JPH03253192A - Television signal transmission system - Google Patents

Abstract

PURPOSE:To send a video signal together with an audio PCM signal with high quality and a data signal through a transmission channel of 6MHz by transmitting a television signal formed resulting from the application of residual side band amplitude modulation of spectrum arrangement having a Nyquist slope to a 1st carrier and from the application of digital modulation to a 2nd carrier. CONSTITUTION:The spectrum arrangement is adopted, in which a video carrier fv is arranged to a frequency location by 4.5MHz from the upper end of a transmission channel 1 whose band width is 6MHz, a video transmission band 2 of the residual side band amplitude modulation system is provided and the Nyquist slope is provided to the frequency band around the carrier fv, and an audio carrier 1 fs having a frequency of fv-fs=(1/4)fsc (fsc is a frequency of a chrominance subcarrier subject to frequency insert and multiplex onto a video signal modulated by a chrominance signal) is allocated to an idle band in excess of 1MHz caused at the lower end of the transmission channel 1 and an audio transmission band 3 using the digital modulation system such as the 4-phase DPSK system and modulated by an audio signal is formed. Thus, the audio PCM transmission with high quality and data transmission are implemented.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a television signal transmission system, and in particular to an audio signal transmission system that is improved to obtain high quality reception output. : (Summary of the invention) A television video signal using a vestigial sideband method with a compressed bandwidth compared to the conventional method is arranged in a television broadcasting/transmission channel with a bandwidth of 6 MHz, and the Nyquist frequency of the vestigial sideband modulation is arranged. A digitally modulated carrier wave containing a digitally modulated audio signal is placed adjacent to the slope to enable data transmission as well as high quality television audio transmission and reduction of adjacent channel mutual interference.

(Prior Art) Conventionally, there is a television broadcasting standard system as a television signal transmission system for transmitting and receiving signals using a broadcast channel with a frequency bandwidth of 6 MHz, and as shown in FIG. 1.25MHz from the bottom of
A video carrier wave fv is placed at a frequency position, an audio carrier wave f^ is placed at a frequency position further 4.5 MHz away from the video carrier wave fv, and a lower side wave is applied to the video carrier wave fv by a video signal with a frequency band of 4.2NH4. Video transmission band 4 subjected to vestigial sideband amplitude modulation with a bandwidth of 1.25 MHz, and
A transmission channel 1 is constituted by an audio transmission band 3 in which an audio carrier wave fa is subjected to frequency modulation using an audio signal.

In addition, as a television signal transmission system that transmits high-quality PCM audio signals and data signals together with video signals, conventionally, standard transmission of television broadcasts or relays via artificial satellites such as broadcasting satellites has been used. As shown in Figure 6, a subcarrier rso is placed at a frequency position of 5.7272 MHz above the video baseband 5 with a frequency band of 4.5 MHz, and audio is digitally modulated with audio and data signals. A digital transmission band 3 is provided, and the main carrier wave is frequency-modulated by this baseband signal. In addition, in this transmission method, the bandwidth is 27 MH
z frequency modulation transmission band is required.

(Problem M to be solved by the invention) Conventionally, when receiving a television broadcast signal from a broadcasting satellite and retransmitting it by CATV, etc., the following retransmission method was used using the above-mentioned transmission method. A transmission method was used.

(1) A method of converting only the carrier wave frequency and retransmitting it in the modulation format of satellite broadcasting, for example, frequency modulation.

(2) After receiving a satellite broadcast wave, it is demodulated to a baseband signal, and the respective carrier waves are re-modulated using the vestigial sideband amplitude modulation method for video signals and the frequency modulation method for audio signals. How to resubmit.

However, although method (1) described above is capable of transmitting and receiving high-quality signals,
Because carrier frequencies are converted so that retransmitted satellite broadcast programs can be received using a tuner, six of the normal broadcast channels with a bandwidth of 6 MHz are used, as shown in Figure 7(a).
There is a drawback that a frequency modulation transmission band of 27 MHz, which is more than four channels, is required to transmit one program using carrier waves with an interval of 38.36 MHz, which is more than four channels.

