JPS62221285A - Transmission signal reproducing device - Google Patents

Abstract

PURPOSE:To multitransmit sound signals with high quality at the same time by permitting a carrier to hold orthogonal relation with video and signals to modulate and transmit and detecting the synchronization of a reception signal with the aid of a signal synchronizing with the carrier so as to reproduce the sound signal. CONSTITUTION:A television signal inputted from an antenna 1 is amplified by a high frequency amplifier circuit 2 and converted into a demodulating intermediate frequency by a frequency converting circuit 3. In terms of the frequency band of a video signal among the output signals of the circuit 3, finally signals R, G and B are obtained and projected on a cathode ray tube 9. The frequency band of a sound signal PCM multitransmitted by a band-pass filter 13 from the output of the circuit 3 is selected and amplified. Then a synchronizing detection circuit 14 detects the synchronization with the aid of the signal synchronizing with the carrier reproduced by a carrier reproduction circuit 15. The sound signal subjected to the PCM transmission is obtained from the obtained signal through a code identifying circuit 16, a digital signal processing circuit 18 and a digital/analog converting circuit 19.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a multiplex transmission system, and relates to a video signal with P
The present invention relates to a playback device that receives a transmission method effective for multiplex transmission of CM audio and audio.

[Conventional technology]

The method of multiplexing digitally encoded PCM audio and video signals is reported in the report of the Satellite Broadcasting Reception Technology Study Group, Part 1, "Satellite Broadcasting Receiver", edited by the Wave Technology Association, published in June 1981. However, PCM is applied to the current NT8C video signal using a 5.7272MHz subcarrier.
Since the audio is multiplexed, it does not meet the bandwidth of current terrestrial television broadcasting, making it difficult to use for terrestrial television broadcasting.

On the other hand, the possibility of multiplex transmission for current terrestrial television broadcasting is described on pages 205 to 208 of Broadcasting Technology Book 2, "Broadcasting Systems," edited by the Japan Broadcasting Corporation, published by the Japan Broadcasting Publishing Association in January 1981. However, a method that can secure a transmission capacity of approximately IM bits/second σ for transmitting two channels of high-quality audio was not included in the H-Pi.

[Problem that the invention seeks to solve]

In contrast to the above conventional technology, there was no method for multiplex transmission of high quality audio signals in the current terrestrial television broadcasting.An object of the present invention is to provide a playback device for multiplex transmission of other signals on an amplitude modulated signal. To provide a transmission number 15 reproducing device that is particularly effective for receiving a transmission system that multiplexes and multiplexes single signals such as high-quality digitally encoded audio signals in current terrestrial television broadcasting. There is a particular thing.

[Means for solving problems]

The above object is achieved by modulating another signal in an orthogonal relationship to the amplitude modulated carrier wave.

In particular, in the case of a video signal that undergoes vestigial sideband amplitude modulation, within the transmission band of both sidebands of the carrier wave, the multiplication factor of the digitally encoded audio signal etc. creates an orthogonal relationship with the video 4M number of the carrier wave. This is achieved by modulating and transmitting the signal, and reproducing the audio signal by synchronously detecting the received signal using a demodulation signal synchronized with the carrier wave from the received signal.

[Effect]

Residual Sideband Amplitude modulated video signal carrier wave has both sidebands.Limited to a general amplitude modulated band, the carrier wave has orthogonal relationship between the video signal and audio No. 18. The shadow of the audio signal on video No. 18 played back by modulating it - f! can be reduced.

By making the degree of modulation of the audio signal lower than that of the video signal,
The influence of the audio signal on the video signal reproduced by rough envelope detection can also be reduced. Furthermore, since the single-voice signal is reproduced through synchronous detection, the orthogonally modulated video signal is not demodulated, so the influence is reduced.

In current terrestrial television broadcasting, residual sideband amplitude variation fA
The band having both side bands is about 1.5 MHz, and it is possible to transmit two channels of digitally encoded high-quality audio at about IM bits/second.

