JPS63276391A - Multiplex transmission method and its transmitter-receiver - Google Patents

Abstract

PURPOSE:To obtain a high-quality audio signal by using a synchronizing signal as a reference signal to detect a ghost, eliminating the ghost in a video signal at first and detecting the ghost of a PCM audio signal itself, to eliminate the ghost of the PCM audio signal. CONSTITUTION:A video signal in a television signal inputted from an antenna 1 is displayed on a cathode-ray tube 9. A PCM audio signal band is selected by a band pass filter 13 to demodulate the digitized PCM audio signal, the signal is detected and demodulated by a synchronizing detection circuit 14 and the ghost component is eliminated by a ghost elimination circuit 201. A digital signal after error detection is stopped by a code identification circuit 16 is outputted via a digital signal processing circuit 18 and a DA conversion circuit 19.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a multiplex transmission method for multiplexing and transmitting a PCM audio signal on a video signal, and a transmitting/receiving device therefor.

[Conventional technology]

Video signals such as television signals, as well as accompanying analog audio signals, as well as digitally encoded PC
There is a demand for multiplexing the use of television broadcast waves by multiplexing M audio signals, and a method for multiplexing such digitally encoded PCM audio signals and video signals is described in the publication published in June 1982, This is reported in the Satellite Broadcasting Reception Technology Investigation Committee Report, Part 1, ``Satellite Broadcasting Receivers,'' edited by the Radio Technology Association. However, this method is not suitable for video signals based on the current NTSC system.
Since this method multiplexes PCM audio using Hz subcarriers, it does not satisfy the predetermined band of current terrestrial television broadcasting and is difficult to use for terrestrial television broadcasting.

On the other hand, the possibility of realizing multiplex transmission for current terrestrial television broadcasting is described in pages 205 to 208 of Broadcasting Technology Book 2 "Broadcasting Systems" published by Japan Broadcasting Publishing Association in January 1988. However, there was no description of a method for securing a transmission capacity of about IM fps/sec for transmitting two channels of high-quality audio.

In other words, it can be said that until then, there was no method of multiplexing and transmitting high-quality audio signals on current terrestrial television broadcasting. Thereafter, as a method for realizing such a method, a signal obtained by amplitude modulating a carrier wave with a video signal, and a signal obtained by amplitude modulating a carrier wave with a video signal,
A method has been proposed in which a second carrier wave having a phase difference of 0 degrees is multiplexed and transmitted with a signal obtained by amplitude modulating a PCM audio signal.

In the method according to this proposal, especially in the case of a video signal that undergoes vestigial sideband amplitude modulation, the digitally encoded audio signal has an orthogonal relationship with the video signal of the carrier wave within the transmission band of both sidebands of the carrier wave. A demodulation signal synchronized with the carrier wave is extracted from the received signal, and the received signal is synchronously detected using this signal to reproduce the audio signal.

According to this method, the video signal carrier wave that undergoes vestigial sideband amplitude modulation is limited to a general amplitude modulated band that has both sidebands, and the carrier wave is used to combine the video signal and the audio signal. Since the signals are modulated in an orthogonal relationship, the influence of the audio signal on the reproduced video signal can be reduced. By making the degree of modulation of the audio signal lower than that of the video signal, it is possible to further reduce the influence of the audio signal on the video signal reproduced by envelope detection. Furthermore, since the audio signal is reproduced through synchronous detection, the orthogonally modulated video signal is not demodulated, so the influence is reduced. In current terrestrial television broadcasting, the band with both sidebands of vestigial sideband amplitude modulation is approximately 1.5 MHz, which has the advantage of being able to transmit two channels of digitally encoded high-quality audio at approximately IM bft/sec. have.

[Problem that the invention seeks to solve]

After conducting various studies on the multiplex transmission method proposed above, it has become clear that the effects of ghosts, which are always a problem in television broadcasting, also appear in reproduced PCM audio signals. If it is a video signal, the screen can be viewed to some extent even if a ghost appears. However, in the case of audio signals, when the effects of ghosts appear, the audio becomes extremely difficult to hear.
I can't stand watching it.

