JPH03268690A - Catv converter - Google Patents

Abstract

PURPOSE:To attain the service of a high quality voice signal by adding a CATV converter able to receive a satellite broadcast signal revised for a CATV line together with a data channel signal to a conventional home use receiver. CONSTITUTION:The gain and selectivity of a CATV input signal 100 are improved. The output is subject to frequency conversion (201) and amplified by an IF amplifier 202. The output is given to a trap circuit 203, in which adjacent video carrier trap and audio carrier trap is implemented, and a video signal is detected by a video detection circuit 204, from which the video signal is outputted. On the other hand, an audio filter 207 detects a satellite broadcast audio digital signal, the signal is fed to an AGC circuit 208, and a digital signal having a peak in a line is decoded 209 to be logical 1 or 0, the audio signal is decoded by an audio decoder 210 and an analog audio signal 218 is extracted, Then a stereo and a monaural output are obtained. Thus, a satellite broadcast signal converted into a signal for a CATV line is received by the converter added to a conventional home use receiver together with a data channel signal.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a CATV converter added to a CATV subscriber side, and particularly to a receiving system capable of receiving modified satellite broadcasting signals.

(Summary of the Invention) This invention relates to a converter added to a home-use receiving terminal device for a CATV line, which receives and demodulates a satellite broadcasting signal sent in the 6 MHz band and has been modified for the CATV line. In addition, the received signal can be frequency-converted for use with other channels and can be received as a terrestrial television signal of another channel, and data channel signals can also be received.

Thus, it is possible to receive high quality audio signals, NTSC video signals and data channel signals without modification to conventional receivers.

(Conventional technology) Conventionally, when transmitting satellite broadcast signals using a CATV line,
In particular, digital audio signals are FDM (frequency division multiplexed)
6M) Iz, which is different from the video signal, or TDM
(Time division multiplexing) transmission methods have been adopted. In this case, channel selection on the receiver side is complicated, making it difficult to operate and having poor channel efficiency.

(Problem to be Solved by the Invention) In the conventional method of transmitting satellite broadcasting signals over CATV lines, the digital audio signal is decoded at the head end, and the audio carrier is transmitted on the 4.5 MHz of the video carrier in the same way as a normal NTSC signal. Two methods have been used: one method is to transmit the digital audio signal after FM modulation, and the other method is to transmit the digital audio signal as it is as a digital signal using FDM or wideband TDM.

The method of transmitting the same signal as normal NTSC had the drawback that it was not possible to receive high-quality audio signal services. Naturally, I couldn't receive data channel service either.

Furthermore, the FDM and TDM systems have problems with the operability of the receiving converter regarding video and audio signal selection.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and provide a receiver capable of receiving satellite broadcasting signals modified for CATV lines, including data channel signals, without making any changes to conventional home receivers. The purpose of this project is to provide a CATV converter that can be added to a computer.

(Means for Solving the Problems) In order to achieve this object, the CATV converter of the present invention is a CATV converter added to the subscriber side of a CATV line.
means for receiving a specific high frequency signal transmitted via a line; means for separating the received high frequency signal into a component containing a video signal and a component containing a digital audio signal;
Means for connecting a component containing a separated video signal to a video terminal of a television monitor via a video detection circuit; and a means for connecting a component containing a separated digital audio signal to an audio terminal of a television monitor via a digital decoding circuit. and means for converting the specific high frequency signal including a video signal and an audio signal into another high frequency signal so that it can be received as a terrestrial television signal of another channel; The present invention is characterized by comprising a means for receiving data channel signals simultaneously transmitted as high-frequency signals.

(Examples) The present invention will be described in detail below by way of examples with reference to the accompanying drawings.

FIG. 1 shows the overall system of input/output signal formats of a CATV converter according to the present invention. Input 100 receives CATV signal,
Element 101 is a CATV converter according to the present invention, output 102 is a video signal, output 103 is an audio signal, which is a stereo left and right signal, and output 104 is a normal empty channel noise signal.
) TV modulation signal, for example, in Tokyo, 2 ch, 5
Output 105 is a data channel signal, output 106 is a clock signal synchronized with the data channel signal, and output 107 is 2.048M bps (
Mbit/5ec) digital data streams.