In addition, in method (2) above, to transmit one program, it is sufficient to provide a normal transmission channel with a bandwidth of 6 MHz, as shown in Fig. 7(b), but when audio transmission is Since it is carried out using a modulation method, it has the disadvantage that it cannot transmit voice PCM signals or data signals that can be transmitted with high quality.

As a retransmission method that compensates for the shortcomings of method (2), a carrier wave provided on a transmission channel different from the video transmission channel is modulated using a digital modulation method, thereby creating a high-quality audio PCM signal and data signal. However, such retransmission methods also have the drawbacks of complicated operations on the receiving side and inefficient use of frequencies and transmission channels.

(Means for Solving the Problems) An object of the present invention is to solve the problems by eliminating the drawbacks of the conventional methods described above, and to expand the required transmission bandwidth beyond the bandwidth of the normal television signal transmission band. In addition, the present invention provides a television signal transmission system that enables high-quality audio PCM transmission and data transmission while maintaining the quality of video transmission without losing the advantage of vestigial sideband transmission of video signals. It's about doing.

That is, in the television signal transmission system of the present invention, a first carrier wave is subjected to vestigial sideband amplitude modulation of a spectral array having a Nyquist slope in a first frequency region including the first carrier wave using a television video signal; This system is characterized in that a second carrier wave provided in a second frequency region adjacent to one frequency region is digitally modulated by an information bit string containing a digitized television audio signal, and a television signal is transmitted.

(Example) The present invention will be described in detail below with reference to the drawings.

First, the spectral array of the television transmission signal according to the transmission system of the present invention is shown in FIG. 1. In the spectral array shown in FIG.
A video carrier wave fv is arranged at a frequency position of 4.5 MHz from the upper end of the transmission channel 1 of z to provide a video transmission band 2 of the vestigial sideband amplitude modulation method. However, in the conventional vestigial sideband amplitude modulation method, as shown in Fig. 5, the vestigial sidebands are constructed by performing double-sideband amplitude modulation on the frequency band of the Nyquist slope that matches the receiving band characteristics. Unlike the above, in the vestigial sideband amplitude modulation method of the present invention, the first
As shown in the figure, the spectral array has a Nyquist slope in the frequency band centered on the video carrier fv on the transmitting side, and as is clear from the comparison with Figure 5, the occupied bandwidth is substantially narrowed compared to the conventional one. In addition to configuring video transmission band 2 that transmits video signals with the same bandwidth of 4.2 MHz, by adopting such a spectral arrangement, in the vacant space with a bandwidth exceeding I MHz that occurs at the lower end of the transmission channel E,
For example, rw f where rsc is the frequency of the color subcarrier modulated by the color signal and frequency interpolation multiplexed on the video signal.
, = fse , and modulates the audio carrier wave f with an audio signal using a digital modulation method such as the 4-phase DPSK method, resulting in a much wider band than before. This constitutes the audio transmission band 3.

FIG. 2 shows an example of the configuration of a transmitting device in the television signal transmission system of the present invention, which transmits video and audio signals in the above-described spectral array. In the illustrated configuration example, the video signal from the input terminal 6 is guided to the amplitude modulator 11, and the video intermediate frequency carrier fVi from the oscillator 10 is
is amplitude modulated, the modulated output signal is guided to a VSBF (vestigial sideband filter) 12, and its spectral array is
The band characteristics of the video transmission band 2 shown in the figure are inverted on the frequency ring and are then supplied to the frequency mixer 13 .

On the other hand, the audio signal from the input terminal 8 is guided to the AD modulator 15, converted into a digital audio signal, and then supplied to the multiplexer 16, where it is multiplexed with the data signal from the input terminal 7 and the control signal from the input terminal 9. The pit stream is converted into a series of bit streams, ie, a pit stream, at a rate of, for example, 2.048 H bits/second, and is guided to a four-phase DPSK (differential phase shift keying) modulator 17 to generate f si −f from the oscillator 10. v, == f v−f.

