JPS62265867A - Reference signal generator for removing ghost - Google Patents

Abstract

PURPOSE:to remove delay a ghost behind>=1/2 a horizontal period, and to remove the ghost up to the area of a pivides signal component by overlapping a television signal with a digital signal string and a pulse system signal as a ghost removal reference signal. CONSTITUTION:The reference signal generation circuit 1 for removing the first ghost generates the digital signal storing, and the reference signal generation circuit 2 for removing the second ghost generates the pulse system signal, for example. A signal overlapping circuit 4 overlaps output signals from the circuits 1 and 2 with the vertical blanking interval of the television signal according to the output from a switching control circuit 5. An error signal string generation circuit 22 in a ghost removal device chooses the digital signal string which si the reference signal from the television signal outputted from a transversal filter 20, and generates an error signal string as a difference from a corresponding and expected signal storing. A control circuit 21 controls the transversal filter 20 by using an algorithm such as a least square error method, and minimizes the error signal storing.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a reference signal generation WZ for ghost removal for removing group delay distortion, single frequency amplitude characteristic distortion, ghost, etc. that occur during the transmission of television signals. It is.

2. Description of the Related Art Conventionally, as the most effective means for removing ghosts generated during transmission of television signals, there is a ghost removal device using a transversal filter as shown in FIG. In this method, the transmission system that generates ghosts is regarded as one filter, and the transversal filter creates a filter characteristic that is the inverse of the transmission system to eliminate ghosts.

The most important point in a ghost removal device using this transversal filter is the reference signal for estimating the filter characteristics of the transmission system. Vertical direction as this reference signal! A differential signal of the leading edge of the III signal was used. (Reference: Two Ohnishi et al., Automatic Ghost Removal from Television Images, NHK Giken Monthly Report, 1975) The conventionally used reference signal will be explained with reference to FIG. 9 and FIG. 1O. In Figure 9, 100
is the leading edge of the vertical synchronization signal, 101 is a ghost, and 102 is a vertical equalization pulse. The ghost 101 is a delayed version of the leading edge 100 of the vertical sync signal. FIG. 10 shows a signal waveform obtained by subtracting the leading edge portion 100 of the vertical synchronization signal and the ghost 101. In synchronization, 103 is a difference signal of the vertical synchronization signal leading edge 100, 104 is a ghost 10
This is a difference signal of 1. Difference signal 1 of the leading edge of the vertical synchronization signal
A difference signal 104 between 03 and the ghost indicates an impulse response of the transmission system, and is used to remove the ghost.

The problem with conventionally using a vertical synchronization signal as a reference signal for ghost removal is that the signal quality of the synchronization signal of the television signal is guaranteed by parameters indicating the signal quality of the video signal, such as DC and DP. This is something that has not been done. Furthermore, the synchronization signal portion of a television signal subjected to RF signal modulation has the highest signal power and is susceptible to nonlinear distortion. Therefore, the correlation between waveform distortion between the video signal and the synchronization signal due to ghosts and the like is not perfect, and when the leading edge of the vertical synchronization signal is used as a reference signal for ghost removal, it is difficult to sufficiently remove ghosts.

Therefore, the Japan Broadcasting Corporation has proposed a ghost removal reference signal (GCR) as shown in FIG. (Reference: Obara et al., A study of reference waveforms for ghost removal T
In the figure, 110 is a bar signal, 111 is a pulse signal, 112 is a color burst, and 113 is a horizontal synchronization signal. Pulse signal 111 is used to estimate the impulse response of the transmission system. Further, the bar signal 110 is used to detect the occurrence of sag by the transversal filter.

Furthermore, as another proposal, a ghost removal reference signal (OCR) as shown in FIG. 3 has been proposed.

(Reference document: Japanese Patent Application No. 6O-15 (i458) Problems to be Solved by the Invention As reference signals for ghost removal, as mentioned above, the vertical equivalent signal, the signal shown in Fig. 3, and the signal shown in Fig. 11 are used. Among these, the use of a vertical synchronization signal is inappropriate because its ghost removal ability is insufficient, as mentioned above, and it is necessary to insert a reference signal for ghost removal within the vertical retrace period. be.

The signal in Figure 11 and the signal in Figure 3 each have their advantages.

It is thought that it has some drawbacks.

