JPS6083473A - Ghost removing device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a ghost removal device in a television receiver.

[Background of the invention] □ When radio waves directly arriving from the transmitting antenna (desired waves) and radio waves reflected from buildings, etc. are simultaneously received by the receiving antenna, the image due to the desired wave and the image due to the reflected wave may become misaligned. A so-called ghost appears. Such ghosts are a major cause of deterioration of image quality in television receivers, and various methods have been attempted to eliminate or prevent ghosts. One such method is a ghost removal method using a transversal filter in the video band. This method connects a large number of Rennobu elements in series, each having a minute delay time determined by the highest frequency component included in the video signal, and each delay element By weighting and adding the outputs using a coefficient circuit and outputting the result, a ghost compensation signal (a video signal containing no ghost components) from which ghost components have been removed is obtained.

An example of a ghost removal device using such a transversal filter is shown in a block diagram in FIG.

In the figure, 1 is a video signal input terminal, 2 is a video signal output terminal, 3 is a transversal filter, 4 is a subtracter, 5 is a reference signal generation circuit, 6 is a differentiation circuit, 7 is a comparator, 8 is a shift register, 9 1 is a subtracter, 10 is a tap gain memory, 11 is a D/A (digital analog) converter, 12 is a synchronization signal separation circuit, and 131 is a timing generation circuit. Filter 3
FIG. 2 is a block diagram showing details of the FIG. In the figure, 14 is an adder, 15 is a delay element with a delay time τ, and 16 is a tap amplifier. Note that the tap amplifier 16 is an amplifier whose amplification gain can be varied by a control voltage inputted via the tap gain memory 10 and the D/A converter 11.

First, an overview of the operation in drawing the circuit shown in Figure 1 will be explained.

The video signal input from input terminal 1 is sent to the next stage circuit from output terminal 2 via transversal filter 3, but if this sent video signal contains a ghost component, this We want to remove the components before sending out. Therefore, it is necessary to detect ghost components contained in the video signal output from the filter 3.

A technically easy method is to select the vertical synchronization signal from the width of the video signal and detect the ghost component superimposed on it (detect the ghost component superimposed on the picture). (If you try to do this, it is difficult to detect ghost components because the picture is a signal that constantly fluctuates).

The video signal at input terminal 1 is sent to synchronization signal separation circuit 1
2, the vertical synchronization signal is separated.

The separated synchronization signal is supplied to the timing generation circuit 13 and used as a reference for timing signal generation. The reference signal generation circuit 5 generates a vertical synchronization signal as a reference signal in accordance with the timing instructed by the timing generation circuit 13. Therefore, if the subtracter 4 subtracts the vertical synchronization signal contained in the video signal that is the output of the filter 3 and the vertical synchronization signal as the reference signal output from the circuit 5, the vertical synchronization signal in the video signal The ghost component that was superimposed on the image is completely removed.

This ghost component is differentiated by a differentiating circuit 6, and the differentiated output is further converted into a digital signal (binarized) by a converter 7, and this digital output is written into a shift register 8.
The write timing is controlled by a timing generation circuit 13. The gain data stored in the tap gain memory 10 is modified according to the data read out from the shift register 8. That is, data is read from the memory 10, modified in the subtracter 9 according to the data read from the shift register 8, and then written to the memory 10 again.

When this process is completed, the tap gain data is read out from the memory 10 and converted into an analog voltage by the D/A converter 11, and then the analog voltage is used as a control voltage for the tap amplifier 1 in the transversal filter 3.
6 to control its amplification gain. As a result, the filter 3 outputs a video signal with reduced ghost components. By repeating the above process, the filter 3 will eventually output a video signal on which no ghost components are superimposed.

The above is an overview of the operation of the ghost removal device shown in FIG. 1, but the explanation will be slightly supplemented with reference to FIG. 3 which shows the signal waveforms of the main parts in FIG. 1.

In FIG. 3, (A) shows a vertical synchronizing signal as a reference signal output from the reference signal generating circuit 5, and F indicates its leading edge. ←) is transpersal filter 3
The vertical synchronization signal included in the video signal output from is shown, and the shaded area shows the superimposed ghost component. (c) shows the ghost component obtained as a result of subtraction in the subtractor 4, and (c) shows its differential output pulse P
It shows.

