JPH08331474A - Multi-system dealing receiver - Google Patents

Abstract

PURPOSE: To provide a multi-system dealing receiver with which arbitrary analog modulated and digital modulated waves are respectively demodulated from a video signal mixing both the modulated waves while using one receiver and an original video signal can be outputted. CONSTITUTION: A synchronizing signal detection circuit 9 detects the synchronizing signal of a base band video signal after analog demodulating processing due to an analog demodulation circuit 6, and a synchronizing signal detection circuit 10 detects the synchronizing signal of a base band video signal after digital demodulating processing due to a digital demodulation circuit 7 and a digital decoder circuit 8. Based on the detected results of synchronizing signals of the synchronizing signal detection circuits 9 and 10, a main control circuit 12 changes the connecting state of a switch 13 and selectively outputs any one of the base band video signal after analog demodulating processing, base band video signal after digital demodulating processing and one of blue back signal selectively outputted from a blue back signal generating circuit 11 for mute to an output terminal 14a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-system compatible receiving apparatus for receiving a video signal in which analog modulated waves and digital modulated waves are mixedly transmitted, and in particular, analog modulation and digital modulation are mixed. The present invention relates to a multi-system compatible receiving apparatus that automatically receives a video signal transmitted by terrestrial broadcasting, cable television (CATV) broadcasting, satellite broadcasting, etc., in response to each modulation method.

[0002]

2. Description of the Related Art At present, video signals are mainly transmitted by analog modulation methods such as vestigial sideband amplitude modulation (VSB-AM modulation) and analog frequency modulation (FM modulation).
In recent years, each method such as terrestrial broadcasting, cable television broadcasting, satellite broadcasting, etc. in which a digital video signal or audio signal is highly efficiently encoded and then directly digitally modulated and digitally transmitted in the same transmission band as a conventional analog modulation method Is proposed. As a method of transmitting a video signal in which the analog modulated wave and the digital modulated wave are mixed as described above, frequency division multiplexing in which each signal is modulated at different frequencies and multiplexed so that their frequency bands do not overlap Depending on the method, transmission of video signals has been proposed for cable television and the like.

[0003]

As a conventional receiving apparatus for receiving a video signal in which the analog modulated wave and the digital modulated wave are mixed, there are an analog receiver for analog demodulation and a digital receiver for digital demodulation. Two machines were prepared, and each of the analog modulated wave and the digital modulated wave was modulated, converted into the original video signal and output.
In this case, there is a problem that the receiving device becomes large and the cost is high because a receiving device matching each modulation system is required.

In a cable television, FM modulation (analog modulation) and QPSK (Quadrature Phase Shi
When signals of ft Keying) modulation (digital modulation) are mixed, when these signals are received by one receiver,
It is necessary to determine whether the received signal is an analog modulation signal or a digital modulation signal and output each modulation signal. In order to make this determination, a cable television uses the fact that each modulated wave is frequency-division-multiplexed and transmitted at a predetermined frequency for each corresponding channel, and the frequency corresponding to each channel is stored in advance. It is conceivable that the modulated wave of a predetermined channel is discriminated and output from the video signal in which the modulated waves are mixed for each. However, with this, if the frequency corresponding to each channel changes, it is not possible to distinguish the modulated wave,
There is a problem that it is not possible to demodulate each modulated wave from a video signal in which an arbitrary analog modulated wave and a digital modulated wave are mixed, convert it to the original video signal and output it.

An object of the present invention is to use a single receiving device to demodulate both modulated waves from a mixed video signal of an arbitrary analog modulated wave and a digital modulated wave and output the original video signal. It is an object of the present invention to provide a multi-system compatible receiving device that can be used.

Another object of the present invention is multi-system compatible reception capable of selectively outputting a baseband video signal after analog or digital demodulation processing by detecting a synchronizing signal of the demodulated baseband video signal. It is to provide a device.

Yet another object of the present invention is to provide an analog demodulated wave and a digital demodulated wave when neither is received.
It is an object of the present invention to provide a multi-system compatible receiver capable of automatically outputting a mute signal.

[0008]

A multi-system compatible receiving apparatus according to claim 1 is a multi-system compatible receiving apparatus for receiving a video signal that is transmitted by mixing analog modulated waves and digital modulated waves. It includes an analog demodulation means for demodulating only analog modulated waves in the transmitted video signal and a digital demodulation means for demodulating only digital modulated waves in the transmitted video signal.

In addition to the configuration of the multi-system compatible receiving device according to claim 1, the multi-system compatible receiving device according to claim 2 detects the presence or absence of a synchronization signal from the baseband video signal after the analog demodulation processing by the analog demodulating means. It further includes an analog sync signal detecting means.

