KR970004444B1 - Ghost eliminating apparatus - Google Patents

Abstract

a synchronization separation(30) separating an analog signal detected in an image-detector(20) into a vertical and horizontal synchronization signal; an A/D converter(40) converting the image-detected analog signal to a digital signal; a line extractor(60) extracting line where a ghost cancelling reference signal is inserted from the digital signal; a first ROM(70) storing and reading the sequence value generated first in order to use as the ghost cancelling reference signal; a linear auto correlation operator(80) performing the linear auto correlation of the ghost cancelling reference signal and the signal read from the first ROM(70); a second ROM(90) storing the ghost cancelling reference signal and data from the linear auto correlation; a subtracter(100) subtracting the data value read from the second ROM(90) from the signal value outputted from the linear auto correlation operator(80); a ghost cancelling filter coefficient operator(110) obtaining and changing the ghost cancelling filter coefficient; a ghost cancelling filter(50) filtering the digital image signal outputted from the A/D converter(40); and a D/A converter(120) converting the digital image signal from which ghost is removed through the ghost cancelling filter(50).

Description

Ghost eliminator

1 is a block diagram of a ghost removing device according to the present invention.

2 is a waveform diagram of a ghost cancellation reference signal according to the present invention.

3 is a waveform diagram of a ghost removal reference signal inserted into a vertical blank line of an image signal according to the present invention.

4 is a waveform diagram of the result of linear autocorrelation when ghost according to the present invention occurs.

5 is a waveform diagram of extracting a ghost generated line according to the present invention.

6 is a waveform diagram of a result of linear magnetic correlation of a signal in which no ghost is generated according to the present invention.

* Description of the symbols for the main parts of the drawings *

10: Tuner 20: Image Detection

30: synchronous separation 40: A / D converter

50: ghost removal filter 60: line extraction unit

70, 90: ROM 80: Linear autocorrelation operation unit

100: subtractor 110: ghost removal filter coefficient calculating unit

120: D / A change part

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to video signal processing, and more particularly, inserts a ghost canceling reference signal into a predetermined position of a part of a vertical blank line of a TV video signal when transmitting a radio wave from a TV station. The present invention relates to a ghost removal apparatus capable of realizing high-quality noise free by detecting and effectively filtering ghosts generated on a transmission path when received.

In general, a ghost is a false image that is attenuated and reappears slightly to the right at a normal position of a screen in a TV image, and a part of radio waves transmitted from a broadcasting station reaches the receiver directly. It may not be received after being reflected by the influence of transmission lines or by mountains or tall buildings. In this case, since the path of the reflected wave is longer than the path of the direct wave, a time delay and attenuation occurs and the reflected wave appears as a ghost image on the TV screen.

Accordingly, an object of the present invention is to effectively remove ghost phenomenon generated on a transmission path through a line extractor, a first ROM, a multiplier, a second ROM, a subtractor, a ghost cancellation field coefficient calculator, and a ghost cancellation filter. An object of the present invention is to provide a ghost removing device capable of realizing high image quality.

A feature of the present invention for achieving this object is a signal from an antenna into which an ghost cancellation reference signal having a predetermined amplitude and at least two or more pulses is inserted at a predetermined position of a part of a vertical blank line of a TV video signal. A tuner for selecting a channel desired by the user from the received signal; Image detection for restoring a signal selected from the tuner to an image signal; Sync separation for separating the image detected analog signal into vertical and horizontal sync signals, respectively; An A / D converter converting the detected analog signal into a digital signal; A line extracting unit extracting only a line into which the ghost elimination reference signal is inserted from the signal converted into the digital signal by the vertical and horizontal synchronizing signals separated by the synchronizing separation; A first ROM for storing and reading a sequence value originally created for use as a ghost removal reference signal; A linear autocorrelator for performing linear autocorrelation between the ghost removal reference signal obtained from the line extracting unit and the ghost removal reference signal read out from the first ROM; A second ROM for storing data values obtained by performing linear autocorrelation between the sequential stored in the first ROM and a ghost cancellation reference signal inserted into a part of a vertical blank line of a transmitter TV video signal; A subtractor for subtracting the data value read from the second ROM from the signal value output from the linear autocorrelator; A ghost elimination filter coefficient calculating unit for obtaining ghost elimination filter coefficients based on the data values output from the subtractor and changing the coefficients of the filter; A ghost cancellation filter for filtering a digital video signal output through the A / D converter to obtain a signal identical to a ghost removal reference signal inserted at the time of transmission according to a filter coefficient value output from the ghost removal filter coefficient calculating unit; And a D / A converter configured to convert a digital video signal from which ghost is removed through the ghost removal filter into an analog video signal.

