JPH089289A - Device for receiving television broadcasting signal - Google Patents

Abstract

PURPOSE:To provide the device for receiving television broadcasting signal capable of eliminating ghosts of received television broadcasting signals at the output without using any special component for a commercially-available video equipment. CONSTITUTION:A video detecting device 13 detects the video of an intermediate frequency signal from a frequency converter 12 and outputs a composite video signal and the voice carrier wave of the 2nd intermediate frequency. A sound detector 14 FM demodulates the sound carrier wave and outputs a monochrome voice signal. In this case, when a television multiplex broadcasting signal is received, the output sound signal of the detector 14 becomes a multiplex sound signal. A ghost eliminating device 15 cancels the ghost component in the composite video signal. An RF module 16 modulates the sound signal of the base band from the detector 14 and the composite video signal of the base band from the ghost eliminating device 15 and converts it into the television signal in the television broadcasting signal band at the output.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a television broadcast signal receiver, and more particularly to a television broadcast which outputs a received audio signal after removing a ghost of a composite video signal obtained by receiving and detecting the television broadcast signal. The present invention relates to a signal receiving device.

[0002]

2. Description of the Related Art Conventionally, a television broadcast signal received by an antenna is not immediately input to an antenna terminal of a television receiver, but the received television broadcast signal is once detected and then subjected to some processing. There is known a television broadcast signal receiving device that modulates again and converts it into a television signal in the television broadcast signal band again, and outputs this signal to the antenna terminal of the television receiver (for example, a television sound multiplex broadcast signal. With respect to the above, Japanese Utility Model Laid-Open No. 61-52858).

As one of such television broadcast signal receiving apparatuses, a ghost removing process is performed on a composite video signal of a composite video signal and a received audio signal obtained by receiving and detecting a received television broadcast signal. Then, the composite video signal after the ghost removal is combined with the above-mentioned received audio signal and then converted again into a television signal in the television broadcast signal band and output, so that an unspecified number of television receivers can receive the image. BACKGROUND ART A television broadcast signal receiving device for making it known has been conventionally known.

FIG. 3 is a block diagram showing an example of a conventional television broadcast signal receiving apparatus for performing the above ghost removal processing. In the figure, the television broadcast signal received by the antenna 31 is supplied to the frequency converter 32 where it is converted into an intermediate frequency band signal (IF signal),
The carrier frequency is supplied to the video / audio separation circuit 33 and the carrier frequency is 5
8.75MHz video carrier and carrier frequency 54.2
It is separated into a 5 MHz voice carrier.

The video carrier, which is the separated IF signal, is supplied to the video detector 34, is detected, and is converted into a composite video signal in the base band. The composite video signal is supplied to the ghost remover 35 to remove the ghost by a known method, and then is modulated again by the modulator 36 into an IF signal having a carrier frequency of 58.75 MHz.

The synthesizing circuit 37 synthesizes the output video carrier (IF signal) of the modulator 36 and the audio carrier (IF signal) separated by the video / audio separating circuit 33, respectively, and thereafter,
The signal is supplied to the frequency converter 38, where the frequency is converted to the television broadcast signal band. As a result, the frequency converter 38 outputs a television broadcast signal in the same band as the television broadcast signal received by the antenna 31 and in which the ghost of the composite video signal is removed.
For example, it is output to the antenna terminal of the television receiver.

[0007]

However, in the television broadcast signal receiving apparatus described above, the synthesizing circuit 37 causes the IF.
Since the video carrier which is a signal and the audio carrier which is an IF signal are respectively synthesized, and the synthesized signal is frequency-converted into a required television broadcast signal band by the frequency converter 38, the IF band synthesizing circuit 37 is used. There is a problem that special components such as a frequency converter 38 for frequency-converting the signals in the IF band and the IF band to the frequency band of the television broadcast signal are required for consumer video equipment, and the entire apparatus becomes expensive.

The present invention has been made in view of the above points,
It is an object of the present invention to provide a television broadcast signal receiving apparatus capable of removing a ghost of a received television broadcast signal and outputting it without using a special component for a consumer video device.

