JPH10174084A - Two-way catv system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the 2-way CATV system capable of 2-way communication for a multiple dwelling house without being affected by noise. SOLUTION: A request signal outputted from a terminal television receiver of each home is outputted at frequencies of 900-1000MHz higher than an upper limit frequency of an outgoing signal sent from a center equipment 1 and it is converted into a frequency of 10-50MHz at a frequency conversion section 12 and outputted when it is outputted from a distributer 7 of a multiple dwelling house, then the effect of noise from house electric appliances is reduced and the signal is transmitted to the center equipment 1 via a conventional transmission line.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CATV system, and more particularly, to a center device capable of transmitting information as an image to a terminal television device of each home and requesting a program from the terminal television device of each home to the center device. And a bidirectional CATV system capable of bidirectional communication.

[0002]

2. Description of the Related Art FIG. 5 is a block diagram showing a conventional bidirectional CATV system. The example shown in FIG. 5 shows a CATV system installed between the center device 1 and an apartment house such as an apartment or an apartment complex.

A video source 101 of the center apparatus 1 is a video signal source for satellite broadcasting, terrestrial broadcasting, or the like. Multi-channel video signals are frequency-division multiplexed by a mixing circuit 102, amplified by an amplifier 103, and given to a distributor 104. And distributed to each district. The distributed video signal is E
The electrical signal is converted into an optical signal by the / O converter 105 and transmitted as a downstream signal via an optical fiber. This optical signal is converted into an electrical signal by the O / E, E / O converter 2 in the receiving area, and applied to the subscriber terminal (also called tap-off) 4 of the apartment house via the bidirectional amplifiers 31 to 33. .

In such a CATV system, a transmission line having a tree-like configuration is formed after each of the bidirectional amplifiers 31 to 33. That is, as shown in FIG. 5, the subscriber terminal 4 is attached behind each of the bidirectional amplifiers 31 to 33, and is connected to the outlet 8 of each home or apartment through a protector. In the present invention, the case where connection to a condominium or other apartment complex is a problem will be described below. Therefore, a case where the bidirectional amplifier shown in FIG.

[0005] The video signal given to the subscriber terminal 4 is given to a distributor 7 via a protector 5 and an amplifier 6, and is distributed to an outlet 8 of each home by the distributor 7, and a terminal in each home is provided. A desired image can be viewed on a television device.

On the other hand, the center device 1 is supplied with an upstream signal from a terminal television device in each home. The upstream signal includes a request signal for specifying a channel of a video to be viewed, a request for connection to the Internet, and the like, a monitoring signal for monitoring the terminal television device, and a video signal from the terminal device. This upstream signal is input to the O / E converter 106 in the center device 1 and is converted into an electric signal.
7, each signal is distributed. The distributed request signal is provided to the receiving device 108, and the monitoring signal is transmitted to the monitoring circuit 109.
, And the video signal is output to the video output circuit 110.

FIG. 6 is a diagram showing frequency bands of an upstream signal and a downstream signal in a conventional general bidirectional CATV system. As shown in FIG. 6, the upstream signal from the terminal television apparatus to the center apparatus 1 uses the 10 to 50 MHz band, and the downstream signal uses the 70 to 450 or 770 MHz band, which includes video signals of many channels. Have been.

The frequency band used for CATV differs between individual systems when viewed in detail, and the following example is also available. That is, the frequency band of the uplink signal is 1
0 to 42 MHz, 10 to 55 MHz, and the lower limit of the frequency band of the downstream signal is 54 MHz or 70 MHz.
Hz, the upper limit is 222 MHz, 280 MHz, 300
MHz, 350MHz, 450MHz, 550MHz,
750 MHz, 770 MHz and the like.

In the present invention, there is no particular effect, so an example using a 10 to 50 MHz band as an upstream signal and a 70 to 450 MHz or 70 to 770 MHz band as a downstream signal will be described as an example.

[0010]

As shown in FIG. 6,
A frequency of 10 to 50 MHz is used as the upstream signal. Noise generated from appliances such as a vacuum cleaner, a television receiver, and a video tape recorder generally used in each household is 30 MHz as shown in FIG. Many below,
The upstream signal used in the bidirectional CATV system is affected by these noises. Further, the final end of the outlet 8 of each home needs to be terminated with a terminating resistor, but there is a case where the terminating resistor is forgotten or the connection is insufficient. Therefore, in apartment houses such as condominiums and housing complexes, the influence of noise is often greater than in ordinary single-family houses. For this reason, in an apartment house such as a condominium or an apartment complex, an up signal is not accepted, so that it is not affected by noise.

