JPH0591432A - Digital audio broadcasting system - Google Patents

Abstract

(57) [Abstract] [Purpose] Even if the bandwidth per channel is narrow, the receiving side receives the digital data channel so that the television signal channel corresponding to this digital data can be automatically received. To [Structure] A digital string h in a channel of digital data received on the receiving side is processed by a PCM decoder 9.
It is divided into an audio signal portion and an independent data portion, and the independent data portion is supplied to the CPU 25 via the data extraction circuit 11 as independent data m. The CPU 25 causes the tuner 23 to select the channel of the television signal indicated by the independent data m. As a result, the receiving side automatically receives the channel of the television signal corresponding to the digital data. In this case, since the independent data added to the digital data of the digital audio channel only specifies one channel, the band per channel may be narrow.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital audio broadcasting system for transmitting and receiving a broadcast signal having a channel of a television signal and a channel of digital data composed of audio signal data and the like, and more particularly, the receiving side has The present invention relates to a digital audio broadcasting system which can automatically receive a channel of a television signal corresponding to this digital data by receiving the channel of digital data.

[0002]

2. Description of the Related Art In cable television (hereinafter referred to as CATV) broadcasting in Japan, video and audio services are dominated by the NTSC system. This NT
In the SC system, since the voice signal is transmitted as the FM signal, the signal-to-noise ratio (hereinafter referred to as the SN ratio) is not sufficiently satisfactory. On the other hand, in the current high-definition audio service in satellite broadcasting (hereinafter referred to as digital audio service), since the audio signal is converted into a carrier wave that is digitally phase-modulated for transmission, a sufficient SN ratio can be obtained. However, since video and audio services require one-to-one correspondence between video and audio, when such a system is adopted in CATV, a carrier that has been digitally phase-modulated is used as a video signal. Must be transmitted with carrier wave, current CATV
It does not fit in the band (6 MHz) per channel in broadcasting. Corresponding to this, assuming that the carrier of which the band is 6 MHz is changed and the digital phase is modulated is transmitted together with the carrier of the video signal, a band of about 8 MHz is required, and a drastic system change is required.

On the other hand, there is a digital voice service in CATV as well, but such a digital data channel is a channel different from a normal television signal channel, and the digital data channel is simply Only the voice service is available, and the CATV receiver cannot be used as an audio device.

[0004]

As described above, in the prior art, when the band per channel is narrow, the digital data channel is different from the normal television signal channel, Only voice services are available on digital data channels.

The present invention eliminates the above-mentioned problems, and even when the band per channel is narrow, the receiving side receives the channel of digital data, so that the channel of the television signal corresponding to this digital data is automatically obtained. It is an object of the present invention to provide a digital audio broadcasting system capable of receiving the.

[0006]

In the digital audio broadcasting system of the present invention, a television signal channel and a digital data channel consisting of independent data and audio signal data for designating the channel of the television signal are provided. A transmitter for transmitting the broadcast signal, a first tuner provided on the receiving side for selecting a digital data channel of the broadcast signal from the transmitter, and the first tuner.
A decoder for separating the digital data of the channel selected by the tuner into the independent data and the audio signal data, and a digital-analog conversion circuit for converting the audio signal data from the decoder into an analog audio signal,
An audio output device which outputs the analog audio signal from the digital-analog conversion circuit, and a second channel which is provided on the receiving side and selects a channel of the television signal designated by the independent data from the decoder , A video demodulation circuit for demodulating the video IF signal of the television signal selected by the second tuner into a video signal, and video display means for displaying the video signal from the video demodulation circuit. It is characterized by having.

[0007]

According to this structure, the first tuner tunes to a channel of digital data composed of independent data and audio signal data, and the second tuner tunes to the television signal specified by the independent data. Channel is selected, so that even if the bandwidth per channel is narrow, the receiving side receives the channel of the digital data and automatically receives the channel of the television signal corresponding to this digital data. You can

[0008]

The present invention will be described below with reference to the illustrated embodiments.

FIG. 1 is a block diagram showing an embodiment in which the digital audio broadcasting system of the present invention is applied to a CATV.

