JPH07147645A - Multiplex signal processor - Google Patents

Abstract

PURPOSE:To restore 'a multiplex signal with no mistake even if the received multiplex signal has a waveform distortion, etc., by applying an orthogonal modulation system of video carriers in a standard band of the existing TV broadcast. CONSTITUTION:Both composite video and multiplex signals are transmitted from the transmitter side by an orthogonal modulation system of video carriers, and an orthogonal demodulating part 102 of the receiver side detects the synchronization of both received signals through two axes orthogonal to each other and demodulates the composite video signal and the multiplex signal separately from each other. The LPFs 103 and 104 eliminate the undesired high frequency components out of the composite video signal and the multiplex signal respectively. A waveform equalizing circuit 105 eliminates the ghosts and crosstalks out of the multiplex signal. A period setting circuit 106 sets and outputs a fixed period based on the composite video signal, and a mean value circuit 107 outputs a mean signal level in a fixed period of the multiplex signal. A delay circuit 108 delays the multiplex signal by a fixed period and outputs this delayed signal to a deciding circuit 110. Then a threshold value setting circuit 109 sets the threshold value based on the mean level of the multiplex signal, and the circuit 110 converts the multiplex signal into the digital data.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applicable to current television signals in order to achieve high image quality, high sound quality, and widen screen aspect ratio while having compatibility with current television broadcasting systems. The present invention relates to a multiple signal processing device that reproduces a multiplexed signal without error.

[0002]

2. Description of the Related Art Currently, NTSC (National Telecommunications) in Japan is
More than 30 years have passed since the color television broadcasting by the levision System Committee system was started in 1960.
Meanwhile, demands for high-definition screens, wide screens such as cinema size screens, and higher sound quality have increased, and various new television systems have been proposed to meet those demands.

The specifications of the current broadcasting are 525 scanning lines and 2: 1.
It has the specifications of interlaced scanning, luminance signal horizontal bandwidth 4.2MHz, and aspect ratio 4: 3 (see, for example, Literature Broadcasting Techniques, Bibliography, Color Television, Japan Broadcasting Corporation, Japan Broadcasting Publishing Association, 1961). Against this background, while maintaining compatibility with current broadcasting, the first generation EDTV (Enhanced EDTV) mainly has a main content such as transmission of a reference signal for the purpose of improving image quality and eliminating ghost interference. Te
levision), so-called clear vision was started in 1989.

Of these, the ghost removing reference signal, so-called GCR signal 160, is a sinX / X rising bar signal 161 and a 0IRE pedestal signal 162 as shown in FIG. 16, which are transmitted in an 8-field sequence (field number 163). To do. On the receiving side, calculation is performed according to the equation (Equation 1).

[0005]

## EQU1 ## ((F1-F5) + (F6-F2) + (F3-F7) + (F8-F4)) / 4 In this way, the sync signal and the burst are removed. If the previous line 164 has the same waveform for each field or frame, the signal of the previous line 164 is also removed. Therefore, the signal other than the sinX / X rising bar signal 161 is flat over two horizontal scanning periods, and the ghost with a delay time of up to about 45 μs can be removed.

Next, what is considered as a second-generation EDTV is a wide screen (aspect ratio 16: 9), high definition and high sound quality while maintaining compatibility with the current television broadcasting system. And so on. In particular, it is necessary to separately transmit the digitally encoded voice signal by using some kind of multiplex transmission line in order to improve the sound quality. Quadrature modulation of video carrier is considered as the multiplex transmission line (for example, refer to the document “Yasumoto et al.“ EDTV Signal System with Expandable Aspect Ratio ”) IEICE 70th Anniversary General Conference.
(Showa 62) See Proceedings Lecture No. 1174).

Quadrature modulation of the video carrier is based on the current NTSC.
This is a method for transmitting multiple signals of approximately 1 MHz while maintaining maximum compatibility with the method (for example, Abe et al., "Transmission of high-definition images by orthogonal modulation of video carrier", IEICE Technical Report CS86- 82 November 1986).

According to this method, a carrier wave orthogonal to a conventional image carrier wave is subjected to carrier suppression amplitude modulation by a multiplexed signal having a band of about 1 MHz, and the amplitude characteristic is opposite to that of a Nyquist filter of a normal television receiver with an odd symmetry. After performing band limitation with the Nyquist filter, the vestigial sideband-modulated N
It is added with the TSC signal and transmitted. When such a signal is received by an ordinary NTSC receiver, the Nyquist filter limits the band, so the multiplex signal becomes a double sideband signal, and when a synchronous detector is used, interference from the multiplex signal is not received. Absent. Therefore, compatibility can be maintained because the conventional image can be received. A digital audio signal is considered as the multiplex signal.

The quadrature modulation method of the video carrier is very excellent as a means for transmitting multiple signals while maintaining compatibility with the conventional television broadcasting method. However, due to the nature of quadrature modulation, linear or non-linear crosstalk may occur between two signals due to transmission distortion, incomplete demodulation at the receiver, or the like. Further, it is also affected by the ghost as in the conventional NTSC signal.

