JPH01241993A - Two-way catv system and its frequency converter - Google Patents

Abstract

PURPOSE:To attain effective block division to a terminal equipment group and to exclude trouble in maintenance and management or the like effectively by interposing a frequency converter having a different frequency characteristic to each of blocks for the center equipment side and the terminal equipment side. CONSTITUTION:Center side frequency converters 11a-11n convert a transmission signal from a center device 10 into carrier frequency different from blocks 30a-30n and sent to a transmission line 20 and the transmission signal from the transmission line 20 is sent from terminal equipment 34a-34n to restore the frequency into the carrier frequency before the frequency-conversion by the terminal equipment side frequency converters 31a-31n. Moreover, the terminal equipment side frequency converters 31a-31n are operated inversely with the center frequency converters 11a-11n except giving a channel frequency of a television broadcast mixed on the way of the transmission line 20 to the terminal equipments 34a-34n via a high pass filter HPF. Thus, the terminal equipment group is blocked effectively and the trouble in the maintenance and management or the like is excluded effectively.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention provides a method for dividing a terminal equipment group into a plurality of blocks when transmitting and receiving transmission signals between - center equipment and a large number of terminal equipment groups. The present invention relates to a new two-way CATV system and its frequency converter, which uses a different carrier frequency for each block and enables transmission and reception via a single transmission path.

Conventional technology In large-scale facilities such as hotels and inns, in addition to TV viewing in each guest room, services such as billing for viewing paid channels such as independent broadcast programs, confirmation of refrigerator usage, and control of security systems are provided. To achieve this, bidirectional CATV systems are widely used in which a center device and a group of terminal devices are connected via a coaxial cable network for common television viewing.

In such a CATV system, data communication between the center device and each terminal device is performed by a so-called hauling selective method.

Therefore, in order to reduce the polling time or to limit the failure area to a small area, the terminal device group is often divided into a plurality of blocks within the system.

There are two ways to divide blocks: a TV common coaxial cable network, in which transmission lines are provided independently for the number of blocks required, and a single transmission line by multiplexing the frequency of the carrier wave of the transmission signal. Two methods are being considered, both of which are commonly used.

The problem to be solved by the invention is that when using the first means of the prior art, when a two-way CATV system is introduced at the time of construction of a hotel, inn, etc., it is difficult to install a transmission line. It is relatively easy to implement since there are few problems.

However, at present, the system is often installed at hotels, inns, etc. that are already in operation, so it is necessary to ensure that the video signal distribution level that allows each guest room to obtain image quality that is suitable for viewing is ensured. It is often difficult to divide a TV coaxial cable network into blocks using the first method due to the structure of the building, taking into consideration fire walls, wiring space, and the like.

Therefore, we have no choice but to take the second method described above, but in this method, the frequency of the carrier wave is divided into multiple blocks, so a terminal device with a different frequency specification is required for each divided block, and maintenance management etc. This inevitably led to the problem that the process would become extremely complicated.

Therefore, an object of the present invention is to take into account the actual state of the prior art, and even when transmitting and receiving transmission signals using carrier waves of different frequencies for each block using a single existing transmission path, all terminal devices A new bidirectional CATV system that only requires blocks with the same frequency specifications.
The purpose is to provide a system and its frequency converter.

Means for Solving the Problems The configuration of the present invention to achieve the object includes: a transmission path for transmitting transmission signals including television broadcast signals, a center device, and a terminal device divided into a plurality of blocks. The center device is connected to the transmission path via a plurality of center-side frequency converters each having a different frequency characteristic, corresponding to each block of the terminal device group, and each block of the terminal device group is The gist of each is that they are connected to the transmission path via the terminal side frequency converter corresponding to the center side frequency converter.

Note that the center side frequency converter has first and second mixers connected in parallel between a first mixer/brancher connected to the center device and a second mixer/brancher connected to the transmission line. Intermediate, first
The second mixer converts the frequency of the transmission signal from the center device and sends it out to the transmission path, and the second mixer converts the frequency of the transmission signal from the transmission path and sends it out to the center device.

In addition, the terminal side frequency converter includes a first mixer/brancher connected to the transmission path and a second mixer/brancher connected to one block of the terminal equipment group.
A high-pass filter and a first and second mixer are interposed in parallel between the mixing and demultiplexing filter of The first mixer converts the frequency of the transmission signal from the transmission line and sends it to one block of the terminal equipment group, and the second mixer converts the frequency of the transmission signal from the transmission path and sends it to one block of the terminal equipment group. It frequency-converts the transmission signal from one block and sends it out to the transmission path.

With this configuration, the transmission signal sent from the center device is frequency-converted to a different carrier frequency for each block by the center-side frequency converter corresponding to each block of the terminal device group, and then Sent to the transmission path.

In this way, when transmission signals with different carrier frequencies are sent out to the transmission path for each block, the terminal side frequency converter frequency converts the transmitted transmission signals, and each block has a terminal that has a receiver. Send to each block of the device group.

In addition, the transmission signal sent from the terminal device to the center device is first converted to a different carrier frequency for each block by the frequency converter on the terminal side, and then transmitted by the frequency converter on the terminal side, by the reverse effect of the operation described above. The signal is reconverted to a unified frequency by the receiver and then received by the center device.

