JPH09271003A - Catv transmission equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to continue cable broadcasting even when a television(TV) broadcasting radio wave to be referred is interrupted. SOLUTION: When a TV broadcasting radio wave is interrupted, a signal detector 41 detects the interruption and switches a changeover switch 43 to the side of a terminal (a). Thereby a video carrier oscillated by a video carrier oscillator 42 is supplied to a video modulator 17 and the TV signal is outputted from the modulator 17. The TV signal is converted into a prescribed channel by a mixer 19 and the converted signal is sent to a cable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CATV transmission device adapted for cable transmission of television broadcast of the same channel as television broadcast radio waves.

[0002]

2. Description of the Related Art In common TV reception such as CATV (cable television), a UHF channel television broadcast radio wave is received and the received UHF channel is converted into a VHF channel or a VHF channel television broadcast radio wave. Is converted to a different VHF channel and transmitted using a cable. At this time, it is also possible to broadcast a self-produced program using a TV modulator. In the case of transmitting television broadcasting by cable, if the shielding performance of the TV receiver is not sufficient, beat transmission interference occurs due to the difference in the image carrier frequency between the television broadcasting radio wave and the television signal transmitted by the cable, resulting in image reception. The screen becomes unsightly.

In order to solve this, (1) if the same channel exists in the conversion channels, that channel is not used. (2) The converted VHF channel is given a frequency offset of about 10 kHz to make the same-channel beat inconspicuous. (3) Increase the input level of the television and increase the DU ratio with the interfering wave. (4) Change the television installation method so that the television broadcast radio waves do not directly enter the television. Although measures such as these have been taken, they were not reliable.

Therefore, as a countermeasure to replace this, there is a method conventionally described in Japanese Utility Model Publication No. 57-1493. This method will be described below with reference to FIGS. 3 and 4. FIG. 3 shows a configuration in which a self-produced program is transmitted by a cable. In FIG. 3, television broadcast radio waves are received by an antenna 110 and supplied to a mixer 111. The mixer 111 frequency-converts the local oscillation signal from the local oscillator 112 and selects the selected television broadcast signal as a video intermediate frequency signal. The video intermediate frequency signal is input to the filter 113, the video carrier is extracted, and is supplied to the limiter 114. The video carrier is input to one input terminal of the phase comparator 115 after the AM component is suppressed by the limiter 114.

An oscillation frequency signal oscillated by a voltage controlled oscillator (VCO) 116 is input to the other input terminal of the phase comparator 115. The phase comparator 115 compares the phase of the input image carrier with the oscillation frequency signal and outputs an error signal according to the phase difference between the two signals. By supplying this error signal to the VCO 116, V
The oscillation frequency of the CO 116 is controlled so that the oscillation frequency of the VCO 116 matches the frequency of the video carrier. The oscillation frequency signal of the VCO 116 is supplied to the video modulator 117 as a carrier wave, and the video signal input terminal 1
The video signal input from 18 is modulated, and the modulated signal is input to the mixer 119. The mixer 119 is supplied with the local oscillator signal from the same local oscillator 112 as the local oscillator signal supplied to the mixer 111, and frequency-converts the modulated signal. As a result, the channel is up-converted to the frequency of the same channel as the selected television broadcast channel, and output from the output terminal 120 to be transmitted through the cable.

In this case, the output signal of the VCO 116 is synchronized with the image carrier of the television broadcast of the selected channel. Therefore, the video carrier of the television transmission signal output from the mixer 119 to the cable is also synchronized with the video carrier of the television broadcast, and the transmission signal cable-transmitted on the same channel as the television broadcast channel is received. Even if the beat interference does not occur.