In FIG. 1, reference numeral 1 is a CATV transmitter of a CATV broadcasting station, and this CATV transmitter 1 is a CAT.
The CATV broadcast signal a is transmitted to the CATV receiver 2 via the V transmission line. In the CATV broadcast signal a, the channel of the television signal according to the NTSC system similar to the conventional one and the four-phase phase modulation system (hereinafter QPSK)
(Hereinafter, referred to as a system) digital audio channel (hereinafter referred to as audio-only digital audio channel) and a newly provided video-added digital audio channel. In a digital audio channel with video, digital data composed of audio signal data, independent data for specifying a channel of a television signal corresponding to the audio signal data, and control signal data is converted into a digital phase-modulated carrier wave. It is converted and sent.

First, the digital receiving system of the CATV receiver 2 will be described.

The CATV broadcast signal a transmitted from the CATV transmission path is selected by the tuner 3 as a channel of a carrier for audio only or digital audio with video, and a carrier b which is digital phase modulated by the QPSK system is supplied to the QPSK demodulator 4. To be done.

A central processing unit (hereinafter referred to as a CPU) 5 controls the tuner 3 for channel selection, and in response to a channel selection command from a key input means 6, frequency data c and band data d of a desired channel are pulse-locked. The signal is supplied to the loop tuning circuit (hereinafter referred to as PLL tuning circuit) 7 and the display 8 is caused to display the desired channel. The PLL tuning circuit 7 creates a band switching voltage e and a tuning voltage f corresponding to the supplied frequency data c and band data d of the channel, and the tuner 3
Supply to. The tuner 3 selects a carrier wave channel according to the supplied band switching voltage e and tuning voltage f, detects the presence or absence of a carrier wave in the selected channel, and outputs the carrier wave detection signal g to the PLL tuning circuit 7
Supply to. The PLL tuning circuit 7 corrects the band switching voltage e and the tuning voltage f corresponding to the carrier wave detection signal g, and causes the tuner 3 to perform accurate channel selection.

The QPSK demodulator 4 receives the Q from the tuner 3.
The carrier wave b digitally phase-modulated by the PSK method is demodulated into a digital train h and a pulse code modulation decoder (hereinafter referred to as PCM).
It is called a decoder) 9. The PCM decoder 9
In the case of digital audio with video, the supplied digital string h
Is divided into a voice signal data portion, an independent data portion, and a control signal data portion, array conversion is performed, and the voice signal data portion is supplied as a digital voice signal i to a digital / analog conversion circuit (hereinafter referred to as a DA conversion circuit) 10. Then, the independent data portion is supplied to the data extraction circuit 11 as the independent data signal j. Although not shown, the PCM decoder 9 supplies the control signal data portion to a predetermined control circuit. Furthermore, the PCM decoder 9
In the case of audio-dedicated digital audio, the supplied digital string h is divided into an audio signal data portion and a control signal data portion, array conversion is performed, and the audio signal data portion is converted into a digital audio signal i, which is transferred to the DA conversion circuit 10. Supply,
The control signal data portion is supplied to a predetermined control circuit. The DA conversion circuit 10 converts the digital audio signal i into an analog audio signal k and supplies it to the audio amplifier 12. The audio amplifier 12 amplifies the analog audio signal k and supplies it as an analog audio signal 1 to one input terminal of the switch circuit 13. The data extraction circuit 11 converts the data array of the independent data signal j into the CPU as the independent data m.
Supply to 25.

Next, the television signal receiving system of the CATV receiver 2 will be described.

C transmitted from the CATV receiver transmission line
The tuner 23 selects a channel of a television signal of the NTSC system for the ATV broadcast signal a, converts the channel into an intermediate frequency signal (hereinafter referred to as an IF signal) n, and I
It is supplied to the F signal detection circuit 24.

The CPU 25 controls the tuning of the tuner 23. If the tuner 3 does not receive the signal, the CP 25
In response to a channel selection command from U5, the frequency data o and band data p of the desired channel are supplied to the PLL channel selection circuit 27, and the desired channel is displayed on the display 8 via the CPU 5. Also, CP
U25 indicates the independent data m from the data extraction circuit 11 when the tuner 3 receives the audio-only digital audio channel and does not cause the tuner 23 to receive the video-added digital audio channel. The frequency data o and the band data p of the channel are supplied to the PLL tuning circuit 27, and the display of the channel indicated by the independent data m is displayed on the display 8 via the CPU 5. The PLL tuning circuit 27 creates a band switching voltage q and a tuning voltage r corresponding to the frequency data o and the band data p and supplies them to the tuner 23. Tuner 2
3 selects a channel of a television signal according to the NTSC system according to the supplied band switching voltage q and tuning voltage r, detects the presence / absence of a carrier in the selected channel, and selects the carrier detection signal s by PLL. It is supplied to the central circuit 27. The PLL tuning circuit 27 corrects the band switching voltage q and the tuning voltage r corresponding to the carrier wave detection signal s, and causes the tuner 23 to perform accurate channel selection.

