JPS6046174A - Ghost eliminating device - Google Patents

Abstract

PURPOSE:To obtain a sufficient ghost eliminating effect by inhibiting temporarily the rewrite of a tap gain memory and keeping the number of times of correction of tap gain constant in any case. CONSTITUTION:If a gate pulse is not generated in a correct timing position, an output (c) of an inverter 32 becomes high-level, and an output (e) of a D-FF 41 becomes low-level, and an output (f) of an AND circuit 33 becomes low-level, and the rewrite of a tap gain memory 10 is inhibited, and clock pulses are led out to a counter 13' in accordance with this inhibition, and therefore, the counting operation is stopped temporarily. Consequently, not only a unstable operation is avoided but also the number of times of correction of the tap gain memory 10 is a certain value determined by the number of bits of the counter 13' in any circumstances. Thus, the number of times of correction of the tap gain memory 10 is kept constant in any case to obtain a sufficient ghost eliminating effect.

Description

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

[Background of the invention]

When radio waves arriving directly from the transmitting antenna (desired waves) and radio waves reflected from buildings etc. are simultaneously received by the receiving antenna, a so-called ghost occurs, where the image of the desired wave and the image of the reflected wave appear misaligned. do. Ghosts that appear on television receivers have become a big problem that degrades the image quality, and various methods have been used to remove and prevent ghosts.One of them is transversal in the video band. There is a ghost removal method using a filter. This method removes ghosts by connecting a large number of delay elements in series, each with a minute delay time determined from the highest frequency component included in the video signal, and adding the outputs of each delay element using a coefficient circuit. This is to obtain a ghost compensation signal.

An example of a ghost removal device using such a transversal filter is shown in a block diagram in FIG. 3, in which 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 is a subtracter, 10 is a tap gain memory, 11 is I)/A( Digital/analog) converter, 1
2 is a synchronization signal separation circuit, 12' is a vertical synchronization signal separation circuit, 13 is a timing generation circuit, and 16' is a counter (timer).0 Figure 2 shows the transversal filter 6 in Figure 1.
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 from the tap gain memory 10 via the D/A converter 11.

First, an overview of the operation of the circuit configuration shown in FIG. 1 will be explained.

The video signal input from the input terminal 1 is sent to the next stage circuit from the output terminal 2 via the transversal filter 6, but if the sent video signal contains a ghost component, We want to remove this component before sending it out. Therefore, it is necessary to detect ghost components contained in the video signal output from the filter 6.

A technically easy method is to select the vertical synchronization signal from among the video signals and detect the ghost component superimposed on it (detect the ghost component superimposed on the picture). If you try to do this, the image is a constantly fluctuating signal, so it is difficult to detect ghost components).

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 16 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 included in the video signal output from the filter 3 and the vertical synchronization signal as a reference signal output from the circuit 5, the vertical synchronization signal in the video signal can be subtracted. The ghost component superimposed on the signal is removed.

This ghost component is differentiated by a differentiating circuit 6, and the differentiated output is further digitized (binarized) by a comparator 7.
A digital output of 1 is written to the shift register 8.

The write timing is controlled by a timing generation circuit 13.

According to the data read out from the shift register 8, the gain data stored in the tap gain memory 10 is corrected. That is, data is read from the memory, 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 from the memory 1o, converted to an analog voltage by the r')/A converter 11, and then applied to the tap amplifier 16 in the transversal filter 3 as a control voltage. to control its amplification gain. the result,
The filter 3 outputs a video signal with reduced ghost components. By repeating the above process a predetermined number of times by the counter 13', finally,
The filter 3 outputs a video signal on which no ghost components are superimposed.

The above is a summary of the operation of the ghost remover (H) shown in Fig. 1, but I will briefly explain it below with reference to Fig. 3, which shows the signal waveforms of the main parts that appear in Fig. 1. Complement.

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. (b) shows the vertical synchronizing signal contained in the video signal output from the transversal filter 5, and the shaded part shows the ghost component that is present. (c) shows a ghost component obtained as a result of subtraction in the subtractor 4, and (b) shows its differential output pulse P. Control l! from the timing generation circuit 13 at the timing of the leading edge F of the vertical synchronization signal! 1 signal (gate pulse) is sent 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 sent to the shift register 8 at a timing T time after the timing of the leading edge F. It will be accumulated. Thus - C1 shift 1. /8 digit raster, stores cornut information consisting of a series of bit numbers, and sequentially de-energizes the information.
It will be output to the device 9.