The audio intermediate frequency carrier wave fsi has the frequency relationship
DPSK modulation is applied to the signal, the modulated output signal is guided to a BPF (band pass filter) 18, and its spectral array is shaped into a band characteristic that is the band characteristic of the audio transmission band 3 shown in the first diagram, which is inverted on the frequency axis. Similarly, frequency mixer 1
Supply to 3. In addition, in that case, in the oscillator 10,
As will be described later, an audio intermediate frequency output fli is generated as the frequency sum of a crystal oscillation output having a frequency (fv −fi) and a crystal oscillation output having a frequency Li, and the frequency difference (f
Make sure that □−fv=) falls within the required error range.

In the frequency mixer 13, VSBP12 and BP
Both filtered output cass vector components from F18 are mixed and guided to the frequency converter 19, and the frequency (fv+
Based on the local oscillation output of fv=)"' (f 3 + f Si), the carrier frequencies of these two spectral divisions are converted to the video carrier frequency 1 and the audio carrier frequency f3 to be transmitted, respectively, and the frequency shown in the first diagram is After forming a spectrum array, it is outputted from the output end 21 as a transmission signal.

Next, a configuration example of a receiving device in the television signal transmission system of the present invention is shown in FIG. 3. In the configuration example shown in FIG. Based on the local oscillation output from the local oscillator 25, the video carrier wave base molecule v and the audio carrier wave component f in the received signal are converted into a video intermediate frequency and an audio intermediate frequency, respectively, and are converted into video intermediate frequencies. It leads to an intermediate frequency amplifier 26 and an audio intermediate frequency amplifier 29. The video intermediate frequency amplifier 26 is
It has a band characteristic that amplifies and passes only the spectral component corresponding to the video transmission band 2 shown in the first diagram,
It consists of a 5AW (surface acoustic wave) filter and an amplifier circuit. Further, the audio intermediate frequency amplifier 29 similarly has a band characteristic of amplifying and passing only the spectral component corresponding to the audio transmission band 3 shown in the first diagram, and is similarly constituted by a SAW filter and an amplifier circuit.

Therefore, the amplified output signal of the video intermediate frequency amplifier 26 is
The video signal is guided to the video detector 27, detected and extracted, and outputted from the output terminal 28.
The video intermediate frequency output f Vi' reproduced using a LL) circuit (not shown) is guided to the audio carrier conversion circuit 30.

On the other hand, the amplified output signal of the audio intermediate frequency amplifier 29 is guided to the audio carrier conversion circuit 30, and based on the video intermediate frequency reproduction output f 94 from the video detector 27, the frequency difference with the audio intermediate frequency reproduction output f Vi' is determined. The audio carrier wave component is converted into a signal component with a stable difference frequency (f, -f, ), and the converted output is sent to a four-phase DPSK demodulator 31.
The transmission side performs four-phase DPSK demodulation, reproduces the bit stream formed by multiplexing the digital audio signal, data signal, and control signal, and outputs the pit stream as it is to the outside from the output end 32. In addition to reproducing data signals and control signals, the pit stream is also led to the DA converter 33, where digital audio bits are extracted and AD converted, restored to analog audio signals, and supplied to the audio multiplex control circuit 34. . In the DA converter 33, the control signal is extracted together with the audio bits and guided to the audio multiplexing control circuit 34.
4, the audio signals decomposed and extracted based on the control signals are outputted to the outside from the output terminals 35, respectively.

Next, FIG. 4 shows an example of the configuration of a retransmission system according to the television signal transmission system of the present invention when receiving a television program signal from a broadcasting satellite and retransmitting it via a cable transmission path such as CATV.