In order to solve this problem, Japanese Patent Laid-Open Publication No.
No. 981 proposes a method of making the frequency band of an upstream signal higher than the frequency band of a downstream signal. However, when this method is applied to an existing transmission line, the cable loss increases as the frequency increases, and a high gain amplifier is required to compensate for this loss, and all existing amplifiers must be replaced. It will be expensive.

Japanese Patent Application Laid-Open No. 4-160890 proposes a method in which the positions of dividing the upstream and downstream signal transmission bands are different for the trunk system and the branch system. However, if the position where the band is divided between the main system and the branch system is changed in this way, frequency conversion will be required on the way, the video signal will be affected by the distortion, and the image quality will not only deteriorate, but also the downstream transmission band Is reduced.

[0013] Therefore, a main object of the present invention is to provide a two-way CATV system capable of two-way communication without being affected by noise even in an apartment house.

[0014]

The invention according to claim 1 is
A bidirectional CATV system in which signals are distributed to a large number of terminal television devices by one subscriber terminal, and each terminal television device and a center device can communicate with each other,
Each terminal television device sends a signal to the center device at a frequency higher than the upper limit frequency of the signal sent from the center device, is connected to the center terminal side of the subscriber terminal, and is sent from each terminal television device. It is provided with frequency conversion means for converting the frequency of the signal to a frequency lower than the lower limit frequency of the signal sent from the center device and sending it to the center device.

In the invention according to claim 2, each terminal television apparatus according to claim 1 generates a signal in a frequency band of about 800 to 1000 MHz.

[0016]

FIG. 1 is a block diagram showing an embodiment of the present invention. 1, in the embodiment of the present invention, a bidirectional amplifier 9 and a frequency converter 12 are connected between a protector 5 and a distributor 7 in a distribution area, and other configurations are the same as those in FIG. It is composed.

As described with reference to FIG. 5, a transmission line having a tree-like configuration is provided after each of the bidirectional amplifiers 31 to 33, but is not shown in FIG. 1 for simplification. In this embodiment, for example, 900 to 1000 M
The frequency converter 12 uses a frequency band of 9 Hz to reduce the influence of noise.
The frequency of 00 to 1000 MHz is converted to 10 to 50 MHz, which is the frequency band of the upstream signal of the conventional CATV system. Thus, the two-way amplifier 31 provided in the transmission system is not affected by noise from home appliances.
The existing ones can be used as .about.33, two-way communication in the apartment house becomes possible, and requests can be accepted.

FIG. 2 is a block diagram of the frequency converter 12 shown in FIG. In FIG. 2, the frequency conversion unit 12
It comprises bandpass filters 121 and 123, an amplifier 122, a mixing circuit 124, and a local oscillation circuit 125. The bandpass filter 121 transmits the 70
The downstream signal in the band of 450 to 770 MHz is extracted and supplied to the amplifier 122. The amplifier 122 amplifies the downstream signal by the loss of the cable and supplies the amplified signal to the distributor 7 shown in FIG. In addition, the 900-1000 MHz upstream signal from each terminal television apparatus is provided to a mixing circuit 124 via a bandpass filter 123, mixed with a local oscillation signal from a local oscillation circuit 125, and
The frequency is converted to a signal of 50 MHz and the bandpass filter 12
1 to the center device 15.

FIG. 3 is a schematic block diagram of a terminal television set provided in each home. The terminal television device 20 includes:
70 to 450 or 7 sent from the center device 1
It includes a distributor 21 for distributing a television broadcast signal and a communication signal among video signals in the 70 MHz band. Distributor 2
The television broadcast signal distributed in 1 is transmitted to the home terminal 22.
Is provided to the television receiver 23 through which the broadcast program is displayed.

On the other hand, the communication signal is received by the downstream receiving section 24 and is given to the control processing section 25. Control processing unit 25
For example, a personal computer 27 is connected, and a request signal is given to the control processing unit 25 by operating a keyboard of the personal computer 27. The control processing unit 25
A 00 MHz uplink signal is transmitted. Instead of two personal computers, a simple remote controller for connecting to the Internet or the like can be connected to this part.

FIG. 4 is a diagram showing frequency bands of an upstream signal and a downstream signal used in one embodiment of the present invention. Next, the operation of the embodiment of the present invention will be described with reference to FIGS. The downlink signal transmitted from the center device 1 to the terminal television device 20 in each home uses the frequency band of 70 to 450 or 770 MHz shown in FIG.

