JPS60127880A - Ghost eliminating device - Google Patents

Abstract

PURPOSE:To keep stable operation even after the processing of ghost elimination by using respectively a signal including the original ghost at the start of eliminating processing and a signal after processing when the eliminating processing is progressed as an input signal of a synchronizing signal generating circuit. CONSTITUTION:A switching circuit 15 is provided to a pre-stage of a synchronizing signal generating circuit 8, a video detection output signal A is applied as an input signal to the switching circuit 15 and also a signal B via the ghost eliminating processing is applied as input signals of the switching circuit 15, and when the ghost eliminating processing is started, the original signal A is outputted and after the processing is progressed, the signal B after processing is outputted and fed to the next stage. The control switched to the signal B after processing is conducted when the signal B after processing enters the stable state by the result of operation of an operating circuit 10.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a ghost removal device that can be used in television receivers.

Conventional configurations and their problems In recent years, when receiving television broadcasts, the deterioration of received images due to various radio wave interferences has become a 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 include developing wall materials that prevent the reflection of radio waves from these buildings, increasing the directivity of receiving antennas, and increasing the horizontal star pattern.
4 Dipercity reception using a power antenna has been implemented, but none of these methods has become widespread due to operational complexity and increased cost.

Therefore, there has been an increasing need to provide a fully automatic ghost removal system that can be built into a television receiver at a low cost.The configuration of a television receiver and a ghost removal device that can implement the present invention will be explained below. do. 1st
The figure shows a part of the configuration of the television receiver. In the figure, reference numeral 1 denotes 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. This complex 1
The video signal A is a signal of 0 to 4.2 MHz in the NTSC system. In a normal Ten Vision receiver, this composite video signal A is directly supplied to both the video signal processing amplifier circuit 3 and the ROM signal processing amplifier circuit 4.

The ghost removal device 2 has a function of manually removing the ghost signal from the composite video signal and then supplying a ghost-free composite video signal B to the circuits 3 and 4. C shown in the figure is supplied to a video display device (CART, etc.) as a display signal without ghosts.

FIG. 2 is a more detailed block diagram of the ghost removal device 20 portion in FIG. 1. This device uses a %eu, +・ranceversal filter 5.

As is generally well known, in a television transmitting and receiving system, the transfer function in the radio wave propagation system is expressed as H(s),
Let G(s) be the transfer function of the propagation system due to ghosts,
The transfer function of the total Nogami propagation system including ghosts is H(
s)・G (s). On the other hand, since the transversal filter 5 and adder circuit 12 in FIG. 2 can have any transfer function, if the control is performed to have the inverse transfer function G""1(s) of the propagation system due to ghosts, , ghosts can be removed.

The other parts in FIG. 2 are this transversal filter 6.
Then, the inverse transfer function G”1(s) corresponding to the ghost of 4
Goth +- detection, operation to automatically control the weighting factor of each tap so that it has.

In the figure, human is the input composite video signal, B is the ghost-removed output composite video output, and D is the synchronization signal.

Ghosts in received television signals are detected by observing the flatness of the signal before and after the beginning (leading edge) of the planar synchronization signal. Ideally, this portion of the signal can be regarded as a unit step function, and if there is a ghost, distortion of the unit step function is detected accordingly. For example, the location and size of a ghost is detected at each sampling point. In order to extract this part of the signal, a timing pulse generation circuit 9 generates each pulse for control 1 based on the output of the synchronization signal generation circuit 8. The output of is weighted by the adder circuit 12, and the composite video signal B via the AGO circuit 13 is added to the clamp/AD conversion circuit γ, and after being clamped to eliminate DC fluctuations, it is AD converted and the ghost information is digitized. It is stored in the memory 11.

The arithmetic circuit 1o processes all the ghost information stored in the memory 11 and generates a signal for controlling the addition 1F coefficient when extracting the output signal from each tap of the 1-lance versal filter 5. This part is usually constructed using a microcomputer.