The CATV converter 101 according to the present invention is configured to be compatible with various receiving terminals.

Outputs 102 and 103 are AV (audio video
This is an output signal corresponding to a monitor of the type (audio/video). Also, the output 104 is an output signal compatible with a normal VHF, tJHF TV receiver. Outputs 105 and 106 are outputs corresponding to future data channel services, output 1
07 is an output corresponding to a future digital input type receiving terminal. Output 108 is a signal that detects a satellite broadcast (BS) audio signal and indicates whether or not the BS signal is coming, and can be indicated by digital carrier detection, carrier lock, clock synchronization lock, or the like.

Although FIG. 2 shows a circuit configuration block diagram of the CATV converter according to the present invention shown in FIG. 1, the circuit configuration of the present invention is not limited to this.

Block 200 is an RF amplification circuit, block 201 is a frequency conversion circuit, block 202 is an IF amplification circuit, block 203 is an adjacent channel and audio signal trap circuit,
Block 204 is a video detection circuit, block 205 is an audio signal detection circuit, signal 206 is a trap switching signal, block 207 is an audio filter, block 208 is an AGC circuit, block 209 is a digital signal decoding circuit, block 210 is an audio decoding circuit, and a block 211 is a frequency conversion circuit, and block 212 is a TV for VHF or Uf (F).
A block 213 represents a video modulation wave and an audio modulation wave mixing circuit, a block 214 represents a data channel extraction circuit, and the like.

Next, the operation of the second illustrated circuit will be explained in detail.

The input signal 100 is the CATV signal mentioned above, and is a normal T
In addition to the V signal, a satellite broadcast signal is multiplexed somewhere in the same 6 MHz band. The satellite broadcasting signal referred to here is a digitally modulated audio signal, QPSK, 16QAM.
, 36QAM, and other modulation methods are possible. As for the modulation frequency, 4.5 MHz, 4.625 MHz, 4.715 MHz, etc. from the video carrier signal are used.

The RF amplifier circuit 200 has improved gain and selectivity characteristics. The output signal frequency-converted by the frequency conversion circuit 201 becomes an IP times signal. It is conceivable to provide two types of IP amplifier circuits 202 in order to prevent interference. In this case, two systems of frequency conversion circuits and two systems of IF amplification circuits are required. The trap circuit 203 includes an upper adjacent video carrier trap (6 MHz above the target video carrier) and an audio carrier trap (−1, 5 MHz above the target video carrier).
MHz or -1,375 M) Iz or -1,285
MHz). For normal terrestrial TV signals, the audio carrier trap is -1.5MHz of the video carrier, but for satellite broadcasting signals, it varies depending on the system, and is 1.375 MHz.
MHz, -1, 285 MHz, etc. have been raised as candidates. The audio signal detection circuit 205 is a circuit for detecting this signal, and switches between the 4.5MH2 trap and other trap circuits using the trap switching signal 206.

The video detection circuit 204 is a video detection circuit that detects the IF signal after passing through the trap circuit 203. The frequency conversion circuit 211 is a frequency conversion circuit for generating a normal terrestrial TV video modulation signal. Of course, the video detection circuit 204
Thereafter, the Haasband signal may be subjected to vestigial sideband AM modulation using a target frequency signal. Audio filter 207 is a filter for extracting a satellite broadcast audio digital signal, amplifies the signal, and is connected to AGC circuit 208 .

The digital signal, which has become a constant peak signal, is decoded by a digital decoding circuit 209 and becomes a digital signal string 107 of "1" and "0". In addition, the carrier regeneration circuit or bit synchronization regeneration circuit that is part of the circuit 209
BS detection signal 1 to determine whether or not a satellite broadcasting signal is being received
08 is output. The digital signal 107 is decoded by one audio decoding circuit 210, and the analog audio signal 2
Get 18. Of course, when stereo, the output is L (left) and R (right), and when mono, the output is the same for L (left) and R (right).