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

1 is a block diagram of a ghost removing apparatus according to the present invention, the tuner 10, the image detection 20, the synchronization separation 30, the A / D converter 40, the line extracting unit 60, the first ROM 70, linear autocorrelation operation unit 80, second ROM 90, subtractor 100, ghost elimination filter coefficient operation unit 110, ghost elimination filter 50, D / A conversion unit 120 Is done.

The tuner 10 is provided to select a channel desired by the user from the signal received from the antenna.

The image detection 20 functions to restore the signal of the channel selected by the tuner 10 to the image signal.

The sync separation 30 functions to separate the image detection 20 signal into vertical and horizontal sync signals, respectively.

The A / D converter 40 is provided to convert the image-detected analog signal into a digital signal.

The line extracting unit 60 functions to extract only the line into which the ghost elimination reference signal is inserted from the digitally converted signal by the vertical and horizontal synchronizing signals separated by the synchronizing separation. The first ROM 70 is provided to store and read the sequential values generated for use as the ghost removal reference signal.

The linear autocorrelation operation unit 80 performs a linear autocorrelation operation on the ghost removal reference signal obtained from the line extracting unit 60 and the ghost removal reference signal read from the ROM 70.

The second ROM 90 has a linear autocorrelation between a ghost removal reference signal inserted at a predetermined position of a part of the vertical blank line of the TV video signal and a sequential value generated for use as a ghost removal reference signal during transmission. Correlation) data value.

The subtractor 100 acts to subtract the data value read from the second ROM 90 from the signal value output from the linear autocorrelation unit 80.

The ghost elimination filter coefficient calculating unit 110 obtains ghost elimination filter coefficients based on the data values output from the subtractor, and changes the coefficients of the filter.

The ghost elimination filter 50 inserts a digital image signal output through the A / D converter 40 into the transmitter according to a filter coefficient value output from the ghost elimination filter coefficient calculating unit 110. Filter to get the same signal as.

The D / A converter 120 is provided to convert the ghost-rejected digital video signal through the ghost removal filter 50 into an analog video signal.

The ghost cancellation apparatus according to the present invention configured as described above, when a TV broadcast station transmits radio waves and inserts and transmits a ghost removal reference signal at a predetermined position of a part of a vertical blank line of a video signal, The user selects a desired channel in the tuner 10 and passes the image detection 20 to restore the selected signal to the image signal.

In the synchronous separation 30, the image detection 20 is divided into vertical and horizontal synchronization signals, and applied to the line extracting unit 60.

Meanwhile, the analog image signal output through the image detection 20 is converted into a digital image signal by the A / D converter 40, and the first ghost removal filter 50 passes the digital image signal as it is. Filter coefficients are set.

The signal passing through the ghost elimination filter 50 is extracted by the line extracting unit 60 using only the vertical and horizontal synchronous signals which are synchronously separated as described above. The ghost removal reference signal extracted as described above is input to a circuit performing linear autocorrelation operation 80, and the linear autocorrelation 80 and the value read from the first ROM 70 in which the original ghost elimination reference signal is stored are stored. Will be A method of generating a signal inserted into a part of the vertical blank line of the transmitter image signal as described above and a ghost cancellation reference signal stored in the first ROM 70 may be described by MHckroyd's Synthesis of Efficient Huffman. Sequence ", IEEE Trans. on Aero. & Electronic Sys., Vol. 8 No. 1, (1972. 1), and the length N of the sequence used to generate the ghost cancellation reference signal used here is 302 and X is used to generate the sequence. The value of is 0.8724. The characteristic of the signal used here has the characteristic of having a peak value at 0 and a very small value at other parts when the value of the linear autocorrelation defined by the following equation (I) is obtained. This is equal to the following expression (2).

Where n = 0, ± 1, ± 2,... , ± N.

Where C, C,... , C is a sequence to use as a ghost removal reference signal, R (n) is an autocorrelation value, X is a value used to create a sequence. The second ROM 90 has a linear autocorrelation value with the one generated for use as a band-limited signal and a ghost cancellation reference signal for transmitting the sequence generated here as a broadcast signal, that is, the same as that stored in the first ROM 70. Is saving. The waveform is the same as the second degree, and the signal inserted into the vertical blank line of the TV video signal by band-limiting it to the transmission band of the video signal is the same as the third degree. In addition, the data value calculated by FIG. 2 is stored in the first ROM 70, and the second ROM 90 stores the waveform of FIG.