Therefore, it has been proposed to insert a multiplex GCR signal for ghost elimination in the vertical blanking period of the multiplex signal (see, for example, J. Hatake et al., "Waveform equalization of wide television system by quadrature modulation", 1990 TV. See Proceedings of Annual Meeting of the Society of John Lecture No. 21-9). This is because when the GCR signal 160 of the NTSC signal as shown in FIG. 17 is the 0IRE pedestal signal 162, the polarity of the multiplexed signal is inverted.
It is characterized in that the CR signal 170 is superimposed. When the multiplex GCR signal 170 of the multiplex signal is superimposed as shown in FIG. 17, the conventional ghost canceller produces the G
Since the CR signal is calculated, the sync signal and the burst are removed from the reproduced ghost removing reference signal, and the crosstalk from the multiplex signal to the NTSC main signal is also removed.
The previous line 164 is for each field (field number 163)
Alternatively, if the same waveform is used for each frame, the signal of the previous line is also removed. Therefore, sinX / X rising bar signal 161
Except for the part, the signal becomes flat over two horizontal scanning periods,
Ghosts with a delay time of up to about 45 μs can be removed. Further, there is no adverse effect on the conventional ghost canceller due to the superposition of the multiplexed GCR signal on the multiplexed signal.

A conventional example in which a transmitted multiple signal is demodulated and converted into digital data of "0" and "1" will be described below with reference to the drawings.

First, signal processing on the transmitting side will be described with reference to FIG. FIG. 7 is a block diagram showing a configuration on the transmission side of a conventional example, in which 701 is a transmission unit, 702 is a transmission antenna, and 703.
Is a multiple signal source, 704 is a composite video signal source, and 705 is a multiple GCR
Signal source, 706 is a GCR signal source, 707 is a switching control circuit, 708 and 709 are switching devices, 708 and 709 are switching devices, 710 and 711 are modulators, 712 is a carrier generation source, 713 is a 90-degree phase shifter, 714 is an inverse Nyquist filter, and 715. Is a VSB filter, and 716 is a combiner. The multiple signal source 703 has a band of 1.0 MHz and has no DC component.
This corresponds to a digitally encoded voice signal or the like. The composite video signal source 704 is an NTSC composite video signal.

The outputs of the multiple signal source 703 and the composite video signal source 704 are supplied to the multiple GCR signal source by the switch 708 and the switch 709, respectively.
705, the multiple GCR signal from the GCR signal source 706 is switched to the GCR signal. The switching control is controlled by a signal supplied from the switching control circuit 707. This is normally done only during one horizontal scanning period of the vertical blanking period.
It is controlled so that the R signal is inserted. Regarding the GCR signal of the composite video signal and the multiplex signal, G shown in FIG.
The CR signal 160 is used. The outputs of the switching devices 708 and 709 are
Quadrature modulation is performed by modulators 710 and 711, respectively. The carrier generation source 712 outputs a carrier, which is supplied to the modulator 711 and also to the 90-degree phase shifter 713. The output of the 90-degree phase shifter 713 is input to the modulator 710. With such a configuration, modulators 710 and 711 operate as quadrature modulators.

The modulated multiplexed signal and the modulated composite video signal are
After passing through the inverse Nyquist filter 714 and the VSB filter 715, respectively, they are added by the combiner 716 and become a combined modulated signal. The transmitting antenna 702 outputs the combined modulated signal.

First, a state of audio signal processing on the transmitting side will be described with reference to the drawings. FIG. 8 is a block diagram showing a configuration example of the multiple signal source 703, in which 801 is an audio source and 8
02 is an A / D converter, 803 is a digital signal processing circuit, 804
Is an adder, 805 is a delay circuit, 806 is a subtractor, 807 is a delay circuit, 808 is a D / A converter, and 809 is a multiple signal source output terminal.

The analog audio signal is output from the audio source 801, and the A / D converter 802 outputs "1" and "0".
The converted digital signal is output to the digital signal processing circuit 803. An error correction code and the like are added in the digital signal processing circuit 803 and output to the adder 804. The adder 804 performs an exclusive OR processing on the output A of the digital signal processing circuit 803 and the output B of the delay circuit 805, and outputs the output C to the delay circuits 805 and 807 and the subtractor 806. The signal input to the delay circuit 805 is delayed for a certain period and added to the adder 804.
Is output B. The signal input to the delay circuit 807 is delayed for a fixed period and output to the subtractor 806. The subtractor 806 subtracts the output data of the delay circuit 807 from the output data of the adder 804 and outputs it to the D / A converter 808. D / A converter 808
Converts an input ternary digital signal of "1", "0", "-1" into an analog signal and outputs the analog signal to the multiple signal source output terminal 809.

FIG. 9A shows "1", "0", "-1" digital signals before D / A conversion in the D / A converter 808 of FIG. With the above configuration, "0" or "-1" always appears after the data "1", and "1" does not appear continuously. FIG. 9B shows the D / A converter 8 of FIG.
The analog signal waveform after D / A conversion in 08 is typically shown. In the waveform, a flat portion or a minimum point always appears next to the maximum point, and the maximum points do not appear continuously. The output signal of the multiple signal source output terminal 809 is a signal having no DC component due to the above processing. The audio signal converted into an analog signal by the above configuration is output from the multiple signal source 703 in the transmitting unit 701 shown in FIG. The signal output from the multiplex signal source 703 is added with a multiplex GCR signal for ghost removal in the transmitting unit 701, then quadrature-modulated and transmitted from the transmitting antenna 702 together with the composite video signal.

