JPH0787362A - Ghost removal circuit - Google Patents

Abstract

PURPOSE:To eliminate the occurrence of a poor grandchild ghost picture which exceeds a permissible minimum level while the cost of parts increase is suppressed. CONSTITUTION:A comparator 15 compares a specified level for obtaining d the minimum permissible level of a grandchild ghost occurring beyond a tap range from a specified level output part 16 with the differential waveform Pg of a ghost component outputted from a subtracter 12 in the tap range period of a transversal filter 3 before a main signal. When the differential waveform Pg exceeds the prescribed level, a signal change-over switch 14 is changed over to the side of ground and correction quantity data St are prevented from being outputted from a converter 13. The circuit constitution is composed of software in microcomputer 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ghost eliminating circuit for eliminating a ghost phenomenon which occurs on a screen of a television receiver or the like due to a difference in route of transmitted radio waves.

[0002]

2. Description of the Related Art FIG. 11 is an explanatory view conceptually showing the cause of ghost appearing in an image on a television receiver.
As shown in this figure, in addition to the radio waves that reach the receiving antenna directly from the transmission tower, which are indicated by the solid lines, the radio waves that reach the receiving antenna after being reflected by the building (or mountains) as shown by the broken lines, and There are also radio waves that reach the antenna terminal of the television receiver directly as shown by the chain line. These radio waves naturally have a path difference from the transmission tower to the antenna terminal, that is, a time difference. Therefore, when these signals are received by the television receiver with a time lag, the received signal is combined with components such as reflected waves and direct waves in addition to the main signal. A ghost corresponding to the delay time and reception level of these radio waves appears outside the main image.
As shown in the figure, of the received signals, assuming that the radio wave in the path indicated by the solid line is the main signal having the highest intensity, the radio wave path indicated by the broken line is longer than the radio path of the main signal,
Since it is a ghost signal component that is delayed in time, it is called a post-ghost, and the path of the radio wave shown by the alternate long and short dash line has a shorter path than the radio wave of the main signal, and is therefore a ghost signal component that is earlier in time The former ghost.

In order to cancel the ghost thus generated, the transmitting side inserts a ghost cancel reference signal (hereinafter referred to as a GCR (Ghost Cancel Referense) signal) into the video signal, and the receiving side based on the GCR signal. A method is known in which a ghost signal component is detected and the characteristics of a transversal filter are varied according to the detected data to remove the ghost signal component from the received signal.

FIGS. 5A and 5B show the GCR signal SGCR.
FIG. 4 is a waveform diagram showing the above. In these figures, HD indicates a horizontal synchronizing signal and BRST indicates a color burst signal. As the GCR signal SGCR, the GC shown in FIG.
The R waveform GCR and the pedestal waveform PDS shown in FIG. 5 (b) are set as a set. The GCR shown in FIG. 5 (a)
The waveform GCR is a bar waveform located behind the horizontal period, its width is 44.7 μs, and its level is 70IRE.
It is said that Further, the rising characteristic is a sin χ / χ ringing characteristic. The pedestal waveform PDS shown in FIG. 5B is at 0 level as shown in this figure.

Then, the GC as the GCR signal SGCR is used.
The R waveform GCR and the pedestal waveform PDS are shown in FIG.
It is inserted in the video signal as shown in (a) to (h). That is, the 8-field period of the video signal is set as a repeating cycle, and the 18th field or the 281H field in the 1st, 3rd, 6th, or 8th field is set to the cycle shown in FIG.
The GCR waveform GCR of (a) is inserted, and the 18th H of each of the remaining 2nd, 4th, 5th, and 7th fields is inserted.
Alternatively, the pedestal waveform of FIG.
PDS is inserted. In this case, the 17th or 280th field of each field is defined as a fixed waveform.

Next, the waveform diagram of FIG. 7 shows these GCR signals.
The detection principle of the ghost signal component based on SGCR is conceptually shown. For example, FIG. 7A shows the waveforms of 17H and 18H in the first field.
It is assumed that the R waveform GCR is inserted, and FIG. 7B shows the waveforms of 17H and 18H in the fifth field, and the pedestal waveform PDS is inserted for this 18H. Then, when the received signal includes a ghost component, the GCR waveform GCR is, for example, as shown in FIG. 7A, a ghost component waveform (BRST (G)) corresponding to the time difference and the level with respect to the main signal component. Represents a color burst signal in the ghost signal component) and represents a waveform change that is combined. By the way, in the video signal, a horizontal synchronization signal HD and a color burst signal 4 fields ahead
BRST is said to be in phase. Therefore, 1 in the first field
By subtracting the 18H pedestal waveform PDS (Fig. 7 (b)) of the fifth field from the 8H GCR waveform GCR (Fig. 7 (a)), the horizontal sync signal HD and the color burst signal BRST of the respective fields are canceled. Therefore, the waveform shown in FIG. 7C is obtained. Then, for example, if this waveform is passed through a differentiating circuit, a differential pulse waveform as shown in FIG. 7 (d) can be obtained. Shows the level and time difference. Based on this, it becomes possible to detect the ghost component.