In the illustrated configuration example, a program signal radio wave from a broadcasting satellite is received by an antenna 36 and sequentially guided to a BS (broadcasting satellite) converter 37 and a BS tuner 38, and the same signal processing as in normal satellite broadcasting reception is performed. and extracts the video signal and pit stream from the program signal. Of the tuner outputs, a video signal is guided to the amplitude modulator 39,
The video intermediate frequency carrier wave fVi from the oscillator 40 is amplitude-modulated, the modulated output signal is guided to the VSBF 41, and its spectral arrangement is changed to a band characteristic in which the band characteristic of the video transmission band 2 shown in the first diagram is reversed on the frequency axis. After shaping the bottom, it is supplied to the frequency mixer 42.

On the other hand, the pit stream is guided to a 4-phase DPSK modulator 43 to receive an audio intermediate frequency carrier rsi from an oscillator 40.
is subjected to DPSK modulation, the modulated output is guided to the BPF 44, the spectral array is shaped into a band characteristic obtained by inverting the band characteristic of the audio transmission band 3 shown in the first figure on the frequency axis, and the same is applied to the frequency mixer 42. supply to. In the frequency mixer 42, the filtered output cass vector components from the VSBF 41 and the BPF 44 are mixed, and the frequency converter 4
5, the frequency from the oscillator 46<t v+ r v
i) Based on the local oscillation output of = (r 3 + r st), the carrier frequencies of these two spectral components were converted into the video carrier frequency fv and the audio carrier frequency fs to be retransmitted, respectively, to form the spectral array shown in the first diagram. Then, it is extracted as a retransmission output from the output terminal 47. Therefore, the spectral arrangement of this retransmission output is the same as the transmission output signal of the transmitting device shown in FIG. 3, and can be similarly received by the receiving device shown in FIG. 4. can.

Here, a mode of frequency relationship setting for stabilizing the frequency of the digitally modulated audio carrier wave during the above-mentioned retransmission or the above-mentioned reception will be explained.

However, in the transmission system with the configuration shown in the second diagram,
When obtaining an audio carrier wave that is digitally modulated by an audio signal, etc., - as a temporal carrier wave, the frequency of a digitally modulated subcarrier wave in the standard transmission system for television broadcasting or relaying via an artificial satellite such as a broadcasting satellite as described above in the prior art. The frequency is the same as fsD (5,7272MHz), and between the color subcarrier f3C and
) using a carrier wave having the relationship f3c, the frequency fsD
After digitally modulating that carrier wave of f, as described above. Based on the frequency relationship f vi fso + (1/4) fsc when -f vi = (1/4) fsc, the frequency f-+ f v = = (1/4) f
The signal is first converted to an audio intermediate frequency called sc, and further converted to an audio carrier frequency of a predetermined channel, and then transmitted.

Note that instead of digitally modulating the carrier wave of frequency rso, a digitally modulated subcarrier wave obtained by receiving a television broadcast wave via an artificial satellite such as a broadcasting satellite may be used as it is.

On the other hand, in the receiving system having the configuration shown in FIG. ) f, C = (27/20) f3C
Frequency sum fvi'-(27/20)rs with the oscillation output of
The audio intermediate frequency playback output f, which was extracted separately by determining c.
Frequency difference with Si′ r s=′ −r vi′ +(2
7/20) When creating rsc, rsi' even after reception
Since the frequency relationship fV,'=(1/4)fsc is maintained, it has the same frequency f3D''(815)fsc as the above-mentioned temporary carrier wave, and is also free from the effects of fluctuations in the local oscillation frequency, etc. It is possible to obtain a stable digitally modulated audio carrier wave that does not undergo any interference.This digitally modulated audio carrier wave is demodulated by a digital demodulator in the BS tuner 38 for receiving television broadcast waves via an artificial satellite such as a broadcasting satellite. can do.