Next, as mentioned above, the correction operation of the stored data in the tap gain memory 10 is started, but the address of the tap gain memory 10 and the number of the tap amplifier 16 in FIG. 2 (CI + C2 . . . ), and in this case, CI, C2Hc3, etc. are corresponded to each other in order of decreasing delay time of the input signal. Tap gain data at the address Corrections will be made.

Once the data in the tap gain memory 10 has been corrected, new tap gain data is given to each tap amplifier -16 of the transversal filter 3. The data is converted into an analog voltage by the D/A converter 11 and applied to each tap amplifier 16. The applied voltage is held in a small capacity capacitor (not shown), but once it has been applied to each tap amplifier, voltage application starts again from the tap amplifier C1, and by repeating this, the capacitor is discharged. is visiting.

The process of ghost detection, data correction in the tap gain memory 10, and control voltage application to each tap amplifier as described above uses the vertical periodic signal as the reference signal. Performed once.

2. Counter 10' specifies the 12 times the above process is repeated. . In other words, during ghost removal, the data in the tap gain memory lJ1[1 is constantly being modified.
Even when there is no ghost, the lower bit of the data oscillates from 0 to 1 every vertical period due to noise contained in the video signal. For this reason, if the ghost removal operation is constantly performed, the S/N ratio will deteriorate (Also, due to disturbances caused by radio waves reflected from the flight line, etc., there is a risk that the operation may become unstable, such as adding a voice trace). There is. For this reason, once the time period when it is estimated that ghost removal has been sufficiently performed has elapsed, all modifications of the tap 1st day 4 memory 10 are prohibited, thereby preventing fluctuations in the tap gain. Incidentally, it is usual to count the output of the vertical synchronizing signal separation circuit 12' which is generated once (60 Hz) in the counter is'+q and i field.

As previously explained, in such a ghost removal device, a gate pulse is supplied from the timing generation circuit 16 to the shift register 8 as a timing signal to start the operation of the register. , it will be explained in detail below that it is extremely important not to make a mistake in the timing of gate pulse generation in order to achieve the effect of ghost component removal.

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 figure, 20 is a clamp circuit, 21 and 22 are sample and hold circuits, 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 28 is a timing pulse This is a generation circuit.

FIG. 4←) is a waveform diagram of each part signal in FIG. 4(A). 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 + FJ2 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 input terminal 1. Here, the video signal is the leading edge F of the vertical synchronization signal.
Only shown. This video signal is transferred to the clamp circuit 20
The levels of the tips of the synchronization signals are aligned in the sample hold circuit 2122 and the tIl signal separation circuit 2.
Sent to 7. 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 synchronization tip voltage between 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.
/2 is determined 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 1/2 of the predetermined level.
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 1 is because the leading edge F of the vertical synchronizing signal is not necessarily vertical. , may be tilted, and even in that case, the point in time when the rising edge of the leading edge F reaches a predetermined level i is regarded as the point in time when the leading edge F has occurred. The selection pulse C is a mask pulse that selects the vicinity of the leading edge F of the vertical synchronization signal.For the generation method of the various timing pulses A, B, and C, please refer to Japanese Patent Application No. 1983- As is clear from the matters described in the specification of No. 72582, the input television signal is synchronously separated in the synchronous signal separation circuit 12 (Fig. 1), only the synchronous signal is extracted, and from this, the vertical synchronous signal section is extracted. Then, by detecting only a group of equalization pulses with an interval of 1 inch (where H indicates a horizontal scanning period) existing in the vicinity thereof, and counting a predetermined number of equalization pulses, as shown in FIG. ) is detected, thereby generating sample pulse A1 mask pulse C, ? Figure 5 is a waveform diagram showing the timing of the gate pulse generated in the circuit of Figure 4 (A) in comparison with the vertical synchronization signal. After explaining the operation with reference to Figure 4, Figure 5 (a)
) vertical synchronization signal leading edge F of a video signal containing a ghost
In response, a gate pulse G as shown in FIG. 5(b) is generated and supplied to the shift register 8. Then, the shift register 8 starts operating and clocks C+, C2,
C31C4 and up to 4 bits all take in low inputs.

At the time of clock C5, a ghost component (the shaded part in FIG. 5(a)) superimposed on the vertical synchronizing signal is detected, and the ghost component (hatched portion in FIG.
) is taken in as a high input.

As a result, the series of ghost information taken into the shift register B becomes (10 (100)).As a result, the gain of the tap amplifier C5 in the transversal filter 6 decreases, and the ghosts are gradually removed.