Another object of the present invention is to provide a television broadcast signal receiving apparatus capable of removing a ghost and outputting a television audio multiplex broadcast signal with the same circuit configuration as a normal television broadcast signal. is there.

[0010]

In order to achieve the above object, the present invention detects a frequency converter for converting a received television broadcast signal into an intermediate frequency band and an intermediate frequency signal output from the frequency converter. A video detector that separately outputs the composite video signal and the audio carrier of the second intermediate frequency, a ghost remover that performs ghost removal processing on the composite video signal extracted from the video detector, and a video An audio detector that detects the audio carrier extracted from the detector and outputs the received audio signal in the baseband, and the output composite video signal of the ghost remover and the output audio signal of the audio detector as the input signals. After receiving and modulating the input received audio signal to the audio carrier of the second intermediate frequency, the composite signal synthesized into the input composite video signal is the desired television broadcast signal. RF and outputting the frequency-converted into frequency
And a module.

Further, according to the present invention, when the television broadcast signal is a television audio multiplex broadcast signal, the audio detector is a main channel signal in the baseband band and a modulated wave frequency division multiplexed to the main channel signal. In this configuration, a multiplexed audio signal composed at least of a sub-channel signal is output as the received audio signal.

[0012]

According to the present invention, the received audio signal in the base band taken out from the audio detector and the composite video signal taken out from the ghost remover are supplied to the RF module, respectively, and the input received audio signal is supplied to the second receiver. After modulating to an intermediate frequency audio carrier, the composite signal synthesized into the input composite video signal is frequency converted to the desired television broadcast signal band and output, so only general-purpose parts are used for consumer video equipment. Thus, it is possible to output a television broadcast signal in a desired television broadcast signal band.

Further, according to the present invention, when a television audio multiplex broadcasting signal is received, the audio detector does not demodulate the sub channel signal, but receives the multiple audio signal in which the sub channel signal is frequency division multiplexed with the main channel signal. Since the configuration is such that it is output as an audio signal, the configuration can be simpler than when an audio multiplex demodulation circuit is used.

[0014]

EXAMPLE Next, an example of the present invention will be described with reference to FIGS.
Will be explained together. FIG. 1 shows a block diagram of an embodiment of a television broadcast signal receiving apparatus according to the present invention. As shown in the figure, in the present embodiment, an antenna 11, a frequency converter 12 that frequency-converts a signal received by the antenna 11, and a video detector 1 that video-detects an output signal of the frequency converter 12.
3, an audio detector 14 for detecting an output audio carrier wave of the video detector 13, a ghost remover 15 for removing a ghost of an output composite video signal of the video detector 12, and an audio detector 14
R for synthesizing both output signals of the ghost remover 15 and the frequency conversion to a desired television broadcast signal band and outputting
And an F module 16.

As shown in FIG. 2, the RF module 16 has a clamp circuit 23 for clamping a composite video signal input via the video input terminal 21 and an audio input terminal 22.
An input filter 24 to which a voice signal is input via, a voice modulation circuit 25 that frequency-modulates the output voice signal of the input filter 24, each output signal of the clamp circuit 23 and the voice modulation circuit 25 are synthesized, and the synthesized signal is obtained. Input terminal 27
It is composed of a mixer circuit 26 for frequency-converting into a desired television broadcast signal band based on a local oscillation frequency inputted further.

Here, the input filter of the ordinary RF module has the pre-emphasis characteristic necessary for the modulation of the audio signal, but the frequency characteristic of the input filter 24 of the present embodiment is obtained by removing this pre-emphasis characteristic. Things
Flat characteristics are set in the sub-channel signal band of the multiplex audio signal, which will be described later.

Next, the operation of this embodiment will be described.
In FIG. 1, a television broadcast signal received by an antenna 11 is supplied to a frequency converter 12, where it is frequency-converted with a local oscillation frequency according to a reception channel and converted into an intermediate frequency (IF) signal. As a result, the frequency converter 12 outputs 58.7 of the desired channel.
An intermediate frequency signal obtained by frequency division multiplexing the 5 MHz video carrier and the 54.25 MHz first intermediate frequency audio carrier is extracted and supplied to the video detector 13.

