JPS62265869A - Reference signal generating circuit for removing ghost - Google Patents

Abstract

PURPOSE:To improve performance removing a ghost by overlapping a digital signal string with an information signal for scramble transmission and using said string as a ghost removal reference signal. CONSTITUTION:A scramble device 2 scrambles the output of a tele vision signal generator circuit 1, and a control circuit 4 controls the scramble device 2 and a digital signal string generating circuit 5. The circuit 5 generates the digital signal string 21 with the information signal 25 for scramble-transmitting a television signal, and a signal overlap circuit 3 overlaps the digital signal string 21 with the scrambled television signal. Since power that the digital signal string 21 has is greater than that of a single pulse, the influence due to noise can be reduced if the digital signal string is used as a reference signal.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is directed to the vertical retrace period of a television signal in order to remove group delay distortion, frequency amplitude characteristic distortion, ghost, etc. that occur during the transmission of a television signal. The present invention relates to a ghost removal reference signal generation circuit for a ghost removal reference signal superimposed on a ghost removal reference signal.

2. Description of the Related Art Conventionally, a differential signal at the leading edge of a vertical synchronization signal has been used as a reference signal for removing ghosts generated during transmission of television signals. (Reference: Onishi et al., ``Automatic Ghost Removal from Television Images,'' NHK Giken Monthly Report, 1972) The reference signal conventionally used will be explained with reference to FIGS. 4 and 5. In FIG. 4, 100 is the leading edge of the vertical synchronizing signal, 101 is a ghost, and 102 is a vertical equalization pulse. The goose +-101 is a delayed version of the vertical sync signal leading edge 100. FIG. 5 shows a signal waveform obtained by subtracting the leading edge portion 100 of the vertical synchronization signal and the ghost 101. FIG. In the figure, 103 is a difference signal of the vertical synchronization signal leading edge 100, and 104 is a ghost 101.
This is the difference signal of Difference signal 10 of the leading edge of the vertical synchronization signal
A difference signal 104 between No. 3 and the ghost indicates the impulse response of the transmission system, and is used to remove the ghost.

In addition, the Japan Broadcasting Corporation has proposed a reference signal (OCR) for ghost removal as shown in Figure 6. -6.Showa 56.2) In the same figure, 1
10 is a bar signal, 111 is a pulse signal, 112 is a color burst, and 113 is a horizontal synchronization signal. Pulse signal 1
11 is used to estimate the impulse response of the transmission system. Further, the bar signal 110 is used to detect the occurrence of sag due to the transversal filter.

Problems to be Solved by the Invention 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 a television signal is not as good as that of a video signal such as DG or DP. This is because the parameters indicating signal quality are not guaranteed. 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.

Furthermore, in the reference signal for ghost removal proposed by the Japan Broadcasting Corporation, the pulse signal 111 is equivalent to a 1.5T pulse (half-width 187
．． 5 ns) pulses are required. (Reference: Ohara et al., System Study of Adapter Type Ghost Canceller, TV Science and Technology Report, IT52-1. 1984) However, in the case of such a pulse signal, proximity is a problem in teletext broadcasting. To obtain information for correction of ghosts, group delay distortion, single frequency amplitude characteristic distortion, etc. (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, even in the time range in which ghosts can be removed, the method using the vertical synchronization signal leading edge 100 as a reference signal,
For ghosts with a delay of 1/2 or more, it is not possible to determine whether the delayed signal is due to the reference signal or another signal.
This will be explained using FIG. FIG. 7 is a signal diagram showing a delay ghost of 1/2 period or more. In the same figure,
100 is the leading edge of the vertical synchronization signal, 102 is the equivalent pulse, 1
05 is a ghost created by the delay of the equivalent pulse 102. FIG. 8 shows the vertical synchronization signal leading edge 100 and the ghost 1.
FIG. 2 is a signal diagram showing a signal obtained by subtracting 05. In the figure, 103 is a differential signal of the leading edge portion 100 of the vertical synchronization signal;
6 is a difference signal of the ghost 105. From FIGS. 7 and 8, the ghost 105 is the ghost caused by the equivalent pulse 102.

It is not possible to distinguish whether this is caused by two ghosts or two ghosts in which the leading edge of the vertical synchronizing signal 100 is delayed.

Therefore, the ghost removal range of the ghost removal device using the vertical synchronization signal leading edge 100 as a reference signal is at most 1/2.
There is only one period of water. In addition, the standard signal for ghost removal proposed by the Japan Broadcasting Corporation has the following signal format:
Ghosts with a delay time of 16.8 microseconds or more cannot be removed for the same reason as above.

In view of the above problems, the present invention uses a digital signal train having an information signal for scramble transmission of the television signal as a part of the digital signal train as a reference signal for ghost removal. It is a signal with higher power than a single pulse signal, can remove ghosts delayed by more than 172 horizontal periods, is transmitted under exactly the same conditions as other video signals, and is an information signal for scrambled transmission of some digital signals. The present invention relates to a transmittable ghost-eliminating signal generator.