The IF signal detection circuit 24 amplifies and detects the video IF signal and detects it as a video IF signal t.
The audio IF signal is amplified and detected, and is supplied to the audio demodulation circuit 29 as the audio IF signal u. The video demodulation circuit 28 converts the amplified and detected video IF signal t into a video signal v and supplies the video signal v to the video output circuit 30. The video output circuit 30 displays the supplied video signal v on the Braun tube 31 as a video. The audio demodulation circuit 29 converts the amplified and detected audio IF signal u into an analog audio signal w and supplies the analog audio signal w to the audio amplifier 32. The audio amplifier 32 amplifies the analog audio signal w and supplies it as the analog audio signal x to the other input terminal of the switch circuit 13.

The switch circuit 13 switches and selects the analog audio signal x from the audio amplifier 32 and the analog audio signal 1 from the audio amplifier 12 based on the control signal y from the CPU 25 and guides it to the output terminal. Here, the CPU 25
The control signal y from is generated by the operation of the key input means 6 and supplied to the CPU 25 via the CPU 5, and specifies the digital voice service or the normal voice. The switch circuit 13 selects the analog voice signal 1 from the voice amplifier 12 in the case of digital voice service, and selects the analog voice signal x from the voice amplifier 32 in the case of normal voice. The audio signal from the switch circuit 13 is output as audio by an audio output device 33 such as a speaker or headphones.

The operation of such a digital audio broadcasting system will be described below.

For simplification of the description, the channel of the digital audio with video is the channel A, the channel of the television signal designated by the independent data of the channel A is the channel B, and the television by the NTSC system similar to the conventional one. The channel of the signal will be described as channel C, and the channel D of the audio dedicated digital audio similar to the conventional one will be described.

When the audio signal transmitted by the carrier wave which has been digitally phase-modulated is received and the video signal corresponding to this audio signal is automatically received, that is, the audio of channel A and the image of channel B are received by CATV. When it is received by the device 2, the channel A is selected by operating the key input means 6 and the digital voice service is selected. As a result, the carrier wave b, which has been digitally phase-modulated by the QPSK method, is converted into a digital train h by the QPSK demodulator 4.
Is demodulated into a voice signal portion, an independent data portion and a control signal portion by the PCM decoder 9, and the voice signal portion is passed through the DA conversion circuit 10 and the voice amplifier 12 as an analog voice signal 1 of one of the switch circuits 13. It is supplied to the input terminal. Further, the independent data portion is supplied to the CPU 25 as the independent data m via the data extraction circuit 11. In this case, since the independent data m indicates the channel B, the CPU 25 supplies the channel selection command of the channel B to the PLL channel selection circuit 27 and the tuner 2
Let channel 3 select channel B. As a result, the IF signal detection circuit 24 causes the video IF signal t of channel B and the sound I.
The F signal u is detected. The video IF signal t in this case is displayed as an image on the cathode ray tube 31 via the image demodulation circuit 28 and the image output circuit 30. On the other hand, the audio IF signal u is supplied to the other input terminal of the switch circuit 13 as the analog audio signal x via the audio demodulation circuit 29 and the audio amplifier 32. Since the digital voice service is selected, the analog voice signal 1 of channel A is led to the output terminal. As a result, the audio signal of the channel A is output from the audio output device 33.

When the channel of the television signal according to the NTSC system similar to the conventional one is received, that is, when the channel C is received, the channel C is selected by operating the key input means 6 and the analog voice service is selected. As a result, the carrier wave b is not supplied to the QPSK demodulator 4, and the QPSK demodulator 4, PCM decoder 9, DA conversion circuit 10, and audio amplifier 12 do not operate.
On the other hand, the CPU 25 supplies a channel selection command for the channel C by operating the key input means 6 to the PLL channel selection circuit 27 and causes the tuner 23 to select the channel C. As a result, the IF signal n of the channel C is detected by the IF signal detection circuit 24 into the video IF signal t and the audio IF signal u. The video IF signal t in this case is displayed on the cathode ray tube 31 via the video demodulation circuit 28 and the video output circuit 30.