For example, in FIG. 11, the pulse signal 111 is required to have a pulse equivalent to 1.5T pulse (half width: 187.5 ns) in order to sufficiently remove ghosts. (Reference: Obara et al., System Study of Adapter Type Ghost Canceller, TV Science and Technology Journal, 1752-1, 1972.
2) In the case of such a pulse signal, it is difficult to obtain information for correcting proximity ghosts, group delay distortion, frequency amplitude characteristic distortion, etc., which are problems in teletext broadcasting. This is because the impulse response to the transmission distortion is expressed as a collection of many pulses in the vicinity of the original pulse. This is because it is difficult to separate the latter pulse from the original pulse.

Also, since it is a single pulse, its signal power is small;
It was easily affected by noise.

Furthermore, when using the pulse signal shown in Fig. 11, for ghosts delayed by 1/2 horizontal period or more, it is difficult to determine whether the delayed signal is due to the reference signal or whether another signal is delayed. It is not possible to determine whether

On the other hand, when using a digital signal train, the signal has higher power than a single pulse signal, and the advantage is that it is also possible to remove ghosts with a delay longer than 1/2 horizontal period using correlation calculations such as the least square error method. There is. On the other hand, it can remove ghosts (there was a restriction on the No. 5 band).

At present, no technical standards have been determined for the ghost removal reference signal, and it is thought that the optimal ghost removal reference signal may differ depending on the image to be transmitted. In other words, there is a problem in that ghost removal performance is determined by which reference signal for ghost removal is used.

Means for Solving the Problems In order to solve the above problems, the present invention provides a first ghost removal reference signal generation circuit that generates a digital signal train, a second ghost removal reference signal generation circuit, and a television set. a signal superimposition circuit having a ghost signal input terminal; and a switching control circuit; the signal superposition circuit includes the first ghost removal reference signal generation circuit and the second ghost removal reference signal
connected to the No. 3 generation circuit and the switching control circuit,
The signal superimposition circuit also controls the output of the first reference signal generation circuit for ghost removal and the output of the second reference signal generation circuit for ghost removal on a field-by-field basis according to the output of the switching control circuit. Alternatively, the signal superimposition circuit may combine the output of the first ghost removal reference signal generation circuit and the second ghost removal reference signal generation circuit according to the output of the switching control circuit. The output of the circuit is switched every horizontal scanning period and superimposed on the television signal, or the signal superimposition circuit superimposes the output of the first ghost removal reference signal generation circuit according to the output of the switching control circuit. and the output of the second reference signal generation circuit for ghost removal within one horizontal scanning period.

Effect of the Invention The present invention uses the above-mentioned means to superimpose a digital signal train on a television signal and use it as a reference signal for ghost removal, thereby producing a signal with higher power than a single pulse signal and with a period of 1/2 or more. By providing a signal from which delayed ghosts can also be removed, and by using, for example, a pulse-based signal as a reference signal for ghost removal, it is intended to provide a signal from which ghosts can be removed up to the high frequency components of the video signal. be.

Embodiment An embodiment of the reference signal generating device for ghost removal according to the present invention will be described below with reference to the drawings.

FIG. 1 shows a reference signal generation circuit for ghost removal according to the present invention. In FIG. 1, ■ is a first ghost removal reference signal generation circuit that generates a digital signal sequence, 2 is a second ghost removal reference signal generation circuit, 3 is a television signal input terminal, and 4 is a signal superimposition circuit. , 5 is the switching side? ffj circuit,
6 is an output terminal.

In FIG. 1, a first ghost removal reference signal generation circuit 1 generates a digital signal train. The second ghost removal reference signal generation circuit 2 generates, for example, a pulse type signal. The signal superimposition circuit 4 converts the respective output signals of the first ghost removal reference signal generation circuit 1 and the second ghost removal reference signal generation circuit 2 into the vertical feedback of the television signal according to the output of the switching control circuit 5. Superimposed on the line period. This output is obtained at output terminal 6, and it is connected to the RF modulator (
(not shown) and then transmitted.

On the receiving side, group delay distortion, frequency amplitude characteristic distortion, ghost, etc. generated in the transmission system are removed by using the above-mentioned reference signal for ghost removal.

