KR960016565B1 - Filter coefficient setting apparatus for ghost cancelling apparatus - Google Patents

Abstract

an analog/digital converting part(10) to convert a video signal received through a channel into a digital signal; a reference signal extracting part(20) extracting a ghost-cancelling reference signal from the video signal; a filter coefficient-operating part(30) outputting filter coefficients; a filter(40) removing ghosts from the video signal; and a switch(44) applying the video signal of the A/D converting means(10) until the video signal is filtered first through the filter and the video signal of the filter(40) after the first filtering to the reference signal extracting part(20).

Description

Filter coefficient setting device of ghost elimination device

1 is a block diagram of a conventional ghost removal apparatus.

FIG. 2 is a block diagram of a filter configured in the ghost elimination device of FIG.

3 is a block diagram of a filter coefficient setting device of the ghost removing device according to the present invention.

* Explanation of symbols for main parts of the drawings

10: analog / digital converter 20: reference signal extractor

30: filter coefficient calculator 40: adder

41: FIR filter 42: adder

43: IIR filter 44: switch

50: digital / analog converter.

The present invention relates to an apparatus for removing ghosts generated during transmission and reception of an image signal, and more particularly, to a filter coefficient setting apparatus of a ghost removal apparatus for setting a coefficient of a filter for removing ghosts. will be.

As part of the method of eliminating ghosts occurring in multiple transmission channels, a broadcasting station transmits a ghost cancellation reference signal in a vertical blank section of a video signal to be transmitted, and the receiving side stores a ghost removal reference signal stored in advance. The ghost removal reference signal is compared to determine the presence and size of the ghost and a method for removing the ghost present in the input video signal based on this has been adopted.

That is, in order to remove the so-called ghost signal generated by reflected waves such as mountains and buildings, the broadcasting station transmits a constant reference signal so that the receiving side knows the characteristics of the transmission channel, and the receiving side uses the ghost characteristic of the channel. A technique for removing ghosts by identifying and filtering by their inverse characteristics is currently being studied.

In this case, the ghost removal reference signal is transmitted on one line during the vertical retrace period in which no video signal exists.

1 is a block diagram showing a general ghost removal apparatus.

As shown, the conventional ghost elimination device receives a signal transmitted from a broadcasting station and is applied to the analog / digital converter 10, and the analog / digital converter 10 converts an image signal from the broadcasting station into a digital signal to convert the reference signal. The extraction unit 20 and the filter 40 are respectively provided.

The reference signal extractor 20 extracts a ghost removal reference signal from the received video signal and transmits the extracted reference signal to the filter coefficient calculator 30. The filter coefficient calculating unit 30 performs fast Fourier transform (FFT) on the ghost removal reference signal output from the reference signal extractor 20, and compares the converted reference signal with a preset ghost reference signal included in the receiver. Is obtained and the obtained coefficient is applied to the filter 40.

The filter 40 removes the ghost by filtering the video signal output from the analog / digital converter 10 according to the filter coefficients of the filter coefficient calculating unit 30 and transfers the ghost to the digital / analog converter 50.

Herein, the filter 40 includes a finite impulse response (FIR) filter 41 for removing proximity ghost and an infinite shock response for removing long ghost as shown in FIG. An Infinite Impulse Response (IIR) filter 43 and an adder 42 for adding the output of the FIR filter 41 and the output of the IIR filter 43.

In this way, the video signal from which the ghost is removed by the filter 40 is converted into the original analog signal by the digital / analog converter 50.

However, the method of setting the filter coefficients using the received ghost removal reference signal takes less time to set the coefficients, but there is a problem that a calculation error occurs because the coefficients are always set using the input signal. .

In order to solve this problem, an adaptive algorithm has been proposed. This adaptive algorithm calculates the error between the reference signal and the filtered reference signal and calculates the coefficient of the filter in the direction of decreasing error. It is efficient to completely eliminate ghost, but it takes a lot of time to set the coefficient. There was a problem.

Accordingly, an object of the present invention is to provide a filter coefficient setting device of a ghost elimination device that can be accurately and quickly set the filter coefficients for removing ghosts.