On the other hand, the request signal input by operating the personal computer 27 shown in FIG. 3 is transmitted by the upstream transmitting section 26 at a high frequency of 900 to 1000 MHz through the distributor 21 of each home. Output to the distributor 7. Then, this upstream signal is provided to the mixing circuit 124 via the bandpass filter 123 of the frequency conversion unit 12,
The mixing circuit 124 sets the frequency of 900 to 1000 MHz to 10 based on the local oscillation signal from the local oscillation circuit 125.
Band-pass filter 1 by converting the frequency to a frequency of
21 to the center device 1 side.

Therefore, according to one embodiment of the present invention, the frequency of the upstream signal output from the terminal television set at each home is transmitted at a high frequency of 900 to 1000 MHz which is not affected by noise from the electric appliances. Then, at the time of leaving the apartment house, the frequency converter 12
Since the signal is converted to a low frequency of 0 to 50 MHz and transmitted, the conventional transmission line amplifier can be used as it is, without being affected by noise, and from each terminal television apparatus to the center apparatus 1. Thus, a request signal can be transmitted.

In the above-described embodiment, the frequency of the uplink signal from uplink transmitter 26 is 900 to 100
Although the description has been given of the case where 0 MHz is used, the frequency of the uplink transmission unit 26 can be optimally used if the frequency is 800 to 1000 MHz. Generally, in a bidirectional CATV system, the upper limit of a frequency band used for a video signal is 770.
MHz is used. Therefore, the frequency of the upstream signal is preferably 770 MHz or more, and preferably 800 MHz or more in consideration of a practical margin.

On the other hand, the home television receiver 2 shown in FIG.
In 3, the BS broadcast may be received. In BS broadcasting, a frequency band of 1035 MHz or more is used. Considering the separation from the BS broadcast, it is preferable to use a frequency of 1035 MHz or less for the uplink signal. It is preferable to use a frequency of the upstream signal of about 1000 MHz with a practical margin. For the above reasons, it is preferable to generate an upstream signal in the frequency band of 800 to 1000 MHz.

Further, depending on the individual CATV system, there is also a system in which the downlink frequency is limited to about 70 to 450 MHz. When it is sufficient to support only such a system, for example, 500 to 5
It is also possible to use 50 MHz. However,
In order for the present invention to be connectable to any system, it is more convenient to support an uplink frequency of 770 MHz, which is most likely to be used in various CATV systems.

[0027]

As described above, according to the present invention, the frequency of the signal output from each terminal television apparatus provided in each home of an apartment house to the center apparatus is determined by the frequency of the signal transmitted from the center apparatus. Since it is sent to the center device at a frequency higher than the upper limit frequency, it is converted to a frequency lower than the lower limit frequency of the signal sent from the center device and sent to the center device, so home appliances in each home Without being affected by noise from
In addition, two-way communication can be performed using the conventional transmission line amplifier as it is.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a specific block diagram of a frequency conversion unit shown in FIG.

FIG. 3 is a schematic block diagram of a terminal television device.

FIG. 4 is a diagram showing frequency bands of an upstream signal and a downstream signal used in an embodiment of the present invention.

FIG. 5 is a block diagram showing a conventional bidirectional CATV system.

FIG. 6 is a diagram illustrating frequency bands of an upstream signal and a downstream signal used in a conventional bidirectional CATV system.

FIG. 7 is a diagram illustrating a frequency band of noise emitted from home electric appliances.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 center device 4 subscriber terminal 5 protector 7 distributor 8 outlet 9, 31 to 33 bidirectional amplifier 12 frequency conversion unit 20 terminal television device 21 distributor 22 home terminal 23 television receiver 24 downstream receiving unit 25 control processing unit Reference Signs List 26 Up transmission unit 27 Personal computer 101 Video source 102 Mixing circuit 103 Amplifier 104 Distributor 105 E / O converter 106 O / E converter 107 Distribution circuit 108 Receiving device 109 Monitoring circuit 110 Video processing circuit 121, 123 Band filter 124 Mixing Circuit 125 Local oscillation circuit

Claims (2)

[Claims] 1. A bidirectional CATV system in which a signal is distributed from one subscriber terminal to a large number of terminal television devices, and each terminal television device and a center device can communicate with each other. The television device sends a signal to the center device at a frequency higher than the upper limit frequency of the signal sent from the center device, is connected to the center device side of the subscriber terminal, and is sent from each of the terminal television devices. A bidirectional CAT, comprising frequency conversion means for converting the frequency of the incoming signal to a lower frequency than the lower limit frequency of the signal sent from the center device and sending it to the center device.
V system. 2. The terminal television device according to claim 1, wherein
2. The bidirectional CATV system according to claim 1, wherein a signal is generated in a frequency band of about 00 MHz.