Therefore, in the actual detection of the ghost component, 18H for every 1st and 5th, 2nd and 6th, 3rd and 7th, 4th and 8th fields in the 8 field period.
4 sets of GCRs with subtraction as described above for
The calculation is performed by obtaining the waveform GCR (including the ghost component) and then taking the average of these. That is, FIG.
Assuming that the GCR waveform GCR or the pedestal waveform PDS shown in the first to eighth fields of (a) to (h) are S _{1 to} S ₈ , respectively, (Equation 1) S = 1/4 {-(S ₅ -S _{1) + (S 6 -S 2} ) - (S 7 -S 3) + (S 8 -S 4)} = performs a computation represented by GCR. If the ghost component is included in the GCR waveform GCR obtained by the above arithmetic processing, for example, a waveform in which the ghost signal component is combined with the main signal component as shown in FIG. 7C can be obtained. Then, after that, the same results as in FIG.
The differential pulse shown in (d) is used to detect the ghost signal component.

Therefore, an example of the ghost elimination circuit to which the above detection method is applied will be described with reference to the block diagram of FIG. In the figure, 1 is a detection circuit for detecting a received signal and outputting a detection signal SY, and 2 is an A / D converter for A / D converting the detection signal SY supplied from the detection circuit 1. Reference numeral 3 denotes a transversal filter, to which the detection signal SY digitized by the A / D converter 2 is input. The transversal filter 3 includes, for example, a delay line with taps, a coefficient unit that gives an arbitrary tap gain (load) to each tap,
It is composed of an adder circuit that obtains the sum of weight outputs for all taps, and has a finite impulse response filter characteristic. Then, as shown in the figure, the output of the transversal filter 3 is supplied to a microcomputer 8 described later,
By controlling the coefficient of the transversal filter 3 based on the correction amount data ST output from the microcomputer 8, the transversal filter 3 generates a cancellation signal corresponding to this and removes the ghost signal component. It will be.

Reference numeral 4 denotes a D / A converter which performs D / A conversion on the output of the transversal filter 3 and outputs it as an analog detection signal SY which has undergone ghost removal processing.
Reference numeral 5 is a terminal for supplying the detected signal SY to other required circuits inside or outside.

Reference numeral 6 denotes a digital signal supplied from the transversal filter 3, which is 18H for each field period.
Alternatively, the GCR signal SGCR (G
Reference numeral 7 denotes a gate circuit for extracting and outputting the CR waveform GCR and the pedestal waveform PDS, and a buffer memory 7 for holding the GCR signal SGCR supplied from the gate circuit 6 for each one field period and outputting it to the microcomputer 8. Show.

Reference numeral 8 shown by a broken line in the drawing is a microcomputer. Therefore, the circuit configuration in the broken line is actually realized by a computer and software, but here it is shown by hardware for convenience of showing the operating means. In this microcomputer 8, the ghost signal component is detected based on the GCR signal SGCR input from the buffer memory 6 every one field period, and the transversal filter 3 is detected according to the detection result.
The correction amount data ST for controlling the coefficient of is output. In this microcomputer 8, 9 indicates a field operation circuit, which is a GCR signal from the buffer memory 6.
For the SGCR, the operation of the 8-field sequence described with reference to FIGS.
A waveform similar to that shown in (c), that is, a signal (GCR + Sg) obtained by combining the GCR waveform GCR and the ghost signal component Sg is obtained. For example, the calculation shown in (Equation 1) above can be rewritten as (Equation 2) S = 1/4 (S ₁ −S ₂ + S ₃ −S ₄ −S ₅ + S ₆ −S ₇ + S ₈ ). In the actual field calculation, the GCR signal SGCR obtained in the field order may be integrated as described above.

Reference numeral 10 indicates a differentiating circuit in which a predetermined time constant is set. The GCR waveform (GCR + Sg) including the ghost signal component output from the field operation circuit 9 is changed to the differential pulse waveform (PGCR + Pg) through the differentiating circuit 9. This differential pulse (PGCR + Pg) is obtained as a waveform similar to that described in FIG. 7D, for example.
Reference numeral 11 is a reference waveform forming circuit, which is a GCR waveform GC.
A differential pulse waveform (PGCR) obtained by differentiating R with a time constant similar to that of the differentiating circuit 10 is generated and output. 12
Indicates a subtractor, which is the signal PGCR input from the differentiating circuit 10.
The signal PGCR input from the reference waveform forming circuit 11 is subtracted from + Pg. Therefore, the output is (PGCR + Pg) -PGCR = Pg. That is, the differential pulse of the ghost signal component obtained by differentiating only the ghost signal component Sg is output. 1
Reference numeral 3 denotes a converter, which obtains data corresponding to the time difference or level of the ghost signal with respect to the main signal based on the signal phase and level of the differential pulse Pg of the ghost signal component input from the subtractor 12, and from this data, the transversal Correction amount S for removing the ghost from the tap coefficient of the filter 3
When the signal ST is set to T and the signal ST is fed back to the transversal filter 3, the pass characteristic of the filter is controlled. The characteristics of the transversal filter 3 gradually converge by removing the ghost signal component Sg by repeating the above-described operation, and the ghost appearing in the displayed image disappears accordingly. I will go.