Next, the signal processing on the receiving side will be described. FIG. 10 is a block diagram showing the configuration of the receiving side in the conventional example. In the figure, 101 is a receiving antenna, 102 is a quadrature demodulation unit, 103 and 104 are low-pass filters, 105 is a waveform equalizing circuit, 110 is a judging circuit, 1001 is a threshold setting circuit, and 111 is a multiple signal output terminal.

When the transmitted signal is received by the antenna 101, the orthogonal demodulation unit 102 synchronously detects the signal received by the antenna 101 on two orthogonal axes, and separates and demodulates the composite video signal and the multiplex signal. The low-pass filter 103 removes unnecessary high frequency components from the composite video signal and outputs it to the waveform equalization circuit 105. The low-pass filter 104 removes unnecessary high-frequency components from the multiplexed signal and outputs it to the waveform equalization circuit 105. The outputs of the low-pass filters 103 and 104 are input to the waveform equalization circuit 105. Then, the linear crosstalk from the composite video signal to the multiplex signal and the ghost of the multiplex signal are removed, and the determination circuit 110
Output to. The threshold setting circuit 1001 sets two different thresholds U and L which are constant in time, and the determination circuit 11
Output to 0. The determination circuit 110 compares the input multiple signal with the threshold value U and the threshold value L, and outputs “0”,
Converted to digital data of "1" and multiplexed signal output terminal
Output to 111.

The quadrature demodulator 102 will be described below.
FIG. 11 is a block diagram showing the configuration of the quadrature demodulation unit 102, in which 1101 is a tuner, 1102 is a Nyquist filter, 1103 is a bandpass filter, 1104 and 1105 are demodulators,
Reference numeral 1106 is a 90-degree phase shifter, 1107 is a carrier wave reproducing circuit, 1108 is a composite video signal output terminal, and 1109 is a multiple signal output terminal.

The synthesized modulated signal transmitted is an antenna
Received at 101 and sent to tuner 1101. The output of the tuner 1101 is converted to the Nyquist filter 1102 and the bandpass filter 1103.
To enter both. The signal that has passed through the Nyquist filter 1102 is demodulated by the demodulator 1104. On the other hand, the signal that has passed through the bandpass filter 1103 is demodulated by the demodulator 1105. In this case, the demodulators 1104 and 1105 are supplied with carrier waves having an orthogonal relationship with each other. That is, the carrier recovery circuit 11
07 reproduces the carrier wave from the output of the Nyquist filter 1102 and supplies it to the demodulator 1104 and the 90 degree phase shifter 1106. Here, the carrier wave reproduced by the carrier wave reproduction circuit 1107 is 90 degrees out of phase with the carrier wave. To generate. The demodulated composite video signal is output to the composite video signal output terminal 1108. On the other hand, the demodulated multiplexed signal is the multiplexed signal output terminal 1109.
Is output to.

Next, the waveform equalizer circuit 105 will be described. FIG. 12 is a block diagram showing the configuration of the waveform equalizer circuit 105. In the figure, 1201 is a composite video signal input terminal and 1202 is a multiple signal input terminal. , 1203 and 1204 are transversal filters, 1205 is a GCR detector, 1206 and 1207 are multiple GCR detectors, 1208 is a coefficient calculation circuit, 1209 is a reference signal generator, 12
Reference numeral 10 is an adder, and 1211 is an output terminal after waveform equalization.

The transversal filter 1203 inputs the composite video signal input from the composite video signal input terminal 1201 and the coefficient output from the coefficient calculation circuit 1208, and has a signal having a characteristic opposite to the crosstalk from the composite video signal to the multiplexed signal. Is generated and output. On the other hand, the transversal filter 1204 inputs the multiplex signal input from the multiplex signal input terminal 1202 and the coefficient output from the coefficient calculation circuit 1208, and outputs a signal obtained by removing the ghost from the multiplex signal.

The GCR detector 1205 extracts the GCR signal from one horizontal scanning period in a predetermined vertical blanking period, performs the calculation shown in (Equation 1), and obtains the waveform of FIG. 13 (a). The one-pixel difference is output to the coefficient calculation circuit 1208. The waveform output to the coefficient calculation circuit 1208 is shown in FIG. 13 (b). Multiple GCR
When the signal detectors 1206 and 1207 extract multiple GCR signals from one horizontal scanning period in a predetermined vertical blanking period and extract crosstalk from the composite video signal to the multiple signals,
The calculation shown in (Equation 1) is performed to obtain the waveform of FIG.
The one-pixel difference of this waveform shown in (d) is calculated by the coefficient calculation circuit 1208.
Output to. FIG. 13D shows a waveform of only crosstalk from the composite video signal to the multiplex signal. When extracting a ghost signal of multiple signals, the calculation shown in the equation (2) is performed.

[0025]

## EQU2 ## (F2-F4 + F5-F7) / 4 The multiplex GCR signal detectors 1206 and 1207 perform the calculation shown in (Equation 2) and output the waveform of FIG. 13 (e) to the coefficient calculation circuit 1208. When removing the crosstalk, the coefficient calculation circuit 1208 uses the output of the GCR detector 1205 and the outputs of the multiple GCR signal detectors 1206 and 1207 to remove the crosstalk from the composite video signal to the multiple signal. Is calculated and output to the transversal filter 1203. When removing the ghost of the multiplexed signal, the multiplexed GCR signal detector 12
Using the outputs of 06 and 1207 and the output of the reference signal generator 1209,
A coefficient for ghost removal of the multiplex signal is calculated and output to the transversal filter 1204. The adder 1210 adds the outputs of the transversal filters 1203 and 1204 and outputs a signal obtained by removing ghosts from the multiplexed signal and crosstalk from the composite video signal to the output terminal 1211 after waveform equalization.

