the same effect as above can be obtained. it can.

[0030]

As described above, according to the present invention, C
In a relay amplifier provided in the ATV network, at least one confluence distributor that distributes a downstream signal to a plurality of downstream transmission systems and merges a plurality of upstream signals and transmits the upstream signals to the upstream transmission system is provided. Further, by having one or more pass-stop frequency bands and selecting one or more pass-stop frequency bands, a through state having no pass-stop frequency band and a frequency band for blocking the passage of noise Since the noise removal filter for setting the above is provided between each of the merging distributor and the downstream transmission system, noise can be reliably removed for each customer terminal or each transmission system.

Therefore, by selecting a plurality of stopbands set in the noise removal filter, noise can be removed according to the noise characteristics in the upstream signal, which facilitates optimum adjustment and reliable maintenance. It is possible to provide a relay amplifier which can be further developed and can further develop a tree type CATV network having bidirectionality.

Further, since the merging distributor and the noise blocking filter are incorporated into one unit, it is possible to provide a repeater amplifier having excellent mountability.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an example.

FIG. 2 is an explanatory diagram for explaining frequency characteristics of a noise removal filter in FIG.

3 is an explanatory diagram for explaining frequency characteristics of the noise removal filter in FIG.

FIG. 4 is a block diagram showing a configuration of another embodiment.

FIG. 5 is an explanatory diagram showing a configuration of a CTV network.

FIG. 6 is a block diagram showing a configuration of a conventional relay amplifier.

FIG. 7 is an explanatory diagram for explaining a problem of a conventional relay amplifier.

[Explanation of symbols]

17, 21 ... Relay amplifiers, 17a to 17c, 21a to 2
1e ... Connection terminal, 18, 22, 23, 24 ... Confluence distributor, 19, 20, 25-28 ... Noise removal filter.

Claims (2)

[Claims] 1. At least one combined arrangement that distributes a downstream signal to a plurality of transmission systems and joins a plurality of upstream signals to an upstream transmission system, and the combined arrangement and the downstream arrangement. A noise removal filter provided between the transmission system and each transmission system, wherein the noise removal filter has one or more pass-stop frequency bands and one or more pass-stop frequency bands. A relay amplifier of a CATV network, which is selected to set a through state having no pass blocking frequency band or a frequency band for blocking passage of noise. 2. The combination arrangement and the noise removal filter are:
The relay amplifier of the CATV network according to claim 1, wherein the relay amplifier is incorporated in one unit.