JPH0783442B2 - Ghost removal device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to elimination of ghost signals by television radio waves, and more particularly to a ghost elimination device that efficiently eliminates ghost signals having a large delay time with respect to a desired wave. is there.

(Prior Art) As a method of removing a ghost, generally, a feedforward method and a feedback method can be considered, and in principle, the ghost can be removed by knowing the delay time of the ghost and the amplitude ratio of the desired wave. The feedforward method measures the delay time and the amplitude ratio, delays the input signal by the delay time of the ghost, and subtracts the signal obtained by multiplying the amplitude ratio from the input signal to remove the ghost component. The feedback method is a method in which the amount applied to the input signal is automatically adjusted until the ghost component remaining after removal converges within a certain range.

When both systems are put to practical use, the reference of the input signal is generally the point A at the boundary between the equalizing pulse of the vertical synchronizing signal and the vertical synchronizing pulse of the television signal of the waveform (a) of FIG. A stepped portion is used in which a flat signal back and forth lasts for a relatively long time. Since the input signal generally contains noise, an error occurs in the measurement of the delay time and the amplitude ratio, so it is common practice to add the signals of the ghost detection part for each frame and obtain the average value to reduce the noise. It is being appreciated.

(Problems to be Solved by the Invention) When point A described above is selected as a reference point for ghost detection, the pulse intervals of the equalizing pulse and the vertical synchronizing pulse before and after the point A are twice the horizontal scanning frequency of the television. Cycle H / 2
Therefore, if a ghost wave arrives with a delay time shorter than approximately H / 2, the delay time and amplitude ratio of the ghost wave to the desired wave can be accurately and easily obtained. When the delay time is longer than / 2, it becomes difficult to accurately and easily obtain the delay time and the amplitude ratio by effectively utilizing the flat signal portion around the reference point A.

Therefore, an object of the present invention is to eliminate the above-mentioned drawbacks, and to provide a ghost removing device capable of easily and accurately removing a ghost wave even for a ghost wave whose delay time is relatively longer than the period H / 2. It is a thing.

(Means for Solving Problems) In order to achieve this object, the ghost removing device of the present invention is
A ghost wave detection unit, a transversal filter control unit, and a transversal filter are provided, and the ghost wave detection unit detects a vertical synchronization signal of an input television signal, and digitally outputs signals before and after the leading edge of the vertical synchronization pulse. Sync detector, A / D for converting signals and storing them
The converter and the first register, and when H is a horizontal scanning cycle, the output signal of the first register is delayed by H / 2, and the original output signal of the first register is subtracted from this delayed signal. H / 2 delay element and subtractor for, and delay the output signal of the subtractor by an integer multiple of H / 2 time,
This delay signal and an output signal of the subtractor are provided with an integer multiple time delay element of H / 2 and an adder for adding, and the transversal filter control unit outputs from the output signal of the ghost wave detection unit. A difference calculator that creates a difference sequence of a digital signal to detect a ghost, a second register that holds the output, and the contents held in the second register are sequentially read, and these are tapped by the transversal filter. A load controller for holding the weight memory in a time-sequential manner, wherein the transversal filter controls a gain of a plurality of taps by a plurality of memory values held in the tap weight memory, and outputs a signal corresponding to a ghost. It is characterized in that it is configured so that a ghost that is generated and has a delay time longer than H / 2 can also be removed.

(Example) The present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 shows a block diagram of the configuration of an embodiment of a ghost removing device according to the present invention.

First, the reference point A of the vertical synchronizing signal of the television signal is generated by the A / D converter 2 in the ghost wave detecting section 1 (see FIG. 2).
The signals before and after are taken into the register 3. Although omitted here, a circuit for adding N vertical synchronization signals and obtaining the average thereof may be added to reduce random noise.

The held vertical synchronization signal is read from the register 3, this output signal is separated into two, one is input to the (−) side of the subtractor 6 and the other is input via the H / 2 delay element 5 to the subtractor 6 Input on the (+) side. The output waveform of the subtractor 6 at this time is the waveform (c) in FIG. In FIG. 2, a waveform (a) is a vertical synchronizing signal waveform fetched in the register 3, a waveform (b) is a waveform obtained by delaying the waveform (a) by H / 2, and a waveform (c) is a waveform (b) to a waveform (a). ) Is a subtracted waveform. The pulse width T of the pulses P and Q of the waveform (c) is about 20 μsec when the television signal is transmitted by the NTSC system, the interval between both pulses is 3H, and the first from the fall of the pulse P to the fall of the pulse Q. A no signal section of about 2.5H occurs in both the field and the second field. If you use this signalless section, H / 2
It is possible to detect ghosts with longer delay times at the same time.

When the ghost delay time is less than the pulse width T, the delay time of the ghost wave can be obtained using the pulse P as a reference pulse. However, when the ghost delay time is longer than the pulse width T, the pulse P is A ghost of a pulse P is generated at a distant place, and when this waveform is differentiated and the delay time of the ghost wave is obtained using the pulse P as a reference pulse,
Differentiated pulses occur at the leading and trailing edges of the ghost of pulse P, making it difficult to uniquely determine the delay time. Therefore, it is advantageous from the point of view of accuracy and easiness of the configuration of the device to adopt a form in which a single differential pulse always comes to one ghost next to the differential pulse at the reference point. The following signal processing is further continued using this pulse P.