The linear autocorrelation operation 80 results (the waveform when ghost is the same as the fourth degree) is inputted to the circuit 100 which subtracts and the data value stored in the second ROM 90, i.e. The sequence of FIG. 2 and the two band-limited sequences are fixed one by one and the other is multiplied by the respective values while moving by one sample. )

The result value subtracted by the subtractor 100 is input to the circuit 110 for calculating the coefficient of the ghost elimination filter, and the ghost elimination filter calculating unit 110 changes the coefficient of the filter, and thus the changed filter coefficient. The line extracting unit 60 extracts only the line including the ghost elimination signal from the signal passing through the ghost elimination filter 50 having the value (when ghost occurs, only the line is extracted from the receiver. ) The loop as described above is repeated.

On the other hand, when it is determined that the ghost is removed in the above-described loop, if it is not completely removed, the absolute value is taken by taking the sixth degree and the difference component, which are waveforms of the data values stored in the fourth degree and the second ROM 100, and adding them. Or, squared and added to obtain the ghost elimination filter coefficient. As described above, the filter coefficients are calculated by the ghost removal filter coefficient calculating unit 110 and the process of passing the image signal is repeated.

When the ghost is completely removed through the loop process as described above, the D / A converter 120 converts the analog image signal and outputs the analog image signal.

As described above, when the TV station transmits radio waves, when the ghost removal reference signal is inserted into a part of the vertical blank line of the video signal and transmitted, the receiver extracts the line extracting unit 60, the first ROM 70, and the linear magnetic field. By calculating the filter coefficient value through the correlation calculating unit 80, the second ROM 90, the subtractor 100, and the ghost elimination filter coefficient calculating unit 110, the image signal is output to the ghost elimination filter 50 having a predetermined filter coefficient value. There is an effect that can realize clean high-definition without noise, so that the ghost can effectively eliminate the ghost completely.

Claims (2)

In the signal received by the antenna from a signal inserted with a ghost cancellation reference signal having a predetermined amplitude at a predetermined position of some lines of the vertical blank of the TV video signal and having at least two or more pulses, when the transmission is inserted. In the ghost removing device having a tuner 10 for selecting a channel and an image detector 20 for restoring a signal selected from the tuner 10 to an image signal, the ghost signal is vertically A synchronization separator 30 for separating each into a horizontal synchronization signal; An A / D conversion unit 40 for converting the analog signal from the image detection unit 20 into a digital signal; A line extracting unit (60) for inserting the ghost removal reference signal into the digital signal by the vertical and horizontal synchronizing signals separated by the synchronization separation unit (30) to extract only the lines; A first ROM (70) for storing and reading a sequential value initially generated for use as a ghost removal reference signal inserted at a predetermined position of a part of a vertical blank line of a TV video signal during transmission; A linear autocorrelation operation unit (80) for performing linear magnetic correlation between the ghost removal reference signal obtained from the line extracting unit (60) and the signal read from the ROM (70); A second ROM (90) for storing a data value obtained by performing linear autocorrelation of a ghost cancellation reference signal inserted into a part of a vertical blank line of the transmitter TV video signal and a sequential value first generated to produce the signal; A subtractor (100) for subtracting the data value read from the second ROM (90) from the signal value output from the linear autocorrelation operation unit (80); A ghost elimination filter coefficient calculating unit (110) for obtaining a ghost elimination filter coefficient based on the data value output from the subtractor (100), and changing the coefficient of the filter; The digital video signal output through the A / D converter 40 is obtained to be identical to the ghost removal reference signal inserted at the time of transmission according to the filter coefficient value output from the ghost removal filter coefficient calculating unit 110. A ghost removal filter 50 for filtering; And a D / A converter (120) for converting the ghost removed digital video signal through the ghost removal filter (50) into an analog video signal. The method of claim 1, wherein the ghost elimination filter coefficient calculation 110 is a result of the linear autocorrelation operation unit 80 to extract the signal extracted from the line extraction 60 and the value read out from the first ROM 70. And a difference coefficient between the data values read out from the second ROM (90), taking an absolute value, and adding or multiplying to obtain a filter coefficient.