JPH0795448A - Ghost eliminating device - Google Patents

Abstract

PURPOSE:To shorten the time in which the tap coefficient of a transversal filter 3 is converged so as to eliminate the ghost by eliminating a need of field operation/averaging for each tap coefficient correction, CONSTITUTION:A high-speed ghost elimination period TR is set in the start stage of ghost elimination, and signal changeover switches 15 to 17 are switched to the sides of terminals (a) to store the GCR waveform (GCR+Sg), which is obtained by a field operation circuit 9, in a waveform memory part 18 as a memory waveform MGCR. In second and following tap coefficient corrections, this memory waveform MGCR is read out and is made pass the transversal filter 3. In the high-speed ghost elimination period TR, a signal changeover switch 14 is switched to the side of the terminal (a) to directly supply the output of a detection circuit 1 to am output terminal 5.

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. 10 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 wave that is the main signal that directly reaches the receiving antenna from the transmission tower for the receiving antenna, there is also the building (or mountains not shown) as shown by the broken line.
A radio wave that reaches the receiving antenna after being reflected by (rear ghost), and further a radio wave that directly reaches the antenna terminal of the television receiver as indicated by the chain line and is positioned before the main signal in time ( There is also a former ghost). 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 components of reflected wave and direct wave are added to the received signal in addition to the main signal, resulting in a display image. In addition to the main image, a ghost corresponding to the time difference of these radio waves and the reception level will appear.

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.

FIG. 7 shows the GCR signal SGCR. In these figures, HD indicates a horizontal synchronizing signal and BRST indicates a color burst signal. As the GCR signal SGCR, the GCR waveform GCR shown in the waveform diagram of FIG.
The pedestal waveform PDS shown in the waveform diagram of (b) is set as one set. The GCR waveform GCR shown in FIG. 7 (a)
Is a bar waveform positioned behind the horizontal period, and its width is 44.7 μsec and its level is 70IRE. Further, the rising characteristic is a sin χ / χ ringing characteristic, and its frequency spectrum is shown in FIG. 7 (c).
As shown in, the characteristics are such that the video band is flat up to approximately 4.2 MHz. In addition, FIG.
The pedestal waveform PDS shown in is set to 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 GCR waveform GCR of FIG. 7A is inserted into the 18th or 281H of each of the 1st, 3rd, 6th, and 8th fields, The remaining second,
18th of each in the 4th, 5th and 7th fields
The pedestal waveform PDS shown in FIG. 7B is inserted into H or 280H. In this case, the 17th or 280th field of each field is defined as a fixed waveform.

Next, the waveform diagram of FIG. 9 shows these GCR signals.
The detection principle of the ghost signal component based on SGCR is conceptually shown. For example, FIG. 9A shows the waveforms of 17H and 18H in the first field.
It is assumed that the R waveform GCR is inserted, and FIG. 9B shows the waveforms of 17H and 18H in the fifth field, and the pedestal waveform PDS is inserted into this 18H. When the received signal contains a ghost component, the GCR waveform GCR is, for example, as shown in FIG. 9A, a waveform of the ghost component (BRST (G)) according to the time difference and 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 (and BRST (G)) are said to be in phase. Therefore, the 18H GCR waveform GCR in the first field (Fig. 9 (a))
By subtracting the pedestal waveform PDS (Fig. 9 (b)) of the fifth field from 18H, the horizontal sync signal HD and the color burst signal BRST of the respective fields cancel each other, so the waveform shown in Fig. 9 (c). Will be obtained. Then, for example, if this waveform is input to the differentiating circuit,
It is possible to obtain a differential pulse waveform as shown in (d),
For example, the differential pulse indicated by arrow A in this figure represents at least the level and time difference of the ghost component with respect to the main signal component. 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 waveform GCR (including the ghost component) is obtained and then the average of these is calculated. 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. 9C 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 a ghost removing circuit to which the above detection method is applied will be described with reference to the block diagram of FIG. In the figure, reference numeral 1 is a detection circuit for detecting a received signal and outputting a detection signal SY, and 2 is a detection signal SY supplied from the detection circuit 1, for example, 4
2 shows an A / D converter that performs A / D conversion at a sampling frequency of fsc (fsc = color subcarrier frequency). 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 is composed of, for example, a delay line with taps, a coefficient unit that gives an arbitrary tap gain (load) to each tap, and an adder circuit that obtains the sum of the load outputs for all taps. It has a filter characteristic of impulse response. Then, as shown in the figure, the output of the transversal filter 3 is supplied to a microcomputer 8 to be described later, and the coefficient of the transversal filter 3 is controlled by controlling the coefficient of the transversal filter 3 based on the correction amount data ST output from the microcomputer 8. The Versal filter 3 generates a cancellation signal corresponding to this and removes the ghost signal component.

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.