[0013]

By the way, when the signal component of the front ghost described in FIG. 11 is removed by the ghost removing circuit having the above-described configuration, the cancellation signal generated by the transversal filter 3 has a pre-ghost signal. The signal component remains, and a ghost called grandchild ghost occurs. Therefore, the principle of generation of the grandchild ghost will be described with reference to FIGS. Here, FIG. 8 conceptually shows the input signal I input to the transversal filter 3. Assuming a pulse-shaped main signal M as shown in this figure, since the front ghost signal g _P is a signal that appears earlier in time than the main signal M, the same pulse-shaped signal positioned before the main signal M in time is also present. Signaled.

By the way, the transversal filter 3 shown in FIG. 4 performs waveform equalization (waveform equalization here means removal of a ghost signal component which is temporally close to the main signal). As conceptually shown in the circuit diagram of FIG. 9, for example, after the input signal I is distributed and supplied to the delay line 21 and the transversal filter unit 20, the respective outputs are combined by the adder 22 to output the output signal. The FIR configuration is set to O. According to this configuration, the delay signal D delayed in the delay line 21 by the number of taps which is earlier in time than the main signal component M in the input signal I,
By adding the cancellation signal E generated by the transversal filter unit 20 by the adder 22, the output signal O in which the ghost signal component is canceled is obtained, and the waveform equalization can be performed. The cancellation signal E is generated by controlling the tap coefficient of the transversal filter unit 20 by the feedback signal indicating the correction amount data ST described above.

Therefore, the case where the previous ghost signal g _P is removed by the above configuration will be described with reference to FIG.
In these figures, the frame shown by the broken line shows the tap range of the transversal filter 3. The tap range indicates the temporal width of the signal affected by the tap coefficient, and is set so as to cover the front and back of the main signal component M as shown in the figure. Since the tap coefficient of the filter is not set immediately after the start of the ghost removal operation, the output signal O ₁ of the transversal filter 3 is shown in FIG.
As shown in, the same signal as the input signal I of FIG. 8 is obtained. Therefore, based on the output signal O ₁ of FIG. 10A, the correction amount data ST is obtained by the operation described in FIG. 3, and the transversal filter 3 has the tap range shown in FIG. 10B within the tap range. Find the tap coefficient k ₁ . In the transversal filter unit 20, based on the tap coefficient k ₁ , as shown in FIG. 10C, the cancellation signal E ₁ composed of the preceding ghost component g ₁ and the main signal component M ₁ is used.
Is generated. Then, when the output signal O ₁ of FIG. 10A and the cancellation signal E ₁ of FIG. 10C are added by the adder 22, as shown in FIG. 10D, the front ghost signal g
_Although the output signal O ₂ from which _P is removed can be obtained, the front ghost component g ₁ which is the component of the cancellation signal E ₁ remains in the output signal O ₂ without being offset. This is called a grandchild ghost, and in this case, it is the first grandchild ghost, so here it is called the first grandchild ghost.

Thereafter, a new correction amount ST is output from the microcomputer 8 based on the output signal O ₂ of FIG. 10 (d), and the transversal filter 3 of FIG.
As shown in (e), in addition to tap coefficient k ₁ , tap coefficient k
₂ is further required. Transversal filter unit 20
Then, using these tap coefficients k ₁ and k ₂ ,
The cancellation signal E ₁ + E ₂ shown in (f) is generated. The cancellation signal E ₁ + E _2, the signal E ₁ (prior ghost components g _1, the main signal component M ₁₎ cancel obtained by the tap coefficient k ₁ and counteracts signal E ₂ (before ghost component obtained by the tap coefficients k ₂ g ₂ and the main signal component M ₂ ). Then, the first grandchild ghost (previous ghost component g ₁ ) generated in the output signal O ₂ is removed by the component of the cancellation signal E ₂ to obtain the output signal O ₃ shown in FIG. However, even at this stage, the cancellation signal E
_{The second} ghost component g _{2 that} is the _second component appears in the output signal O ₃ as the second grandchild ghost. When the second grandchild ghost signal component g ₂ is located beyond the tap range, it is not possible to generate a cancellation signal any more, so that it is impossible to remove further grandchild ghosts and the main signal M Will remain with.

At this time, the second grandchild ghost signal component g ₂
There is no practical problem as long as the level is attenuated to a level at which it is imperceptible at least when it becomes a display image (this is called the minimum allowable level), but the front ghost signal does not affect the building in the strong electric field area. It often occurs in a television receiver using a joint viewing system provided in a building such as. Therefore, when the level of the grandchild ghost existing beyond the tap range is equal to or higher than the allowable minimum level, this appears as an image. In addition, since such a grandchild ghost is further temporally positioned before the original position of the previous ghost due to the overlapping removal processing, the ghost is displayed in a position apart from the main video in the actual display image. . For this reason, the grandchild ghost image tends to be relatively conspicuous, and in some cases has a problem that the image becomes unsightly as compared with the case where the ghost removal is not performed.