According to the third aspect of the invention, in addition to the structure of the first aspect of the invention, the multimode receiver detects the presence or absence of a sync signal from the baseband video signal after digital demodulation processing by the digital demodulation means. It further includes digital sync signal detecting means.

According to a fourth aspect of the invention, in addition to the configuration of the first aspect of the invention, the multi-mode receiver detects the presence or absence of a sync signal from the baseband video signal after the analog modulation processing by the analog modulation means. Analog sync signal detection means, digital sync signal detection means for detecting the presence or absence of a sync signal from the baseband video signal after digital demodulation processing by the digital demodulation means, and analog demodulation detected by the analog sync signal detection means According to the presence or absence of the synchronizing signal of the processed baseband video signal, and the presence or absence of the synchronizing signal of the digital demodulation-processed baseband video signal detected by the digital synchronizing signal detecting means,
It further includes a selection unit that selectively outputs the baseband video signal after the analog demodulation processing or the baseband video signal after the digital demodulation processing.

According to a fifth aspect of the present invention, in addition to the configuration of the fourth aspect of the receiver according to the fourth aspect, the selecting means includes a baseband after demodulation processing from the analog and digital synchronizing signal detecting means. When neither the sync signal of the video signal is detected, the mute signal is output.

[0013]

In the multi-system receiver according to the first aspect of the present invention, the receiver is provided with the analog demodulating means for demodulating only the analog modulated wave of the transmitted video signal and the digital demodulating means for demodulating only the digital demodulated wave. It is possible to demodulate both modulated waves with one receiving device and output the original video signal.

In the multi-system compatible receiver according to claim 2, in addition to the operation of the multi-system compatible receiver according to claim 1, it is possible to detect the presence or absence of a synchronization signal from the baseband video signal after analog modulation processing. Therefore, it is possible to easily detect whether or not the transmitted video signal includes an analog modulated wave.

In the multi-system compatible receiver according to claim 3, in addition to the operation of the multi-system compatible receiver according to claim 1, the presence or absence of a synchronization signal can be detected from the baseband video signal after digital demodulation processing. Therefore, it is possible to easily determine whether or not the transmitted video signal includes a digital modulation wave.

In the multi-system compatible receiver according to claim 4, in addition to the operation of the multi-system compatible receiver according to claim 1, depending on the presence or absence of a synchronizing signal of the baseband video signal after analog and digital demodulation processing. Since the baseband video signal after analog demodulation processing or the baseband video signal after digital demodulation processing can be selectively output, analog or digital modulation is performed on the video signal transmitted by a simple method of detecting the synchronization signal. It is possible to determine whether a wave is included, and it is possible to automatically output the baseband video signal after the analog demodulation processing or the baseband video signal after the digital demodulation processing according to the determination result.

In the multi-system compatible receiver according to claim 5, in addition to the operation of the multi-system compatible receiver according to claim 4, synchronization of the baseband video signal after demodulation processing from the analog and digital sync signal detecting means. If both signals are not detected, the mute signal is output.
When no video signal is input, muting can be performed automatically, and unnecessary screens are not displayed.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A multi-system receiver according to an embodiment of the present invention will be described below. In the following examples, analog modulated waves (for example, FM modulated waves) and digital modulated waves (for example, QPSK modulated waves, Q) in cable television broadcasting
AM (Quadrature AmplitudeModulation) modulation wave, etc.)
The case where a mixed video signal of and is received by a frequency division multiplex system will be described, but in other broadcasting forms such as terrestrial broadcasting and satellite broadcasting, the analog modulated wave and the digital modulated wave are transmitted by the frequency division multiplex method. The present invention can be similarly applied to any video signal or audio signal to be reproduced.

FIG. 1 is a block diagram showing the configuration of a multi-system compatible receiver according to an embodiment of the present invention. Referring to FIG. 1, the multi-system compatible receiver includes an input terminal 1, an RF amplifier 2, a tuner 3, a local oscillator 4, an automatic gain control amplifier 5, an analog demodulation circuit 6, a digital demodulation circuit 7, and a digital decoding circuit 8. , Sync signal detection circuits 9 and 10, a mute blue back signal generation circuit 11, a main control circuit 12, a switch 13, and output terminals 14a and 14b.

A reception signal (RF signal) in which analog modulated waves and digital modulated waves are mixed is input to the input terminal 1 via a cable for cable television broadcasting, for example. The input received signal is amplified by the RF amplifier 2 and supplied to the tuner 3. In the tuner 3, a predetermined channel is selected using the oscillation signal output from the local oscillator 4, and a video signal corresponding to the selected channel is output to the automatic gain control amplifier 5. The gain of the intermediate frequency signal (IF signal) output from the tuner 3 is controlled by the automatic gain control amplifier (AGC) 5 so as to have a predetermined gain.

