JP2570887B2 - Ghost eliminator for television signal - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ghost elimination device for a television signal used for a television receiver, a video device handling a television signal, and the like.

[Prior Art] An example of a conventional ghost removing apparatus will be described with reference to FIG.

Reference numeral 1 denotes a transversal filter which receives a television signal and corrects waveform distortion to remove a ghost component. In this embodiment, the transversal filter is constituted by a digital filter which varies a filter coefficient. Such a transversal filter can remove a ghost component by setting a filter coefficient having a phase opposite to that of the ghost component included in the input signal, for example. The output of the transversal filter 1 becomes an output video signal and is also supplied to a waveform extraction circuit 3. The waveform extraction circuit 3 extracts a predetermined period including a specific pattern signal from a television signal, performs predetermined waveform conversion such as differentiation as necessary, and outputs the result. This specific pattern signal is a pattern capable of detecting a reference timing in one horizontal scanning line period, and an example of a typical specific pattern signal is shown in FIG.

4 (a) and 4 (b) each show a step-like signal superimposed on a part of one horizontal scanning period. In the case of FIG. 4 (a), for example, the rising edge of the step-like signal In the case of FIG. 4 (b), for example, the falling edge of the step signal can be used as the reference timing. For example, a pulse-like signal as shown in FIG. 4 (c) can be obtained by differentiating the falling edge portion of the step-like signal in FIG. 4 (b). FIG. 4D shows a narrow step-like signal superimposed on the vertical synchronizing signal. In this case, the rising or falling edge can be used as the reference timing.

The specific pattern signal extracted by the waveform extraction circuit 3 is subjected to a waveform conversion process such as differentiation, and then compared with a reference signal generated from a reference waveform generation circuit 5 by a subtractor 4 as a comparison means. The output of the subtractor 4 is supplied to the magnification setting circuit 6 as an error signal. The magnification setting circuit 6 determines a magnification for determining a filter coefficient to be set in the transversal filter 1, and the coefficient setting circuit 2 sets a filter coefficient of the transversal filter 1 based on the magnification set here. Generate coefficient data for

As described above, a ghost removal circuit is formed by the closed loop formed by the transversal filter 1, the waveform extraction circuit 3, the subtractor 4, the reference signal generation circuit 5, the magnification setting circuit 6, and the coefficient setting circuit 2. That is, the reference timing is obtained from the specific pattern signal in the input television signal, and the filter coefficient of the transversal filter 1 is sequentially changed according to the error signal obtained from the reference timing and the reference signal, thereby removing the ghost component. Thus, the closed loop control is performed.

[Problems to be Solved by the Invention] However, since the coefficient data set by the coefficient setting circuit 2 is not band-limited, the frequency band components included in the coefficient data are components other than the frequency band components included in the reference signal (high band). Component), and the out-of-band component may cause the transversal filter 1 to perform an erroneous filtering operation. In such a case, there is a drawback that convergence to an incorrect ghost state or convergence to a ghost removal state is delayed.

SUMMARY OF THE INVENTION The present invention has been made to overcome the above-described drawbacks of the related art. When generating coefficient data set in a transversal filter, a frequency band component of a reference waveform corresponding to the coefficient data is generated. Only a low-pass filter coefficient having such a characteristic as to pass only the frequency component and blocking other frequency components (high-frequency components) is given to the coefficient data set in the transversal filter.
It is an object of the present invention to provide a television signal ghost elimination device that prevents a malfunction of a ghost elimination function.

Means for Solving the Problems In order to achieve the above object, the present invention includes a transversal filter provided in an input television signal path, and includes a predetermined pattern including a specific pattern signal for detecting a ghost from a television signal. The signal of the television signal is extracted by extracting the signal of the period, setting the coefficient data according to the error signal obtained by comparing the reference timing and the reference signal in the specific pattern signal, and changing the filter coefficient of the transversal filter. A ghost removing device that removes a ghost, wherein a low-pass filter coefficient that removes unnecessary high-frequency components of the coefficient data is set in a transversal filter in response to an influence of a component outside a frequency band of a reference signal. And a band limiting means for providing

[Advantage of the Invention] According to the television signal ghost elimination device having the above-described configuration, the coefficient data for setting the filter coefficient of the transversal filter can be made to have no unnecessary band component. It is possible to reduce adverse effects due to components outside the frequency band, prevent malfunction of the ghost removal function, and quickly converge to the ghost removal state.