The weighting coefficient correction circuit 6 is used to actually generate a weighted 1-series number for each tap based on the calculation results of the calculation circuit 10 and to compose the poem, and normally the output of this performance circuit 1o is a digital signal. If the weighting coefficient is an analog signal, a DA conversion circuit is required, and in that case it is also included.Also, since this detection → calculation → weighting is performed repeatedly by a so-called adaptive equalization method, The weighting coefficients are modified one after another many times, and it is necessary to store the previous coefficients in the memory 11. Also, circuit 7
The sampling frequency of the AD conversion circuit inside is required to be three times the band frequency because it handles composite video signals, and is compatible with NTSC.
The system uses 10.7M, which is three times the chroma subcarrier frequency.
Hz is often used. Therefore, this AD conversion circuit is required to be high-speed. Similarly, the memory 11 is often a high-speed one, and since a microcomputer is also used as the input circuit 1○, it is not so fast, and the memory 11 is used only when the AD conversion circuit is handling the vertical synchronization signal part. It is possible to perform operations using so-called DMA (direct memory access), which is independent from the microcomputer.

Further, in order to keep the amplitude of the composite video signal B from which ghosts have been removed constant, an AGG circuit 13 is provided after the adder circuit 12 to receive an appropriate sampling pulse from the timing pulse generation circuit 9 and keep the amplitude of the synchronization signal constant. . Reference numeral 14 denotes a reset circuit 1, which generates a reset pulse E to start the ghost removal operation and supplies it to each block. The human input signal of the synchronization signal generation circuit 8, which is the basis for generating important timing pulses, is always the signal A containing ghosts. Therefore, even during the period when the ghost removal process is completed and a ghost-free image is displayed, the output signal of the synchronization signal generation circuit 8 becomes unstable depending on the state of the composite video signal, and the timing pulses mentioned above become unstable. There is a possibility that the operation of the ghost removal device may become unstable.

OBJECTS OF THE INVENTION In view of the above-mentioned problems, an object of the present invention is to maintain stable operation at all times even after Go21~removal processing.

Structure of the Invention The present invention uses the original ghost-containing signal at the start of the removal process 11.1 as the input signal of the synchronization signal generation circuit in the ghost removal device, and the processed signal when the removal process has progressed appropriately. This is a ghost removal device that uses

Description of examples A block diagram of one embodiment of the present invention is shown in FIG.

Blocks in FIG. 3 that are the same as those in FIG. 2 are given the same numbers. Further, since the ghost removal operation was explained in the conventional example, the explanation thereof will be omitted.

The features of this circuit will be explained using FIG. 3.

A switching circuit 15 is provided before the synchronization signal generation circuit 8,
As the input signals of the switching circuit 15, one is the video detection output signal, and the other is the signal B that has been subjected to ghost removal processing.
When the ghost removal process starts, the original signal A is output, and after the process has progressed, the processed signal B is output and supplied to the next stage. Here, the control to switch to the processed signal B is performed when the processed signal B enters a stable state based on the calculation result of the calculation circuit 1o. The specific circuit of the switching circuit 16 is well known and will therefore be omitted, but a television/video signal switching circuit used in a television receiver, for example, may be used.

Effects of the Invention As described above, according to the present invention, by providing a switching circuit, it is possible to improve the timing pulse generation circuit of a ghost removal device, which conventionally had unstable elements, into a stable circuit. A ghost removal device with high added value can be realized.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a main part of a television receiver including a ghost removal device, FIG. 2 is a block diagram of a conventional ghost removal device, and FIG. 3 is a block diagram of a ghost removal device according to an embodiment of the present invention. It is a diagram. 5... Transversal filter, 6... River/weighting (thread number correction circuit, 7... Clamp/AD conversion circuit, 8... Synchronization signal generation circuit, S...・・・
- Timing pulse generation circuit, 1○... Arithmetic circuit, 11... Memory, 12... Addition circuit, 15... lJJ conversion circuit. Figure 1 Japanese Patent Application Publication Sho GO-127880 (4)

Claims (1)

[Claims] Ka Hhu Road,! : , l-lance versal filter i-, (7) filter, a weighting coefficient correction circuit and arithmetic circuit for controlling the filter, an AD conversion circuit for producing ghost (■), a memory, a timing pulse generation circuit, and a synchronization signal generation circuit, a switching circuit for switching an input signal to the synchronization signal generation circuit, means for supplying a ghost-reduced signal and a non-ghost-removed signal as inputs to the switching circuit; A ghost removal device comprising a control means for controlling a switching circuit using the output of the 6-bit shade circuit to control which of the two inputs is selected.