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 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 the microcomputer 8, reference numeral 9 denotes a field operation circuit, and G from the buffer memory 7
The CR signal SGCR is subjected to the operation of the 8-field sequence described with reference to FIGS. 8 and 7 and (Equation 1) to obtain a waveform similar to that shown in FIG. 9C, that is, a GCR waveform.
A signal (GCR +) in which GCR and the ghost signal component Sg are combined.
Sg) is obtained. For example, the calculation shown in (Equation 1) 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 denotes 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 with reference to FIG.
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 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 tap coefficient of the Versal filter 3 is set to a correction amount ST for obtaining a cancellation signal for removing the ghost, and the signal S
When T 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.

[0014]

As described above, the field operation circuit 9 has the value of 8 shown in (Equation 1) or (Equation 2).
The field sequence is calculated, for example, as shown in FIG.
GCR waveform GCR and ghost signal component S similar to those shown in
The signal (GCR + Sg) in which g is combined is obtained. That is, 4 sets of GCR waveforms within 8 field periods
We obtain the GCR (including the ghost component) and then take the average of these. However, when the ghost is removed from the received electric wave of the weak electric field, the detected signal SY obtained by detecting the received electric wave contains a lot of noise components, and therefore the main signal is calculated in one 8-field sequence operation. In some cases, it is not possible to obtain a GCR waveform (GCR + Sg) including a ghost signal component having an S / N ratio capable of sufficiently detecting the ghost signal component included in the.

Therefore, in the normal microcomputer 8, for example, the GC input from the buffer memory 7 is used.
It is configured to measure the S / N ratio of the R signal SGCR. Then, in the field operation circuit 9, the measured S /
A predetermined number of 8-field sequence operations that are set according to the N ratio are performed, and the results are further averaged. That is, in averaging the 8-field sequence operation results, if the 8-field sequence operation results are increased, the noise component is suppressed accordingly, so that at least the ghost component can be detected. Therefore, it is possible to obtain a GCR waveform (GCR + Sg) including a ghost signal component having an / N ratio. Then, after this, similarly, the correction amount data ST is finally supplied from the converter 13 to the transversal filter 3 via the differentiating circuit 10. Therefore, after that, the ghost component can be removed from the detection signal SY having a poor S / N ratio by repeating the above processing operation. That is, “8 field sequence operation / averaging of the number of times corresponding to the measured S / N ratio (field operation circuit 9)” → “differential pulse conversion (differential circuit 10)” → “subtraction by reference waveform (PGCR) ( Subtractor 12) ”→“ Conversion of subtraction result (differential pulse Pg of ghost component) to correction amount data ST (converter 13) ”is repeated in the microcomputer 8, and thus the transversal filter 3 Will gradually converge so as to remove the ghost signal component Sg.

However, in the series of processing operations described above, the 8-field sequence operation requires a particularly long time. Therefore, when the S / N ratio of the received radio wave is poor as described above, or when the 8-field sequence operation is performed a plurality of times, the time required to correct the characteristics of the transversal filter 3 once is actually It takes about 30 seconds to 1 minute. For example, until the pass characteristic of the transversal filter 3 finally converges so as to remove the ghost signal component, the characteristic of the transversal filter 3 needs to be modified about 10 times, Therefore, before the ghost image disappears from the screen,
If it is long, it takes about 10 minutes, which is a problem that it takes a very long time.

[0017]

In order to solve the above problems, the present invention solves the above-mentioned problems by providing a transversal filter for removing a ghost signal component from an input signal and a ghost signal component for each field from the output of the transversal filter. A field operation unit for extracting the included GCR signal and performing a predetermined operation process to obtain an averaged waveform, a ghost detection unit for detecting a ghost signal component from the averaged waveform from the field operation unit, and detection of the ghost detection unit In the ghost elimination circuit having the filter characteristic variable data output unit for setting the filter characteristic variable data for correcting the pass characteristic of the transversal filter based on the result, the averaged waveform can be stored as waveform data. A waveform memory section is provided and a high-speed ghost removal period is set. Possible and the. In the high speed ghost removal period, first, the pass characteristic of the first transversal filter is corrected based on the averaged waveform obtained by the field calculation unit, and the averaged waveform is stored in the waveform memory unit as the waveform data. Is to be memorized as. Therefore, when the pass characteristics of the transversal filter are corrected for the second time and thereafter, the waveform data stored in the waveform memory unit is made to pass through the transversal filter, and further supplied to the ghost detection unit without passing through the field operation unit. I decided to configure it.

The high-speed ghost removing period is set at the start of the ghost removing operation. Further, a signal switching unit that can switch the input signal to be directly supplied to the output side without passing through the transversal filter is provided, and at least when the pass characteristics of the transversal filter are corrected at least during the high speed ghost elimination period. From now on, the signal switching unit is configured to directly supply the input signal to the output side.