On the other hand, the audio IF signal u is sent to the audio demodulation circuit 29.
And the other input terminal of the switch circuit 13 via the audio amplifier 32. Here, the switch circuit 13 is
Since the normal voice is specified by the key input means 6,
The analog audio signal x from the audio amplifier 32 is switched and selected and led to the output terminal. As a result, the switch circuit 13 outputs the sound signal of the normal sound of the channel C, and the sound output device 33 outputs the sound of the normal sound.

When a digital audio service without video is provided, that is, when channel D is received,
By operating the key input means 6, the channel D is selected and the digital voice service is selected. This allows
The carrier b, which is digitally phase-modulated on channel D, is Q
The audio signal portion supplied to the PSK demodulator 4, demodulated into a digital string h by the QPSK demodulator 4, and divided by the PCM decoder 9 is input to one side of the switch circuit 13 via the DA conversion circuit 10 and the audio amplifier 12. Supplied to the terminal.
Further, since the independent data portion does not exist, the data extraction circuit 11 does not operate, and the CPU 25 does not operate the PLL channel selection circuit 27. Therefore, no image is displayed on the cathode ray tube 31 and the analog audio signal x is not output from the audio amplifier 32. Since the digital voice service is selected by operating the key input means 6, the switch circuit 13 guides the analog voice signal 1 of the channel D to the output terminal. As a result, the sound of the channel D is output from the sound output device 33.

When channel B is received by normal voice,
That is, when the CATV receiver 2 receives the image of the channel B, it is sufficient to select the channel A and the normal sound by operating the key input means 6, or select the channel B and the normal sound. As a result, the tuner 23 selects the channel B, and the video IF signal t of the channel B is displayed on the cathode ray tube 31 as an image.

On the other hand, the audio IF signal u is the audio demodulation circuit 2
9, and is supplied to the other input terminal of the switch circuit 13 via the audio amplifier 32. Here, the switch circuit 13 is
Since the normal sound is designated by the key input means, the switch circuit 13 outputs the sound signal of the normal sound of the channel B, and the sound output device 33 outputs the sound.

According to such an embodiment, by operating the key input means 6 to select a channel of digital audio with video and a digital audio service,
The video signal of the channel corresponding to the digital audio with video can be automatically displayed on the cathode ray tube, and by operating the key input means 6, a normal television signal can be received in the same manner as in the past, or digital audio without video can be received. Can perform service. Further, since the independent data added to the digital data of the video-added digital audio channel only specifies one channel, the embodiment can be sufficiently put into practical use in the band of 6 MHz and no major system change is required. Further, since the conventional CATV receiver can receive the same television signal channel as the conventional NTSC system and the same digital audio channel as the conventional one, the compatibility with the conventional system is high.

[0029]

As described above, according to the present invention, 1
Even if the band per channel is narrow, the receiving side receives the digital data channel, so that the television signal channel corresponding to this digital data can be automatically received. A service can be provided in which the image of the channel of the television signal is added to the signal. Further, since it is not necessary to change the band per channel, it can be easily applied to a narrow broadcasting system broadcasting system such as CATV broadcasting, and has a high reciprocity with a conventional system.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a digital audio broadcasting system according to the present invention.

[Explanation of symbols]

 1 CATV transmitter 2 CATV receiver 3,23 tuner 5,25 CPU 9 PCM decoder 10 DA conversion circuit 11 data extraction circuit 24 IF signal detection circuit 28 video demodulation circuit 33 audio output device

Claims (1)

[Claims] 1. A transmitter for transmitting a broadcast signal having a channel of a television signal and a channel of digital data consisting of independent data for designating the channel of the television signal and audio signal data, and a receiving side. A first tuner provided to select a channel of digital data of a broadcast signal from the transmitter, and digital data of a channel selected by the first tuner are separated into the independent data and the audio signal data. Decoder, a digital / analog conversion circuit for converting the audio signal data from the decoder into an analog audio signal, an audio output device for audio output of the analog audio signal from the digital / analog conversion circuit, and the receiving side And the television specified by the independent data from the decoder. No. 2 channel for selecting the channel of the signal, a video demodulation circuit for demodulating the video IF signal of the television signal selected by the second tuner into a video signal, and the video signal from the video demodulation circuit And a video display means for displaying the video.