The audio filter 215 is a filter for extracting a normal TV audio signal, and after amplification, it is decoded by an audio decoding circuit 216 and becomes L and R analog audio outputs 219. The signals 218 and 219 are the switching signal 20
The audio output R is selected by the switch 217 controlled by the
It becomes the L signal 103. Also, this signal is transmitted to the audio modulation circuit 2.
12, the signal becomes an audio modulation wave of an empty TV channel, is mixed with a video modulation wave by a mixer 213, and is output as a signal exactly the same as the terrestrial TV signal of signal 104. In Tokyo, 2ch is often used.

Further, the data channel extraction circuit 214 corresponds to future data channel services other than video and audio, and is a circuit that extracts and reconstructs data channel signals from the digital signal string 107. Although the transmission capacity varies depending on whether the audio is in A mode or B mode, stereo, or monaural, a large-capacity data channel can be constructed. The extracted and reconstructed signal sequence is an output signal 105, and the clock signal synchronized therewith is an output signal 106.

As described above, it goes without saying that the method used for audio decoding is not limited to that shown in the second diagram, but can also be decoded by a normal intercarrier method.

(Effects of the invention) With conventional CATV converters, high-quality audio of satellite broadcasting signals, future data channel services, etc.
It was not possible to receive the signal as a lz band signal. A method of transmitting audio signals in completely different bands was also considered, but this had the drawback that it was difficult for the receiver to select between video and audio.

Furthermore, a method has been put into practical use in which the CATV head end receives and duplicates satellite broadcasting signals and receives the signals as they are in the same format as terrestrial TV, but in this case, the burden on the converter is was small, but had the drawback of not being able to receive high-quality voice or future data channel services. According to the converter of the present invention, it is possible to receive a service with exactly the same audio quality as when receiving satellite broadcasting, and a data service using future data channels. Further, future A-mode stereo audio services of 3 and 4 channels, and monaural audio services of 2 and 3.4 channels can be received by simply changing the circuit configuration shown in the second diagram.

Overall, the circuit shown in the second figure can be fully integrated into an IC using current IC technology, and the cost of the converter will hardly increase.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the overall system of input/output signal formats of the CATV converter according to the present invention, and FIG. 2 is a block diagram showing the circuit configuration of the CATV converter according to the present invention. 100... Input signal 101... CATV converter 102... Video signal output 103... Audio signal output 104... VHF, UHF modulation signal output 105...
Data channel signal output 106...Clock signal output 107...Digital data signal output 108...B
S detection signal output 200...RF amplifier circuit 01 02 03 04 05 06 07 08 09 210°11 12 13 14 17 218°...Frequency conversion circuit...IF amplifier circuit...Trap circuit...Video Detection circuit...Audio signal detection circuit...Trap switching signal 215...Audio filter...AGC circuit...Digital decoding circuit 216...Audio decoding circuit...Frequency conversion circuit...Audio modulation Circuit...Mixing circuit...Data channel extraction circuit...Switch 219...Analog audio signal Figure 1 Main evening January 3 CATV equipment/8-Yu no Iri, Tagai 1
9nt

Claims (1)

[Claims] 1. In a CATV converter added to the subscriber side of a CATV line, the converter has means for receiving a specific high-frequency signal transmitted via the CATV line in a predetermined band, and means for separating a high frequency signal into a component containing a video signal and a component containing a digital audio signal; a means for connecting the separated component containing a video signal to a video terminal of a television monitor via a video detection circuit; and means for connecting a component containing a digital audio signal to an audio terminal of a television monitor via a digital decoding circuit, and converting the specific high frequency signal containing a video signal and an audio signal into another high frequency signal. and means for making it receivable as a terrestrial television signal of another channel;
A CATV converter characterized by comprising means for making it possible to also receive data channel signals simultaneously transmitted using the specific high frequency signal.