JPS61140288A - Catv system - Google Patents

Abstract

PURPOSE:To eliminate spurious disturbance due to crosstalk by installing the so-called first half of a conventional CATV converter indoor and selecting a channel from the indoor of a subscriber. CONSTITUTION:Up-converters 19 corresponding to the number of subscribers are stored in a storage house 20. On the other hand, in the housing 6 of a subscriber, a branching device 21, a down-converter 23 and a television receiver 5 are connected in cascade by a subscriber cable 3 and a channel selection section 22 is connected to the branching device 21. The channel selection section 22 transmits a channel selection signal at the subscriber side to a reception section in the housing 20 via the branching device 21 and the subscriber cable 3, the reception section processes the channel selection signal and a local oscillator in the up-converter 19 is controlled to the reception state of a prescribed CATV channel. As a result, the selected channel signal is frequency-converted to the UHF band and transmitted to the subscriber through the cable 3.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a CATV system, and particularly to an ATV system that eliminates spurious interference, prevents unauthorized viewing of pay programs, and improves system maintainability.

[Prior art and its problems]

In the current typical CkTV system, a CATV cable carrying a large number of CATV channel signals is brought into the subscriber's house, a CATV converter and a TV receiver are installed indoors, and the CATV converter is used to select channels for viewing. Figure 2 shows a part of this system.
) is the CATV trunk cable, (2) is the branch, (3)
is subscriber cable. Further, (4) indicates a CATV converter, (5) a TV receiver, and (6) a subscriber's indoor unit. The subscriber cable from the 1 branch (2) is connected indoors (6) to the CAT''l/converter (4), which selects the desired channel from a large number of channels and broadcasts the selected channel to the general public. The frequency is converted to an empty channel in television broadcasting (a channel in which television radio waves are not used) and input to the television receiver (5).

(4) The CAT4 converter converts a large number of CATV channels sent over a wide band of about 50 h to 500 MHz to the empty channel (usually a low channel) in order to avoid spurious interference. Known double super converter (
It consists of an up-down converter). Then, the first IP of this converter (intermediate frequency → is 600
MHz or higher.

FIG. 3 shows the block configuration of the main parts of this CATV converter. In FIG. 3, the CATv channel signal input to the input terminal (7) is input to the first mixer (9) where it passes through the band pass filter (8). Here, it is mixed with the local oscillator signal from the first local oscillator of (II).
The signal of the desired CATV channel is transmitted from the second bandpass filter to the first IP frequency (for example, the center frequency is 650
MHz). Note that Uυ is a tuning section for setting the oscillation frequency of the first local oscillator to a frequency corresponding to a channel to be tuned. The signal from the bandpass filter cLa is passed through a second mixer (11
A fixed oscillation signal from a local oscillator (14) is mixed and converted (down-converted) to the frequency of the empty channel as a second IP, and its output is inputted into the television receiver (5) shown in Figure 1 from the beginning. .

However, in recent years, pay programs have been increasingly broadcast on CATV systems, and in this case, CTV converters are used that allow pay programs to be viewed only by special subscribers. A typical method of this method is to transmit the TV signal with the synchronization signal suppressed, and if the TV signal is received as is, the TV receiver will not be able to synchronize, but if the image is normal, it will be transmitted. (This is called scrambling), and when received by a special subscriber's converter, the synchronized signal is restored (called descrambled) for viewing. Converters with such special functions are the third type.
A configuration in which a descrambling function is added to the converter shown in the figure is not shown in FIG. 3.

However, there have been many incidents among regular subscribers, such as modifying their own converters and illegally watching paid programs, or taking away the converter 8 when using the converter 8.CA'14
Furthermore, it has been pointed out that the C TV converter has a complicated configuration and is difficult to maintain, as it is installed inside the subscriber's house.There are problems with the current CATV itself. Ta.

[Means for solving problems]

In order to solve the above-mentioned problems, the present invention provides a plurality of single super up converters that select one of the CATV channel signals and convert the frequency to the frequency of the F band in the distributor connected to the CATV cable. Each of the upconverters is connected to each subscriber by a subscriber cable, and the distributor and the plurality of upconverters are housed in a hangar, and the hangar is installed outside the subscriber. The system operator can centrally manage this hangar, and each subscriber has a single super down converter and a tuning unit that converts the frequency of the CATV channel signal converted to the UHF band from the up converter to the available TV channel. This channel selection section controls the channel selection of the up-converter.