Next, the threshold value setting circuit 1001 shown in FIG.
Sets two different thresholds that are constant over time. For distinction, one of the two thresholds having a higher signal level is referred to as a threshold U, and the one having a lower signal level is referred to as a threshold L. The threshold setting circuit 1001 outputs the threshold U and the threshold L to the determination circuit 110.

Next, the decision circuit 110 shown in FIG. 10 has a threshold value setting circuit 1 and the multiplexed signal input from the waveform equalization circuit 105.
The magnitudes of the threshold U and the threshold L, which are input from 001 and are constant in time, are compared. That is, at the identification point of the code, the data (maximum point of the waveform) larger than the threshold value U at the boundary of the threshold value U is judged as "1", and the threshold value L
The data (local minimum point) smaller than the threshold value L is judged to be "1" with the boundary as the boundary, and the data which is neither larger than the threshold value U nor smaller than the threshold value L is judged to be "0". Figure
Reference numeral 14 (a) shows how the input multiplexed signal is compared with the threshold U and threshold L set by the threshold setting circuit 1001. The relationship of each signal level at the identification point of the code when the correct judgment is made is as shown in the equation (3).

[0028]

## EQU3 ## Minimum point <threshold value L <threshold value U <maximum point As a result, the multiplexed signal is converted into a binary data string of "1" and "0" by the decision circuit 110 shown in FIG. It is output to the multiplexed signal output terminal 111. FIG. 14B shows a multiplexed signal converted into binary digital data of "1" and "0".

[0029]

The above-described quadrature modulation of the video carrier is very excellent as a means for transmitting multiple signals while maintaining compatibility with the conventional television broadcasting system. However, due to the nature of quadrature modulation, crosstalk from the composite video signal to the multiplex signal may occur due to transmission distortion, incomplete demodulation in the receiver, or the like.
Further, it is also affected by the ghost as in the conventional NTSC signal. Due to these crosstalks or ghosts,
Distortion may occur in the waveform of the received multiplex signal, which may hinder the multiplex signal reproduction.

For this reason, the waveform equalizing circuit 105 as shown in FIGS. 10 and 12 may be provided on the receiving side as in the conventional example. The waveform equalizing circuit 105 removes a ghost of a multiplexed signal and crosstalk from the composite video signal to the multiplexed signal. However, even when the waveform equalization circuit is provided, there is a problem that the waveform of the received multiplexed signal is distorted. This problem will be described below.

In quadrature modulation of the video carrier, crosstalk having a non-linear component may occur from the composite video signal to the multiplex signal due to the influence of the non-linear characteristic in the transmission system. However, the above-mentioned configuration of the waveform equalizing circuit has a problem that it is not possible to remove the non-linear component of the crosstalk from the composite video signal to the multiplex signal. Further, depending on the removal performance of the waveform equalization circuit, crosstalk from the composite video signal having a high frequency component or a large amplitude component to the multiplex signal may remain without being removed. Due to these various causes, distortion occurs in the multiple signal waveform. As a result, the quality of digital voice may be deteriorated.

FIG. 15 shows how erroneous digital data is reproduced when the multiple signal waveform is distorted in the conventional receiving side configuration. FIG. 15 (a) shows the state of the distortion component of the multiplexed signal whose signal level has increased during the period from time t1 to time t2. As a cause of this, crosstalk from the composite video signal which cannot be completely removed by the waveform equalization circuit 105 to the multiplex signal, etc. can be considered. FIG. 15B shows how the waveform of the multiple signal having the distortion component shown in FIG. 15A is compared with the threshold values U and L. Here, the signal level of the multiplexed signal is high during the period from time t1 to time t2.
On the other hand, the two different threshold values U and L are temporally constant. That is, in the case of FIG. 15B, time t1
From t2 to t2, the relationship of each signal level at the code identification point is as shown in the equation (4).

[0033]

## EQU00004 ## Threshold value L <minimum point <threshold value U <maximum point When the multiplexed signal waveform of FIG. 15 (b) is maximum or minimum at the code identification point, the determination result is originally "1". Should be judged. FIG. 15 (c) shows the comparison determination result.
"0" is the point that should be judged as "1" during the period from time t1 to t2.
There are several erroneous decisions. This is because the signal level of the multiplex signal is distorted only during the period from time t1 to time t2, and the minimum point that should originally be determined as "1" becomes higher than the threshold value L. As described above, in the above-described conventional configuration in which the multiplexed signal is compared with the threshold value which is constant in time, when the signal level of the multiplexed signal varies due to distortion or the like, an error may occur in the reproduced data.

The present invention solves the above-mentioned conventional problems and is an apparatus for removing crosstalk from a composite video signal to a multiplex signal and restoring a new multiplex signal within the band defined by the NTSC transmission standard without error. The purpose is to provide.