[0018]

In order to solve the above-mentioned problems, the present invention solves the above-mentioned problems by providing a transversal filter having a finite tap range and capable of removing ghost signal components, and an output from the transversal filter, for example. A detector for extracting a GCR signal and detecting a ghost signal component with respect to a main signal component based on the GCR signal, and a filter characteristic variable for varying the pass characteristic of a transversal filter based on the detection information of the detector. In a ghost elimination circuit having a variable filter characteristic data output section for outputting data, first, within a tap range before the main signal component, first obtain the minimum allowable level of the grandchild ghost remaining when the ghost signal component is eliminated. To set the specified level according to the temporal distance from the main signal component. It was decided. Then, the specified level is compared with the level of the previous ghost signal component, and when the level of the previous ghost signal component is larger than the specified level, control is performed so that the filter characteristic variable data output unit does not output the filter characteristic variable data. It was decided to provide a control unit. Then, this prescribed level is set based on the level of the differential pulse obtained by differentiating the ghost signal component by a predetermined time constant. Further, the operations of the control unit and the like are configured by software of a microcomputer.

[0019]

The specified level for obtaining the minimum permissible level of the grandchild ghost occurring outside the tap range is set based on the waveform level obtained by differentiating the ghost component obtained from the GCR signal, and the specified level and the previous ghost signal component are set. By comparing the levels of the above, and not setting the filter characteristic variable data when this exceeds the specified level, the preceding ghost signal component passes through the transversal filter without being removed. Therefore, the grandchild ghost of the previous ghost will not occur. If the control unit, the detection unit, the filter characteristic variable data output unit, etc. are configured by a microcomputer, the above operation can be realized by software.

[0020]

1 is a block circuit diagram showing an embodiment of a ghost eliminating circuit according to the present invention. The same parts as those in FIG. 4 are designated by the same reference numerals and the description thereof will be omitted. In the figure, 14 is a signal changeover switch, which is provided with terminals t _{1 to} t ₃ . Then, the terminal t ₁ is connected differential pulse Pg of the ghost component signal from the subtracter 12, the terminal t ₂ is connected to ground, terminal t ₃ is connected to the input of the converter 13. Further, when the switch is switched, the terminal t ₃ is connected to the terminals t ₁ and t
_The terminal t ₃ is switched to the terminal t ₂ when the output of the AND gate 18 described later is at the H level and to the terminal t ₁ when the output is at the L level. It Therefore, in this signal changeover switch 14, the output of the AND gate 18 is set to the L level and the terminal t
_{When 3} and the terminal t ₁ are connected, the differential pulse Pg of the ghost component signal is supplied to the converter 13 to set the correction amount data ST, and the AND gate 18
When the output of is set to the H level and the terminals t ₃ and t ₂ are connected, the signal is not supplied to the converter 13 and the correction amount data ST is not set.

Reference numeral 15 denotes a comparator, which compares the level of the absolute value of the differential pulse Pg of the ghost component signal input from the subtractor 12 with the specified level input from the specified level output section 16 described next. . In this case, when the level of the differential pulse Pg exceeds the specified level, H
If the level is not exceeded, set the L level to AND gate 18
It is supposed to be output to. Reference numeral 16 is a specified level output unit, which outputs a specified level that changes according to the temporal distance from the main signal component from the start time to the end time of the timer unit 17. The specified level will be described later. 17
Is a timer unit. The timer unit 17 is supposed to start from the time point of the first tap range of the transversal filter 3 and end at the time point of the main signal component. For example, during this time, the specified level output unit 16 and the AND gate 18 are set to H level.
It is supposed to output the level. Reference numeral 18 denotes an AND gate, to which signals from the comparator 15 and the timer unit 17 are input.

Next, an outline of the operation of the ghost elimination circuit of the present embodiment having the above-mentioned configuration will be described with reference to the explanatory view of FIG. In these figures, the main signal component M ₁ (broken line) and the ghost signal components Pg _{1 to} Pg ₄ (solid line) indicated by the ghost component differential pulse are shown on the time axis in lengths corresponding to the levels thereof. In this case, in the ghost signal components Pg _{1 to} Pg ₄ , the one that is present before the main signal component M _{1 in} time is the previous ghost (Pg 1
₁ , Pg ₃ , Pg ₄ ), and the one that exists later is the post-ghost (Pg ₂ ). Moreover, the frame of a broken line has shown the tap range. This tap range indicates the temporal width of the signal affected by the tap coefficient of the transversal filter 3 as described in FIG. 10, and is set so as to cover the front and back of the main signal component M _1. There is. If the ghost signal component is located within this tap range, it is possible to remove the ghost signal by weighting the tap coefficient. In addition, L _B shown in FIGS. 2B and 2C indicates the specified level output from the specified level output unit 16. This specified level is output over the period from the start of the tap range to the time at which the main signal component M ₁ is actually located, as shown in the figure. To a predetermined level. And at this regulated level,
For example, when the preceding ghost signal component within the tap range is removed as shown in FIG. 9, a level (a level at which the unremovable grandchild ghost that occurs outside the tap range cannot be visually sensed ( An original front ghost signal component having an allowable minimum level) is assumed, and is set based on the level obtained according to the temporal distance of such a front ghost signal component with respect to the main signal. Further, in the case of the present embodiment, this prescribed level is set corresponding to the level when the ghost signal component is differentiated into a pulse by the same time constant as that of the differentiation circuit 10. As a result, it becomes possible to compare the level of the ghost signal component obtained from the subtractor 12 with the differential pulse Pg as shown in FIG.

