JPS5936484A - Ghost eliminating device - Google Patents

Abstract

PURPOSE:To improve the ghost eliminating performance, by connecting an AGC circuit to an output side of a transversal filter and storing the output of the AGC circuit in a memory as ghost information after A/D-converting the output of the AGC circuit. CONSTITUTION:The AGC circuit 12 is provided at the succeeding stage of the transversal filter 5, an output of the AGC circuit 12 is given to a video signal processing amplifier circuit and a chroma signal processing amplifier circuit at the succeeding stage and the other output is applied to an A/D converter 7. The output of the A/D converter 7 is stored in a memory 11 as ghost information and the ghost information stored in the memory 11 is processed at an operating circuit 10, the output controls a weighting coefficient correcting circuit 6 so as to correct the weighting coefficient of the transversal filter 5.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a device for removing ghosts occurring in a television transmitting/receiving system.

Conventional configurations and their problems In recent years, when receiving television broadcasts, deterioration of received images due to various radio wave interferences has become a common problem. In particular, the so-called ghost phenomenon, in which received images become double or triple, has become more common, mainly due to the rise in the heights of buildings in urban areas. Countermeasures against this problem include the development of wall construction materials that prevent the reflection of radio waves from these buildings, higher directivity of receiving antennas, and diversity reception using horizontally stacked antennas, but all of these methods have operational issues. It has not become widespread due to its complexity and rising costs. Therefore, a need has arisen to provide a fully automatic ghost removal system that can be built into television receivers at low cost.

First, a cost removing device that can be applied to a television receiver will be explained. FIG. 1 shows a part of the configuration of the television receiver. In the figure, (1) is an intermediate amplified video detection circuit which amplifies and detects an intermediate frequency modulated signal from a tuner to obtain a baseband composite video signal A. This composite video signal A is NTS
In the C method, the signal is 0 to 4.2 RfHz. In a normal television receiver, this composite video signal A is supplied to both the video signal processing amplifier circuit (3) and the chroma signal processing amplifier circuit (4). Ghost remover (
2) is after inputting the composite video signal A and removing the Gooset signal.

Circuits (3) and (4) have the function of supplying a video signal B without K ghosts. The cFi signal shown in the figure is supplied to a video display device (such as CR1) as a display signal free of ghosts.

FIG. 2 is a more detailed block diagram of the ghost removal device (2) in FIG. 1. A feature of this device is that it can be used with a transversal filter (5).

As is generally well known, in the television transmission and reception system, if the transfer function in the radio wave propagation system is H(S) and the transfer function in the ghost propagation system is G(S), then
The transfer function of the signal propagation system of the daughter 7 which is connected to the ghost is H.multidot.G (S). On the other hand, since Tofunsparsarfil (5) U can have any transfer function, ghosts can be removed by controlling the propagation system due to ghosts to have an inverse transfer function G-1 (St).

The other parts in Figure 2 are this transversal filter (
5) is the inverse transfer function G″″1 depending on the ghost at that time.
(2) Ghost (extrusion, calculation, usage coefficient generation, and operation before storage) are performed to automatically control the weighted VF and number of each tap so that
is the input video signal, and B is the input video signal.

- is the output py combined video signal from which Jt has been removed, and D is a synchronization signal.

Detection of ghosts in received television signals is performed by observing the flatness of the signal before and after the beginning (leading edge) of the vertical synchronization signal. It can be regarded as a function, and if there is a ghost, the distortion of the unit step function is detected accordingly.For example, the position and size of the ghost are detected at each sampling point.(9) is for its control. This timing pulse generation circuit generates a sampling pulse based on the output of the synchronous N4 circuit (8) in order to extract this portion of the signal.

The video signal B processed by the L-Lance persal filter (5) is added to the clamp Φ conversion circuit (7), and after being clamped to eliminate DC fluctuations, the A/D variable conversion circuit is used. The sampled portion is converted into a digital signal and stored in a memory (11) as ghost information.

Memo for the arithmetic circuit IJO! J (Processing the ghost information accumulated in Ill, transversal filter (5)
A signal is generated to control the m target coefficient when extracting the output value from each tap. This part is normally constructed using a microcomputer.

The weighting coefficient correction circuit (6) is for actually generating and holding a weighting coefficient for each tap based on the calculation result of the calculation circuit 01. Usually, the output of this calculation circuit 0Q is a digital signal. Therefore, if the weighting coefficient is an analog signal, a D-A conversion circuit is required, and in that case, it is also included.

Furthermore, since this process of detection → finding → addition coefficient is repeated many times using the so-called adaptive equalization method, the weighted number is modified one after another many times. It is necessary to store the previous coefficient in memory (Ill).

In addition, since the sampling frequency of the A7'D conversion circuit in the clamp/■ conversion circuit (7) handles video signals, it is necessary to be three times the band frequency. is often used. Therefore, this A/D conversion circuit is required to be high-speed. In many cases, the memory (11) also has a similar crystal speed.

Since a microcomputer is also used as the arithmetic circuit OCt, it is not very fast, and the Φ conversion circuit is
Note only when dealing with the ζ synchronization No. 1a part') Ill
The operation by so-called DMA (Direct Memory Access), which disconnects the memory from the microcomputer, can be eliminated.

In this way, this number of circuit bags can be mainly composed of digital circuits including microcomputers, and the transversal filter (5) can also be integrated using solid-state slow sail lines of CCD%, so it is easy to compare. It can be built into a television receiver at a relatively low cost.

In this conventional ghost removal device, as shown in FIG.
The amplitude of the current image signal decreases, resulting in an image with less contrast. As a result, viewers have to adjust the contrast every time they change the reception channel, which is a hassle. Furthermore, since the width of the input signal to the conversion circuit for detecting the first ghost word also becomes smaller, the accuracy of ghost detection decreases, which is undesirable because ghost erasing performance decreases.