The intermediate frequency signal output from the automatic gain control amplifier 5 is input to the analog demodulation circuit 6 and the digital demodulation circuit 7, respectively. The analog demodulation circuit 6 demodulates the input signal into a baseband video signal,
It outputs to the synchronizing signal detection circuit 9 and the terminal a1 of the switch 13, respectively. On the other hand, the digital demodulation circuit 7 demodulates the input signal into digital data, and then performs deinterleaving, error correction, derandomization, frame separation, packet separation, and other processing to obtain highly efficient encoded digital data. To the digital decoding circuit 8. The digital decoding circuit 8 decodes the high-efficiency coded digital data into a baseband video signal and outputs the baseband video signal to the synchronization signal detection circuit 10 and the terminal b1 of the switch 13, respectively.

If not only the video signal but also the audio signal is included in the received signal input to the input terminal 1, the audio signal is processed in the same manner as described above, and the analog demodulation circuit 6 outputs the baseband audio signal. Terminal a2 of switch 13
In addition, the baseband audio signal is output from the digital decoding circuit 8 to the terminal b2 of the switch 13, respectively.

Further, a blue back signal is output from the mute blue back signal generation circuit 11 to the terminal c1 of the switch 13 as a video mute signal. Also,
When the reception signal input to the input terminal 1 includes a voice signal, a non-voice signal which is a mute signal for voice is output to the terminal c2 of the switch 13.

The sync signal detection circuit 9 detects the sync signal of the input baseband video signal and outputs a detection flag to the main control circuit (MPU) 12. Similarly, the sync signal detection circuit 10 detects the sync signal of the input baseband video signal and outputs a detection flag to the main control circuit 12. The synchronization signal detection circuits 9 and 10 can use the same circuit because the baseband video signal output from the analog demodulation circuit 6 and the baseband video signal output from the digital decoding circuit 8 are the same signal.
Further, the baseband video signals output from the analog demodulation circuit 6 and the digital decoding circuit 8 are input to one synchronization signal detection circuit in a time division manner, and the detection flag of the synchronization signal of each baseband video signal is mainly transmitted in a time division manner. You may make it output to the control circuit 12.

The main control circuit 12 detects the sync signal detection flag, and controls the switch 13 to connect to the terminals a1 and a2 when the sync signal is detected from the analog demodulated baseband video signal. However, when the sync signal is detected from the baseband video signal after the digital demodulation processing, the switch 13 is controlled so as to switch to the terminals b1 and b2, and the sync signal detection circuits 9 and 10 are also provided.
If the synchronization signal of the baseband video signal is not detected from both of the above, the switch 13 is controlled to be connected to the terminals c1 and c2.

As a result, when the sync signal detection circuit 9 detects a sync signal from the analog demodulated baseband video signal, the analog demodulated baseband video signal is output from the output terminal 14a and the output terminal is output. 14
The baseband audio signals after the analog demodulation processing are output from b. When a synchronization signal is detected from the baseband video signal after digital demodulation processing, the baseband video signal after digital demodulation processing is output from the output terminal 14a, and the baseband audio after digital demodulation processing is output from the output terminal 14b. Each signal is output. Further, when neither of the sync signal detection circuits 9 and 10 detects a sync signal, a blue back signal is output from the output terminal 14a and a voiceless signal is output from the output terminal 14b. Also, the output terminals 14a and 1
The video signal and audio signal output from 4b are output to a monitor (not shown), a predetermined image is displayed, and audio is output.

By detecting the sync signal of the baseband video signal after analog or digital demodulation processing according to the above operation, the received signal corresponding to the channel selected by the tuner 3 is an analog modulation wave or a digital modulation wave. It becomes possible to easily detect whether it is a wave. In addition, the switch 1 is used by using the detection result of this synchronization signal.
Since the connection state of No. 3 is automatically controlled by using the main control circuit 12, the optimum video signal or audio signal is automatically obtained according to the modulation system of the received signal corresponding to the channel selected by the tuner 3. It is possible to output from the output terminal 14a or 14b. As a result, it is possible to demodulate both modulated waves from a video signal in which an arbitrary analog modulated wave and a digital modulated wave are mixed by using one receiving device and automatically output the original video signal. Operability is improved. Further, since the RF amplifier 2, the tuner 3, the local oscillator 4, and the automatic gain control amplifier 5 are shared by the analog demodulation process and the digital demodulation process, the receiving device itself can be downsized and its cost can be reduced. It will be possible.