The waveform when the difference signal of the waveform (c) of FIG. 2 has a ghost is shown in the waveform (e) of FIG. The second waveform (c) in FIG.
The waveform is the same as the waveform (c) in the figure, the waveform (d) is the waveform only for the ghost, and the waveform (e) is the sum of the waveform (c) and the waveform (d). The waveform (e) of FIG. 3 is delayed by time T and 2T, waveform (f) and waveform (g) are created, and waveforms (e), (f), and (g) are added to form a waveform ( h) is obtained. In Fig. 1, the delay element is used for the calculation during this period.
7,8 and adder 9 are used.

In the waveform (h) of FIG. 3, a pulse (width is 3T) as a reference pulse is obtained in the section L, and a stepped waveform, that is, a ghost reference point P ₀ is obtained at the boundary between the section L and the section M. ing. Therefore, when the delay time of the ghost waveform in the section M is 3T or less including the detection of the ghost having the delay time longer than H / 2, the differential pulse is 1 for each ghost. Since only one is obtained, the step waveform in the vertical synchronizing signal is the same as the case of the reference point A. Therefore, for example, the configuration described in the specification of Japanese Patent Application No. 61-4148 “ghost removing device” which is the applicant of the present invention is the same. The delay time and the amplitude ratio can be obtained with high accuracy and with a relatively easy configuration.

The configuration after the transversal filter control unit in the first illustrated configuration is almost the same as the configuration described in the above-mentioned Japanese Patent Application No. 61-4148 applied to the apparatus of the present invention. In this case, the transversal filter control unit 10 is a ghost. Detection of difference calculator
The method of extracting by 11 is used, and the transversal filter 15 for ghost removal is controlled by using the signal of this difference series.

The principle of ghost elimination using this difference series is, as described in Japanese Patent Application No. 61-4148, the difference series waveform (j) after A / D conversion of the input signal waveform (i) in FIG.
make. Since the difference value corresponding to the ghost portion of this difference series is equal to the amplitude of the ghost, it can be used for tap weighting of the transversal filter. However, in the differential series wave system (j), when a difference component appears near the reference point P ₀ of the input signal waveform (i) other than the reference point P ₀ due to the rounding of the waveform, this is treated as zero.

The fifth configuration example is a configuration block diagram for realizing the fourth waveform. In Fig. 5, the input signal is the A / D converter 2
The vertical synchronizing signal is fetched via 0 and its waveform is stored in the register 22. Next, the contents of the register 22 are sequentially read out, and the difference calculator 23 obtains a difference value between the sample point and the next sample point for each sample point. With the help of the base point determiner 21, the output signal of the difference calculator 22 is sequentially written in the tap weight holding unit 24 with the reference point P ₀ of the signal as address 0. The transversal filter 25 is controlled by the tap weight holder 24, the output signal thereof becomes the signal waveform (k) in FIG. 4, and the ghost is canceled by the adder 26 shown in FIG.

(Effects of the Invention) The present invention is directed to the ghost wave detection of the above-mentioned Japanese Patent Application No. 61-4148 "ghost removing device" including a ghost wave detection unit, a transversal filter control unit, a transversal filter, etc., which the applicant previously applied. According to the device of the present invention, it is possible to detect a ghost wave delayed by more than H / 2 period (H is a horizontal scanning period), which is difficult in the prior art, and a simple structure is added to the conventional structure. As a result, the removal capacity can be expanded and the accuracy can be increased.

[Brief description of drawings]

FIG. 1 shows a block diagram of the configuration of a first embodiment of a ghost eliminating device according to the present invention, and FIG. 2 shows the difference between a vertical synchronizing signal and a signal obtained by delaying this by H / 2 in the present invention. FIG. 3 shows various signal waveform diagrams for the purpose of delaying the second differential signal shown in FIG.
Various signal waveform charts for obtaining the sum signal are shown, and FIG. 4 and FIG. 5 show a waveform chart and a block diagram thereof, respectively, for explaining a procedure for implementing ghost elimination using a difference sequence in the present invention. . 1 …… Ghost wave detector, 2,20 …… A / D converter 3,12,22 …… Register, 4 …… Synchronous detector 5 …… H / 2 delay element, 6 …… Subtractor 7,8 ...... Delay element, 9,16,26 …… Adder 10 …… Transversal filter controller, 11,23 …… Difference calculator 13 …… Read controller, 15,25 …… Transversal filter 21 …… Base point Determinator, 24 …… Tap-weighted retainer

Claims (1)

[Claims] 1. A ghost removing apparatus for removing a ghost of a television signal, wherein the removing apparatus includes a ghost wave detecting section, a transversal filter control section and a transversal filter, and the ghost wave detecting section is an input television. A vertical synchronous signal of the John signal, a synchronous detector for converting the signals before and after the leading edge of the vertical synchronous pulse to a digital signal and storing them, an A / D converter and a first register; Is the horizontal scanning period, the output signal of the first register is delayed by H / 2, and the original output signal of the first register is subtracted from this delayed signal. And an output signal of the subtractor is delayed by an integer multiple of H / 2, and the output signal of the subtractor and the output signal of the subtractor are added by an approximate H / 2 integer multiple time delay element and adder. The transversal filter control unit, a difference calculator that forms a difference series of digital signals for detecting a ghost from the output signal of the ghost wave detection unit, and a second register that holds the output, And a read controller for sequentially reading the contents held in the second register and causing the tap weight memory of the transversal filter to sequentially hold the contents, wherein the transversal filter stores the tap weight memory in the tap weight memory. The ghost elimination is characterized in that the gains of the taps are controlled by the retained memory values, the signal corresponding to the ghost is generated, and the ghost having the delay time longer than H / 2 is also eliminated. apparatus.