[0035]

In order to solve the above problems and to achieve the object, the first means of the present invention is a period setting means for setting a fixed period from a composite video signal in a quadrature modulation system of a video carrier. An average value means for obtaining an average signal level of the multiplexed signal after waveform equalization in a certain period, a delay means for delaying the multiplexed signal after waveform equalization for a certain period and outputting the signal, and an output from the average value means. A threshold value setting means for setting and outputting a threshold value, and a judging means for comparing the output of the delay means with the output of the threshold value setting means and converting the multiplexed signal into digital data for output. Is.

A second means is a period setting means for setting a constant period from the composite video signal in an orthogonal modulation method of a video carrier, and an average value for obtaining an average signal level of the multiplexed signal after waveform equalization in the constant period. Means, delaying means for delaying the multiplexed signal after waveform equalization for a fixed period to output the signal, a period for obtaining an average signal level of the multiplexed signal by the averaging means, and output of the delaying means Subtracting means for subtracting the output, threshold setting means for setting and outputting a threshold value, output of the subtracting means and output of the threshold setting means are compared to convert the multiplexed signal into digital data. And a determination means for outputting the output.

[0037]

In the first means of the present invention, the period setting means sets a fixed period from the composite video signal, the average value means obtains the average signal level of the multiplexed signal in the fixed period, and the average value means makes the multiplexed signal. During the period for obtaining the average signal level, the multiplexed signal after waveform equalization is delayed for a certain period by the delay means, and the threshold value setting means sets a threshold value according to the average signal level of the multiplexed signal. The comparison between the output and the threshold value set by the threshold value setting means by the judging means is such that even if the average signal level fluctuates due to the distortion of the waveform of the multiplexed signal, the threshold corresponding to the fluctuation. Since the value and the multiple signal are compared, they can be correctly converted into digital data.

Further, in the above-mentioned second means of the present invention,
A period is set from the composite video signal by the period setting means, an average signal level of the multiplex signal is obtained by the average value means, and an average signal level of the multiplex signal is obtained by the average value means, after waveform equalization. The multiplex signal is delayed by the delay means for a certain period of time, the subtraction means outputs a signal obtained by subtracting the output of the average value means from the output of the delay means, the threshold value setting means sets a threshold value, and the subtraction means The comparison between the output and the threshold value set by the threshold value setting means is to cancel the fluctuation amount by the subtraction means even when the average signal level fluctuates due to the distortion of the waveform of the multiplexed signal. , Can be correctly converted to digital data.

[0039]

First Embodiment Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of a multiple signal processing apparatus according to the first embodiment of the present invention.
6 is a period setting circuit, 107 is an average value circuit, 108 is a delay circuit, 1
Reference numeral 09 denotes a threshold value setting circuit, and the other same constituent elements as those in FIG. 10 are designated by the same reference numerals and the description thereof will be omitted.

The mutual relation and operation of each component will be described.
The transmitted composite modulated signal is received by the antenna 101, and the orthogonal demodulation unit 102 separates and demodulates the composite video signal and the multiplexed signal. The low-pass filter 104 outputs a signal from which unnecessary high frequency components outside the band of the multiplexed signal are removed to the waveform equalization circuit 105. The low-pass filter 103 outputs a signal from which unnecessary high frequency components of the composite video signal are removed to the waveform equalization circuit 105. The waveform equalization circuit 105 outputs a signal obtained by removing the ghost of the multiplex signal of the crosstalk from the composite video signal to the multiplex signal to the average value circuit 107 and the delay circuit 108. The period setting circuit 106 sets a fixed period from the composite video signal and outputs it to the average value circuit 107. The average value circuit 107 calculates the average signal level of the multiplexed signal after waveform equalization in a certain period and outputs it to the threshold value setting circuit 109. The delay circuit 108 delays the waveform-equalized multiplex signal during the period in which the average value circuit 107 obtains the average signal level of the multiplex signal for a certain period, and outputs the delayed signal to the determination circuit 110. The threshold value setting circuit 109 sets a threshold value based on the average signal level of the input multiplexed signal and outputs it to the determination circuit 110. Judgment circuit 110 converts the multiplexed signal into digital data based on the threshold value and outputs the multiplexed signal.
Output to 111.

The manner in which the multiplex signal is restored will be described in detail. The received multiplex signal is demodulated by the quadrature demodulation unit 102 separately from the composite video signal. Subsequently, the waveform equalization circuit 105 removes the crosstalk from the composite video signal to the multiplex signal and the ghost of the multiplex signal, and outputs.
Now, a case will be described in which the waveform equalization circuit 105 has a limited removal performance, and a ghost or the like remains as a distortion component in the multiplexed signal. FIG. 5 is a waveform diagram for explaining the operation of FIG. 1. As an example, it is assumed that a distortion component having a shape in which the signal level rises during the period from time t1 to t2 as shown in FIG. 5A remains.
FIG. 5B shows a state of the multiplexed signal waveform after the waveform equalization having the distortion component shown in FIG. That is, time t1
It shows a multiple signal waveform having a shape in which the signal level rises during the period from t2 to t2. It is assumed that a flat portion or a minimum point always appears next to the maximum point in the multiple signal waveform, and the maximum points do not appear continuously. Period setting circuit
An average value circuit 106 sets a period T from the composite video signal.
Output to. The average value circuit 107 obtains the average level of the signal over the period T of the multiplex signal waveform shown in FIG.
Output to the threshold setting circuit 109. The average signal level is updated every period T. This state is shown in FIG. The threshold value setting circuit 109 sets two different threshold values according to the average signal level and outputs them to the determination circuit 110. For the sake of distinction, the high threshold of the signal level is U and the low threshold is L. The threshold U and the threshold L are updated every period T according to the fluctuation of the average signal level obtained over the period T of the multiplex signal waveform. The delay circuit 108 delays the multiplexed signal after waveform equalization for a period of T and outputs the delayed signal to the determination circuit 110. FIG. 5 (d) shows a state of comparison between the multiple signal waveform and the threshold value U and the threshold value L in the determination circuit 110.
Unlike the conventional example in which the threshold value is constant over time, the threshold value U and the threshold value L are set according to the fluctuation of the average level of the multiplexed signal. The threshold U and the threshold L are
It falls within the range between the maximum and minimum points of the multiple signal waveform.
Therefore, in the case of FIG. 5D, the relationship between the signal levels is