° An object of the present invention is to convert a first signal obtained by amplitude modulating a first carrier wave with a video signal and a second carrier wave whose phase is shifted by 90 degrees with respect to the first carrier wave into a PCM audio signal. In a multiplex transmission method in which at least a second signal obtained by amplitude modulation is multiplexed and transmitted, the reproduction P after transmission is
The purpose of the present invention is to eliminate the effects of ghosts that appear in commercial audio to obtain high-quality audio.In other words, the purpose of the present invention is to provide a multiplex transmission method and a transmitting/receiving device for the purpose. do.

[Means for solving problems]

The ghosts that appear in the PCM audio signal include the ghost of the video signal and the ghost of the PCM audio signal itself, so it is necessary to take measures to make it possible to separate both ghosts, and to provide a ghost removal circuit that removes both separated ghosts. By providing this, the above object is achieved.

[Effect]

A first signal obtained by amplitude modulating a first carrier wave with a video signal and a second carrier wave whose phase is shifted by 90 degrees with respect to the first carrier wave, obtained by amplitude modulating a PCM audio signal. In the multiplex transmission method of multiplexing and transmitting at least a second signal, the PCM audio signal is located in the remaining area excluding a certain arbitrary specific range within the vertical blanking period of the video signal. the first signal and the second signal are multiplexed, and the specific range allows a specific signal, such as a synchronization signal, within the range to be used as a reference for ghost detection of the video signal. Therefore, it is decided not to multiplex PCM audio signals.

The signal used as the reference signal for detecting the thickness of the ghost component in the received video signal is not a signal with a constant amplitude change like a picture pattern, but a signal with a constant amplitude like a synchronization signal. used. Therefore, the synchronization signal used as a reference signal for ghost component detection is separated from the PCM audio signal in advance so that the two do not mix. When a ghost is detected using such a synchronization signal as a reference signal, it is first used to remove the ghost of the video signal, then the ghost of the PCM audio signal itself is detected, and then the ghost of the PCM audio signal is removed using it. I do.

〔Example〕

As an embodiment of the present invention, FIG. 1 shows an example of a receiver in which a digitally encoded PCM audio signal is multiplexed and transmitted to a current terrestrial transmission television.

In the figure, 1 is an antenna, 2 is a high frequency amplifier circuit, and 3 is an antenna.
is a frequency conversion circuit, 4 is an intermediate frequency amplification circuit, 5 is a video signal detection circuit, 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, and 10 is an audio intermediate frequency amplification circuit. circuit, 11 is an audio FM detection circuit, 12
13 is an audio signal output terminal, 13 is a band pass filter, 14.
202 is a synchronous detection circuit, 15 is a carrier wave regeneration circuit, 16 is a code identification circuit, 17 is a clock regeneration circuit, 18 is a digital signal processing circuit, 19 is a digital-to-analog conversion circuit (hereinafter abbreviated as DAC), and 20 is a 20M transmission circuit. 201 is a ghost removal circuit, and 203 is a 90-degree phase shifter.

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 demodulation, and amplified by an intermediate frequency amplifier circuit 4. Tuning is performed by changing the local oscillation frequency of the frequency conversion circuit 3. The video signal band from the signal amplified by the intermediate frequency amplification circuit 4 is detected by the video signal detection circuit 5,
From the luminance signal output from the video signal amplification circuit 6 and the color difference signal output from the color difference signal demodulation circuit 7, the primary color signal demodulation circuit 8 converts R,
Three primary color signals of 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 10, detected and demodulated by the audio FM detection circuit 11, and an audio signal is obtained at the audio signal output terminal 12. The above is the same as a conventional television receiver.

In addition to the above, in order to demodulate the digitally encoded PCM audio signal, the bandpass filter 13 selects and amplifies the PCM audio signal band multiplexed from the output of the frequency conversion circuit 3, and in the synchronous detection circuit 14, The carrier wave regenerated by the carrier regeneration circuit 15 is transferred to a 90 degree phase shifter 20.
3, a signal synchronized with a carrier wave phase-shifted by 90 degrees is used to detect and demodulate a signal modulated with a component orthogonal to the amplitude modulation component of the carrier wave, and a ghost removal circuit 201 removes the ghost component.

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 regeneration circuit 17 is a circuit that extracts a transmission clock from the output signal of the ghost removal circuit 201, and detects a point where the error rate of the output signal of the ghost removal circuit 201 is low (the so-called maximum opening of the eye pattern).
is necessary for digital encoding. The digital signal subjected to error detection and correction is converted into an analog signal by a DAC 19 and returned to an audio signal, which is then obtained at an output terminal 20 for an audio signal transmitted by PCM.