The operation of the ghost removing circuit is as follows.
For example, as shown in FIG. 2A, when there is a front ghost signal component Pg ₁ or a rear ghost signal component Pg ₂ outside the tap range with respect to the main signal component M ₁ ,
The terminals t ₃ and t ₁ of the signal changeover switch 14 are connected by the operation described later. As a result, since the differential pulse Pg of the ghost signal component obtained by the subtractor 12 is supplied to the converter 13, the correction amount data ST for removing the ghost signal corresponding thereto is set. Therefore, the normal ghost removal processing is performed. However, since the previous ghost signal component Pg ₁ is outside the tap range, the coefficient setting in the transversal filter 3 is not performed and the removal is not performed.

Further, as shown in FIG. 2B, when the front ghost signal component Pg ₃ exists within the tap range and the level of the front ghost signal component Pg ₃ is smaller than the prescribed level L _B , In the same manner as in the case of FIG. 2A, the terminal t ₃ and the terminal t ₁ of the signal changeover switch 14 are connected and the normal ghost removal processing is performed. In other words, if the previous ghost is removed, a grandchild ghost will occur outside the tap range as described above, but if the original previous ghost is smaller than the specified level as in this case, the displayed grandchild ghost level is the minimum allowable level. It is lower than that, and it is attenuated to such a degree that it can be visually ignored, so that there is no practical problem.

Then, as shown in FIG. 2C, when the preceding ghost signal component Pg ₄ exists within the tap range and the level thereof exceeds the specified level L _B , the signal changeover switch 14 is connected to the terminal. The t ₃ and the terminal t ₂ are connected. Since the terminal t ₂ is connected to the ground,
The 0 level is input to the converter 13. Therefore, at this time, the correction amount data ST is not set, and the ghost signal of the previous ghost signal component Pg ₄ is not removed and is output from the transversal filter 3 together with the main signal. That is, if the previous ghost signal having a level higher than the specified level L _B is removed as in this case, the grandchild ghost that occurs outside the tap range will be higher than the allowable minimum level, and will be visually recognizable at the time of display. You will have a sufficient level. In addition, such a grandchild ghost image tends to be conspicuous because it is displayed at a position relatively distant from the main image. Therefore, if the previous ghost signal is not removed in this way, such a ghost image is not displayed. In this case, the original previous ghost signal component is displayed without being removed, but the image of this ghost signal component is usually displayed very close to the main image, and thus tends to be inconspicuous.

Next, the operation of each functional circuit section when executing the above operation will be described with reference to the timing chart of FIG. Here, FIG. 3A shows the output waveform of the timer unit 17, and FIG. 3B shows the differential pulses Pg _{1 to} Pg ₄ of the ghost signal component and the specified level L _B (curved line of broken line). Pg _{1 to} Pg ₄ are outputs of the subtractor 12, and the specified level L _B is output from the specified level output unit 16 to the comparator 15. FIG. 3C shows the output of the comparator 15. As described above, when the differential pulse of the input ghost signal component exceeds the specified level, the H level is output. Figure 3 (d) shows A
The output of the ND gate 18 is shown. As described in FIG. 1, the outputs of the comparator 15 and the timer unit 17 are input to the AND gate 18, respectively. Therefore, this A
The ND gate 18 outputs the H level when the outputs of the comparator 15 and the timer unit 17 are both at the H level, and otherwise outputs the L level. In the signal changeover switch 14, when the H level is outputted from the AND gate 18, the signal changeover switch 14 is changed over to the ground side (terminal t ₂ → t ₃ ), and when it is at the L level, the subtracter 12 side (Terminal t ₂ → t ₁ ) can be switched. Further, FIG. 3E shows the position of the main signal component M.

In these figures, the time point T ₁ indicates the start time point of the tap range of the transversal filter 3. For example, before this time T _1, as shown in FIG. 3B, the differential pulse P of the previous ghost component outside the tap range
When g ₁ is obtained, the timer unit 17 is not activated and the L level is input to the AND gate 18 as shown in FIG. Further, the comparator 15 is in a state in which the specified level L _B is not output at this time,
Therefore, the specified level is 0 level. As a result, as a result of comparing the level of the differential pulse Pg ₁ and the 0 level (specified level), the H level is output as shown in FIG. 3C. In this case, the output of the AND gate 18 shown in FIG. 3D is at the L level, so that the signal changeover switch 14 is connected to the subtracter 12 side and the converter 13 and the output operation of the correction amount data ST is possible. To be in a state. But,
Since the differential pulse Pg ₁ of the preceding ghost component is outside the tap range, the transversal filter 3 does not set the coefficient, and therefore the preceding ghost signal corresponding to the differential pulse Pg ₁ is not removed.

When the tap range starts at the time point T ₁ , the timer section 17 outputs the H level as shown in FIG. 3 (a). This H level is T ₄ where the main signal component M (FIG. 3 (e)) is actually located.
It is continuously output until the point.