[0043]

## EQU5 ## The minimum point <threshold value L <threshold value U <maximum point is satisfied, and the judgment circuit 110 makes a correct judgment. That is, the determination circuit 110 determines that at the identification point of the code, data that is larger than the threshold U (maximum point) with the threshold U as the boundary.
Is judged as "1", and the threshold L
Smaller data (minimum point) is judged as "1", and data which is neither larger than the threshold value U nor smaller than the threshold value L is judged as "0". The digital data after the determination is output from the multiple signal output terminal 111.

As a result of the above, according to the present embodiment, even if distortion occurs in the multiple signal waveform, it is effective in converting into digital data without error at the code identification point.

(Second Embodiment) A second embodiment of the present invention will be described below with reference to the drawings. The second embodiment is almost the same as the first embodiment, and the detailed description of the overlapping points will be omitted.

FIG. 2 is a block diagram showing the configuration of a multiple signal processing apparatus according to the second embodiment of the present invention, in which 201 is a subtracting circuit and 202 is a threshold setting circuit, and the other configurations are the same as those in FIG. The elements are given the same numbers and their explanations are omitted.

The mutual relation and operation of each component will be described.
From the process of receiving the transmitted composite modulated signal by the antenna 101, the signal from which the crosstalk from the composite video signal to the multiplex signal and the ghost of the multiplex signal are removed by the waveform equalization circuit 105, the average value circuit 107 and the delay The processing up to the output to the circuit 108 is the same as in the case of the first embodiment already described. The period setting circuit 106 sets a certain period from the composite video signal and outputs it to the average value circuit 107. The average value circuit 107 calculates the average signal level of the multiplexed signal after waveform equalization in a certain period and outputs it to the subtraction circuit 201. The delay circuit 108 delays and subtracts the multiplexed signal after the period waveform equalization in which the average value circuit 107 obtains the average signal level in the fixed period of the multiplexed signal.
Output to 201. The threshold setting circuit 202 sets an input threshold and outputs it to the determination circuit 110. The determination circuit 110 converts the multiplexed signal into digital data based on the threshold value and outputs it to the multiplexed signal output terminal 111.

The manner in which the multiplex signal is restored will be described in detail. The received multiplex signal is demodulated by the quadrature demodulation unit 102 separately from the composite video signal. Subsequently, the waveform equalization circuit 105 removes the crosstalk from the composite video signal to the multiplex signal and the ghost of the multiplex signal, and outputs.
Now, a case will be described in which the waveform equalization circuit 105 has a limited removal performance, and a ghost or the like remains as a distortion component in the multiplexed signal. FIG. 6 is a waveform diagram for explaining the operation of FIG. 2. As an example, it is assumed that a distortion component having a shape in which the signal level rises during the period from time t1 to t2 as shown in FIG. 6A remains.
FIG. 6B shows the state of the multiple signal waveform after the waveform equalization having the distortion component shown in FIG. That is, time t1
It shows a multiple signal waveform having a shape in which the signal level rises during the period from t2 to t2. It is assumed that a flat portion or a minimum point always appears next to the maximum point in the multiple signal waveform, and the maximum points do not appear continuously. Period setting circuit
An average value circuit 106 sets a period T from the composite video signal.
Output to. The average value circuit 107 obtains the average level of the signal over the period T of the multiplex signal waveform shown in FIG.
Output to the subtraction circuit 201. The average signal level is updated every period T. This state is shown in FIG. Delay circuit 108
Is a subtraction circuit 20 that delays the multiplexed signal after waveform equalization for a period of T
Output to 1. The subtraction circuit 201 subtracts the output of the average value circuit 107 from the output of the delay circuit 108, and outputs it to the determination circuit 110.
Therefore, even if the average signal level changes due to waveform distortion or the like, the subtraction circuit 201 cancels the change. Therefore, the amplitude of the multiplexed signal is always kept within a substantially constant range. The threshold value setting circuit 202 sets two different threshold values and outputs them to the determination circuit 110. For the sake of distinction, the high threshold of the signal level is U and the low threshold is L. The threshold U and the threshold L are constant with time. FIG. 6D shows how the multiple signal waveform in the decision circuit 110 is compared with the threshold value U and the threshold value L. The determination circuit 110 sets the data (maximum point) larger than the threshold U as a boundary at the code identification point to "1".
And the data smaller than the threshold L (minimum point) with the threshold L as the boundary is judged as “1”, and the data which is not larger than the threshold U and not smaller than the threshold L is judged. Judge as "0". As shown in FIG. 6D, even if the multiplex signal waveform is distorted and the average signal level fluctuates, the amplitude of the multiplex signal is always kept within a substantially constant range. Therefore, the maximum point and the minimum point of the waveform have a relationship satisfying the equation (6) at the identification point of the code.