FIG. 2 shows an embodiment of a transmitter that generates the signals transmitted in the above embodiment. 21 is an audio signal input terminal, 22 is an FM
23 is an audio signal carrier wave generator, 24 to 26 are video signal (R, G, B) input terminals, 27 is a matrix circuit, 28 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, and 36 is a low 37 is a 90 degree phase shifter, 38 is a modulator for PCM audio signals, 39 is an adder, 40 is a VSB filter 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 RGB input to the video input terminals 24 to 26 are divided into a luminance signal and a color difference signal by a matrix circuit 27, each processed by a luminance signal processing circuit 28 and a color difference signal processing circuit 29, and then added by an adder 30. do. The carrier wave from the video signal carrier wave generator 32 is modulated by the signal after the addition using the video modulator 31, and the band is limited to the television broadcast band by the VSB filter 40, and then the adder 4
1, the signal is added to the audio signal and transmitted from the antenna 42.

The above is the same as conventional terrestrial television broadcasting. Add the following to transmit high-quality audio to the above signals.

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 for detecting and correcting errors that occur during transmission, and performs increment processing.
Unnecessary high frequency components are removed through a low pass filter 36 suitable for the transmission rate of the digital code. Using this digitally encoded audio, a video signal carrier wave whose phase is shifted by 90 degrees via a 90 degree phase shifter 37 is modulated by a modulator 38 for PCM audio signals, and an adder 39 modulates the carrier wave by the video signal. and add. As a result, the video carrier wave is modulated so that the video signal and the PCM audio signal have an orthogonal relationship.

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. 43 in Figure 3 is the V of the video signal.
In the spectrum after the SB filter, 44 shows the spectrum of the FM-modulated audio signal, and 45 in FIG. 4 shows the spectrum of the digitized PCM audio signal. Here P
The spectrum of the CM audio signal is the transmission rate) IM bit/
The spectrum is shown when the carrier wave of a signal with a roll-off rate of 0.5 in seconds is modulated.

In Figure 3, -0.75M H for the video carrier.
The spectrum below z is attenuated by a VSB filter with residual sideband amplitude modulation. 4.2
There is a spectrum in which the video signal is FM modulated up to MHz, and an audio carrier wave is FM modulated in the vicinity of 4.5 MHz. Since both sidebands are transmitted for ±0.75 MHz with respect to the video carrier wave, general amplitude modulation (DS
You can think of it as B). Orthogonal to the carrier wave that has both sidebands (that is, with a phase difference of 90 degrees), signals within ±0.75 MHz are made to correspond to digital codes 1 and 0, as shown in Figure 4. When modulated with amplitudes A and -A,
When the video signal is 1, the carrier wave vector is cosQ) cl± A sin ωc0t
(1). Here, ωC is the angular frequency of the carrier wave.

If you expand (1) 2 above, It is.

Let us now consider interference from a PCM audio signal to a received video signal. If the video signal detection circuit performs synchronous detection with cosQC・t, cos
Only the QC-t coefficients (that is, only the video signal) are reproduced and do not cause interference. Further, in the case where the video signal detection circuit performs envelope detection, interference can be reduced by lowering the value of A below 1. For example, if A is 0.1,
J "777 Ki 1.005, which is 0.00 compared to 1
5 signal (approximately -46 dB), but the video signal S
It is considered that there is no practical problem if the N ratio is 40 dB or more.

On the other hand, 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 A of the pcM audio signal is 0.1, the S
The N ratio is about 26 dB.

On the other hand, when considering the relationship between the SN ratio and bit error rate of a digital signal using a general binary signal, the SN ratio is 17.4d.
B is 10-4. 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.

However, if a ghost is added to the signal due to reflection from a building or the like on the transmission path, the output of the synchronous detection circuit 14 will include a ghost component of the video signal in addition to the ghost component of the multiplexed PCM audio signal. PCM correctly.
It becomes impossible to restore the audio signal.

That is, the video signal P having the pulse waveform shown in FIG. 6(a)
When multiplexing the 3-clock PCM audio signal PCM shown in (b), if a ghost with a delay time τg is added to each signal in the transmission path, the output signal of the synchronous detection circuit 14 in FIG. 3 shown in Figure 6(c) and (d)
is the sum of the two signals.