At the time T ₁ , the prescribed level L _B of the curve characteristic preset by the prescribed level output section 17 in accordance with the H level output from the timer section 17 (FIG. 3B).
Will be output to the comparator 16.
Then, during the period from the time T _{1 to the} time T _{4 from the} time when the main signal component M is located, for example, the time T _{1 in} FIG.
_When the differential pulse Pg ₄ of the preceding ghost component having a level higher than the specified level L _B is input to the comparator 15 as shown at time _{2, the} comparator 15 outputs the H level as shown in FIG. Is output to the AND gate 18. Then, at this point, since the H level of the comparator 15 and the H level of the timer unit 17 are input to the AND gate 18, this AN
The H level is output from the D gate 18 as shown in FIG. Therefore, at this time, the signal changeover switch 1
Since 4 is switched to the ground side (terminal t ₂ → t ₃ ),
The correction amount data ST is not set in the converter 13, and the preceding ghost signal component corresponding to the differential pulse Pg ₄ passes without being removed by the transversal filter 3.

Further, for example, as shown at time T _{3 in} FIG. 3B, when the differential pulse Pg ₃ of the preceding ghost component having a level smaller than the specified level L _B is obtained,
The state in which the L level is output from the comparator 15 (see FIG. 3).
Since it is in (c)), the L level is also output from the AND gate 18, whereby the signal changeover switch 14 is changed over to the subtracter 12 side (terminal t ₂ → t ₁ ). Therefore, the converter 13 sets and outputs the correction amount data ST based on the differential pulse Pg ₃ . In the transversal filter 3, the tap coefficient is set by the correction amount data ST, and the ghost signal component corresponding to the differential pulse Pg ₃ is removed.

In this way, the main signal component M (see FIG.
At time T ₄ where (e)) is located, the timer unit 17 ends the timer time and stops the output of H level (FIG. 3).
(A)). Further, the output of the regulated level L _B is also stopped at this point (FIG. 3 (b)). After this, for example, at time T ₅ (within the tap range), the differential pulse Pg ₂ of the rear ghost signal component
Is obtained, the comparator 15 outputs the H level, but since the output of the timer unit 17 is already in the L level, the AND gate 18 continues to output the L level. Therefore, since the signal changeover switch 14 continues to be changed over to the subtracter 12 side (terminal t ₂ → t ₁ ), this differential pulse Pg ₂ is changed by the converter 13 by the correction amount S.
After being converted into T, the transversal filter 3 sets the tap coefficient to remove the ghost signal component according to the differential pulse Pg ₂ . The operation of each functional circuit section as described above realizes the ghost removal processing as described with reference to FIG.

It should be noted that the circuit configuration shown in FIG. 1 and the operation timings of FIG. 3 accompanying it are merely examples, and
Modifications can be made as long as the same operation as described above is realized. Further, even when a ghost detection signal other than the GCR signal is inserted in the video signal, the present invention can be applied based on the ghost detection signal. Further, although the ghost elimination circuit of this embodiment has been described as being incorporated in, for example, a television receiver or the like, it may be configured as a ghost elimination device which is separate from such equipment. Further, the internal circuit configuration of the microcomputer 8 is actually a processing operation by software as described above, but it is also possible to configure these by hardware parts or the like. However, if it is configured by a microcomputer as in the present embodiment, the operation of each circuit unit can be realized by software, so that it is unnecessary to add electronic parts and the like, and it is advantageous that the cost increase can be avoided.

[0033]

As described above, the ghost elimination circuit of the present invention changes the original previous ghost signal component level having the allowable minimum level of the grandchild ghost outside the tap range according to the temporal distance from the main signal. Is set as a specified level obtained based on the level obtained from the differential waveform of the GCR signal, and the removal processing is not performed for the previous ghost signal component exceeding this specified level, so that the allowable minimum level is exceeded. It prevents the generation of grandchild ghosts. The grandchild ghost image that exceeds the allowable minimum level tends to be conspicuous because it is displayed at a position far away from the main image, so that such an unsightly image can be eliminated. Further, the operation of various circuit units necessary for realizing the above-mentioned effect is actually executed by software processing of the microcomputer, so that there is an effect that cost increase can be suppressed.

[Brief description of drawings]

FIG. 1 is a block circuit diagram showing a ghost elimination circuit according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing an outline of the operation of the ghost elimination circuit of the present embodiment.

FIG. 3 is a flowchart showing the operation of the ghost elimination circuit of this embodiment.

FIG. 4 is a block circuit diagram showing a ghost elimination circuit in a conventional example.

FIG. 5 is a waveform diagram showing a GCR signal.

FIG. 6 is a waveform diagram showing a method of inserting a GCR signal in a video signal.

FIG. 7 is a waveform diagram showing a field operation for detecting a ghost signal component.

FIG. 8 is an explanatory diagram showing an input signal including a main signal component and a previous ghost signal component.

FIG. 9 is a block diagram conceptually showing the structure of a transversal filter.

FIG. 10 is an explanatory diagram showing a process of generation of a grandchild ghost.

FIG. 11 is an illustration showing the occurrence of a ghost.