[Metal practice]

Below, as an embodiment of the present invention, an example of a receiver in which digitally encoded PCM audio No. 18 is multiplexed and transmitted to a current terrestrial transmission television channel is not shown in FIG.

1 is an antenna, 2 is a high frequency amplification circuit, 3 is a frequency conversion circuit, 4 is an intermediate frequency amplification circuit, 5 is a video signal detection (b) path, 6 is a video signal amplification circuit, 7 is a color difference signal demodulation circuit, 8 is a primary color Signal demodulation circuit, 9 is a cathode ray tube, 10 is an audio intermediate frequency amplification circuit, 11 is an audio FM detection circuit, 12 is an audio P signal output terminal, 13 is a band pass filter, 14 is a synchronous detection circuit, 15 is a carrier wave regeneration circuit, 16 is a code identification circuit, 1
7 is a clock regeneration circuit, 18 is a digital signal processing circuit, and 19 is a digital/7° analog conversion circuit (hereinafter referred to as DAC).
2o is an output terminal for the PCM-transmitted audio signal.

A television signal inputted from an antenna 1 is amplified by a high frequency amplifier circuit 2, frequency-converted by a frequency conversion circuit 3 to an intermediate frequency for restoration, and amplified by an intermediate frequency amplifier circuit 4. Tuning is performed by changing the local oscillation frequency of the frequency conversion circuit 30. The video signal band from the signal amplified by the intermediate frequency amplification circuit 4 is detected by the video signal detection circuit 5, and the signal is output from the output of the video signal amplification circuit 6 and the output of the color difference demodulation circuit 7. Primary color signal demodulation circuit 8 from color difference g1
The three primary colors of blue, G, and B are obtained and projected onto a cathode ray tube 9.

On the other hand, the audio signal band is amplified by the audio intermediate frequency amplification circuit IO, and detected and demodulated by the audio FM detection circuit 11 to obtain an audio signal at the audio signal output terminal 12.

The above is the same as the conventional 1M television receiver.

In addition to the above, in order to demodulate the digitally encoded PCM audio signal, frequency conversion and repair 3 u) select and amplify the PCM audio signal band multiplexed from the output by the band pass filter 13, and 14, using a signal synchronized with the carrier wave regenerated at carrier regeneration times $15, ``CW1 transmission wave l111! A signal modulated with a component orthogonal to the modulation component is detected and demodulated. The resulting signal is converted into a digital code using a code identification circuit 16 at a point with a low error rate, and a digital signal processing circuit 18 detects and corrects errors occurring during transmission using an error detection and correction code. The clock recovery circuit 17 is a circuit that extracts a transmission lock from the output signal of the synchronous detection circuit 14, and digitally encodes the output signal of the synchronous detection circuit 14 at a point where the error rate is low (the so-called maximum opening of the eye pattern). It is necessary to do so. The digital signal subjected to error detection and correction is converted into an analog signal by the DAC 19 and returned to an audio signal, which is then obtained at the output terminal 20 of audio No. 15 transmitted by PCM.

An example of the transmitter that generates No. 15 transmitted in the above example is shown in Fig. WJ2. 21 is an audio signal input terminal, 22 is an FM modulator, 23 is an audio signal carrier generator, 24.~2
6 is a video signal input terminal, 27 is a matrix circuit, 28
29 is a luminance signal processing circuit, 29 is a color difference signal processing circuit, 30 is an addition circuit, 31 is a video modulator, 32 is a video signal carrier generator, 33 is an input terminal for an audio signal to be transmitted by PCM, 34
is an analog-to-digital converter (hereinafter abbreviated as ADC),
35 is a digital signal processing circuit, 36 is a low-pass filter, 37 is a 90-degree phase shifter, 38 is a modulator for PCM audio signal, 39 is an adder, and 40 is a V8B for residual sideband amplitude modulation. 41 is an adder, and 42 is an antenna.