Here, P(GQ) is the detection output of the ghost component P(G) of the video signal P, PCM' is the detection output of the PCM audio signal PCM, and PCM(GQ) is the detection output of the ghost component PCM of the pcM audio signal. (G) is the detection output.

This will be explained below using FIG. 7.

FIG. 7(a) is a vector diagram regarding the video signal P,
FIG. 7(b) is a vector diagram regarding the PCM signal.

Further, in FIG. 7, I and Q are two detection axes that are orthogonal to each other.

If that ghost is added to the signal in the transmission path,
The carrier wave of the desired signal (video signal P, !: PCM audio signal PCM) and its ghost signal (ghost P of the video signal
(Q) and the carrier wave of the ghost PCM (G)) of the PCM signal, a phase difference ψ (due to the delay time of the ghost from the desired signal) occurs.

The detection axis of the PCM signal in the synchronous detection circuit 14 is in the vector direction shown by Q in FIG. As shown in b), components projected onto the axis Q, that is, three signal components shown by the following equations are included.

FIG. 8 shows 2 generated at the output of the synchronous detection circuit 14 of FIG.
A specific example of a ghost removal circuit 201 that removes two unnecessary signals (the Q-axis component P (C; Q) of the ghost portion of the video signal and the Q-axis component PCM (GQ) of the ghost portion of the PCM signal will be shown.

In Fig. 8, parts with the same numbers as in Fig. 1 indicate parts with the same function, and 210, 21
1 are transversal filters, 212 and 21, respectively.
3 are ghost detection circuits, and 214 and 215 are subtraction circuits.

Transversal filter 210. Ghost detection circuit 2
A set of ghost removal circuits from 12 and subtraction circuit 214 is used to remove unnecessary signals P (C,Q),
Transversal filter 211, ghost detection circuit 2
13 and another set of ghost removal circuits from the subtraction circuit 215 are used to remove the unnecessary signal PCM(GQ).

Regarding the operation of the ghost removal device itself using a transversal filter, for example, see the document "TV Ghost Canceller" (Toshiba Review, Vol.

36, 隘7. P, 625-P, 630. This is well known, so I won't go into details, but in short, a signal containing a ghost component is input to a transversal filter, and the ghost component is extracted from the output of the transversal filter. The operating principle is to detect the ghost component and further input the detected ghost component to a transversal filter to cancel out the ghost component contained in the signal.

In FIG. 8, two transversal filters are used in a two-stage configuration to remove unnecessary signals (ghost components), and the reason for this will be explained below.

As is clear from the above equation (3) and FIG. 6, in order to remove the two unnecessary signals P(GQ) and PCM(GQ) with one transversal filter, that is, one set of ghost removal circuits, There are the following problems.

(1) Since the output of the synchronous detection circuit 14 does not include the video signal P, the synchronous detection circuit 1 does not contain the video signal P.
4 is the input signal of the transversal filter, the Q-axis component P (G Q
) cannot detect a ghost signal to cancel it.

(2) Video signal P and PCM Since the audio signal PCM is modulated by each of two carrier waves whose phases are orthogonal to each other, the signal amplitude generated at the output of the synchronous detection circuit 14 is
As shown in equation (3) above, there is no proportional relationship.

The reason for (1) above will be explained in detail below using FIGS. 9 and 10.

FIG. 9 shows the transversal filter 2 in FIG.
11 is a block diagram showing an example of the configuration of No. 11. FIG.

In FIG. 9, 310 is an input signal terminal, 311 is a tapped delay line, 312a to 312e are tap amplifiers, 313 is an adder, and 314a to 314e are control signals for controlling each coefficient of the tap amplifiers 312a to 312e. The input terminal 315 is an output signal terminal, which has a minute delay time.

In order to use the transversal filter 211 shown in FIG. 9 to create a signal that cancels the ghost of amplitude a and delay time τg from the desired signal shown in FIG. The desired signal shown in Figure (a) is input, and among the output signals of the tapped delay line 311, the output of the tap whose delay time is τg (if τg = nτ, the nth tap from the input terminal side) is output. Only the coefficients of the tap amplifier 312 to which the signal is supplied are set by the control signal input from the control signal input terminal 314 so that the amplitude ratio of the ghost to the desired signal (a in the case of FIG. 10 (a)) is achieved. . As a result, as shown in FIG. 10 (b), the output 315 of the adder 313 can obtain a signal whose gain is controlled to the amplitude a of the desired signal and which is delayed by the delay time τg from the desired signal. By subtracting this signal from the input signal, it is possible to obtain the signal shown in FIG. 10 (c) from which ghosts have been removed.