[Explanation of symbols]

 3 Transversal Filter 8 Microcomputer 9 Field Operation Circuit 10 Differentiation Circuit 11 Reference Waveform Forming Circuit 12 Subtractor 13 Converter 14 Signal Changeover Switch 15 Comparator 16 Specified Level Output Section 17 Timer Section 18 AND Gate

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[Procedure amendment]

[Submission date] December 22, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0003

[Correction method] Change

[Correction content]

In order to cancel the ghost thus generated, the transmitting side inserts a ghost cancel reference signal (hereinafter referred to as a GCR (Ghost Cancel Reference ) signal) into the video signal, and the receiving side is based on this GCR signal. A method is known in which a ghost signal component is detected and the characteristics of a transversal filter are varied according to the detected data to remove the ghost signal component from the received signal.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0005

[Correction method] Change

[Correction content]

Then, the GC as the GCR signal SGCR is used.
The R waveform GCR and the pedestal waveform PDS are shown in FIG.
It is inserted in the video signal as shown in (a) to (h). That is, the 8-field period of the video signal is set as a repeating cycle, and the 18th field or the 281H field in the 1st, 3rd, 6th, or 8th field is set to the cycle shown in FIG.
The GCR waveform GCR of (a) is inserted, and the 18th H of each of the remaining 2nd, 4th, 5th, and 7th fields is inserted.
Alternatively, the pedestal waveform of FIG.
PDS is inserted. In this case, the 17th or 280th field of each field is defined as a fixed waveform.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction content]

Reference numeral 4 denotes a D / A converter which performs D / A conversion on the output of the transversal filter 3 and outputs it as an analog detection signal SY which has undergone ghost removal processing.
Reference numeral 5 is an output terminal for supplying the detected signal SY to other required internal or external circuits.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0011

[Correction method] Change

[Correction content]

Reference numeral 8 shown by a broken line in the drawing is a microcomputer. Therefore, the circuit configuration in the broken line is actually realized by a computer and software, but here it is shown by hardware for convenience of showing the operating means. In the microcomputer 8, the ghost signal component is detected based on the GCR signal SGCR input from the buffer memory 7 every one field period, and the transversal filter 3 is detected according to the detection result.
The correction amount data ST for controlling the coefficient of is output. In this microcomputer 8, 9 indicates a field operation circuit, which is a GCR signal from the buffer memory 7.
For SGCR, performs an operation of 8 field sequence described with reference to FIG. 5 and FIG. 6 and (Equation 1), for example, FIG. 7
A waveform similar to that shown in (c), that is, a signal (GCR + Sg) obtained by combining the GCR waveform GCR and the ghost signal component Sg is obtained. For example, the calculation shown in (Equation 1) above can be rewritten as (Equation 2) S = 1/4 (S ₁ −S ₂ + S ₃ −S ₄ −S ₅ + S ₆ −S ₇ + S ₈ ). In the actual field calculation, the GCR signal SGCR obtained in the field order may be integrated as described above.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction content]

Reference numeral 10 indicates a differentiating circuit in which a predetermined time constant is set. The GCR waveform (GCR + Sg) including the ghost signal component output from the field operation circuit 9 is passed through the differentiating circuit 10 to generate the differential pulse waveform (PGCR + Pg).
Is changed to. This differential pulse (PGCR + Pg) is obtained as a waveform similar to that described in FIG. 7D, for example. Reference numeral 11 is a reference waveform forming circuit, which generates and outputs a differential pulse waveform (PGCR) obtained by differentiating the GCR waveform GCR with a time constant similar to that of the differentiating circuit 10.
Reference numeral 12 denotes a subtractor, which is a signal input from the differentiating circuit 10.
The signal PGCR input from the reference waveform forming circuit 11 is subtracted from PGCR + Pg. Therefore, the output is (PGCR + Pg) -PGCR = Pg. That is, the differential pulse of the ghost signal component obtained by differentiating only the ghost signal component Sg is output.
Reference numeral 13 is a converter, which obtains data corresponding to the time difference and level of the ghost signal with respect to the main signal based on the signal phase and level of the differential pulse Pg of the ghost signal component input from the subtractor 12, and from this data, the transversal The tap coefficient of the filter 3 is set to the correction amount ST for removing the ghost, and the signal ST is fed back to the transversal filter 3, whereby the pass characteristic of the filter is controlled. The characteristics of the transversal filter 3 gradually converge by removing the ghost signal component Sg by repeating the above-described operation, and the ghost appearing in the displayed image disappears accordingly. I will go.

[Procedure correction 6]

[Document name to be amended] Statement

[Correction target item name] 0026

[Correction method] Change

[Correction content]

Next, the operation of each functional circuit section when executing the above operation will be described with reference to the timing chart of FIG. Here, FIG. 3A shows the output waveform of the timer unit 17, and FIG. 3B shows the differential pulses Pg _{1 to} Pg ₄ of the ghost signal component and the specified level L _B (curved line of broken line). Pg _{1 to} Pg ₄ are outputs of the subtractor 12, and the specified level L _B is output from the specified level output unit 16 to the comparator 15. FIG. 3C shows the output of the comparator 15. As described above, when the differential pulse of the input ghost signal component exceeds the specified level, the H level is output. Figure 3 (d) shows A
The output of the ND gate 18 is shown. As described in FIG. 1, the outputs of the comparator 15 and the timer unit 17 are input to the AND gate 18, respectively. Therefore, this A
The output of the comparator 15 and the timer unit 17 is shared by the ND gate 18.
At the H level, the H level is output, and at other times, the L level is output. When the AND gate 18 outputs the H level at the signal changeover switch 14, the signal changeover switch 14 is connected to the ground side (terminal
t ₃ → t ₂ ) and when it is at the L level, it is switched to the subtracter 12 side (terminal t ₃ → t ₁ ). Further, FIG. 3E shows the position of the main signal component M.