[0019]

According to the above structure, the GCR waveform (including the ghost component) obtained by once performing the 8-field sequence operation / averaging can be stored and held in the waveform memory section. Therefore, in the high speed ghost removal period, if the tap data is input to the transversal filter to store the waveform data stored in the waveform memory unit, the 8-field sequence calculation / averaging is performed for each tap coefficient correction. Since it is not necessary to do so, ghost removal can be performed faster. Further, by setting this high-speed ghost removal period at the start of the ghost removal operation, when the condition of the ghost that occurs due to the switching of channels etc. becomes different from the previous one, the high-speed ghost removal will be performed first. Is done. In addition, the waveform data will pass through the transversal filter during the high speed ghost removal period. At this time, if the input signal (video detection signal) is directly supplied to the output terminal, the high speed ghost removal period In, the image display is not interrupted.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a block circuit diagram showing an embodiment of the ghost removing circuit of the present invention. The same parts as those in FIG. 7 are designated by the same reference numerals and the description thereof will be omitted. In this figure, reference numerals 14 to 17 denote signal changeover switches, which have terminals a, b, and c, respectively, and the terminal c can be selectively changed over to either of the terminals a and b. . The signal changeover switch 14 is switched to the terminal a when the control signal Cs2 output from the microcomputer 8 is at the L level and to the terminal b when it is at the H level.
Further, the signal changeover switches 15, 16 and 17 are switched to the terminal a when the control signal Cs1 is at the L level and to the terminal b when the control signal Cs1 is at the H level.

In the case of this embodiment, the detection signal SY output from the detection circuit 1 is branched, one is supplied to the A / D converter 2 side, and the other one is connected to the terminal a of the signal changeover switch 14. Connected. The output of the D / A converter 4 is connected to the terminal b of the signal changeover switch 14, and the terminal c is connected to the output terminal 5. Therefore, when the signal changeover switch 14 is switched to the terminal a side, the output of the detection circuit 1 is directly supplied to the output terminal 5, and when it is switched to the terminal b side, the normal transversal filter 3 is used. Then, the detection signal SY from which the ghost component has been removed by passing through is supplied to the output terminal 5 via the D / A converter 4.

The terminal a of the signal changeover switch 15 is A
The output of the / D converter 2, the output of the waveform memory 18 described later at the terminal b, and the transversal filter 3 at the terminal c.
Is connected to each input. Therefore, when the signal changeover switch 15 is changed over to the terminal a side, the detection signal SY digitized by the A / D converter 2 is supplied to the transversal filter 3 and is changed over to the terminal b side. If so, the memory waveform MGCR output from the waveform memory 18 is supplied to the transversal filter 3.

In the signal changeover switch 16, the terminal a is connected to the output of the gate circuit 6, the terminal b is connected to the output of the transversal filter 3 not passing through the gate circuit 6, and the terminal c is connected to the input of the buffer memory 7. Therefore, when the signal changeover switch 16 is switched to the terminal a side, the GCR signal SGCR output from the gate circuit 6 is supplied to the buffer memory 7, and when it is switched to the terminal b side, It serves as a signal path for directly supplying the output of the transversal filter 3 not passing through the gate circuit 6 to the buffer memory 7.

The signal changeover switch 17 is provided inside the microcomputer 8. Therefore, at least this signal changeover switch can be embodied by an algorithm for ghost elimination. The terminal a of the signal changeover switch 17 is connected to the output of the field operation circuit 9, the terminal b is connected to the output from the buffer memory 7 not via the field operation circuit 9, and the terminal c is connected to the differentiation circuit 10.
Connected to. Thus, when the signal changeover switch 17 is switched to the terminal a, the output of the field arithmetic circuit 9 is input to the differentiating circuit 10, and when it is switched to the terminal b side, the output of the buffer memory 7 is output. It is input to the differentiating circuit 10.

Further, in the present embodiment, the waveform memory unit 1
8 are provided. The output of the field operation circuit 9 is input to the waveform memory unit 18 as shown in the figure. That is, as described above, a GCR including a ghost signal component obtained by averaging the operation results of a plurality of 8-field sequences set according to the S / N ratio of the GCR signal SGCR.
Waveform (GCR + Sg) data will be input.
Then, the waveform memory unit 18 stores and holds the waveform (GCR + Sg) input as described above as a memory waveform (MGCR), and the memory waveform (MGCR) is switched by the read control of the microcomputer 8 described later. The operation of outputting to the terminal b of the switch 15 is performed.

Reference numeral 19 denotes a trigger circuit, for example, when the user turns on the power or operates a key for switching the channel or starting the ghost removal, the ghost removal operation is started to the microcomputer 8 based on the key operation. A trigger pulse Pt for instructing is output.