Therefore, the transversal filter 211 uses the desired signal to create a signal that cancels the ghost.
Even if a certain signal is input to the transversal filter 211 from only ghosts as shown in FIG. 3(c), a signal that cancels out the ghosts cannot be obtained.

Therefore, the following conditions are imposed on the configuration of the ghost removal circuit 201 shown in FIG.

(1) As an input signal to a transversal filter capable of removing the Q-axis component P (GQ) of the ghost part of the video signal, the synchronous detection circuit 202 detected with the detection axis ■ in Fig. 7 as the reference axis is used. Input the output signal Vl.

However, VI=P+, P(Gl)+PCM(Gl) −(4
) (2) Q-axis component P (G Q
) and the Q-axis component PCM (G
Q) are detected separately and independently, rather than in a mixed form, and the coefficients of each transversal filter are set.

From the above condition (1), the ghost removal circuit 2 shown in FIG.
01, the input signal of the transversal filter 210 is set to VI, which is the output signal of the synchronous detection circuit 202. Furthermore, in order to satisfy condition (2), a waveform for ghost detection shown below is created and transmitted on the transmitting side.

Generally, in order to detect the Q-axis component P (GQ) of the ghost portion of a video signal, it is necessary to detect a portion (usually 10H to 15H) of the video portion within the vertical retrace period of the television broadcast wave that does not include a teletext signal, etc. The horizontal synchronization signal of is used as a reference signal for this purpose.

Therefore, in the ghost detection circuit 212, as shown in FIG.
When using an arbitrary horizontal synchronization signal in a portion that does not include a teletext signal or the like within the vertical retrace period as shown in a) as a ghost detection reference signal, the PCM audio signal ( In order to prevent the Q-axis component PCM (qQ) of its ghost portion from being mixed with the horizontal synchronization signal as the reference signal, as shown in Fig. 11(b)
As can be seen, at least one horizontal period (approximately 63
．． During the period S corresponding to 5 μs), it is necessary to take measures on the transmitting side so as not to transmit the PCM audio signal.

As a result, the output of the subtraction circuit 214 in FIG.
Since only the PCM audio signal (PCM) and its ghost Q-axis component PCM(GQ)L are generated, the transversal filter 211 is used to remove the Q-axis component PCM(GQ) of the ghost component of the PCM audio signal. As a result, the output of the subtraction circuit 215 is a PCM audio signal (PCM
) can be restored correctly.

Note that the Q-axis component PCM (G
As a detection method for Q), the document “Waveform equalization layer for teletext broadcasting J
(Proceedings of the 1985 Television Society National Conference, P.
By using the method described in 397-P, 398), a PCM audio signal (PCM) of any period can be used as a reference signal for ghost detection.

FIG. 12 shows another configuration example of the ghost detection circuit 201. In the same figure, parts with the same numbers as in FIG.
22 is a subtraction circuit.

The ghost removal circuit 201 shown in FIG. 8 uses the output signal of the synchronous detection circuit 202 shown in FIG. 1 as the input signal of the transversal filter 210, but this signal includes contains the I-axis component P(Gl) of the ghost portion of the video signal, so the subtraction circuit 21
A grandchild ghost occurs in the output signal of No. 4.

Therefore, in the ghost removal circuit 201 shown in FIG.
To solve this problem, transversal filter 2
20, a ghost detection circuit 221 and a subtraction circuit 222 are newly provided, and these remove the I-axis component P(CI) of the ghost part of the video signal contained in the output signal of the synchronous detection circuit 202, and then the transversal input to filter 210;

As the ghost detection reference signal in the ghost detection circuit 221, the horizontal synchronization signal shown in FIG. 11 may be used.

In the above explanation, the horizontal synchronization signal in the vertical retrace period is used as the reference signal for detecting ghosts in video signals. However, the same effect can be obtained even if ghosts are detected using this signal.