FIG. 2 is a block diagram showing an example of the configuration of the first reference signal generation circuit 1 for ghost removal shown in FIG. Second
In the figure, 11 is a signal train generation circuit, 12 is a modulation circuit,
The first ghost removal reference signal generation circuit l is configured as described above. In FIG. 2, a signal train generated by a signal train generation circuit 11 is modulated by a modulation circuit 12. A typical example of this modulation method is the NRZ modulation method.

FIG. 3 is a waveform diagram showing an example of a ghost removal benefit signal superimposed during the vertical retrace period. In opening and opening, 3
0 is a digital signal train, 31 is a signal train superimposition period, 32 is a color burst, and 33 is a horizontal synchronizing signal. In this example, the vertical synchronizing signal during the vertical retrace period and the signal string superimposition period 31 shown in FIG.
A digital signal sequence 30 is obtained by superimposing the signal sequence as a binary NRZ signal.

Further, the output of the signal string generation circuit 11 is one or more kinds of predetermined signal strings, or a pseudorandom signal string.

Here, the pseudo-random signal sequence refers to a signal sequence obtained by sequentially selecting signal sequences to be superimposed on a television signal from a signal sequence obtained based on a random signal generation algorithm such as an M sequence, or a read-only memory. This signal sequence is determined by sequentially selecting the signal sequence to be superimposed on the television signal from the signal sequence recorded on the TV, etc., and indicates a signal sequence that can be considered to be almost random. Further, the predetermined one or more kinds of signal strings refers to one or more kinds of signal strings arbitrarily selected from the pseudo-random signal strings, or a specific signal string suitable for ghost removal. Indicates one or more types of signal strings.

Next, a description will be given of how the superimposed digital signal sequence is used as a reference signal for ghost removal.

FIG. 4 is a circuit configuration diagram showing a ghost removal device using a transversal filter as an example of a ghost removal device. In the figure, 20 is a transversal filter, 21 is a control circuit, and 22 is an error signal train generation circuit. A television signal containing ghosts is processed by a transmission system that generates group delay distortion, three frequency amplitude characteristic distortions, ghosts, etc., and finally a transversal filter 20 having opposite characteristics. Ghosts etc. are removed. From this output signal, the error signal string generation circuit 2
In step 2, an error signal train is generated corresponding to the waveform distortion due to the group delay distortion, single frequency amplitude characteristic distortion, and removal errors such as ghosts. The error signal sequence and the transversal filter 20
Based on the human input signal, the transversal filter 20tJI? II, and control is performed so that the error signal sequence is minimized, that is, the group delay distortion, 1-frequency amplitude characteristic distortion, ghost, etc. are removed.

The error signal sequence is obtained by selecting the digital signal sequence, which is a reference signal, from the television signal that has been transmitted and from which the group delay distortion, 1-frequency amplitude characteristic distortion, ghost, etc. have been removed by the transversal filter 20; It is obtained as a difference between the expected signal string corresponding to the selected digital signal string that is included in the error signal string generation circuit 22 or calculated by the error signal string generation circuit 22.

The power of the digital signal train is greater than the power of a single pulse. Therefore, the digital signal string is 1, t5 it
By doubling the signal, there is less influence from L-rich noise when using a conventional single pulse.

Further, by using the least square error method or the like as a control method for the transversal filter 20, and calculating the correlation between the error signal sequence and the input signal sequence etc. to obtain the tap weight correction amount, the error signal sequence is Even if the signal contains an error caused by a signal other than the reference signal, the influence can be removed. Therefore, it is also possible to remove ghosts with a delay longer than 1/2 horizontal period.

On the other hand, the advantage of the reference signal for ghost removal using a pulse-based signal is that the frequency characteristics extend to high frequencies, as described above. Therefore, it is possible to remove ghosts up to the high frequency range of the video signal. Even in the case of a pulse-based reference signal, ghost removal can be performed using the ghost removal apparatus shown in FIG.

FIG. 5 shows an example of a waveform diagram of a reference signal for ghost removal using a pulse type signal. The example signal in Figure 5 is 5in.
The X/X signal is used. This signal is characterized by having almost flat frequency characteristics within the band.

Next, a method of signal superimposition will be described. FIG. 6 is an example of a waveform diagram when the first reference signal for ghost removal and the second reference signal for ghost removal are superimposed between the vertical retrace corners for each field. In this case, for example, 18
It is efficient to use the same horizontal period, such as H and 281H, in terms of vertical retrace period.