When a control signal (gate pulse) having the timing of the leading edge F of the vertical synchronization signal is sent from the timing generation circuit 13 to the shift register 8 and the operation of the shift register 8 is started from that point, the binary output of the pulse P is as follows. It will be taken into the shift register 8 at a timing one hour after the timing of the leading edge F. In this way, the shift register 8 seeds ghost information consisting of a series of bit numbers,
Then, the information is sequentially outputted to the subtracter 9.

Next, as mentioned above, the correction operation of the stored data in the tap gain memory 10 is started.
There is a correspondence with the numbers (C11"2...), and in this case, C11C2, C3..., in descending order of the delay time of the input signal. The tap gain data at the corresponding addresses are corrected.

When the modification of the data in the tap gain memory 10 is completed, new tap gain data is given to each tap amplifier 16 of the transversal filter 3, but the data read from the tap gain memory 10 is It is converted into an analog voltage by the D/A converter 11,
applied to each tap amplifier 16. The applied voltage is held in a capacitor with a small capacitance (not shown), but after it has been applied to each tap amplifier, the voltage is again applied to the tap amplifier C1.
Voltage application starts from , and by repeating this,
Prevents capacitor discharge.

Ghost detection as described above, tap gain memory 1
Since the vertical synchronization signal is used as a reference signal, the data correction at 0 and the control voltage application to each tap amplifier are performed once per field, and are repeated until no ghost is detected. In this way, ghosts can be gradually removed.

As previously explained, in such a ghost removal device, a gate pulse is supplied from the timing generation circuit 1.3 to the shift register 8 as a timing signal for starting the operation of the register. However, in order to achieve the effect of removing ghost components, it is extremely important not to make a mistake in the timing of gate pulse generation, which will be explained in detail below with reference to FIGS. 4 and 5. .

FIG. 4(a) shows in particular detail only the circuit portion that creates the gate pulses supplied to the shift register 8 from the video signal input to the terminal 1, in the circuit portion M in FIG. 1, as M'. FIG.

In the same figure, 20 is the number of clamp times N5.21 p 22
are each a sample hold circuit, 23 is an average value circuit,
24 is a comparator, 25 is an AND circuit, 26 is a gate pulse generation terminal, 27 is a synchronization signal separation circuit, and 28 is a timing pulse generation circuit. FIG. In the figure, only a vertical synchronization signal is shown as a video signal. F indicates the leading edge of the vertical synchronization signal, and both El and E2 indicate equalization pulses.

Refer to Figures 4 (a) and (b). First, a video signal as shown in FIG. 4(b) is input to the video signal terminal l. Here, the video signal is the leading edge F of the vertical synchronization signal.
Only shown. This video signal is transmitted to the circuit 20
At , the edges of the synchronizing signal are aligned and sent to the sample and hold circuits 21 and 22 and the synchronizing signal separation circuit 27. The output of the synchronization signal separation circuit 27 is input to a timing pulse generation circuit 28, and various timing signals indicated by A, B, and C are generated.

In the sample and hold circuit 21, the pedestal voltage between the equalization pulse E1 and the leading edge F of the vertical synchronization signal is sampled by the timing pulse A.

In the sample hold circuit 22, the same synchronization tip voltage of the vertical synchronization signal leading edge F and the equalization pulse E2 is the sample pulse B.
sampled by These voltages are average value circuit 2
3, the average value, that is, 1 of the amplitude of the vertical synchronization signal.
72 is detected and input to the comparator 24. on the other hand,
A clamp circuit 20 is connected to the other input of the comparator 24.
The output of is input. Therefore, the signal amplitude of the vertical synchronization signal in the input video signal is at a predetermined level of 172.
The output of the comparator 24 changes from low to high when it reaches . Since there is a synchronization signal every horizontal period,
By selecting only the vertical synchronizing signal portion using the selection pulse C and the AND circuit 25, a desired gate pulse can be obtained.

The reason for choosing the point at which the output of the comparator 24 changes from low to high when the amplitude of the vertical synchronizing signal reaches a predetermined amplitude of 100 is that the leading edge F of the vertical synchronizing signal is not necessarily vertical. , may be tilted, so even in that case, the point in time when the rising edge of the leading edge F reaches a predetermined level of 100 is regarded as the point in time when the leading edge F occurs. Further, the selection pulse C has the role of a mask pulse that selects the vicinity of the leading edge F of the vertical synchronization signal.