(Effect of the invention) As is clear from the above explanation, conventionally, the bandwidth was 6 MH.
In the transmission channel of z, high-quality audio P is transmitted along with the video signal.
It has been impossible to transmit CM signals and data signals, but according to the present invention, it is possible to transmit high-quality video signals at the same time.
High quality audio PCM signal, e.g. sampling frequency 32K
Hz, 14 bit quantization, 4 audio signals with quasi-instantaneous compression 10 bits, or sampling frequency 48 KHz,
Two quantized 16-bit audio signals and a data signal are
For example, since it is possible to transmit at a speed of 2.048 Mbit/s, it is possible to satisfy both of the requirements of effective frequency utilization and high quality transmission for a standard transmission channel with a bandwidth of 6 MHz.

In particular, when a television program signal and data signal from an artificial satellite such as a broadcasting satellite are simultaneously received using a standard transmission band and retransmitted via a cable transmission line such as CATV, other programs may be According to the method of the present invention, even if a transmission channel is adjacent to a transmission channel that is transmitting according to the standard method, high-quality signal transmission can be performed without causing mutual interference with the adjacent transmission channel. Moreover, there is an advantage that the occupied frequency bandwidth can be reduced to 176 or less, compared to the case where the frequency modulation signal, which is the standard method for satellite broadcasting, is retransmitted after only frequency conversion.

In addition, in the retransmission method shown in Fig. 5, which converts the received satellite broadcast signal into a conventional amplitude modulation television signal and retransmits it, even if the satellite broadcast uses an audio PCM signal, the retransmission will be difficult. Since the high quality of PCM transmission is lost during retransmission, it is also difficult to use the pay television system that uses data transmission, facsimile broadcasting, broadcasting for PCs, and television broadcasting. The transmission system of the present invention has the remarkable effect of being able to solve all at once the major problem or drawback of this type of conventional transmission system, which is that it cannot support various data broadcasts such as music broadcasts.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of a spectrum arrangement for television signal transmission according to the present invention, FIG. 2 is a block diagram showing an example of the configuration of a transmission system in the present invention television signal transmission system, and FIG. FIG. 4 is a block diagram showing an example of the configuration of a receiving system in the invention television signal transmission system; FIG. Diagram showing the spectral array of standard format television broadcasting. Figure 6 is a diagram showing the spectral array of standard format television broadcasting via satellite. Figure 7 (a) and (b) are diagrams showing the spectral array of standard format television broadcasting via satellite. FIG. 3 is a diagram illustrating examples of channel arrangements for retransmitting broadcasts; ■...6 MHz transmission channel 2.4...Residual sideband video transmission band 3...Audio transmission band 5...Video baseband 6 to 9.21.22.28.32.35.47 ... Input/output terminal 10, 20.40.46... Oscillator 11, 39... Amplitude modulator 12, 41-V S B F 13, 24.42... Frequency mixer 15... AD Converter 16... Multiplexer 17, 43 -... 4-phase DPSK modulator 18, 44... BPF 19, 45... Frequency modulator 23... High frequency amplifier 25... Local oscillator 26... ...Video intermediate frequency amplifier 27...Video detector 29...Audio intermediate frequency amplifier 30...Audio carrier conversion circuit 31...4-phase DPSK demodulator 33...DA converter 34...Audio Multiplex controller 36...Antenna 37...BS converter 38...BS tuner

Claims (1)

[Claims] 1. The first carrier wave is transmitted by the television video signal to the first carrier wave.
Television audio that is subjected to vestigial sideband amplitude modulation of a spectral array having a Nyquist slope in a first frequency region including a carrier wave, and digitized to a second carrier wave provided in a second frequency region adjacent to the first frequency region. A television signal transmission method characterized by transmitting a television signal configured by digitally modulating an information bit string containing the signal. 2. The television signal transmission system according to claim 1, wherein the information bit string includes a data signal and a digital control signal. 3. A third carrier wave transmitted from an artificial satellite is subjected to frequency modulation using the television signal, and the demodulated television signal is transmitted. The television signal transmission system according to item 2.