Further, the method shown in FIG. 4 is a case where the television transmission signal transmitted by the cable is a television rebroadcast program. In FIG. 4, the operations of the antenna 121, the mixer 122, the local oscillator 123, the filter 124, and the limiter 125 are the same as those of the blocks having the same names shown in FIG. The second antenna 126 receives a television broadcast wave to be rebroadcast, and the received signal is frequency-converted by the local oscillator signal from the voltage controlled oscillator 131 in the second mixer 127. , An intermediate frequency signal. The intermediate frequency signal is input to the filter 128, the image carrier is extracted, and is supplied to the limiter 129. This video carrier is
After the AM component is suppressed by the limiter 129, it is input to the other input terminal of the phase comparator 130.

In this manner, the video carrier signal is input to the two input terminals of the phase comparator 130,
An error signal corresponding to the phase difference between both video carrier signals is output. By supplying this error signal to the VCO 131, the oscillation frequency of the VCO 131 is controlled, and the frequency of the image carrier input from the limiter 125 to the phase comparator 130 is adjusted to the frequency of the video carrier input from the limiter 129 to the phase comparator 1.
The frequencies of the video carrier waves input to 30 come to match.

As a result, the frequencies of the video intermediate frequency signal output from the mixer 122 and the video intermediate frequency signal output from the mixer 127 are synchronized. Then, the video intermediate frequency signal output from the mixer 127 is up-converted by the local oscillator signal from the local oscillator 123 in the mixer 132 and output from the output terminal 133 to the cable. The video carrier of the television signal output to the cable is equal to the video carrier of the television broadcast radio wave received by the antenna 121, and the transmitted video signal is the television broadcast received by the second antenna 126. It becomes a video signal of radio waves. This allows the rebroadcast program to be transmitted by cable without causing beat interference.

[0010]

However, in the above-mentioned method for preventing beat interference, the television broadcast radio wave synchronized with the video carrier of the television signal transmitted by the cable is stopped at midnight. . Then, the reference image carrier wave is not input to the phase comparator, so that the predetermined oscillation frequency signal cannot be obtained from the VCO. Therefore, there is a problem that the television transmission signal is not output from the CATV transmission device. In this way, even if the self-produced program is being broadcast, if the television broadcast ends, the broadcast of the channel for synchronization is lost, and the self-produced program is broadcast within the service time of the television broadcast. There was a problem that it could only be done.

Therefore, according to the present invention, the television transmission signal of a predetermined channel can be sent to the cable even when the television broadcast radio wave is stopped.
It is an object of the present invention to provide a CATV transmission device that can also broadcast a self-produced program.

[0012]

In order to achieve the above object, a CATV transmission device of the present invention is a CATV transmission device for transmitting a television signal whose carrier is a frequency signal assigned to a channel of a television broadcast radio wave. In, reproduction means for obtaining a signal synchronized with a broadcast wave of a television broadcast radio wave, television signal generation means for generating the television signal using a signal output from the reproduction means as a carrier wave, and reproduced by the reproduction means. Oscillating means for oscillating a signal having a frequency substantially equal to the frequency of the carrier wave,
Detection means for detecting the presence or absence of television broadcast radio waves, and when the detection means detects that the television broadcast radio waves are stopped, the oscillation means instead of the carrier wave output from the reproduction means Is supplied to the television signal generating means.

In the CATV transmission device, the television signal generating means is a video modulator, and the video signal of a self-produced program is input to the video modulator. Further, in the CATV transmission device, the television signal generating means is a mixer, and the video signal supplied to the mixer is a television broadcast wave whose channel is different from that of a television broadcast wave in which the reproducing means reproduces a carrier wave. This is the video signal extracted from the radio wave.