In the ghost removing circuit of the present embodiment configured as described above, the high speed ghost removing period is set at the start of the ghost removing operation, and during this high speed ghost removing period, the field operation circuit 9 first Obtain the GCR waveform (GCR + Sg) including the ghost signal component by the 8-field sequence operation / averaging, correct the tap coefficient of the transversal filter 3 for the first time, and use this signal as the memory waveform (MGCR) in the waveform memory. The tap coefficient can be stored and held in the unit 18 and the tap coefficient can be corrected based on the memory waveform (MGCR) stored and held in the waveform memory unit 18 from the second ghost removing step. That is, once the signal is obtained by the 8-field sequence calculation / averaging and stored in the waveform memory unit 18, thereafter, the 8-field sequence calculation / averaging is not performed for each series of processing for obtaining the tap coefficient. However, the same signal as the memory waveform (MG
CR). For example, when a certain channel is being received, the basic condition of the ghost that occurs is that a significant change does not usually occur even after a certain amount of time has passed. Therefore, first, the waveform obtained by the 8-field sequence operation / averaging is Even if it is used for the subsequent tap correction, there will be no particular problem. Therefore, if a series of processes for obtaining the tap coefficient is performed by supplying this memory waveform (MGCR) to the transversal filter 3, it is possible to omit particularly time-consuming 8-field sequence calculation / averaging. Therefore, the processing up to the convergence of the tap coefficient of the transversal filter 3 for removing the ghost can be speeded up, and the time can be greatly shortened.

The operation of the ghost elimination circuit of this embodiment will be described below with reference to the timing chart of FIG. 2 and the waveform chart of FIG. Here, FIG. 2A shows the output timing of the trigger pulse Pt output from the trigger circuit 19, and FIG. 2B shows the timing of the processing sequence in the microcomputer 8. Also,
FIG. 2C shows the output timing of the control signal Cs1 as shown in FIG.
2D shows the output timing of the control signal Cs2, and FIG.
(E) shows the stored contents of the waveform memory unit 18.

First, before the time point T ₁ , the ghost elimination circuit of this embodiment is in a period during which the steady process shown in FIG. 2B is being performed. In the case of this steady process, the control signal Cs1 is output at the L level and the control signal Cs2 is output at the H level, as shown in FIGS. As a result, the signal changeover switch 14 is connected to the terminal b side, and the signal changeover switches 15 to 17 are connected to the terminal a side, respectively. When each of the signal changeover switches 14 to 17 is in the above-mentioned state, the detection signal SY output from the detection circuit 1 is the A / D converter 2 → (the signal changeover switch 1
5 →) transversal filter 3 → D / A converter 4 → (signal changeover switch 14 →) is output through the signal path indicated by the output terminal 5, and the loop for correcting the tap coefficient of the transversal filter 3 is the transversal filter 3 → Gate circuit 6 → (Signal changeover switch 16) → Buffer memory 7 → Field arithmetic circuit 9 → (Signal changeover switch 17) → Differentiation circuit 10 → Subtractor 12 (subtraction by reference waveform PGCR of reference waveform forming circuit 11)
→ Converter 13 → The signal path is represented by the transversal filter 3.

That is, the ghost elimination circuit shown in FIG. 6 has the same configuration as that of the ghost elimination circuit. Therefore, the steady-state processing here means that the measured S / N is measured by the microcomputer 8 as described above. 8 times corresponding to the ratio
Field sequence operation / averaging (field operation circuit 9) "→" Differential pulse conversion (differential circuit 10) "→" Reference waveform (PGCR) subtraction (subtractor 12) "→
“Conversion of the subtraction result Pg to the correction amount data ST (converter 1
3) ”, a series of processing operations are repeated to remove the ghost.

Next, at time T ₁ , it is assumed that the user has turned on the power or operated a key to switch channels or start ghost removal. Then, accordingly, the trigger pulse Pt is output from the trigger circuit 19 as shown in FIG. In response to this trigger pulse Pt,
The microcomputer 8 will start the ghost removing operation again. At the start of the ghost removal operation, for example, the tap coefficient set in the transversal filter 3 is preferably cleared to the initial value. Alternatively, it is conceivable that the tap coefficient calculated for each channel can be stored so that the tap coefficient corresponding to the currently selected channel is set when the power is turned on or the channel is switched.

In this embodiment, at the time of starting the ghost removing operation (time T ₁ ), the high speed ghost removing period T _R for performing the ghost removing processing faster than the above-described steady processing is set. This high-speed ghost removal period T _R corresponds to the T _{1 to} T ₃ period shown in the figure, and further, this period is the T _{1 to} T ₂ period in which 8-field calculation / averaging processing is performed as shown in FIG. 2B. Then, it is divided into T _{2 to} T ₃ periods for actually obtaining the correction amount data ST.