An audio carrier wave from an audio signal carrier generator 23 is FM-modulated by an audio signal from an audio signal input terminal 21 in an FM modulator 22 . The three primary color signals of l(, GB) input to the video input terminals 24 to 26 are
! The luminance signal processing circuit 28 is divided into a luminance signal and a color difference signal.
After processing f in the color difference signal processing circuit 29, the adder 30 adds them. The carrier wave from the video signal carrier generator 32 is modulated by the signal after the addition using the video modulator 31, band-limited to the television broadcasting band by the VSB filter 40, and added to the audio signal by the adder 41 to be sent to the antenna. 42.

The above is the same as conventional terrestrial television broadcasting. The following is added to the above No. 18 in order to transmit high quality audio.

Add the audio signal to be multiplexed to the input terminal 33, and send the audio signal to A.
The DC 34 converts it into a digital signal, and the digital signal processing circuit 35 adds a code to detect and correct errors that occur during transmission, and performs interleaving processing.
Unnecessary high frequency components are removed through a low pass filter 36 suitable for the transmission rate of the digital code. This digitally encoded audio is passed through a 90i phase shifter 377 to a 90i
Degree phase shifted video 116 carrier wave ftPCM audio g! The modulator 3B for the video signal modulates the video signal, and the adder 39 modulates the video signal by the video signal modulator 3B.
It is added to the I4 carrier wave. As a result, the video carrier wave is modulated in an orthogonal relationship with the video signal and the PCM audio signal.

The modulated spectrum is shown in FIGS. 3 and 4, and a vector diagram of the modulation state of the video signal of the video carrier wave and the PCM audio signal is shown in FIG. Figure 3) 43 is the V of the video signal
8B is the spectrum after filtering, 44 is the spectrum of the F'M modified v4 audio signal.

45 shows the spectrum of the digitized PCM audio signal. Here, PCM f voice (ii go
The i-spectrum is the spectrum obtained when the carrier wave of a signal with a transmission rate of 1 bitf second and a roll-off rate of 0.5 is modulated.

ctram is shown.

In Figure 3, -0.75MHz for the video carrier
The lower J spectrum is trued by a V8B filter with residual sideband amplitude modulation. 4.
For video signals up to 2 MHz, there is a spectrum in the vicinity of 4.5 MHz where the audio carrier wave is FM modulated. Since both sidebands are transmitted for ±0.75 MHz with respect to the video 1-line carrier wave, general amplitude modulation (08B
). If a signal within ±Q, 75MH1 is orthogonal to the carrier wave having both side bands and is modulated with an amplitude A and one signal corresponding to digital codes 1 and 0 as shown in Fig. 4, the carrier wave vector is when the video signal is set to 1.

(2) ωct-1zA actual ωct (1). Here, ωC is the angular frequency of the carrier wave.

Expanding equation (1), we get It is.

Let us now consider interference from a PCM audio signal to a received video signal. When the video signal detection circuit performs synchronous detection using Jωct, the coefficient σ) of 3ωcl (that is, the video signal Q) is reproduced and does not cause interference, regardless of the value of A. In addition, if the video signal detection circuit performs envelope detection, interference can be reduced by lowering the value of A below 1. For example, if AfjI:0.1, J""
Machu 1.005.

Although a signal of 0.005 (approximately -46 dB) compared to 1 has an effect, it is considered that there is no practical problem as long as the 8N ratio of the video signal is 40 cfB or more.

However, interference with the PCM audio detection circuit from the video signal can be eliminated by demodulating only the component orthogonal to the carrier wave in the synchronous detection circuit 14, as shown in FIG. Considering the signal level to noise ratio (hereinafter referred to as the SN ratio), if the SN ratio of the video signal is a practical level of 40 dB, the bandwidth is about 4 times the transmission bandwidth of the PCM audio signal, IMHz. The S/N ratio of the PCM audio signal is 46 dB, but if the modulation level of the PCM audio signal is 0.1, it is 8.
The N ratio is approximately 2ωB.