FIG. 5 is a waveform diagram showing the timing of the gate pulse generated in the circuit of FIG. 4(A) in comparison with the vertical synchronizing signal.

After going through the process of explaining the operation with reference to FIG.
) vertical synchronization signal leading edge F of a video signal containing a ghost
In contrast, a gate pulse q as shown in FIG. 5 (+) is generated and supplied to the shift register 8. Then, the shift register 8 starts its full operation and clocks C1, C2, C
3, C4 and up to 4 bits all incorporate raw human power.

At the time of clock C5, a ghost component (shaded area in FIG. 5(a)) superimposed on the vertical synchronization signal is detected and transmitted through the differentiating circuit 6 and comparator 7 as shown in FIG. 5(C).
The pulse output P is taken in as a high input, not shown in . As a result, the series of ghost information taken into the shift register 8 becomes [10000]. This increases the taps in the transversal filter 3! The gain of the Ii device C5 is reduced and the ghost is gradually removed.

Now, in such a ghost removal device, a CO whose delay time can be determined by the driving clock frequency is used as a delay element constituting the transversal filter.
Generally, a charge transfer element such as D is used. C.C.
D samples the input signal at the clock cycle,
In order to convert this into charge and transfer it, a low-pass filter is required for its output. Therefore, the delay caused by this low-pass filter is also added to the delay of the signal actually output from the transversal filter 3.

As a result, the video signal outputted from the transversal filter 3 as shown in □ in FIG. 5(d) is delayed by the delay amount τd caused by the low-pass filter than that shown in FIG. 5(a). Since the video signal band is 4 MHz, according to the sampling theorem, the delay time τ of the COD delay element is about 100 ns (the driving clock frequency is 10 MHz).
Hz) is often selected. Therefore, this low-pass filter has a pass band of 4 to 2, and IOMH,
It is necessary to have an attenuation degree of 40 dB or more, and the delay time τd is about 100 to 200 ns. This corresponds to one or two delay elements.

Therefore, the output P1 of the differentiating circuit 6 as shown in FIG. becomes ctoooooo). As a result, in the transversal filter 3, although not shown for convenience, the gain of the tap amplification hC6 decreases, and a portion of the ghost component remains as shown in FIG. 2(f).

Therefore, in order to eliminate this drawback, a conventional method has been developed in which a low-pass filter having the same characteristics as that connected to the output section of the transversal filter 3 is arranged at the input or output section of the circuit section M in FIG. An example is shown as a block diagram in FIG. In the figure, 30.31 is a low-pass filter with the same characteristics including the delay time caused by it, M is the same gate pulse generation circuit as shown in Figure 4 (A), and M is the timing generation circuit M in Figure 1.
, other parts excluding the gate pulse generation circuit M (
(reference signal generation timing generation circuit). Further, the same components as those mentioned above are given the same numbers.

This operation will be explained below using FIG. 7. A vertical synchronizing signal (video signal) superimposed with a ghost signal as shown in FIJ<8) is input to the video signal input terminal 1. Since this signal is input to the transversal filter 3 and passes through the low-pass filter 31, it is delayed by a time τd compared to the video signal before passing.

On the other hand, since the video signal input is also input to the low-pass filter 30, its output is also delayed by the time τd as shown in (b).The output of the low-pass filter 30 is shown as M in Figure @6. Since the gate pulse is supplied to the gate pulse generation circuit, the gate pulse is also generated with a delay of time τd from the input video signal. This is shown in Figure 7 (C)
Shown below. Therefore, the shift register 8 starts its operation with a delay of time .tau.d compared to the conventional case, and takes in the low power from clocks C19C2°C3 and C4 up to the 4th bit.

At the time of clock C5, the differential output as shown in FIG. 7(d) is obtained in the differentiating circuit 6, so this differential output is taken into the shift register 8 as a high input. As a result, the series of ghost information input to the shift register 8 becomes [10000], and the tap increase in the transversal filter 3 is 1llTi? The gain of device C5 is reduced to eliminate the ghost.