First, in the period of T _{1 to} T ₂ , the control signal Cs2 is set to the L level output state as shown in FIG. 2 (d). Therefore, the signal changeover switch 14 is switched to the terminal a side, and the detection signal SY output from the detection circuit 1 is directly supplied to the output terminal 5. Further, the control signal Cs1 is also output at the L level as shown in FIG. 2C, and the signal changeover switches 15, 16 and 17 are changed over to the terminal b side. As a result, T ₁ ~
In the T ₂ period, the following processing operation is performed.

In this case, the detection signal SY output from the detection circuit 1 is directly supplied to the output terminal 5 via the signal changeover switch 14, while being branched and passed from the A / D converter 2 via the signal changeover switch 15. It is also supplied to the transversal filter 3. Therefore, the gate circuit 6 extracts the GCR signal SGCR from the detection signal SY which is the output of the transversal filter 3 and supplies it to the buffer memory 7 via the signal changeover switch 16. Then, the field operation circuit 9 performs 8-field sequence operation / averaging processing based on the GCR signal SGCR input from the buffer memory 7. On this occasion,
The number of 8-field sequence operations is S / of the GCR signal SGCR measured by the microcomputer 8 as described above.
If it is set based on the N ratio and performed multiple times,
These calculation results will be further averaged. As described above, the T _{1 to} T ₂ period is a period for obtaining the GCR waveform (GCR + Sg) including the ghost signal component sufficiently suppressed by the field arithmetic circuit 9 until the noise component can be detected by the ghost. The GCR waveform (GCR + Sg) including the ghost signal component is output to the signal changeover switch 17 and the waveform memory unit 18.

When the T ₁ -T ₂ period has ended as described above, the process for obtaining the correction amount data ST is next performed T
_The period is _{2 to} T ₃ . During this T _{2 to} T ₃ period, the control signal Cs2 is maintained at the L level as shown in FIG. 2 (d). As a result, the output terminal 5 has the same T _1-
As in the T ₂ period, the detection signal S output from the detection circuit 1
Y is being directly supplied.

On the other hand, the control signal Cs1 is in the H level output state as shown in FIG. 2 (c), whereby the signal changeover switch 15 is changed over to the terminal b side. Therefore, the signal input to the transversal filter ₃ during this T _{2 to} T ₃ period is the memory waveform (MGCR) from the waveform memory unit 18. Further, since both the signal changeover switches 16 and 17 are also changed over to the terminal b side, the memory waveform (MGC
R) passes through the gate circuit 6 and the field operation circuit 9 and is input from the buffer memory 7 to the differentiating circuit 10. By forming the signal path in this way, the signal passing through the transversal filter 3 is not the detection signal SY but the memory waveform (MGCR), that is, the ghost component is detected based on the memory waveform (MGCR). Then, the correction amount of the tap coefficient is obtained. Since this memory waveform (MGCR) is a GCR waveform which has already been subjected to 8 field sequence calculation / averaging processing, the gate circuit 6 for extracting the GCR signal and the field calculation circuit 9 for performing 8 field sequence calculation / averaging
There is no need to pass through again. Therefore, these functional circuit sections are omitted by forming the signal path.

After the signal path is formed as described above, in the period T _{2 to} T ₃ , first, as shown in the processing sequence of FIG. 2B, the first tap coefficient correction period T
_C1 will be set. Immediately after the time point T ₂ which is the start time point of the first tap coefficient correction period T _C1 , the ghost signal component obtained by the field sequence operation / averaging process of the field operation circuit 9 in the previous T _{1 to} T ₂ period. The GCR waveform (GCR + Sg) including is already output to the signal changeover switch 17 and the waveform memory unit 18. Therefore, in the microcomputer 8, first, a GCR waveform (GCR + Sg) including the ghost signal component is input to the waveform memory section 18, and a process of "memorizing" this as a memory waveform (MGCR) is performed. For example, when the GCR waveform GCR shown in FIG. 3A is used as the main signal component and the waveform as shown in FIG. 3B is the ghost signal component Sg, 8 field sequence calculation /
A GCR waveform (GCR + Sg) including a ghost signal component obtained by averaging has a waveform as shown in FIG. 3C. In this case, this waveform is stored in the waveform memory unit 18 as a memory waveform (MGCR). It will be held as data. Therefore, in the waveform memory unit 18 in the T _{2 to} T ₃ period, the memory waveform (MGCR) is stored as shown in the waveform memory unit contents of FIG.