FIG. 7 is an example of a waveform diagram when the first ghost removal reference signal and the second ghost removal reference signal are superimposed on different horizontal periods within the L field. , for example, two horizontal periods of 18H and 19H can be used.

FIG. 8 is an example of a waveform diagram when the first reference signal for ghost removal and the second reference signal for ghost removal are superimposed in the same horizontal period within one field.

As shown in FIGS. 6, 7, and 8, there are two cases in which a digital signal train is used as a reference signal for ghost removal to perform techo-cost removal, and another reference signal for ghost removal, such as a pulse type signal. The ghost removal performance of the ghost removal device can be improved by using the ghost removal method in combination with the case where ghost removal is performed using.

Effects of the Invention As described above, according to the present invention, by superimposing a digital signal train on a television signal as a first reference signal for ghost removal, a signal with higher power than a single pulse signal is generated. In addition, by using correlation calculations such as the least square error method, it is possible to remove ghosts delayed by 1/2 horizontal period or more, and by superimposing, for example, a pulse-based signal as a second ghost removal reference signal, it is possible to remove Ghosts can be removed up to high frequencies of signal components, thereby improving the ghost removal performance of the ghost removal device.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of the present invention, FIG. 2 is a block diagram showing an example of the configuration of the first ghost removal reference signal generation circuit of the present invention, and FIG. FIG. 4 is a block diagram of the ghost removal device; FIG. 6 is a waveform diagram showing an example of the waveform of the ghost removal reference signal of the present invention; FIG. 7 is a waveform diagram of the ghost removal reference signal of the present invention. FIG. 8 is a waveform diagram showing another example of the waveform of the reference signal for ghost removal of the present invention, and FIG. 5 is a waveform diagram showing another example of the waveform of the reference signal for ghost removal of the present invention. FIG. 9, FIG. 10, and FIG. 11 are waveform diagrams showing an example of a reference signal. FIG. 9 is a waveform chart showing a conventional ghost removal reference signal. l...First ghost removal reference signal generation circuit, 2...Second ghost removal reference signal generation circuit, 4...Signal superimposition circuit, 5... ...Switching control circuit, 11...Signal train generation circuit, 12...
... Modulation circuit, 20 ... Transversal filter, 21 ... f, II m circuit, 22.
...Error signal string generation circuit, 30...Digital signal string, 31...Signal string superimposition period. Name of agent: Patent attorney Toshio Nakao (1 person) Figure 1 JJ-11 Horizontal circumference double number Figure 3 Jθ Figure 4 7? θ Jθ---Teleful No. 4 gj J2-fj Larhurst Figure 6 J3J, 3 JJ JjJ#-f'/
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- Kozut's difference edict / / θ - - Hai blind code / / / - - - No X Luzui g / / 2 - - 1 eta Rahanu) / / J - - Ichi Kasukudo's i word Figure 10 Figure 11

Claims (4)

[Claims] (1) A first reference signal generation circuit for ghost removal that generates a digital signal train, a second reference signal generation circuit for ghost removal, a signal superimposition circuit having a television signal input terminal, and a switching control circuit. The signal superimposition circuit includes the first ghost removal reference signal generation circuit and the second ghost removal reference signal generation circuit.
A ghost removal reference signal generation device, characterized in that the ghost removal reference signal generation circuit is connected to the ghost removal reference signal generation circuit and the switching control circuit. (2) The signal superimposition circuit switches the output of the first reference signal generation circuit for ghost removal and the output of the second reference signal generation circuit for ghost removal for each field by the output of the switching control circuit. The reference signal generator for ghost removal according to claim 1, wherein the reference signal generator is superimposed on a television signal. (3) The signal superimposition circuit switches the output of the first reference signal generation circuit for ghost removal and the output of the second reference signal generation circuit for ghost removal every horizontal scanning period by the output of the switching control circuit. The reference signal generating device for ghost removal according to claim 1, wherein the reference signal generator is superimposed on a television signal. (4) The signal superimposition circuit switches between the output of the first reference signal generation circuit for ghost removal and the output of the second reference signal generation circuit for ghost removal within one horizontal scanning period by the output of the switching control circuit. The reference signal generating device for ghost removal according to claim 1, wherein the reference signal generator is superimposed on a television signal.