On the other hand, even if we consider the relationship between the SN ratio of a digital signal and the pit error rate using a general binary signal, the SN ratio is 17.4d.
B is 10. When the S/N ratio of the video signal is 40 dB, the S/N ratio of the PCM audio signal is 26 dB, which is a practically sufficient value for digital signal transmission.

Another embodiment of the invention is shown in FIG. Received number 15 is the first
This is the same as in the figure, and the same reference numerals as in FIG. 1 indicate the same functions. 3 is a frequency conversion circuit, 46 is a mixing circuit, 4
7 is a voltage controlled local oscillator, 48 is a synchronous detector, 49
50 is a reference signal generator, 50 is a low-pass filter, 51 is a carrier wave regeneration circuit composed of G components 48 to 50, 52 is an adder, and 53 is a channel selection circuit.

The difference from FIG. 1 is that in FIG. 1, the carrier wave regenerating circuit 15 generates a signal and detects it in the synchronous detection circuit 14 in synchronization with the PCM audio signal that is modulated orthogonally to the carrier wave image No. 16. In contrast, the modulation of the PCM audio signal in FIG. 6 is particularly effective when the DC component is small, such as in the old model of differential PSK. Utilizing the orthogonal relationship between the PCM audio signal modulation and the carrier wave of the video signal, the synchronous detector 48 detects the phase difference between the reference signal generator 49 and the intermediate frequency signal including the carrier wave, and By feeding back the component to the voltage-controlled local oscillator via the adder 52, the output of the synchronous detector 48 is made into a detected output in synchronization with the output of the reference signal generator which is a mixed wave of intermediate frequency. Note that the first channel selection circuit 53 changes the oscillation frequency of the local oscillator 47 by changing the DC voltage at the time of channel selection.

According to the embodiments shown in FIGS. 1 to 6, the transmitter shown in FIG.
ig to traditional television-based video and audio communications.
/: can be transmitted without causing fK interference, and these signals can be reproduced using the receivers shown in FIGS. 1 and 6.

FIG. 7 shows another embodiment of the invention. In Figure 7,
54 is a video synchronous detection circuit, 55 is a phase shifter, and the same symbols as in FIG. 1 indicate the same functions.

Since the signal A6 synchronized with the carrier wave is obtained in the carrier wave reproducing circuit 15, the video signal is synchronously detected using this signal. The output of the carrier regeneration circuit 15 is transmitted to the synchronous detector 1
4 is used to demodulate the signal modulated by the orthogonal component of the carrier wave, so it takes approximately 90 to synchronously detect the video signal.
If you do a degree phase shift, it will work. The signal is detected by the video synchronous detection circuit 54 via the phase shifter 55 for this purpose. Note that if the phase difference due to the delay time difference between the intermediate frequency amplification circuit 4 and the bandpass filter 13 is a problem, the phase shift cover setting value of the phase shifter 55 may be changed from 90 degrees.

FIG. 8 shows an embodiment similar to that shown in FIG. 6. According to this embodiment in both FIGS. 7 and 8, synchronous detection can also be used for detecting the video signal, which has the effect of further reducing the influence of orthogonal components on the video reproduction signal.

FIG. 9 shows nine further embodiments of the present invention.

56 is a phase shifter, 57 is a band pass filter, 58 is a PLL
The same functions are indicated by the same reference numerals as in FIG. 7. A carrier wave is extracted from the output of the frequency conversion circuit W63 using a band pass filter 57, a signal synchronized with the carrier wave is obtained using a PLL 1 path 58, and a signal synchronized with the carrier wave is obtained using the phase shifters 55 and 56. Send to 54. The rest is the same as in FIG. 7, but according to this embodiment, a bandpass filter 57 and a PLL circuit 58 are used only to reproduce the 1g signal synchronized with the carrier wave, so that the influence on other signals is reduced. Since it can be designed with a smaller number, it is more stable and has the effect of reducing the influence between each reproduction signal of video and audio.