However, if a very large ghost is input or if impulse noise is mixed in by the ignition of the car, this gate pulse may occur at a position completely different from the leading edge F of the vertical synchronization signal.

That is, FIG. 6(a) shows the television signal near the vertical synchronizing signal section, and FIG. 6(b) shows the waveform obtained by extracting only the equalized pulses at iH intervals with synchronization separation of 1-.6 (not shown) Count the equalization pulses using a counter, and if there are 6, then 6
As mentioned above, it is sufficient to sequentially generate each tying pulse, A, B, and C, after a predetermined number of pulses have been counted.

However, as shown in (a), when impulse noise N is mixed into the television signal and exceeds the leading level of the synchronization signal Sy, this noise N is also considered to be a synchronization signal, and (C)
The equalization pulse becomes the equalization pulse ■' as shown in . Noise 11 is
If it occurs between the synchronization signal Sy and the equalization pulse (-1), which are separated by 1H period, the interval between the noise N and the synchronization signal Sy will be 1'-11, which means that the noise N and the synchronization signal Sy are separated by 1H period. Equalization pulse (1)' with synchronization signal 5) r4
As a result, two more equalization pulses are generated in (c) than in (c). As a result, each timing pulse A, B, C will not occur at the vertical synchronization signal, but at the much earlier equalization pulse EO. In this case, the timing diagram shown in FIG. 5 becomes as shown in FIG. 7.

In FIG. 7, (a) is an equalization pulse Eo1 in the television signal (b) is a gate pulse that is generated by mistake at an incorrect timing. A synchronizing signal as a reference signal generated separately from the equalization pulse Eo in the television signal is subtracted by a subtracter 4 (see FIG. 1) and differentiated by a differentiating circuit 6. Since the equalization pulse Pro has a narrower pulse width than the vertical synchronization signal serving as the reference signal, the output of the differentiating circuit 6 is as shown in (C).

That is, even if there is no ghost, if the timing of gate generation is incorrect due to impulse noise, a differential output P' for correcting tap C3 is generated in this case. As a result, the ghost removal device ends up adding ghosts instead of suppressing them.

The above explained the case where only one impulse noise was mixed in, but in general, impulse noise is completely random,
In addition, since a large number of gate pulses are mixed in, the gate pulses are generated all over the television signal, and a situation arises in which each tap is corrected with a picture signal.

Furthermore, if a strong ghost exists, the picture signal will be mixed into the synchronization signal section, causing the synchronization separation to malfunction.
Wrong gate generation timing.

Due to these circumstances, conventional ghost removal devices have the drawback of causing unstable operation depending on environmental conditions, and significantly deteriorating image quality.

[Objective of the Invention 1] The object of the present invention is to eliminate the drawbacks of the prior art described above, and to provide a ghost removal device that operates stably even in the presence of impulse noise and powerful ghosts, and that can provide a sufficient removal effect. It is about providing.

[A chest of inventions]

In order to achieve the above object, the present invention provides a means for monitoring whether the gate pulse is generated in proper synchronization with the vertical synchronization signal, and if the gate pulse is not generated correctly due to the presence of impulse noise or a strong ghost. If it is determined to be no, rewriting the tap gain memory is temporarily prohibited, and the counting operation of the timer is also temporarily prohibited to prevent unstable jrj operation. However, it is characterized in that the number of times the tap gain is corrected is constant.

[Embodiments of the invention]

Next, an embodiment of the present invention will be described with reference to the drawings.0 Fig. 8 shows a main part of an embodiment of the present invention (i.e., a circuit section added according to the present invention to a conventional ghost removal device). It is a block diagram. In the same figure, 30 and 31 are D-type flip-flops, 32 is an inverter, and 33 is an A-type flip-flop.
The ND circuit 34 is a synchronous signal obtained by synchronous separation (fourth
The input terminal of the output of the synchronizing signal separation circuit 27 in Figure A), '5
5 is sample pulse A (timing pulse generation circuit 28
36 is a sample pulse B (timing pulse B from the circuit 28) input terminal, and 37 is a memory write control signal output terminal (a write control signal to the tap gain memory 10 in FIG. 1). ),
5th is an AND circuit, 39 is a vertical synchronization signal input terminal, 40
is a clock pulse output terminal to the counter 13'.

FIG. 9 is a waveform diagram showing signal waveforms at various parts in the circuit of FIG. 8.