The video detector 13 performs video detection of the intermediate frequency signal to obtain a baseband composite video signal which is a detection signal of a video carrier and a carrier frequency of 4.5 MHz.
The audio intercarrier signal of z, that is, the audio carrier of the second intermediate frequency is output. The voice carrier of the second intermediate frequency is supplied to the voice detector 14, where it is FM demodulated and converted into a monaural voice signal in the baseband.

However, when the television broadcast signal received by the antenna 11 is a television voice multiplex broadcast signal, the output voice signal of the voice detector 14 is:
A main channel signal in the same band as the baseband monaural audio signal, a sub-channel signal that is a frequency modulation wave, and a control channel signal that is an amplitude modulation wave are frequency-division-multiplexed into a multiplexed audio signal.

As is well known, the sub-channel signal is a sub-audio signal in the case of dual audio broadcasting and a difference signal between the left audio signal and the right audio signal in the case of stereo audio broadcasting. The frequency-modulated signal has its center frequency set to twice the horizontal scanning frequency. The control channel signal is a control signal for identifying stereo audio broadcasting or dual audio broadcasting, and is a signal obtained by amplitude-modulating a subcarrier having a frequency 3.5 times the horizontal scanning frequency.

In a general television receiver, an audio multiplex demodulation circuit is used to demodulate the multiplex audio signal to demodulate and output a stereo audio signal or a dual audio signal. In this embodiment, audio detection is performed. The container 14 is as described above.
The sub-channel signal and the control channel signal of the multiplex audio signal are not demodulated, and the RF module 16 remains as the multiplex audio signal.
Audio input terminal (22 in FIG. 2).

On the other hand, the composite video signal extracted from the video detector 13 is a band sharing multiplexed signal of a luminance signal having an upper limit frequency of about 4 MHz and a carrier color signal having a color subcarrier frequency of 3.58 MHz, and is a ghost. It is supplied to the remover 15. The ghost remover 15 is a known circuit that cancels a ghost component in a composite video signal by a known method using, for example, a feedback type or feedforward type transversal filter. As the ghost removing device 15, for example, a commercially available ghost removing unit (model number: GCU-1 manufactured by NEC Corporation) is used.
01) can be used.

The composite video signal from which the ghost component has been canceled by the ghost remover 15 is input to the video input terminal (21 in FIG. 2) of the RF module 16. RF
The module 16 modulates the baseband audio signal from the audio detector 14 and the baseband composite video signal from the ghost remover 15 and converts it into a television signal in the television broadcast signal band for output. Is.

That is, as shown in FIG. 2, the composite video signal from the ghost remover 15 is supplied to the clamp circuit 23 via the video input terminal 21, and the direct current reproduction is performed here. It is input to the input terminal. Further, the voice signal or the multiple voice signal from the voice detector 14 is supplied to the voice modulation circuit 25 via the voice input terminal 22 and the input filter 24, respectively, and the frequency of 4.
The carrier of 5 MHz is frequency-modulated to be a voice carrier of the FM modulated wave, and then input to the second input terminal of the mixer circuit 26.

The mixer circuit 26 is the above clamp circuit 23.
Corresponding to a desired receiving channel, in which the composite video signal from the audio signal and the audio carrier from the audio modulation circuit 25 are frequency-division-multiplexed, and the multiplexed signal is input from the local oscillation circuit (not shown) via the input terminal 27. By performing frequency conversion (carrier wave suppression amplitude modulation) with the local oscillation frequency, the television carrier signal is generated by frequency-converting into the television channel band of the desired channel whose image carrier frequency is equal to the above local oscillator frequency. Is output to the output terminal 28.