〔Effect of the invention〕

As explained above, according to the present invention, a first signal obtained by amplitude modulating a first carrier wave with a video signal and a second signal whose phase is shifted by 90 degrees with respect to the first carrier wave. A multiplex transmission method that multiplexes and transmits at least a second signal obtained by amplitude modulating a carrier wave with a PCM audio signal, which eliminates the effects of ghosts that appear in reproduced PCM audio after transmission, thereby achieving high quality audio. It has the advantage of being obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the receiving side in one embodiment of the present invention, FIG. 2 is a block diagram also showing the transmitting side, FIG. 3 is a spectrum diagram of a video signal and an analog audio signal, and FIG.
The figure is a spectrum diagram of a digitized PCM audio signal, Figure 5 is a vector diagram showing the modulation state of the video signal and PCM audio signal, and Figure 6 is a waveform diagram showing the video signal, PCM audio signal, and their ghost components. , FIG. 7 is a vector diagram explaining detection using two orthogonal axes for a video signal and a PCM audio signal, FIG. 8 is a block diagram showing a specific example of the ghost removal circuit in FIG. 1, and FIG. 10 is a waveform diagram used to explain the operation of the transversal filter; FIG. 11 is a waveform diagram showing the reference signal for ghost detection used in the present invention; FIG. This figure is a block diagram showing another specific example of the ghost removal circuit in FIG. 1. Explanation of symbols 13.36...Band pass filter, 14.202...
・Synchronous detection circuit, 15...Carrier regeneration circuit, 16...
- Code identification circuit, 17... Clock regeneration circuit, 18° 35... Digital signal processing circuit, 19... Digital-to-analog conversion circuit, 37.203... 90 degree phase shifter, 34... Analog-digital conversion circuit, 38
...Modulator, 39...Adder, 210, 211, 2
20... Transversal filter, 212, 213
．． 221... Ghost detection circuit, 214, 215°2
22...Subtraction circuit agent Patent attorney Akio Namiki Figure 3 Figure 4 District 6 Figure 7 Figure i0 Figure (b) Figure 11 'r-S (Cicada 63.5 ps) →

Claims (1)