However, in such a ghost removal device, the gate pulse G generated by the gate pulse generation circuit shown in FIG.
delayed by g. For this purpose, the ghost information mentioned above,
As a result, the taps that should be corrected cannot be handled correctly, and a sufficient ghost suppression effect cannot be obtained.

Further, in the case of the above conventional example, two low-pass filters such as 30 and 31 with exactly the same characteristics are required, and the amount of delay cannot be adjusted inside the ghost gland castor.

In this way, in the conventional ghost removal device, when a charge transfer device such as a CCD or the like is used as a delay element, the ghost 10
The correspondence between the information and the tap becomes inaccurate.

Even in the conventional example that takes into account the delay of Sarani and low-pass filter M, the gate pulse generation delay cannot be ignored, and there is still a problem that the correspondence between the ghost II signal and the tap becomes inaccurate, and a sufficient suppression effect cannot be obtained. 〇 [Object of the invention] The object of the present invention is to eliminate the above-mentioned drawbacks of the prior art and to reduce CO2
An object of the present invention is to provide a ghost removal device that can obtain a sufficient suppression effect even when a transversal filter configured as shown in D is used. In the ghost removal device of the receiver, a pulse generation timing adjustment circuit is placed in the signal path to adjust the timing in the process from the input video signal to the generation of gate pulses, thereby eliminating ghost information and tap information. It is characterized by accurate correspondence.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 8 is a block diagram showing one embodiment of the present invention. In the same figure, 31 is a low-pass filter arranged at the output part of the transversal filter 3, 32 and 33 are pulse generation timing adjustment circuits, and It controls time.

Further, M is the same gate pulse generation circuit as shown in FIG. 4(A), and M is the other part (reference signal generation timing generation circuit). Further, the same components as those mentioned above are given the same numbers.

FIG. 9 is a block diagram showing in detail the pulse generation timing adjustment circuit 33 in FIG.
35 is a shift register, 35 is an output selection switch of the shift register 34, 36 is a decoder for generating a selection signal for the switch 35, 37 is an external data input terminal for output selection of the decoder 36, and 38 is a gate pulse output terminal after generation timing adjustment. Other parts with the same numbers as above have the same functions.

This operation will be explained below using FIGS. 8, 9, and 10. The video signal input terminal 1 has a
A video signal containing a ghost component as shown in a) is input. Since this signal is input to the transversal filter 3 and passes through the low-pass filter 31, the signal at the video signal output terminal 2 is delayed by a time τd compared to the input signal, as shown in FIG. 9(b). .

On the other hand, the video signal input is input to the gate pulse generation circuit M' shown in FIG. 8 or 9, and its output is gate-delayed, and the gate pulse generator circuit M' is delayed by a time τg as shown in FIG. 10(C). G occurs. This gate pulse G
is input to the pulse generation timing adjustment circuit 33. In the same circuit 33, the gate pulse G is first inputted to the shift register 34, delayed by a desired time, and output as shown in Figure @9.

At this time, the output of the decoder 36 is selected according to the data set and input in advance from the external data input terminal 37, and the selection switch 35 of the output stage of the desired shift register 34 is selected.
(Which one of St to S4) is closed and output to the gate pulse output pin 1,38. In this way, the gates A and SG also have a time τ compared to the video signal input.
This occurs with a delay of d, as shown in FIG. 10(d). Hereinafter, in the conventional example shown in FIG. 6, a low-pass filter is connected before the gate pulse generation circuit M, but similarly to this case, the shift register 8 operates with a delay of time τd from the input video signal. Start, Figure 10 (e
) is taken in as the differential output P. At this time, it should be noted that, for example, in the Q portion of (e), a differential output that is a high input does not appear (this point will be described later). The series of ghost information captured in this way reduces the gain of tap amplifier C5 and eliminates ghosts.

Furthermore, in the above, it is also necessary to consider the delay of the reference video signal output from the reference signal generation circuit 5. As explained above, the difference between the output video signal of the low-pass filter 31 and the reference video signal from the circuit 5 is taken, and from this the difference is calculated by the differentiating circuit 6 as shown in FIG.
A differential output P as shown in e) is obtained and used as ghost position information. Therefore, the leading edge F of the output video signal of the 11-pass filter 31 in FIG.
If the timing does not match, for example, (
The differential output appears at the position of the differential output waveform calculation in e), causing the shift register 8 to take in incorrect ghost position information.