Immediately after T ₂ , the control signal Cs1 is set to the H level, so that the signal changeover switch 17
Has been switched to the terminal b side, but at this time, already
The GCR waveform (GCR + Sg) including the ghost signal component output from the field operation circuit 9 is differentiated when the terminal connection of the signal changeover switch 17 is changed from the terminal a to the terminal c in the previous T _{1 to} T ₂ period. It is assumed that the signal is input to the circuit 10. Therefore, the microcomputer 8
As the memory waveform (MGCR) is stored in the waveform memory unit 18, the GCR waveform (GCR + Sg) including the ghost signal component input to the differentiating circuit 10 is “differentiated” as shown in the period T _C1 . Differential pulse (PGCR + P
g) is obtained. Then, the subtractor 12 "subtracts" the reference waveform PGCR formed by the reference waveform forming circuit 11 from the differential pulse PGCR + Pg to obtain the differential pulse Pg of the ghost signal component. Next, based on the differential pulse Pg of the ghost signal component, the correction amount data ST
The process of "converting" to is performed by the converter 13. Then, the tap coefficient of the transversal filter 3 is changed by the correction amount data ST. In this way, within the first tap coefficient correction period T _C1 , as shown in FIG. 2B, the “memory” process of the waveform memory unit 18 and the differentiating circuit 10 are performed.
The "differentiation", the "subtraction" by the subtractor 12, and the "conversion" processing by the converter 13 are performed.

During the second and subsequent tap coefficient correction periods T _{C2 to} T _Cn , the field arithmetic circuit 9 does not perform the 8-field sequence operation / average processing again,
The operation is to obtain the correction amount data ST based on the memory waveform MGCR stored in the waveform memory unit 18.

In this case, the microcomputer 8 is shown in FIG.
(B) As shown in the second tap coefficient correction period T _C2 , the memory waveform first stored in the waveform memory unit 18
The MGCR “read” process is performed, and the memory waveform MGCR is supplied to the transversal filter 3 via the signal changeover switch 15. At this time, the memory waveform MGCR output through the transversal filter 3 in synchronization with the read timing for the waveform memory unit 18
Is directly input to the buffer memory 7 through the terminal b → terminal c of the signal changeover switch 16 and is “held”. At this time, the memory waveform held in the buffer memory 7
Since the MGCR passes through the transversal filter 3 in which the tap coefficient is corrected for the first time, for example, as shown in FIG.
The memory waveform MGCR (= GCR + Sg) is shown in which the ghost component Sg is reduced as shown in (d).

Next, the microcomputer 8 directly inputs the memory waveform MGCR held in the buffer memory 7 to the differentiating circuit 10 through the path from the terminal b to the terminal c of the signal changeover switch 17 without passing through the field operation circuit 9. . Then, the differentiating circuit 10 "differentiates" the memory waveform MGCR to generate a differential pulse (PGCR + Pg), and then the subtracter 12 "subtracts" with the reference waveform PGCR to obtain the differential pulse Pg of the ghost signal component. This is “converted” into a correction amount ST by the converter 13 and output to the transversal filter 3. As a result, the transversal filter 3 newly obtains the second tap coefficient. That is, in this case, "reading" of the memory waveform MGCR / "holding" of data in the buffer memory 7, "differentiation" in the differentiating circuit 10, "subtraction" by the subtracter 12, and converter 13
By performing the "conversion" process by, the tap coefficient is corrected.

After that, the processing is repeated in the same manner as the second tap coefficient correction period T _C2 . That is, thereafter, the field sequence calculation / average processing of the field calculation circuit 9 is not performed. Then, for example, the n-th tap coefficient correction period T _{Cn in} which the ghost signal component is finally reduced to a predetermined level or less ends and the tap coefficients of the transversal filter 3 are converged. The time when this tap coefficient is converged is T ₃
At this point, the high speed ghost elimination period T _R ends.

By the way, this high-speed ghost elimination period T _R
In at least the period T _{2 to} T ₃ , the signal passing through the transversal filter 3 is not the detection signal SY but the memory waveform MGCR. Therefore, as in the present embodiment, in the high speed ghost elimination period T _R , the control signal Cs2 is set to L level to switch the signal changeover switch 14 to the terminal a side, and the detection signal SY is directly supplied to the output terminal 5. If so, the image display will not be interrupted. In addition,
Since the detection signal SY passes through the transversal filter 3 in the period T _{1 to} T ₂ , the signal changeover switch 14 may be switched to the terminal b side in this period.
At this time, since the transversal filter 3 has not yet obtained a new tap coefficient, the image quality does not change in either signal path.

After the high speed ghost elimination period T _R ,
As shown after the time point T _{3 in} FIG. 2B, the state is switched to the state in which the steady process is performed again. That is, from the T ₃ point on, the control signal Cs2 is passed through a transversal filter 3 is in H level (see FIG. 2 (d)) and is for signal changeover switch 14 is switched to the terminal b side, an output terminal 5 The detected signal SY is supplied. At this time, the tap coefficients of the transversal filter 3 are already in a converged state for removing the ghost, so that the display image is one in which the ghost component is sufficiently removed.