[Claims] 1. A first signal obtained by amplitude modulating a first carrier wave with a video signal and a second carrier wave whose phase is shifted by 90 degrees with respect to the first carrier wave are used as PCM audio. and a second signal obtained by amplitude modulating the video signal, the method further comprises: a second signal obtained by amplitude modulating the video signal; the first signal and the second signal are multiplexed such that the PCM audio signal is located; A multiplex transmission method characterized in that a PCM audio signal is not multiplexed so that it can be used as a reference. 2. A first signal obtained by amplitude modulating a first carrier wave with a video signal and a second carrier wave whose phase is shifted by 90 degrees with respect to the first carrier wave are amplitude modulated with a PCM audio signal. A transmitting device that multiplexes and transmits at least a second signal obtained by transmitting an input PCM audio signal, the input PCM audio signal is transmitted during the remaining period excluding a certain arbitrary specific range within the vertical retrace period of the video signal. Analog-to-digital conversion circuit (3)
4) and a digital signal processing circuit (35) that encodes the output signal from the analog-to-digital conversion circuit (34).
) and a low-pass filter (3) that removes high-frequency components contained in the output signal from the digital signal processing circuit (35).
6), a modulator (38) that amplitude-modulates the second carrier wave using a PCM audio signal that is an output signal from the low-pass filter (36) to obtain the second signal; 38). A transmitting device characterized by comprising: an adder (39) that adds and multiplexes the second signal and the first signal as an output signal from the adder (39) and outputs the multiplexed signal. 3. A first signal obtained by amplitude modulating a first carrier wave with a video signal and a second carrier wave whose phase is shifted by 90 degrees with respect to the first carrier wave are amplitude modulated with a PCM audio signal. and the obtained second signal, and the PCM audio signal is located in the remaining area excluding a certain arbitrary specific range within the vertical blanking period of the video signal. The first signal and the second signal are multiplexed, and the specific range is such that a specific signal such as a synchronization signal within the range can be used as a reference for ghost detection of the video signal. , a receiving device for multiplexed signals transmitted without multiplexing PCM audio signals, which includes a frequency conversion circuit (3) that demodulates the received multiplexed signal and converts it into an intermediate frequency; ) a bandpass filter (13) for passing within a band having both sidebands in the vestigial sideband in the output signal from the bandpass filter (13); and a bandpass filter (13) that synchronizes the output signal of the bandpass filter (13) with the first carrier wave. A carrier wave regeneration circuit (
15) and the output signal of the carrier regeneration circuit (15) at 90
a 90-degree phase shifter (203) that shifts the phase by 90 degrees; and an output signal of the 90-degree phase shifter (203)
) for synchronously detecting the output signal of the first synchronous detection circuit (14
), and a second circuit for synchronously detecting the output signal of the bandpass filter (13) using the output signal of the carrier wave regeneration circuit (15).
a synchronous detection circuit (202), and a digital PCM which receives each output signal from the first and second synchronous detection circuits (14, 202) and outputs the output signal from the first synchronous detection circuit (14). A ghost removal circuit (201) that removes a ghost component added to an audio signal, a clock recovery circuit (17) that extracts a transmission clock from an output signal from the ghost removal circuit (201), and a clock recovery circuit (201) that removes a ghost component added to an audio signal. a code identification circuit (16) that performs code identification of the output signal from the ghost removal circuit (201) using the clock output from the code identification circuit (17); and a code identification circuit (16) that performs error correction, etc. on the output signal of the code identification circuit (16). a digital signal processing circuit (18) that performs
) A digital-to-analog conversion circuit (19) that converts the output signal of the device from digital to analog. 4. In the receiving device according to claim 3, the ghost removal circuit (201) includes a first transversal filter (210) to which the output signal of the second synchronous detection circuit (202) is supplied. , a first subtraction circuit (214) that subtracts the output signal of the first transversal filter (210) from the output signal of the first synchronous detection circuit (14), and the first subtraction circuit (214). ) detects a ghost of the video signal added to the output signal of the first transversal filter (21
a first ghost detection circuit (212) that controls a coefficient of 0) to remove a ghost of the video signal added to the output signal of the first subtraction circuit (214);
A second transversal filter (211) is supplied with the output signal of the subtraction circuit (214), and the output signal of the second transversal filter (211) is supplied with the output signal of the first subtraction circuit (214). A second subtraction circuit (215) that subtracts from 211) to control the coefficients of the second subtraction circuit (
a second ghost detection circuit (215) for removing the ghost of the PCM audio signal added to the output signal of the PCM audio signal (215);
3), the first ghost detection circuit (21
In 2), the ghost of the video signal is detected based on a specific signal such as a synchronization signal within the specific range in which the PCM audio signal within the vertical blanking period of the video signal is not multiplexed. Receiving device. 5. In the receiving device according to claim 3, the ghost removal circuit (201) includes a third transversal filter (220) to which the output signal of the second synchronous detection circuit (202) is supplied. , a third subtraction circuit (222) that subtracts the output signal of the third transversal filter (220) from the output signal of the second synchronous detection circuit (202), and the third subtraction circuit (222). ) detecting a ghost of the video signal added to the output signal of
Thereby, the third transversal filter (2
20) by controlling the coefficient of the third subtraction circuit (222).
a third ghost detection circuit (221) for removing the ghost of the video signal added to the output signal of the third subtraction circuit (222); and a first transversal filter (222) that is supplied with the output signal of the third subtraction circuit (222). 210), and the output signal of the first transversal filter (210) is transmitted to the first transversal filter (210).
A first subtraction circuit (214) subtracts the signal from the output signal of the synchronous detection circuit (14), and a ghost of the video signal added to the output signal of the first subtraction circuit (214) is detected. The coefficients of the first transversal filter (210) are controlled by the first subtraction circuit (210).
14) a first ghost detection circuit (212) for removing the ghost of the video signal added to the output signal;
a second transversal filter (211) to which the output signal of the first subtraction circuit (214) is supplied;
a second subtraction circuit (215) that subtracts the output signal of the transversal filter (211) from the output signal of the first subtraction circuit (214);
) is added to the output signal of the PCM audio signal, and the coefficients of the second transversal filter (211) are controlled accordingly to the output signal of the second subtraction circuit (215). The attached PC
a second ghost detection circuit (213) that removes a ghost of the M audio signal;
A receiving device characterized in that a ghost in the video signal is detected based on a specific signal such as a synchronization signal within the specific range on which a CM audio signal is not multiplexed.