According to the present invention as described above, when the received television broadcast radio wave is used to generate a television signal synchronized with the video carrier wave and the cable is transmitted, the television broadcast radio wave is stopped. When oscillated, a television signal is generated by using an oscillating means capable of obtaining a signal having a frequency substantially equal to the frequency of the video carrier signal. Therefore, even if the television broadcast radio wave is stopped, the television signal can be transmitted to the cable. As a result, when the self-produced program is being broadcast, the self-broadcasting can be performed even if the service time of the television broadcast is not available.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION First embodiment of CATV transmission apparatus of the present invention
FIG. 1 is a block diagram showing the configuration of the embodiment. FIG. 1 shows a configuration in which a self-produced program is transmitted via a cable. In FIG. 1, 10 is an antenna for receiving television broadcast radio waves, and 11 is a desired channel on which the received television broadcast radio waves are selected. Is a mixer for frequency-converting the image intermediate frequency into a mixer, 12 is a local oscillator for supplying a local oscillator signal to the mixer 11, 13 is a filter for extracting the image carrier from the converted image intermediate frequency signal, and 14 is the extracted image carrier. Is a limiter for suppressing the AM component of.

Further, 15 is a phase comparator which constitutes a part of the PLL circuit, and 16 is a voltage controlled oscillator (V whose oscillation frequency is controlled by an error signal output from the phase comparator 15).
CO), 17 is a video modulator that modulates a video carrier with a video signal of a self-produced program, and 19 is a mixer for up-converting the modulated video carrier to a frequency of a predetermined channel. Further, reference numeral 40 denotes a control unit, which includes a signal detector 41 for detecting the presence or absence of the video intermediate frequency signal output from the mixer 11, a video carrier oscillator 42 for oscillating a frequency substantially equal to the carrier of the video carrier, and a changeover switch. And 43.

Next, the operation of the CATV apparatus configured as described above will be described. Television broadcast radio waves are received by the antenna 10 and supplied to the mixer 11. The mixer 11 frequency-converts the local broadcast signal from the local oscillator 12 to convert the television broadcast signal of only the selected channel into a video intermediate frequency signal. The video intermediate frequency signal of the selected channel is input to the filter 13 and only the video carrier is extracted and supplied to the limiter 14. The video carrier is input to one input terminal of the phase comparator 15 after the AM component is suppressed by the limiter 14.

The oscillation frequency signal oscillated by the voltage controlled oscillator (VCO) 16 is input to the other input terminal of the phase comparator 15 via the changeover switch 43. The phase comparator 15 compares the phase of the input video carrier with the oscillation frequency signal and outputs an error signal corresponding to the phase difference between the two signals. By supplying this error signal to the VCO 16, the oscillation frequency of the VCO 16 is controlled. As a result, the oscillation frequency of the VCO 16 is controlled so as to match the frequency of the video carrier. That is, the phase comparator 15, the VCO 16, and the changeover switch 43
The L circuit will be configured.

The oscillation frequency signal of the VCO 16 is supplied as a carrier wave to the video modulator 17, and is modulated by the video signal of the self-produced program input from the video signal input terminal 18. Then, the modulated signal is input to the mixer 19, is up-converted by the local oscillator signal from the local oscillator 12 in the mixer 19, and is output from the output terminal 20. Since the local oscillator signal output from the local oscillator 12 is commonly supplied to the mixer 11 and the mixer 19, the self-produced program is connected to the output terminal 20 by the channel of the selected television broadcasting. Not going to be broadcast over the cable.

The operation as described above is when the movable contact c of the changeover switch 43 is switched to the fixed contact b. The changeover switch 43 is controlled by the output of the signal detector 41. When the signal detector 41 detects that the video intermediate frequency signal is being output from the mixer 11, the changeover switch 43 is changed over.
Can be switched as shown. Therefore, the VCO
The output signal of 16 becomes synchronized with the video carrier of the selected television broadcast. Therefore, the video carrier of the television transmission signal output from the mixer 19 to the cable is also the video carrier of the television broadcast. Will be synchronized with. As a result, beat interference does not occur even when a transmission signal transmitted through a cable on the same channel as a television broadcast channel is received.