Note that although the orthogonal modulation is made to correspond to binary values such as digital values 1 and 0 to A and -, it is also possible to transmit multi-values in consideration of transmission capacity.

In addition, although the fundamental sideband components of orthogonal modulation are described within the transmission band of both sidebands of vestigial sideband amplitude modulation, if a slight deterioration of the error rate in digital transmission is allowed, some parts may be outside the band. Out-of-line transmission is also possible.

〔Effect of the invention〕

According to the present invention, a carrier wave that is amplitude modulated can be modulated in an orthogonal relationship to the modulation and transmitted, and can be reproduced as a signal synchronized with the received carrier wave, so that a signal different from the modulation can be received. effective.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention, FIG. 2 is an IA configuration diagram of an embodiment of the transmitting side for implementing the present invention, FIG. 3 is a spectrum diagram for explaining the present invention, and FIG. The figure is a spectrum diagram for explaining the present invention, FIG. 5 is a vector diagram for explaining the present invention, FIG. 6 is a block diagram of another embodiment of the present invention, and FIG. FIG. 8 is a block diagram of another embodiment of the present invention, and FIG. 9 is a block diagram of still another embodiment of the present invention. 13 , 57...Band pass filter 14...Synchronized detection circuit 15...Carrier recovery circuit 16...Data strobe circuit 17...Clock recovery circuit 18...Digital signal processing circuit 19...DAC46 ... Mixing circuit 47 ... Local oscillator 48 ... Synchronous detector 4
9... Reference signal generator 5o... Low pass filter 52... Adder 53... Tuning circuit 5
4... Video synchronous detection circuit 55.56... Phase shifter 5
8...PLL circuit representative patent attorney Katsuo Ogawa - Mozu Name 4 Figure item motion image reform frequency - & (MHI) Issue 5

Claims (1)

[Claims] 1. In a method of amplitude modulating and transmitting a carrier wave, a signal transmitted by modulating an orthogonal component of the carrier wave with a signal other than the amplitude modulation signal is received. Transmission signal regeneration device. 2. A transmission signal reproducing device according to claim 1, characterized in that a signal other than the amplitude modulation signal is a digitally encoded signal. 3. In claim 1, the carrier wave is modulated in vestigial sideband amplitude with a video signal, so that fundamental double-sideband waves exist in a band having both sidebands within the vestigial sideband,
A transmission signal reproducing device characterized in that a signal other than the video signal is modulated into an orthogonal component of the carrier wave and transmitted. 4. In claim 3, there is provided a frequency conversion circuit that converts the carrier wave into an intermediate frequency to be demodulated, a video signal demodulation circuit that amplitude-detects the output signal of the frequency conversion circuit and demodulates the video signal, and the frequency conversion circuit. a bandpass filter for passing an output signal of the means within a band having both sidebands within the vestigial sideband; a carrier regeneration circuit for obtaining a carrier wave component for reproduction synchronized with a carrier wave of the output signal of the bandpass filter; A synchronous detection circuit that synchronously detects the output signal of the band-pass filter with the output signal of the carrier regeneration circuit and demodulates the signal modulated into orthogonal components, and converts the output signal of the synchronous detection circuit into a digital waveform at a point with a low error rate. A transmission signal reproducing device comprising: a waveform shaping circuit for converting; and a digital signal processing circuit for detecting and correcting errors in the output signal of the waveform shaping circuit and reproducing signals other than the digitally encoded video signal. 5. In claim 4, the local oscillator used for frequency conversion of the frequency conversion circuit is a voltage controlled oscillator, and the carrier wave regeneration circuit is configured with a phase detector and a reference signal oscillator, and the reference signal oscillator and A transmission signal regeneration device, characterized in that the phase difference between the signal and the input signal of the carrier regeneration circuit is detected by the phase detector, and the local oscillator is controlled by the output signal of the phase detector.