That is, the center-side frequency converter converts the transmission signal from the center device into a different carrier frequency for each block and sends it out to the transmission path, and also converts the transmission signal from the transmission path into a carrier frequency that is different for each block and sends out the transmission signal from the transmission path from each terminal device. It functions to return to the carrier frequency before frequency conversion by the terminal side frequency converter. In addition, the terminal side frequency converter functions in the opposite way to the center side frequency converter, except that it passes the TV broadcast channel frequency mixed in the middle of the transmission path to the terminal device side via a high-pass filter. .

It works as described above.

Example Examples will be described below with reference to the drawings.

The bidirectional CATV system includes a center device 10, center-side frequency converters 11a, llb...lln, a transmission line 20, and terminal-side frequency converters 31a, 31b...31.
n, and blocks 30a'-30b...30n obtained by dividing the terminal device groups 34a, 34b... into a plurality of blocks (FIG. 1).

The center device 10 includes a control device that performs a hauling selection method, etc., as well as a group of terminal devices 34a, 34b, etc.
The blocks 30a, 30b...30n include the same number of high-frequency modulators (hereinafter referred to as modems), and the output terminals a1b...n drawn out from each modem are as follows:
A mixing/branching filter 20a forming part of the transmission path 20 via the center side frequency converters 11a, llb...1-1n
It is connected to the.

The center side frequency converters 11a, llb... each include a first and second mixer 13a, each having an oscillator 14a, 14b connected between the first and second mixer/brancher 12a, 12b, 13b in parallel (Fig. 2),
The second mixer/brancher 12a is connected to the center device 10, while the second mixer/brancher 12b is connected to the mixer/brancher 20a of the transmission line 20. However, the first mixing/branching filter 12a
The output of the second mixer/brancher 12b is input to the second mixer/brancher 12b via the first mixer 13a, and the output of the second mixer/brancher 12b is input to the first mixer/brancher 12b via the second mixer 13b. Wave device 12
It is configured to be input to a.

Note that the first and second mixers 13a and 13b perform frequency conversion by adding or subtracting the oscillation frequencies from the oscillators 14a and 14b and the input frequencies from the mixer/branchers 12a and 12b, respectively. shall be taken as a thing.

A video center 50 is connected to the mixer/brancher 20a, which includes a relay device that receives public television broadcasting and retransmits it, and an independent broadcasting device such as a video tape recorder.
Figure 1).

The transmission line 20 has a mixer/demultiplexer 20 at each end thereof.
a, 20b, and the output of the terminal side mixing/branching filter 20b is divided and connected to the terminal side frequency converters 31a1Blb..., and the terminal side frequency converters 31a, 31b... ... mixer/brancher 3
3. Connected to 33... Each block 30a,
The mixing/branching filter 33 of 30b... has a terminal control device CT.
A plurality of terminal devices 34a including R and a television receiver TV,
34b... are connected. Here, it is assumed that the terminal control device CTR has functions of checking pay channel viewing, checking refrigerator usage, controlling the security system, etc. in response to polling from the center device 10, and each includes a modem.

The terminal side frequency converters 31a, 31b, . . . each have a high-pass filter HPF that passes only the channel frequency of the television broadcast, and an oscillator 37a between the first and second mixer/branchers 35a, 35b, respectively. , 37b are interposed between the first and second mixers 36a and 36b (FIG. 3). In other words, the terminal side frequency converters 31a, 3
1b... is basically a center-side frequency converter element, except that a high-pass filter ■PP is added to guide the output of the first mixer/brancher 35a to the second mixer/brancher 35b. la, 1
It has the same configuration as 1b..., and the first mixing/branching filter 35
a is connected to the mixer/brancher 20b of the transmission line 20, while the second mixer/brancher 35b connects each block 30a, 30
b... is connected to the mixing/branching filter 33.

The operation of the bidirectional CA TV system having such a configuration is as follows.

Now, the center device 10, via a modem (not shown),
It is assumed that downstream signals for each block 30a, 30b...30n can be sent out as transmission signals from the output terminals a, b...n, respectively. However, all of these downlink signals are unified to the same carrier frequency F (hereinafter referred to as downlink signal F), and in the downlink signal F', each block 30a, 30b, . . .
It is assumed that data signals for polling for the terminal device groups 34a, 34b, . . . in the terminal device group 30n are included. Each terminal device 34a, 34b... responds to the polling from the center device u10 by using the uplink signal as a transmission signal.
These uplink signals are all unified to the same carrier frequency f (hereinafter referred to as uplink signal f), and the modem of the center device 10 has all output terminals a, b, . . .
- For n, it is assumed that only this carrier frequency f can be received.