When the television broadcast service time ends and the television broadcast radio wave is stopped, the mixer 11 stops outputting the video intermediate frequency signal. Then, the signal detector 41, which has detected that the video intermediate frequency signal is no longer output, switches the changeover switch 43 from the fixed contact b to the fixed contact a, and the image modulator 17
Then, the carrier oscillated by the image carrier oscillator 42 is supplied. The frequency of the carrier wave is set to be substantially equal to the frequency of the image carrier of the selected television broadcast, and in the image modulator 17, the image carrier oscillator 4
Carrier waves from 2 are modulated by the video signal of the self-produced program. This modulated signal is up-converted by the mixer 19 by the local oscillation signal from the local oscillator 12 to have a frequency of a predetermined channel, and the output terminal 20.
Will be output from.

As a result, even if the television broadcast wave is stopped, the self-produced program can be broadcast by the carrier wave from the image carrier wave oscillator 42. In this case, the frequency and phase of the video carrier wave will be slightly different from the video carrier wave of the television broadcast wave, but since the television broadcast wave is stopped, beat interference does not occur.

Next, FIG. 2 is a block diagram showing the configuration of the second embodiment of the CATV transmission device of the present invention. FIG.
2 shows a configuration in which a rebroadcast program is transmitted by cable. In FIG. 2, the operations of the antenna 21, the mixer 22, the local oscillator 23, the filter 24, and the limiter 25 are the same as those of the block having the same name shown in FIG. Since it works, its explanation is omitted. In addition, the second antenna 26
Receives the television broadcast wave of the channel to be rebroadcast, and the signal received by the second antenna 26 is input to the mixer 27. The second mixer 27 is supplied with the local oscillation signal from the voltage controlled oscillator (VCO) 31 via the changeover switch 43, whereby the signal of the selected channel is frequency-converted into the video intermediate frequency signal. It

This video intermediate frequency signal is filtered by the filter 28.
And the video carrier is extracted. This video carrier is supplied to the limiter 29, and after its AM component is suppressed, it is input to the other input terminal of the phase comparator 30.
In this way, the video carrier signal from the limiter 25 and the limiter 2 are connected to the two input terminals of the phase comparator 30.
The video carrier signal from 9 is input, and both video carrier signals are compared in phase. Then, an error signal corresponding to the phase difference is output from the phase comparator 30, and the oscillation frequency of the VCO 31 is controlled by this error signal. As a result, the frequency of the video carrier input from the limiter 25 to the phase comparator 30 matches the frequency of the video carrier input from the limiter 29 to the phase comparator 30.

The video signal output from the mixer 27 is input to the mixer 32, up-converted to the channel selected, and output from the output terminal 33. This output is transmitted by a cable (not shown). In this case, the frequency of the video carrier of the video intermediate frequency signal output from mixer 22 and the frequency of the video carrier of the video intermediate frequency signal output from mixer 27 are synchronized as described above. The video carrier of the television signal output from the output terminal 33 becomes equal to the video carrier of the television broadcast radio wave received by the antenna 21, and the transmitted video signal is received by the second antenna 26. It becomes a video signal of broadcast radio waves. As a result, even if the rebroadcast program transmitted through the cable is received, it can be received without causing beat interference.

The operation of the CATV device shown in FIG. 2 described above is performed when the movable contact c of the changeover switch 43 is changed over to the fixed contact b. The changeover switch 43 is switch-controlled by the output of the signal detector 41, and when the signal detector 41 detects that the intermediate frequency signal is being output from the mixer 22, the changeover switch 43 is as shown in the drawing. Can be switched. In this case, as described above, the oscillation frequency of the VCO 31 is controlled so that the frequencies of both video carriers input to the phase comparator 30 are equal. Therefore, the video carrier of the television transmission signal output from the mixer 32 to the cable is synchronized with the video carrier of the intermediate frequency signal output from the mixer 22. As a result, even if a rebroadcast program transmitted by cable on the same channel as a television broadcast channel is received, beat interference does not occur.