The operation will be explained with reference to FIGS. 8 and 9. First, when the gate pulse is generated at the correct timing, that is, the synchronous separation output (54) shown in FIG. 9(a) is inputted from the terminal 34 to each input terminal of the D flip-flop 30. D flip flop! 10.31 each C
The sample pulses A (55) and B (56) shown in FIG.
) is input. Therefore, the outputs of the inverter 32 and the D flip-flop 31 are as shown in (e) of FIG. 9(a),
As shown in (e), the output of the AND circuit 63 (
f) also becomes high level, and the tap gain memory 10 can be rewritten.

Further, since the AND circuit 38 performs an AND operation on the write control signal (f) and the vertical synchronizing signal separation output (g), the clock pulse shown in (h) is derived from the clock pulse output terminal 4o of the counter 13'. Therefore, the counter 13' counts 1 in response to the rewriting of the tap gain memory 10.

However, if the gate pulse is generated not at the normal timing position F but at a shifted timing position EO,
Through the same process as explained in FIG. 9(a), the output (c) of the inverter 32 becomes high level, the output (e) of the D flip-flop 31 becomes low level, and the output (f) of the AND circuit 33 becomes high level. ) becomes low level, and rewriting of the tap gain value %IJ10 is prohibited.

In this case, since the write signal (f) falls before the vertical synchronization signal (g) is generated, the output of the AND circuit 38, that is, the clock pulse (h) to the counter 13' is not generated, and the clock pulse (h) to the counter 13' is not generated. There is no change in the count value of ′.

Furthermore, as in the case of FIG. 9(c), when the gate pulse is generated not at the normal timing position F but at the shifted timing position 1]2, by the same process,
The output (c) of the inverter 32 is at a low level, and the output (2) of the flip-flop 61 is at a high level, so that rewriting of the tap gain memory 1o is prohibited. Also,
As is already clear, since the one-in control signal (f) remains at a low level, no clock pulse is supplied to the counter 13'.

In this way, the gate pulse is at the correct timing fuF
If this does not occur, rewriting of the tap gain memo 9 is prohibited, and correspondingly, the clock pulse is not derived to the counter 13', so that the counting operation can be temporarily stopped.

Therefore, as mentioned in Section 2, it is possible to avoid unstable operation, and also to use the tap gain memory 1 under any environment.
The number of zero corrections can be set to a constant value determined by the number of pits in the counter 13'. [Effects of the Invention] As described above, according to the present invention, the impulse Not only can deterioration of removal performance and unstable operation be prevented in the presence of noise or powerful ghosts, but also a sufficient ghost removal effect can be obtained in any case by keeping the correction e of the tap gain memory constant.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a conventionally known ghost removal device, FIG. 2 is a block diagram showing details of the transversal filter in FIG. 1, and FIG. 3 is a waveform diagram showing signal waveforms of important parts in FIG. 1. , FIG. 4 (a) is a block diagram showing the gate pulse generation section in (a), FIG. 4 (b) is a waveform diagram showing the signal waveforms of each part in FIG. A timing diagram showing the timing relationship between the gate pulse and the differential pulse, FIG. 6 is a waveform diagram showing the television signal and its synchronization separation output, and FIG. 7 is a timing diagram showing the timing relationship between the gate pulse and the differential pulse in the case of malfunction. There is Fig. 8. Symbol explanation 1...Video signal input terminal 2...Video signal output terminal 6...Transversal filter 4...Subtractor 5...Reference signal generation circuit 6...Differentiating circuit 7... Comparator 8... Shift register 9... Subtractor 10... Tap gain memory 11... D/A converter 12... Synchronization signal separation circuit 13... Timing generation circuit 3f1, 31...D-type flip-flop 32...Inverter 36...AND circuit 12'...Vertical synchronization signal separation circuit 13'...Counter 68...AND circuit representative patent attorney Akio Takahashi Heaven cQ (J Rokushin Asahi 11 songs ☆ Guri Be 11 Hikari 5 ku porridge 7 yu

Claims (1)

[Claims] 1) A transversal filter, a tap gain memory that stores the tap gain of each tap amplifier included in the filter, a predetermined reference signal included in the video signal that has passed through the filter, and a separately created reference signal. means for detecting the location of a ghost component with respect to a particular temporal reference location relative to a reference signal by comparison; and modifying the tap gain data stored in the tap gain memory in accordance with the detected location information. In the ghost removal apparatus, the ghost component includes means for controlling the gain of each tap amplifier in the filter according to modified data, and means for counting the number of times of detection, modification, and control. A detecting means is provided for detecting whether or not the existing position is correct with respect to the specific temporal reference position, and when the existing position is not correct, the tap gain data stored in the tap gain memory is corrected. 1. A ghost removing device characterized in that the counting operation of the counting means is prohibited.