OBJECTS OF THE INVENTION It is an object of the present invention to provide an apparatus that can provide sufficient ghost elimination performance and also provide images with a constant contrast.

Structure of the Invention The present invention comprises a transversal filter to which an image signal is applied to its input, a conversion circuit for digitally converting the video signal processed by the transversal filter, and ■A memory that stores the output of the conversion circuit as ghost information 1, an arithmetic circuit that processes the ghost information accumulated in this memory and generates a signal to control the weighting coefficient of the transparser 7 letter; Transparency is calculated based on the calculation results of the ticket ticket circuit.
A transparser microfiber is provided with a Kato coefficient correction circuit for instructing a weighting coefficient, a timing pulse generation circuit for supplying a timing pulse representing a specific period of a composite video signal to a sex conversion circuit, a memory, and the arithmetic circuit.
An AGC circuit that controls the output level μ to be constant is connected to the output, and the output of this AGC circuit is applied to a width conversion circuit as a signal to be converted, and a ghost-removed video signal is obtained from the output of the AGC circuit. shall be.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 3 to 6. FIG. 3 is a block diagram of an embodiment of the ghost removal device according to the present invention, in which the same reference numerals are used for the same blocks as in FIG. 2 (prior art).

The difference between the 3rd meter and the conventional one is the transversal filter (
5) An AGC circuit 021 is provided at the rear stage, and one output of the AGC circuit θ is sent to the video signal processing amplifier circuit and chroma signal processing amplifier circuit at the rear stage, and the other output is clamped at the required amplitude of the converter.・■ Supply to the conversion circuit (7).

With this configuration, the AGC circuit Q21 can always keep the signal amplitude constant after ghosts are eliminated, so it is possible to obtain a stable image without ghosts. Furthermore, the A/
Since the input signal amplitude to the D converter is also constant, Φ
Conversion'ls? The input signal range of r can be effectively utilized, the ghost detection accuracy can be improved, and the ghost cancellation performance can be improved.

FIG. 4 shows the configuration of the AGC circuit (121), and No. 5N shows the timing of the sampling pulse D for detecting the synchronization signal amplitude.The operation will be explained. First, the output signal A of the transversal filter (5) described above / f: Gain-side 011 circuit that can be controlled by DC voltage (supplied to one chicken to obtain output signal B and signal to clamp/A/D conversion circuit (7).

Next, the signal clamped by the clamp/A/D conversion circuit (7) [E in Fig. 5] and the sampled signal D [D in Fig. 5] generated by the timing pulse generation circuit (9) mentioned above are In addition to the synchronization signal amplitude detection circuit Q51, the amplitude of the synchronization signal is detected and converted into a constant current pressure. This output voltage is applied to the control voltage generating port m (44'r) and converted into an appropriate control voltage.This output voltage controls the gain control circuit O with θ). As shown in FIG. 4, since these have a feedback configuration, it is possible to always keep the amplitude of the same signal υ constant. Since the specific circuits of each Glock are well known, their explanation will be omitted here.

The effect of the configuration shown in FIG. 3 will be explained by comparing it with that of the conventional configuration using the waveforms shown in FIG. FIG. 6(a) shows the waveform of the leading edge of the vertical synchronization signal when a ghost-free signal is received, and the amplitude is F. Next, the waveform when a signal with a 1/2 positive ghost is received is shown in FIG. 6←), and the signal after this signal is passed through the conventional ghost removal circuit is shown in FIG. 6C). At this time, the ghost signal has been eliminated, but the amplitude has become (2/3)·F, causing a problem. 6) is the signal after being passed through the ghost removal circuit shown in FIG.

Effects of the Invention As described above, according to the present invention, the ghost signal detection accuracy is improved and the ghost cancellation performance is improved. Furthermore, images can always be enjoyed with a constant contrast. Therefore, a desirable ghost removal device can be provided.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of a ghost removal device built into a television receiver, and Fig. 2 is a configuration diagram of a conventional ghost removal device.
FIG. 3 is a configuration diagram of an embodiment of the ghost removal device of the present invention, FIG. 4 is a configuration diagram of the main part of FIG. 3, FIG. 5 is a waveform diagram of the main part of FIG. FIG. 2 is a comparative explanatory diagram of the device of FIG. 1 and a conventional device. (2)...Ghost removal device% (5)...Transpast filter, (6)...Weighting coefficient correction circuit, (
7)...Clamp/Φ conversion circuit, (9)...Timing pulse J1 circuit 0...Arithmetic circuit, (11)...
・Memo! J, Q2+...AGC circuit, 03...gain control circuit, α41...control voltage generation circuit, 0υ...
・Synchronization signal amplitude detection circuit agent Yoshihiro Morimoto Figure 1

Claims (1)

[Scope of Claims] L: A Φ conversion circuit that digitally converts the video signal after being processed by a transparsal filter to which a composite video signal is applied to its input, a %-density transformer/<-sal filter, and a Φ conversion circuit. a memory for storing the output of the width conversion circuit as ghost information; and an arithmetic circuit for processing the ghost information accumulated in the memory to generate a signal for controlling the weighting coefficient of the transparser μ filter. , a weighting coefficient correction circuit for instructing a weighting coefficient according to the calculation result of the calculation circuit; A timing bus generation circuit that provides a timing l<μ bus representing A ghost removal device that applies a signal to be converted to a Φ conversion circuit and obtains a ghost-removed video signal from the output of the AGC circuit. 2. A patent claim in which the AGC circuit is configured to detect the amplitude at the leading edge of the vertical synchronization signal. The ghost removal device according to item 1.