When the television broadcast service time ends and the television broadcast radio wave is stopped, the mixer 22 stops outputting the intermediate frequency signal. Then, the signal detector 41, which has detected that the intermediate frequency signal is no longer output, switches the changeover switch 43 from the fixed contact b to the fixed contact a, and causes the mixer 27 to oscillate the local oscillation generated by the second local oscillator 44. Issue. The frequency of the local oscillator signal is the frequency of the video carrier component of the video intermediate frequency signal output from the mixer 27.
Video carrier of the selected television broadcast (mixer 22
Output) is almost equal to the frequency. The video intermediate frequency signal output from the mixer 27 is up-converted by the mixer 32 to generate a local oscillation signal from the local oscillator 23 so that the video intermediate frequency signal is output as a frequency of a predetermined channel from the output terminal 20. become.

As a result, even if the television broadcast radio wave received by the antenna 21 is stopped, the rebroadcast program can be broadcast on the channel determined by the local oscillator signal from the local oscillator 44. In this case, the frequency and phase of the broadcast image carrier wave will be slightly different from the image carrier wave of the television broadcast wave, but since the television broadcast wave is stopped, beat interference does not occur. In the configuration shown in FIG. 2, for example, the television broadcast received by the antenna 21 is VHF broadcast and the television broadcast received by the antenna 26 is UHF broadcast, so that the program of the UHF broadcast is a rebroadcast program. Can be broadcast on the VHF channel as a cable.

[0029]

As described above, the present invention utilizes the received television broadcast radio wave to generate a television signal synchronized with the video carrier wave and transmit it by cable. When the wave was stopped,
A television signal is generated by using an oscillating means capable of obtaining a signal having a frequency substantially equal to the frequency of the video carrier signal. Therefore, even if the television broadcast radio wave is stopped, the CATV transmission device can transmit the television signal to the cable. As a result, when a self-produced program or a rebroadcast program is being broadcast, cable broadcasting can be performed even when the service time is not TV broadcasting.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a first embodiment of a CATV transmission device of the present invention.

FIG. 2 is a block diagram showing a configuration of a second embodiment of a CATV transmission device of the present invention.

FIG. 3 is a block diagram showing a configuration of a conventional CATV transmission device.

FIG. 4 is a block diagram showing another configuration of a conventional CATV transmission device.

[Explanation of symbols]

 10, 21, 26 Antenna 11, 19, 22, 32 Mixer 12, 23, 27, 44 Local oscillator 13, 24, 28 Filter 14, 25, 29 Limiter 15, 30 Phase comparator 16, 31 Voltage controlled oscillator (VCO ) 17 video modulator 18 video input terminal 20 output terminal 40 control unit 41 signal detector 42 video carrier oscillator 43 switch

Claims (3)

[Claims] 1. A CATV transmission device for transmitting a television signal using a frequency signal assigned to a channel of a television broadcast radio wave as a carrier, and a reproducing means for obtaining a signal synchronized with the broadcast wave of the television broadcast radio wave. Television signal generating means for generating the television signal using the signal output from the reproducing means as a carrier wave, oscillating means for oscillating a signal having a frequency substantially equal to the frequency of the carrier wave reproduced by the reproducing means, and television broadcasting. A detection means for detecting the presence or absence of a radio wave, and when the detection means detects that the television broadcast radio wave is stopped, the signal from the oscillation means is replaced with the carrier wave output from the reproduction means. Is supplied to the television signal generating means. 2. The CATV transmission device according to claim 1, wherein the television signal generating means is a video modulator, and a video signal of a self-produced program is input to the video modulator. 3. The television signal generating means is a mixer, and the video signal supplied to the mixer is extracted from a television broadcast radio wave whose channel is different from the television broadcast radio wave in which the reproducing means reproduces a carrier wave. The CATV according to claim 1, wherein the CATV is a video signal.
Transmission equipment.