At the same time, the control signal Cs1 is set to the L level (FIG. 2 (c)) and the signal changeover switches 15 and 1 are set.
Since each of 6 and 17 is switched to the terminal a side, T
The signal path is the same as that before _one time point, and the correction amount data ST is obtained based on the detection signal SY. Therefore,
From the time point T ₃ onward, the field operation circuit 9 performs the 8-field sequence operation / averaging process, which requires a considerable amount of time for each correction of the tap coefficient as compared with the high-speed ghost removal period T _R. However, at this point, for example, the removal of the ghost signal component has been completed to a level equal to or lower than the predetermined detection level, so after that, following the removal of the ghost signal component at the steady processing speed causes a particular problem. There will be no. The memory waveform MGCR stored in the waveform memory unit 18 may be cleared at the time point T ₃ as shown in FIG. 2 (e), for example.

FIG. 4 is an explanatory view conceptually showing a comparison between the conventional ghost removal only by the steady process and the high speed ghost removal process of the high speed ghost removal period T _R of this embodiment. Figure 4
(A) shows a video signal, and VD corresponds to one field for each vertical synchronization signal VD. Further, the circle mark for each field indicates the GCR signal SGCR. Also, FIG.
FIG. 4B shows a steady processing sequence, and FIG. 4C shows a high-speed processing sequence. In this case, the 8-field sequence calculation is performed four times and the averaging process is performed on the result. In order to converge the tap coefficients of the transversal filter 3 in the related art, 8-field sequence calculation is performed, for example, four times as shown in the period P ₁ of FIG. 4B, and then these calculation results are averaged. → A series of processes of detecting a ghost signal component by differentiation → subtraction and converting it to a correction amount
It must be repeated every time the tap coefficient of the transversal filter 3 is modified.

However, in the fast ghost elimination period T _R of this embodiment, first, as shown in the period P ₂ , the 8-field sequence operation (4 times) and averaging are performed only once, and then the averaging is performed. The GCR waveform is “stored” in the waveform memory unit 18 as the memory waveform MGCR, and “differentiation” → “subtraction” is performed based on the averaged GCR waveform, and the “conversion” processing is performed to further correct the first correction amount data. ST
Ask for. Then, as the tap coefficient correction processing from the second time onward, the 8-field sequence operation / averaging processing is not performed as shown in the period P ₃ , and the above-mentioned “waveform memory unit 1
It is sufficient to repeat a series of processes of "differentiation" → "subtraction" → "conversion" based on the memory waveform MGCR after "reading of memory waveform MGCR of 8 / holding of memory waveform MGCR of buffer memory 7". .

As described above, the 8-field sequence operation is a process that requires a considerable amount of time. On the other hand, in comparison with this, "reading of the memory waveform MGCR of the waveform memory unit 18 / holding of the memory waveform MGCR of the buffer memory 7" is performed. The processing time is very short. Therefore, as can be seen by comparing FIGS. 4B and 4C, the time required for the series of processing operations for obtaining the correction amount data ST for the second time and thereafter is much shorter in the high-speed processing sequence of this embodiment. Will be things. As a result of the tap coefficient of the transversal filter 3 being corrected by such a high-speed processing sequence from the second time onward, the time until the removal of the ghost signal component is converged is significantly shortened compared to the conventional case.

The circuit configuration shown in FIG. 1 is merely an example, and can be changed as long as the processing operation described by the processing sequence of FIG. 2B is realized. In addition, when a ghost detection signal other than the GCR signal used in the above embodiment is inserted in the video signal,
The present invention can be applied based on this ghost detection signal. For example, the waveform diagrams of FIGS. 5A and 5B show a ghost detection signal inserted in a predetermined line for each field of a video signal in the United States, where HD is a horizontal synchronizing signal and BRST is The color burst signal is shown. The present invention can be applied to such a ghost detection signal. Further, as described above, the internal circuit configuration of the microcomputer 8 is actually a processing operation by software, but it is also possible to configure each of these functional circuit units by a hardware component 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. Further, although the ghost elimination circuit of this embodiment is incorporated in, for example, a television receiver or the like, it may be possible to configure it as a ghost elimination device separate from such a device.

[0050]

As described above, the ghost elimination circuit of the present invention sets a high speed ghost elimination period, and during this period, a GCR waveform (including a ghost component) obtained by performing 8 field sequence operation / averaging once. ) Is stored in the waveform memory unit and the GCR waveform read from the waveform memory unit is looped to the transversal filter from the second tap coefficient modification and thereafter, so that 8 fields can be stored for each modification of the tap coefficient. Sequence operation (multiple times) /
There is no need to perform averaging. Since the time required for 8-field sequence calculation / averaging is considerably long, the time required for the second tap coefficient correction and thereafter is very short, and the tap coefficients of the transversal filter converge until the ghost is removed. The time can also be significantly shortened. Therefore, there is an effect that the waiting time until obtaining the image from which the ghost is removed is very short.