Therefore, as shown in Figure @8, a pulse generation timing adjustment circuit 32 is connected. The details of the circuit 32 are exactly the same as those in FIG. 9 showing the details of the pulse generation timing adjustment circuit 33, and the operation is also exactly the same. Therefore, the 10th
As shown in the figure, the video signal generated by the reference signal generation circuit 5 passes through the pulse generation timing adjustment circuit 32 and is input to the subtracter 4 with a delay of time τd.

In this way, the generation timing of all pulses is adjusted, so that the ghost information stored in the shift register 8 can correctly correspond to the taps to be corrected, and sufficient ghost information can be obtained. A suppressive effect can be obtained.

〔Effect of the invention〕

As described above, according to the present invention, when a charge transfer element is used as a delay element constituting a transversal filter, the influence of the low-pass filter required on the output side can be completely eliminated, so You can obtain a ghost suppression effect. In addition, since the circuit can be built into an LSI, the number of parts does not increase.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an example of a conventional ghost removal device, Fig. 2 is a block diagram showing details of the transversal filter 3 in Fig. 1, and Fig. 3 shows signal waveforms of main parts in Fig. 1. Waveform diagram, FIG. 4(A) is a block diagram showing the details of the main part of the circuit portion M in FIG. 1, FIG. 4(B) is a waveform diagram of each part signal in the circuit of FIG. 4(A), Fig. 5 is a waveform diagram showing the timing of the gate pulse generated in the circuit of Fig. 4 (a) in comparison with the vertical synchronization signal, and Fig. 6 is a block diagram showing an example of a ghost removal device with conventional delay countermeasures. 7 is a signal waveform diagram of each part of FIG. 6, and FIG. 8 is a block diagram showing one embodiment of the present invention.
FIG. 9 is a block diagram showing details of the pulse generation timing adjustment circuits 32 and 33 in the eighth FXJ, and FIG. 10 is a signal waveform diagram of each part in FIG. 8. Description of symbols 1...Video signal input terminal, 2...Video signal output terminal, 3...Transversal filter, 4...Subtractor, Four-base ratio signal generation circuit, 6...differentiation circuit, 7...music comparator,
8...Song shift register, 9...Subtractor, 10
... Song tap gain memory, 11... D/A converter, 12... Song synchronization signal separation circuit, 13... Timing generation circuit, 14... Song adder, 15... ...
・Delay element, 16...Tap amplifier, 20...
... Clamp circuit 1.21, 22 ... Sample hold circuit, 23 ... Average value circuit, 2
4... Comparator, 25... Song AND circuit,
26... Music clock pulse generation terminal, 27... Music synchronization signal separation circuit, 28... Timing pulse generation circuit, 30, 31... Low pass filter, 32.
33... Song pulse generation timing adjustment circuit, 34... Song shift register, 35... Output selection switch,
36...Decoder, 37...External data input terminal, 38...Pulse generation terminal Agent Patent attorney Akio Namiki Figure 1 Figure 2 Figure M 3 Figure ゝ- 1)-1' Figure 5 Figure 6 Figure 9 Figure 37 Figure 10

Claims (1)

[Claims] 1) A transversal filter configured by using a charge transfer element as a delay element, a low-pass filter connected to its output side, and a tap gain memory that stores the tap gain of each tap amplifier included in the transversal filter. The timing is determined by passing a predetermined reference signal included in the video signal that has passed through the transversal filter and the low-pass filter and the first pulse generation timing adjustment circuit (hereinafter sometimes simply referred to as the timing adjustment circuit). means for detecting a ghost component by comparing the adjusted and separately prepared reference signal; and a second timing adjustment circuit that detects a position signal indicating a specific temporal reference position related to the reference signal included in the video signal. after adjusting the timing via a means for detecting the temporal position of the ghost component using it as a reference, and correcting the tap gain data stored in the tap gain memory according to the detected position information. and means for removing ghost components from the video signal passed through the transversal filter and the low-pass filter by controlling the gain of each tap amplifier in the transversal filter using the modified data K[e]. 2. A ghost removal device comprising: a ghost removal device, wherein the amount of timing adjustment in each of the first and second timing adjustment circuits is adjustable.