The present invention for achieving this object, the analog / digital conversion unit for converting a video signal received through the channel into a digital signal; A reference signal extractor for extracting and outputting a ghost removal reference signal from an input video signal; A filter coefficient calculating section for outputting filter coefficients according to the difference between the ghost removal reference signal and the reference signal set; A filter for removing ghost from the video signal of the analog / digital converter according to the filter coefficient and outputting the ghost; An analog / digital converter, a reference signal extractor, and a filter. The video signal from the analog / digital converter is first filtered through the filter according to a predetermined switching signal. And, after the first filtering, a switch for applying the image signal of the filter to the reference signal extracting unit.

Hereinafter, with reference to the accompanying drawings will be described in detail the present invention.

First, the filter 40 of this invention is comprised like FIG.

As shown in the figure, the filter 4 of the present invention has a FIR filter 41 for removing near ghost, an IIR filter 43 for removing long ghost, and a FIR filter 41 as in the related art. It can be seen that it includes an adder 42 for adding the output of the output of the IIR filter 43 and the switch 44 is further configured.

Here, the switch 44 selectively applies the received image signal converted into digital or the image signal added by the adder 42 to the reference signal extractor 20, and the reference signal extractor 20 Similarly, the ghost removal reference signal is extracted from the video signal and applied to the filter coefficient calculating unit 30. In this case, as described above, since the input image signal or the filtered operation signal is applied to the reference signal extractor 20 through the switch 44, the filter coefficient calculator 30 may reference the received image signal or the filtered operation signal. Is applied to the FIR filter 41 and the FIR filter 43.

In the present invention configured as described above, the switch 44 is controlled by the filter coefficient calculating unit 30 or another control unit, and the switching time point should be controlled as follows.

That is, when an image signal is received by the receiver, the filter coefficient calculating unit 30 or the like causes the switch 44 to apply the image signal of line ① (in the state of being received and converted into digital) to the reference signal extraction unit 20. To control. As described above, when the received video signal is applied to the reference signal extractor 20, the filter coefficient calculator 30 filters the predetermined filter coefficient according to the difference between the ghost removal reference signal of the received video signal and the set reference signal. 41) and (42).

In accordance with the filter coefficients, the filters 41 and 42 filter the received video signals, and the video signals of the filters 41 and 42 are added by the adder 42 to remove ghosts of the video signals. However, if the filter coefficient is set according to the difference between the received video signal and the set reference signal, ghost cannot be completely eliminated due to a calculation error as described above.

To this end, in the present invention, if the video signal is first filtered by the filter 40 according to the filter coefficient of the ghost removal reference signal of the received video signal, the adaptive algorithm is continuously performed using the filtered video signal. That is, at the time when the filtered signal from the adder 42 is first output (this time can be set by an experiment or the like), the switch 44 causes the image signal of the adder 42, which is line # 2, to be used as the reference signal extracting unit. It was applied to (20). In this case, since the reference signal is the filtered video signal of the adder 42, the filter coefficient calculating unit 30 resets the filter coefficients according to the difference between the filtered ghost removal reference signal and the set reference signal to the filters 41 and 42. By applying, the filter coefficients are set to make the ghost removal reference signal of the filtered video signal and the set reference signal the same.

That is, in the present invention, when a video signal is first received, a predetermined filter coefficient is set according to a ghost removal reference signal in the video signal to filter the video signal, and an adaptive algorithm is performed on the filtered video signal. In this way, when the ghost is removed, the filter coefficients are set by using the received ghost removal reference signal, which saves the time required to set the coefficients, and then the accuracy of the filter coefficients is improved by the adaptive algorithm. It can be.

As described above, the present invention can save the time required for setting the filter coefficients required to remove the ghost compared to the adaptive algorithm, and can improve the precision of the filter coefficients up to the filter coefficient precision of the adaptive algorithm.

Claims (1)

An analog / digital converter 10 for converting an image signal received through a channel into a digital signal; A reference signal extracting unit 20 for extracting and outputting a ghost removal reference signal from the received input signal; A filter coefficient calculator 30 for outputting filter coefficients according to the difference between the ghost removal reference signal of the reference signal extractor 20 and the set reference signal; A filter 40 for removing ghost from the video signal of the analog / digital converter 10 and outputting the ghost according to the filter coefficients; The analog / digital converter 10, the reference signal extractor 20, and the filter 40 are arranged between the video signal from the analog / digital converter 10 according to a predetermined switching signal. Switch 44 for applying the video signal of the analog / digital converter 10 to the reference signal extractor 20 after the initial filtering. Filter coefficient setting device of the ghost removal device having a.