Further, in the above embodiment, the interlock switch 13 having the two output terminals 14a and 14b is used in consideration of the audio signal. However, when switching only the video signal, it has one output terminal. A switch may be used.
Also, in order to detect that analog demodulation and digital demodulation have been completely performed, the presence or absence of a sync signal of the baseband video signal is detected. However, by detecting other characteristics of the baseband video signal, the tuner can be detected. It may be possible to detect whether the received signal selected by 3 is an analog modulated wave or a digital modulated wave. For example, when the video signal is a composite video signal, the subcarrier signal may be detected. Further, as the synchronization signal of the baseband video signal, either a vertical synchronization signal or a horizontal synchronization signal may be used.

[0029]

Since the multi-system receiver according to claim 1 is provided with the analog and digital demodulation means, respectively, one receiver can be used to generate arbitrary analog modulated waves and digital modulated waves. Both modulated waves can be demodulated from the mixed video signals to output the original video signal.

In addition to the effect of the multi-system receiver of claim 1, the multi-system receiver of claim 2 can detect the presence or absence of a synchronization signal from the baseband video signal after analog modulation processing. Therefore, it is possible to determine that the analog modulated wave is being received by a simple method, and if the sync signal of the baseband video signal after analog modulation processing is detected, the baseband video after analog modulation processing is detected. It is possible to preferentially output the signal.

In addition to the effect of the multi-system compatible receiver according to claim 1, the multi-system compatible receiver according to claim 3 can detect the presence or absence of a synchronization signal from the baseband video signal after digital demodulation processing. Therefore, it is possible to determine that the digitally modulated wave is being received by a simple method, and when the sync signal of the baseband video signal after digital modulation processing is detected, the base after digital demodulation processing is given priority. A band video signal can be output.

In addition to the effect of the multi-system receiving device according to claim 1, the multi-system receiving device according to claim 4 is dependent on the presence or absence of a synchronizing signal of a baseband video signal after analog or digital demodulation processing. Since the baseband video signal after analog demodulation processing or the baseband video signal after digital demodulation processing can be selectively output, the baseband after analog demodulation processing is automatically performed according to the modulation system of the received video signal. A band video signal or a baseband video signal after digital demodulation processing can be output.

In addition to the effect of the multi-system receiver of claim 4, the multi-system receiver of claim 5 synchronizes the demodulated baseband video signal from the analog and digital sync signal detecting means. If both signals are not detected, the mute signal can be output. Therefore, if there is no signal, the mute signal can be automatically output as a video signal without displaying an unnecessary screen. It is possible to improve the operability of the device.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a multi-system compatible receiver according to an embodiment of the present invention.

[Explanation of symbols]

 1 Input Terminal 2 RF Amplifier 3 Tuner 4 Local Oscillator 5 Automatic Gain Control Amplifier 6 Analog Demodulation Circuit 7 Digital Demodulation Circuit 8 Digital Decoding Circuit 9, 10 Sync Signal Detection Circuit 11 Mute Blueback Signal Generation Circuit 12 Main Control Circuit 13 Switch 14a, 14b output terminals

Claims (5)

[Claims] 1. A multi-system compatible receiving device for receiving a video signal transmitted by mixing an analog modulated wave and a digital modulated wave, the analog demodulating means demodulating only the analog modulated wave of the video signal. And a multi-system compatible receiving device including a digital demodulation means for demodulating only the digitally modulated wave of the video signal. 2. The multi-system compatible receiving apparatus according to claim 1, further comprising an analog sync signal detection means for detecting a sync signal from the baseband video signal after the analog demodulation processing by the analog demodulation means. 3. The multi-system compatible receiving apparatus according to claim 1, further comprising digital sync signal detection means for detecting a sync signal from the baseband video signal after the digital demodulation processing by said digital demodulation means. 4. An analog sync signal detecting means for detecting a sync signal from the baseband video signal after the analog demodulation processing by the analog demodulation means, and a sync signal from the baseband video signal after the digital demodulation processing by the digital demodulation means. Sync signal detecting means for detecting the sync signal, presence or absence of a sync signal of the baseband video signal after analog demodulation processing detected by the sync signal detecting means for analog, and detected by the sync signal detecting means for digital A selection unit which selectively outputs the baseband video signal after the analog demodulation processing or the baseband video signal after the digital demodulation processing according to the presence or absence of the synchronizing signal of the baseband video signal after the digital demodulation processing. Item 1. The multi-system compatible receiver according to item 1. 5. The selecting means outputs a mute signal when neither the analog sync signal detecting means nor the digital sync signal detecting means detects the sync signal of the baseband video signal after the modulation processing. Item 4. The multi-system compatible receiver according to Item 4.