The downlink signal F transmitted from the center device 10 is −] 1
- Via the center side frequency converter 11a, llb...
The signal is input to the mixing/branching filter 20a. Center side frequency converter 11. a, llb..., the downlink signal F is passed through the first mixer/brancher 12a to the first mixer],
3a, the downlink signal F is combined with the oscillation frequency of the oscillator 14a by the first mixer 13H, and the downlink signal FaSFb of the carrier frequency Fa, Fb...
..., and is sent to the mixer/brancher 20a of the transmission line 20 via the second mixer/brancher 12b. However, the oscillation frequency of the oscillator 14a is the center side frequency converter 11a,
llb..., and therefore, the downlink signal Fa reaching the center-side mixing/branching filter 20a
.

Fb... has different carrier frequencies Fa, Fb... for each block 30a, 30b....

A multiplexed video signal (hereinafter referred to as a television signal Ft) of a channel frequency Ft of television broadcasting from the video center 50 is input to the mixing/branching filter 20a. therefore,
The transmission signal sent from the mixer/brancher 20a to the transmission line 20 is a mixture of downlink signals Fa, do b... device 20b, terminal side frequency converter 31a, 31b...
* is input to each block 30a, 30b, . . .

In the terminal side frequency converters 31a, 3], b..., the downlink signal FaSFb... is sent to the first mixer 36
is synthesized with the oscillation frequency of the oscillator 37a by
While all the signals are reconverted into downstream signals of the same carrier frequency F, the television signal Ft passes through a high-pass filter HPF,
The data is output as is to each block 30a130b, . . . . Therefore, all the terminal devices 34a, 34b, . . . , all blocks 30a, 30b, . You will be able to use

The same is true for the uplink signal f sent out from each terminal device 34a, 34b..., and each block 30a,
30b..., the terminal side frequency converter 31, a, 3
The upstream signal f is output by the second mixer 36b of 1b...
After being converted into upstream signals f, f... Therefore, it is sufficient for each terminal device 34a, 34b, . . . to have the same frequency specifications for all blocks 30a, 30b, .

In the above explanation, the center side frequency converter 1F,
a, 11-b... and terminal side frequency converters 31a, 31
b... means blocks 30a130b, respectively.
・These correspond to blocks 30a and 3
In principle, the number of sets matching the number of 0b... is required. However, now, the center device 10 and the terminal devices 34a, 34b, etc. have the same frequency characteristics, and the downlink signal f from the former can be directly received by the latter, and the uplink signal f from the latter It goes without saying that if both can be directly received by the former, one set of the same wave number converters can be omitted. Furthermore, as described above, when using the number of frequency converters equal to the number of blocks 30a, 30b, . . . , the frequency characteristics of the center device 10 and the terminal devices 34a, 34b, . They do not necessarily have to be the same.

As described in detail, the present invention includes a transmission path for transmitting a transmission signal, a center device, and a group of terminal devices divided into a plurality of blocks, and the center device side and the terminal device side are connected to each other. By interposing a frequency converter that has different frequency characteristics for each block, it is possible to transmit transmission signals using carrier waves with different frequencies for each block. Not only can these terminal devices be effectively divided into blocks, but all blocks need to have the same frequency specifications, which makes it possible to effectively eliminate the complexity of maintenance and management. effective.

Further, the frequency converter according to the present invention has the practical effect that such a bidirectional CATV system can be easily constructed.

[Brief explanation of the drawing]

Figures 1 to 3 show examples, with Figure 1 being an explanatory diagram of the overall configuration system, and Figures 2 and 3 being diagrams explaining the configuration system of the center side frequency converter and terminal side frequency converter, respectively. It is. HPF...High-pass filter 1o...Center device 1
1a, 1lb-11n...center side frequency converter 12a, 35a...first mixer/brancher 12b, 35b
...Second mixer/brancher 13 as 36 a...First mixer 13b, 36b...Second mixer 20...Transmission line

Claims (1)

[Scope of Claims] 1) A transmission path for transmitting transmission signals including television broadcast signals, a center device connected to the transmission path, and a group of terminal devices divided into a plurality of blocks and connected to the transmission path. The center device is connected to the transmission path via a plurality of center-side frequency converters each having a different frequency characteristic in correspondence with each block of the terminal device group, and each block of the terminal device group , each of which is connected to the transmission path via a terminal-side frequency converter corresponding to the center-side frequency converter. 2) A first mixer/brancher connected to the center device, a second mixer/brancher connected to the transmission line, and a second mixer/brancher interposed in parallel between the first and second mixer/brancher. 1 and a second mixer, the first mixer converts the frequency of the transmission signal from the center device and sends it to the transmission path, and the second mixer includes:
A center-side frequency converter for a bidirectional CATV system according to claim 1, which converts the frequency of a transmission signal from a transmission path and sends it to a center device. 3) A first mixer/brancher connected to the transmission line, a second mixer/brancher connected to one block of the terminal device group, and the first mixer/brancher connected to one block of the terminal device group.
and a second mixer/brancher, and a high-pass filter and first and second mixers, the high-pass filter comprising:
Of the transmission signals from the transmission path, only the television broadcast channel frequency is passed through and sent to one block of the terminal device group, and the first mixer converts the frequency of the transmission signal from the transmission path to the terminal device group. the second block.
2. The terminal-side frequency converter for a bidirectional CATV system according to claim 1, wherein the mixer converts the frequency of a transmission signal from one block of the terminal equipment group and sends it to the transmission path.