[Embodiments of the invention]

FIG. 1 shows a part of the CATV system of the present invention. Components in this figure that are the same as those in FIG. 2 are given the same numbers and their explanations will be omitted. In Figure 1, αη is a branch cable branched from the main cable (1), α barrel is a distributor, and α9 is a CAT
A single super up-converter for converting the frequency of a V-channel signal into a UHF band, (to) a distributor, and a storage for storing the up-converter 0. and,
The up converters H are stored in this hangar according to the number of subscribers. On the other hand, the subscriber's indoor (6)
A branch Qη, a down converter (C), and a television receiver (5) are connected in cascade to the subscriber cable (3), and a channel selection section (2) is further connected to the branch @.

Next, the operation will be explained. The up-converter housed in the hangar (1) is composed of a well-known singel super, and selects one of the CATV channel signals input from the distributor α barrel and converts it into a signal with a center frequency of, for example, 650 MH in the UHF band.
Frequency conversion is performed as a z signal.

This upconverter consists of the first half of the conventional CATV converter shown in FIG.
It includes a mixer (9), a first local oscillator (IQ), and a band-pass filter A3 that have almost the same configuration.This up-converter is installed for each subscriber and is fixed to each subscriber. Only one channel of the signal is frequency-converted to the frequency of In addition to the up-converter (I!J), it also houses a power supply section, a storage section for contract status for paid programs, and a reception section for control signals for channel selection sent from the subscriber's channel selection section@.

Among these, common parts are stored together.

On the subscriber side, the tuning section (2) sends the tuning signal to the splitter t2.
J, the subscriber cable (3) is sent to the receiving section (not shown) in the hangar ■, where the tuning signal is processed and sent to the local oscillator (not shown) in the up converter a. (3) is controlled to receive a predetermined CATV channel, and the selected channel signal is frequency-converted to the UHF band and sent to the subscriber side via the subscriber cable (3). A low frequency, for example 4 MHz, is used as the channel selection signal. The selected channel signal sent to the subscriber can be composed of a well-known singel super, for example, the latter half of the conventional CATV converter shown in FIG. The second local oscillator α3, the second local oscillator a4, and the band-pass filter α may be substantially the same.

〔Effect of the invention〕

As described in detail above, in the present invention, the first half of the configuration of the conventional CATV converter is installed inside the subscriber's house and the channel is selected from inside the subscriber's house, so that great effects can be obtained as described below. .

That is, (1) Since the two local oscillators for frequency conversion are separated into outdoor and indoor areas, spurious interference due to mutual interference is eliminated.

(2) Therefore, the shielding of the converter itself does not need to be as strict as in the past, making structural design easier.

(3) The down converter installed inside the subscriber's premises is smaller and easier to handle.

(4) Since the signal converted to the UHF band is sent to the subscriber, this frequency is high, while the tuning control signal from the tuning section is low, so the two frequencies are far apart, and the tuning control signal is 7. This prevents them from entering the converter and interfering with each other.

(5) Since the part that stores the contract status for pay programs can be installed in the hangar, it becomes impossible for general subscribers to modify the converter and view the program illegally.

(6) Since three common facilities for each subscriber can be installed in the hangar, the facilities can be used effectively.

(7) The system operator can centrally manage the hangar 8, resulting in excellent maintainability.

[Brief explanation of the drawing]

FIG. 1 shows a block configuration of the CATV system of the present invention, FIG. 2 shows a part of a typical conventional CATV system, and FIG. 3 shows a block configuration of the conventional CATV converter shown in FIG. (1) Trunk cable (2), r2υ branch (3) Subscriber cable (4) CA TV converter (5) TV receiver (6) Subscriber indoor (I barrel Distributor A9 Up converter (2) Tuning section (To) Down converter

Claims (1)

[Claims] A plurality of single super up converters that select one of the CATV channel signals and convert the frequency to a UHF band frequency are connected to a distributor connected to a CATV cable, and the distributor and the plurality of single super up converters are connected. A single super down converter is housed in a hangar installed outside the subscriber's house, and a single super down converter is installed inside the subscriber house for converting the frequency-converted CATV channel signal to the UHF band from one of the up converters to the frequency of an empty television channel. A CATV system comprising: a channel selection section; and the channel selection section controls channel selection of the up-converter.