[0049]

## EQU6 ## Minimum point <threshold value L <threshold value U <maximum point The digital data after the determination is output from the multiple signal output terminal 111.

As a result, according to the present embodiment, it is effective to convert the digital signal into the digital data without error at the code identification point even when the multiple signal waveform is distorted.

In the first and second embodiments, the average value circuit 107 may have the configuration shown in FIG.
In FIG. 3, 301 is a multiplexed signal input terminal after waveform equalization, 302
Is an integration period input terminal, 303 is an integrator, 304 is a multiplier, 305
Is an average signal level output terminal.

The operation of this configuration will be described. The multiplexed signal after waveform equalization is input to the integrator 303 from the multiplexed signal after waveform equalization input terminal 301. Integration period T is the integration period input terminal 3
Input from 02 to the integrator 303 and the multiplier 304. Integrator
303 integrates the multiplexed signal input from the multiplexed signal input terminal after waveform equalization 301 over the period T input from the integration period input terminal 302, and multiplies the integrated value for each period T by a multiplier 304.
Output to. The multiplier 304 calculates the average signal level by multiplying the input integral value by the reciprocal 1 / T of the integration period, and outputs the average signal level to the average signal level output terminal 305.

Further, under the condition that no ghost is generated in the multiplex signal and crosstalk from the composite video signal to the multiplex signal is not generated, in FIG. 1 of the first embodiment or FIG. 2 of the second embodiment. The waveform equalizing circuit 105 and the low-pass filter 103 are unnecessary, and the configuration shown in FIG. 4 (a) or 4 (b) is obtained. Even in this configuration example, correct digital data can be reproduced as in the above case.

[0054]

As described above, according to the first aspect of the present invention, in the restoration of the multiplexed signal by the orthogonal modulation method of the video carrier, the period setting means sets a fixed period, and the average value means makes the multiplexed signal constant. The average signal level in the period is obtained, and the average signal means obtains the average signal level of the multiplexed signal. The period-waveform-equalized multiplexed signal is delayed by the delay means, and the threshold setting means responds to the average signal level of the multiplexed signal. When a threshold value is set and the output of the delay means and the threshold value set by the threshold value setting means are compared by the judging means, the average signal level fluctuates due to distortion of the waveform of the multiplexed signal. However, since the threshold value according to the fluctuation is compared with the multiplexed signal, it is possible to correctly convert the digital data.

Further, according to the second invention, in the restoration of the multiplexed signal by the quadrature modulation method of the video carrier, the period setting means sets a fixed period, and the averaging means sets the average signal level in the fixed period of the multiplexed signal. Obtain the average signal level of the multiplexed signal by the average value means, delay the multiplexed signal after the period waveform equalization by the delay means, and output the signal obtained by subtracting the output of the average value means from the output of the delay means by the subtraction means, Setting the threshold value by the threshold value setting means and comparing the output of the subtraction means with the threshold value set by the threshold value setting means means that the average signal level varies due to distortion of the waveform of the multiplexed signal. Even if it occurs, the subtraction means cancels the variation, so that the digital data can be correctly converted.

In any of the first and second aspects of the present invention, it is possible to more accurately restore the multiplexed signal in the same band as the conventional one.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a multiplex signal processing device according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a multiplex signal processing device according to a second embodiment of the present invention.

FIG. 3 is a block diagram showing a configuration of an embodiment of the average value circuit shown in FIGS. 1 and 2 in the present invention.

4 is a waveform equalization circuit 105 and a low pass filter 103 of FIG.
Block diagram showing the configuration of a multiplex signal processing device with the omission of
(a), the waveform equalizing circuit 105 and the low-pass filter 103 of FIG.
Block diagram showing the configuration of a multiplex signal processing device with the omission of
It is (b).

5A and 5B are waveform diagrams for explaining the operation of FIG. 1, where FIG. 5A is a diagram showing a distortion component of a multiplexed signal, FIG. 5B is a diagram showing a waveform of a distorted multiplexed signal, and FIG. Figure showing average signal level,
(d) is a diagram showing a comparison between a multiplexed signal and a threshold value.

6A and 6B are waveform diagrams for explaining the operation of FIG. 2, where FIG. 6A is a diagram showing a distortion component of a multiplexed signal, FIG. 6B is a diagram showing a waveform of a distorted multiplexed signal, and FIG. Figure showing average signal level,
(d) is a diagram showing a comparison between a multiplexed signal and a threshold value.

FIG. 7 is a block diagram showing a configuration of a transmission side of a conventional example.

8 is a block diagram showing a configuration example of a multiple signal source 703 of FIG.

9 is a diagram showing an example (a) of a multiplexed signal before D / A conversion and an example (b) of a multiplexed signal after D / A conversion in the D / A converter 808 of FIG.

FIG. 10 is a block diagram showing a configuration of a receiving side of a conventional example.

11 is a block diagram showing a configuration of a quadrature demodulation unit 102 in FIG.

12 is a block diagram showing a configuration of a waveform equalization circuit 105 of FIG.