As described above, the RF module 16 is a device for simultaneously synthesizing, modulating and frequency converting the composite video signal of the base band and the audio signal, and is an inexpensive one generally used for general consumer video equipment. It is a device. In the past, this RF module 16 could not be used for synthesizing the composite video signal in the intermediate frequency band and the audio signal in the intermediate frequency band, but in the present embodiment, this RF module 16 was used.
Since it is possible to generate a desired television broadcast signal by using, the entire apparatus can be constructed at low cost.

As described above, the input filter 24
Has a flat frequency characteristic at least in the band of the multiplex audio signal. Therefore, when the multiplex audio signal is output from the audio detector 14, this multiplex audio signal is pre-emphasized by the transmitting side. So
If the signal passes through the input filter 24, it can be supplied to the audio modulation circuit 25 in a pre-emphasis state, and the audio modulation circuit can normally modulate the multiplexed audio signal.

The present invention is not limited to the above embodiment, and the input filter 24 may be omitted, for example, and the television broadcast signal received in the above embodiment is of the NTSC system. Although the present invention has been described as an example, it goes without saying that the present invention can be applied to other television broadcasting signals such as PAL system.

[0029]

As described above, according to the present invention,
A television broadcast signal in which a ghost has been removed in a desired television broadcast signal band by using only general-purpose components such as a video detector, an audio detector, a ghost remover, and an RF module for consumer video equipment. Can be generated, so that the cost can be reduced as compared with the conventional case.

Further, according to the present invention, the voice detector is configured to output, as a reception voice signal, a multiple voice signal in which the main channel signal and the sub channel signal are frequency division multiplexed without demodulating the sub channel signal. By
Since the ghost can be removed and output from the television audio multiplex broadcast signal with the same circuit configuration as that of the normal television broadcast signal without using the audio multiplex demodulation circuit, the entire apparatus can be inexpensively constructed also from this. .

Further, according to the present invention, the input filter in the RF module is configured to have a flat frequency characteristic at least in the multiple audio signal band, so that the multiple audio signal remains pre-emphasized at the transmitting side. Is supplied to the audio modulation circuit, the multiplex audio signal can be normally modulated in the audio modulation circuit.

[Brief description of drawings]

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

FIG. 2 is a block diagram of an example of the RF module of FIG.

FIG. 3 is a block diagram of an example of a conventional device.

[Explanation of symbols]

 11 antenna 12 frequency converter 13 video detector 14 audio detector 15 ghost remover 16 RF module 23 clamp circuit 24 input filter 25 audio modulator circuit 26 mixer circuit 27 local oscillation frequency input terminal

Claims (3)

[Claims] 1. A frequency converter for frequency-converting a received television broadcast signal into an intermediate frequency band, and an intermediate frequency signal output from the frequency converter is detected to detect a composite video signal and an audio carrier of a second intermediate frequency. , A ghost remover that performs ghost removal processing on the composite video signal extracted by the video detector, and a voice carrier extracted by the video detector. An audio detector for outputting a received audio signal in the baseband, and an output composite video signal of the ghost remover and an output received audio signal of the audio detector as input signals respectively, and the input received audio signal is 2 After modulating to an audio carrier of an intermediate frequency, the synthesized signal synthesized to the input composite video signal is frequency-converted into a desired television broadcast signal band and output. Television broadcast signal receiving apparatus characterized by having an RF module for. 2. When the television broadcast signal is a television audio multiplex broadcast signal, the audio detector is a main channel signal in a baseband band and a modulated wave frequency-division-multiplexed with the main channel signal. The television broadcast signal receiving apparatus according to claim 1, wherein a multiplexed audio signal at least composed of a sub-channel signal is output as the received audio signal. 3. The RF module receives an output reception voice signal of the voice detector, an input filter having a flat frequency characteristic in at least the multiple voice signal band, and an output reception voice signal of the input filter. An audio modulation circuit for modulating the audio carrier wave of the second intermediate frequency, an output composite video signal of the ghost remover and an output audio carrier wave of the audio modulation circuit are frequency-division-multiplexed to a desired television broadcast signal band. 3. The television broadcast signal receiving apparatus according to claim 2, further comprising a mixer unit for frequency conversion.