[Procedure Amendment 7]

[Document name to be amended] Statement

[Name of item to be corrected] 0029

[Correction method] Change

[Correction content]

At the time T ₁ , the prescribed level L _B of the curve characteristic preset by the prescribed level output section 17 in accordance with the H level output from the timer section 17 (FIG. 3B).
Will be output to the comparator 16.
Then, during the period from the time T _{1 to the} time T _{4 from the} time when the main signal component M is located, for example, the time T _{1 in} FIG.
_When the differential pulse Pg ₄ of the preceding ghost component having a level higher than the specified level L _B is input to the comparator 15 as shown at time _{2, the} comparator 15 outputs the H level as shown in FIG. Is output to the AND gate 18. Then, at this point, since the H level of the comparator 15 and the H level of the timer unit 17 are input to the AND gate 18, this AN
The H level is output from the D gate 18 as shown in FIG. Therefore, at this time, the signal changeover switch 1
Since 4 can be switched to the ground side (terminal t ₃ → t ₂ ),
The correction amount data ST is not set in the converter 13, and the preceding ghost signal component corresponding to the differential pulse Pg ₄ passes without being removed by the transversal filter 3.

[Procedure Amendment 8]

[Document name to be amended] Statement

[Name of item to be corrected] 0030

[Correction method] Change

[Correction content]

Further, for example, as shown at time T _{3 in} FIG. 3B, when the differential pulse Pg ₃ of the preceding ghost component having a level smaller than the specified level L _B is obtained,
The state in which the L level is output from the comparator 15 (see FIG. 3).
Since it is in (c)), the L level is also output from the AND gate 18, whereby the signal changeover switch 14 is changed over to the subtracter 12 side (terminal t ₃ → t ₁ ). Therefore, the converter 13 sets and outputs the correction amount data ST based on the differential pulse Pg ₃ . In the transversal filter 3, the tap coefficient is set by the correction amount data ST, and the ghost signal component corresponding to the differential pulse Pg ₃ is removed.

[Procedure Amendment 9]

[Document name to be amended] Statement

[Correction target item name] 0031

[Correction method] Change

[Correction content]

In this way, the main signal component M (see FIG.
At time T ₄ where (e)) is located, the timer unit 17 ends the timer time and stops the output of H level (FIG. 3).
(A)). Further, the output of the regulated level L _B is also stopped at this point (FIG. 3 (b)). After this, for example, at time T ₅ (within the tap range), the differential pulse Pg ₂ of the rear ghost signal component
Is obtained, the comparator 15 outputs the H level, but since the output of the timer unit 17 is already in the L level, the AND gate 18 continues to output the L level. Therefore, since the signal changeover switch 14 continues to be switched to the subtracter 12 side (terminal t ₃ → t ₁ ), the differential pulse Pg ₂ is corrected by the converter 13 by the correction amount Sg.
After being converted into T, the transversal filter 3 sets the tap coefficient to remove the ghost signal component according to the differential pulse Pg ₂ . The operation of each functional circuit section as described above realizes the ghost removal processing as described with reference to FIG.

[Procedure Amendment 10]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 1

[Correction method] Change

[Correction content]

[Figure 1]

[Procedure Amendment 11]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 2

[Correction method] Change

[Correction content]

[Fig. 2]

[Procedure Amendment 12]

[Document name to be corrected] Drawing

[Name of item to be corrected] Fig. 10

[Correction method] Change

[Correction content]

[Figure 10]

Claims (4)

[Claims] 1. A transversal filter having a finite tap range and capable of removing a ghost signal component from an input signal; and a ghost detection signal extracted from an output of the transversal filter to detect the ghost. It is possible to set and output the filter characteristic variable data for varying the pass characteristic of the transversal filter based on the detection means for detecting the ghost signal component based on the signal and the detection information of the detection means. In the ghost elimination circuit having the variable filter characteristic data output means, when the previous ghost signal component located before the main signal component is eliminated, the specified level based on the minimum allowable level of the grandchild ghost remaining outside the tap range. Is set according to the temporal distance from the main signal component, and Before comparing the levels of the ghost signal components, if the level of the preceding ghost signal components is higher than the specified level, control so that the filter characteristic variable data output means does not output the filter characteristic variable data. A ghost elimination circuit characterized by being provided with control means capable of performing the above. 2. The ghost elimination circuit according to claim 1, wherein the ghost detection signal is a GCR signal inserted at a predetermined position of a video signal. 3. The specified level is set based on a level of a differential pulse obtained by differentiating the ghost signal component by a predetermined time constant.
Alternatively, the ghost elimination circuit according to claim 2. 4. The ghost elimination circuit according to claim 1, 2 or 3, wherein at least the control means is constituted by software of a microcomputer.