Means for Solving the Problems In order to solve the above problems, the present invention is a circuit that superimposes a reference signal for ghost removal on the vertical retrace period of a television signal, and is suitable for high-definition television signal transmission. It generates a digital signal sequence having information for the purpose.

Effect of the Invention The present invention uses the above-described means to superimpose a digital signal train having an information signal for a television digital signal on a part of the digital signal train on a television signal and use it as a reference signal for ghost removal. It is a signal with higher power than a single pulse signal, can remove ghosts delayed by 1/2 horizontal period or more, and is transmitted under exactly the same conditions as other video signals, while providing information for scrambled transmission of television signals. The present invention provides a reference signal generation circuit for ghost removal that enables signal transmission.

Embodiment FIG. 1 is a circuit configuration diagram showing an embodiment of a reference signal generation circuit for ghost removal according to the present invention. In the figure, 1 is a television signal generation circuit, 2 is a scrambling device, and 3 is a television signal generating circuit.
4 is a control circuit, and 5 is a digital signal train generation circuit. This operation will be explained below. A scrambler 2 scrambles the output of the television signal generator 1. A control circuit 4 controls the scrambler 2 and the digital signal train generator 5.

The digital signal string generation circuit 5 generates a digital signal string containing scramble information.

The signal superimposition circuit 3 superimposes the digital signal train on the scrambled television signal.

FIG. 2 is a waveform diagram showing an example of a reference signal for ghost removal superimposed during the vertical retrace period. In the same figure, 2
1 is a digital signal train, 22 is a signal train superimposition period, 23 is a color burst, and 24 is a horizontal synchronizing signal. In this example, the vertical synchronization signal during the vertical retrace period and the signal string superimposition period 2 shown in FIG.
2, a signal train is superimposed as a binary NRZ signal to obtain a digital signal train 21.

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

FIG. 3 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, 11 is a transversal filter, 12 is a tap gain control circuit, and 13 is an error signal train generation circuit. A television signal containing a ghost is processed by a transmission system that generates group delay distortion, frequency amplitude characteristic distortion, ghost, etc., and finally a transversal filter 11 having opposite characteristics. Ghosts etc. are removed. From this output signal, an error signal train generation circuit 13 generates an error signal train corresponding to the waveform distortion due to the group delay distortion, two-frequency amplitude characteristic distortion, ghost, etc. removal error. The tap gain control circuit 12 is controlled by the error signal train and the input signal of the transversal filter 11.
The transversal filter 11 is controlled using an algorithm such as the least square error method so that the error signal sequence is minimized, that is, the group delay distortion 3 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, frequency amplitude characteristic distortion, ghost, etc. have been removed by the transversal filter 11;
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 13 or calculated by the error signal string generation circuit 13.

The power of the digital signal train is greater than the power of a single pulse. Therefore, if a digital signal train is used as a reference signal, the influence of noise will be less than if a conventional single pulse is used.

Further, by using the least square error method or the like as a control method for the transversal filter 11, and calculating the correlation between the error signal sequence and a human input signal sequence, etc., to obtain the correction amount of the tap weight, the error signal sequence can be adjusted. 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.

As described above, according to this embodiment, by using a digital signal train having an information signal for scramble transmission of a television signal as a reference signal for ghost removal,
A signal with higher power than a single pulse signal, and 1/2
It is possible to obtain a reference signal for ghost removal which can also remove ghosts delayed by more than the horizontal period and which is transmitted under exactly the same conditions as other video signals, thereby making it possible to improve the ghost removal effect more than in the past.

Effects of the Invention As described above, based on the present invention, a digital signal train having an information signal for scrambled transmission is superimposed on a television signal and used as a reference signal for ghost removal, thereby producing a single pulse signal. It is possible to remove ghosts with a delay longer than 1/2 horizontal period by using a signal with a higher power than that of
And a basis for ghost removal transmitted under exactly the same conditions as other video signals! 1! This improves the ghost removal performance and enables the transmission of information signals for scrambled transmission of television signals.

[Brief explanation of drawings]

FIG. 1 is a block diagram in one embodiment of the present invention, and FIG.
The figure is a waveform diagram showing a reference signal for ghost removal of the present invention,
FIG. 3 is a circuit configuration diagram showing a ghost removal device, and FIGS. 4, 5, 6, and 7. FIG. 8 is a waveform diagram showing a conventional ghost removal reference signal. 1...Television signal generation circuit, 2...
... Scramble device, 3... Signal superimposition circuit,
4... Control circuit, 5... Digital signal string generation circuit, 11... Transversal filter, 12... Tap gain control circuit, 13...
...Error signal string generation circuit, 21...Digital signal string, 22...Signal string superimposition period, 23
. . . Color burst, 24 . . . Horizontal synchronization signal, 25 . . . Scramble information signal. Name of agent: Patent attorney Toshio Nakao and one other person Figure 1 Figure 2? 4z4 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] In a ghost removal reference signal generation circuit that superimposes a reference signal for ghost removal on the vertical retrace period of a television signal, a part of the digital signal string is used as an information signal for scrambled transmission of the television signal, and the other parts are A reference signal generation circuit for ghost removal, characterized in that it generates a digital signal sequence that is a random digital signal sequence.