13A and 13B are waveform diagrams illustrating the operation of each block in FIG. 12, where FIG. 13A is a diagram showing a GCR signal and FIG.
FIG. 3 is a diagram showing pixel differences, (c) is a diagram showing crosstalk of GCR signals appearing in multiplex signals, (d) is a diagram showing one-pixel differences in multiplex signals, and (e) is a diagram showing multiplex GCR signals. .

14A and 14B are waveform diagrams illustrating the operation of the threshold value setting circuit 1001 in FIG. 10, where FIG. 14A is a diagram showing a comparison between a multiplexed signal and a threshold value, and FIG. 14B is binary digital data after judgment. It is a figure which shows the multiplexed signal of a column.

FIG. 15 is a waveform diagram illustrating a case where erroneous digital data is reproduced when distortion occurs in the configuration of the conventional receiving unit, (a) is a diagram showing a distortion component of a multiplexed signal, and (b) is a diagram. FIG. 7 is a diagram showing a comparison between a multiplex signal and a threshold value, and FIG. 7C is a diagram showing a multiplex signal of a binary digital data string after determination.

FIG. 16 is a diagram showing a current GCR signal.

FIG. 17 is a diagram showing a current GCR signal and multiple GCR signals.

[Explanation of Codes] 101 ... Receiving antenna, 102 ... Quadrature demodulating section, 103, 104 ...
Low-pass filter, 105 ... Waveform equalization circuit, 106 ... Period setting circuit, 107 ... Average value circuit, 108 ... Delay circuit, 10
9, 202 ... Threshold setting circuit, 110 ... Judgment circuit, 111 ...
Multiple signal output terminal, 201 ... Subtraction circuit, 303 ... Integrator.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication location H04N 7/081 (72) Inventor Akira Kisoda 1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric Industrial Co., Ltd. (72) Inventor Yasuyo Ogata 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Kenichiro Hayashi, 1006 Kadoma, Kadoma City, Osaka Prefecture (72) Inventor, Handa Koji Osaka Prefecture Kadoma City 1006 Kadoma, Matsushita Electric Industrial Co., Ltd. (72) Inventor Yoshio Yasumoto Osaka Kadoma City, Kadoma 1006 Matsushita Electric Industrial Co., Ltd.

Claims (4)

[Claims] 1. A signal in which a first video carrier is amplitude-modulated by vestigial sideband with a composite video signal and a signal in which a second carrier orthogonal to the first video carrier is amplitude-modulated by carrier suppression with a multiplex signal. Quadrature demodulation means for receiving the combined signal, synchronously detecting the combined signal in two orthogonal axes, and separating and demodulating the composite video signal and the multiplexed signal; and an unnecessary high frequency component from the demodulated composite video signal. , A first low-pass filter that outputs a first signal from which the signal is removed, a second low-pass filter that outputs a second signal from which unnecessary high-frequency components have been removed from the demodulated multiplexed signal, and the first low-pass filter Waveform output and the output of the second low-pass filter as input, a waveform equalizing means for outputting a waveform equalized signal, and a period setting means for setting and outputting a fixed period from the demodulated composite video signal. A mean value means for inputting the output of the period setting means and the output of the waveform equalizing means to obtain an average signal level of the output of the waveform equalizing means for a certain period and outputting the average signal level; Delay means for outputting a signal whose output is delayed for a certain period, threshold setting means for outputting at least one threshold value based on the output of the average value means, output of the delay means and the threshold value A multiple signal processing device, comprising: a determining means for converting the data into digital data based on the output of the setting means. 2. A signal obtained by subjecting a first video carrier wave to a vestigial sideband amplitude modulation with a composite video signal, and a signal obtained by subjecting a second carrier wave orthogonal to the first video carrier wave to a carrier suppression amplitude modulation with a multiplex signal. Quadrature demodulation means for receiving the combined signal, synchronously detecting the combined signal in two orthogonal axes, and separating and demodulating the composite video signal and the multiplexed signal; and an unnecessary high frequency component from the demodulated composite video signal. , A first low-pass filter that outputs a first signal from which the signal is removed, a second low-pass filter that outputs a second signal from which unnecessary high-frequency components have been removed from the demodulated multiplexed signal, and the first low-pass filter Waveform output and the output of the second low-pass filter as input, a waveform equalizing means for outputting a waveform equalized signal, and a period setting means for setting and outputting a fixed period from the demodulated composite video signal. A mean value means for inputting the output of the period setting means and the output of the waveform equalizing means to obtain an average signal level of the output of the waveform equalizing means for a certain period and outputting the average signal level; Delay means for outputting a signal obtained by delaying the output for a fixed period, subtraction means for outputting a signal obtained by subtracting the output of the delay means from the output of the average value means, and threshold for outputting at least one threshold value A multiplex signal processing device comprising: setting means; and determination means for converting the output of the subtraction means and the output of the threshold value setting means into digital data. 3. The waveform equalizing means uses an output of the first low-pass filter as a first input signal and an output of a second low-pass filter as a second input signal, and outputs the first input signal from the first input signal. 3. The multiplex signal processing apparatus according to claim 1, wherein at least one of crosstalk to two input signals and a ghost of the second input signal is output to output a waveform equalized signal. 4. The average value means is composed of an integrating means for integrating and outputting the multiplexed signal, and a multiplying means for multiplying the output of the integrating means by the reciprocal of the integration interval and outputting the result. 1. The multiple signal processing device according to 1 or 2.