Embodiment An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. The same parts as those described in the description of the related art are denoted by the same reference numerals, and description thereof will be omitted as appropriate.

FIG. 1 is a block diagram showing a configuration of an embodiment of a television signal ghost removing apparatus according to the present invention.

In FIG. 3, it is shown in FIG. 3 that the ghost eliminator is constituted by closed loop control by a transversal filter 1, a waveform extracting circuit 3, a subtractor 4, a reference signal generating circuit 5, a magnification setting circuit 6, and a coefficient setting circuit 2. This is the same as in the case of the prior art.

In this example, the output of the coefficient setting circuit 2 is further supplied to a counter 7 (detection means). The counter 7 counts the number of times that the coefficient setting circuit 2 has generated the coefficient data until the ghost state is eliminated, and when the number of times has reached a predetermined number or more, the band limiting circuit 8 (band limiting means). Activate. The band limiting circuit 8 provides the transversal filter 1 with a low-pass filter coefficient having a predetermined frequency characteristic shown in FIG.

 Next, the operation of the above embodiment will be described.

The filter coefficient of the transversal filter 1 is made variable based on the coefficient data generated by the coefficient setting circuit 2, and the ghost removing action is performed as in the case of the conventional technique. If the coefficient data contains unnecessary high-frequency components outside the frequency band of the reference signal, ghosts cannot be sufficiently removed. In this embodiment, the closed loop control is repeated until the ghost is sufficiently suppressed, and each time new coefficient data is generated by the coefficient setting circuit 2, the coefficient data constantly has an unnecessary high frequency component. It is desirable to apply an unnecessary high-frequency component removal filter every time the calculation is performed. However, this increases the processing time, so the number of calculations is counted by the counter 7, and the unnecessary high-frequency component removal processing is performed every time the count value reaches a predetermined value. At this time, since the counter 7 activates the band limiting circuit 8, unnecessary high frequency components other than the frequency band component of the reference signal are not output to the output of the transversal filter 1, and the loop quickly converges to a correct convergence state. Will be.

[Effects of the Invention] As described above, according to the present invention, unnecessary high-frequency components other than the frequency band of the reference signal are removed in response to the influence of components outside the frequency band of the reference signal. In addition, malfunction of a loop for removing ghosts and delay of convergence can be prevented.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of a television signal ghost removing apparatus according to the present invention, FIG. 2 is a diagram showing frequency characteristics by a band limiting circuit in FIG. 1, and FIG. 4 (a) to 4 (d) are block diagrams showing a configuration of an example of a ghost removing device for a television signal, and FIGS. 4 (a) to 4 (d) are waveform diagrams showing a waveform example of a specific pattern signal contained in a television signal and a waveform obtained by differentiating the same It is. 1 ... transversal filter, 2 ... coefficient setting circuit, 3 ... waveform extraction circuit, 4 ... subtractor, 5 ... reference signal generator, 6 ... magnification setting circuit, 7 ... counter (detection means) , 8... Band limiting circuit (band limiting means).

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Tatsushi Takaguchi 3-12-12 Moriyacho, Kanagawa-ku, Yokohama-shi, Kanagawa Prefecture Inside of Victor Company of Japan, Ltd. (56) References JP-A-57-145446 (JP, A) Kaihei 2-141172 (JP, U)

Claims (1)

(57) [Claims] A transversal filter provided in an input television signal path, extracting a signal for a predetermined period including a specific pattern signal for detecting a ghost from a television signal, and extracting a reference timing in the specific pattern signal By setting coefficient data in accordance with an error signal obtained by comparing the signal with a reference signal generated in the apparatus, and changing the filter coefficient of the transversal filter in accordance with the coefficient data. In a ghost removal device that removes a ghost of a signal, in order to remove unnecessary high frequency components having the coefficient data,
A television signal, comprising: a band limiting unit that passes only a frequency band component of the reference signal and provides a low-pass filter coefficient for removing other frequency components to coefficient data set in the transversal filter. Ghost removal device.