Further, the high speed ghost removal period is always set at the first stage of starting the ghost removal operation, that is, the high speed ghost removal period is set by the trigger pulse output from the trigger circuit in response to power-on or channel switching. By doing so, when the condition of the ghost signal component is different from the previous one, high-speed ghost elimination is performed first, so that, for example, a television incorporating the ghost elimination circuit of the present invention. A receiver or the like can be made convenient. In addition, since the detection signal cannot be obtained from the output of the transversal filter during the high speed ghost removal period, the image detection signal is stopped by configuring the video detection signal to be directly supplied to the output terminal within this period. It doesn't happen.

[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 a timing chart showing the operation of the ghost elimination circuit of this embodiment.

FIG. 3 is a waveform diagram showing a memory waveform obtained by the ghost elimination circuit of this embodiment.

FIG. 4 is an explanatory diagram conceptually showing a processing sequence in the ghost elimination circuit of the present embodiment.

FIG. 5 is a waveform diagram showing a GCR waveform used in the United States.

FIG. 6 is a block circuit diagram showing a ghost elimination circuit in a conventional example.

FIG. 7 is a waveform diagram and a frequency spectrum showing a GCR signal.

FIG. 8 is a waveform diagram showing a method of inserting a GCR signal in a video signal.

FIG. 9 is a waveform diagram showing a field operation for detecting a ghost signal component.

FIG. 10 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, 15, 16, 17 Signal Changeover Switch 18 Waveform Memory 19 Trigger Circuit

─────────────────────────────────────────────────── ───

[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 GCR waveform GCR of FIG. 7A is inserted into the 18th or 281H of each of the 1st, 3rd, 6th, and 8th fields, The remaining second,
18th of each in the 4th, 5th and 7th fields
The pedestal waveform PDS shown in FIG. 7B is inserted at H or 281H . 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] 0007

[Correction method] Change

[Correction content]

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 waveform GCR (including the ghost component) is obtained and then the average of these is calculated. 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. 9C 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.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Change

[Correction content]

Reference numeral 10 denotes 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 with reference to FIG. 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 denotes 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 transformer The tap coefficient of the Versal filter 3 is set to a correction amount ST for obtaining a cancellation signal for removing the ghost, and the signal ST is fed back to the transversal filter 3 to control the pass characteristic of the filter. . And
By repeating the above operation, the characteristics of the transversal filter 3 gradually converge so as to remove the ghost signal component Sg, and the ghost appearing in the displayed image disappears accordingly. Becomes

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0020

[Correction method] Change

[Correction content]

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a block circuit diagram showing an embodiment of the ghost elimination circuit of the present invention . The same parts as those in FIG. 6 are designated by the same reference numerals and the description thereof will be omitted. In this figure, reference numerals 14 to 17 denote signal changeover switches, which have terminals a, b, and c, respectively, and the terminal c can be selectively changed over to either of the terminals a and b. . The signal changeover switch 14 is switched to the terminal a when the control signal Cs2 output from the microcomputer 8 is at the L level and to the terminal b when it is at the H level.
Further, the signal changeover switches 15, 16 and 17 are switched to the terminal a when the control signal Cs1 is at the L level and to the terminal b when the control signal Cs1 is at the H level.

[Procedure correction 6]

[Document name to be amended] Statement

[Correction target item name] 0050

[Correction method] Change

[Correction content]

[0050]

As described above, the ghost elimination circuit of the present invention sets a high speed ghost elimination period, and during this period, a GCR waveform (including a ghost component) obtained by performing 8 field sequence operation / averaging once. ) Is stored in the waveform memory unit and the GCR waveform read from the waveform memory unit is looped to the transversal filter from the second tap coefficient modification and thereafter, so that 8 fields can be stored for each modification of the tap coefficient. Sequence operation (multiple times) /
There is no need to perform averaging. Since the time required for the 8-field sequence calculation / averaging is considerably long, the time required for the tap coefficient correction after the second time is very short, and the tap coefficient of the transversal filter may be converged to eliminate the ghost. The time can be significantly shortened. Therefore, there is an effect that the waiting time until obtaining the image from which the ghost is removed is very short.

[Procedure Amendment 7]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 1

[Correction method] Change

[Correction content]

[Figure 1]

[Procedure Amendment 8]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 7

[Correction method] Change

[Correction content]

[Figure 7]

Claims (4)

[Claims] 1. A transversal filter capable of removing a ghost signal component from an input signal, and a predetermined calculation process for a ghost detection signal including a ghost signal component extracted for each field from an output of the transversal filter. And a ghost detecting means capable of detecting the ghost signal component by the averaged waveform output from the field calculating means, and a detection output of the ghost detecting means. A ghost elimination circuit having a filter characteristic variable data output means capable of setting and outputting filter characteristic variable data for correcting the pass characteristic of the transversal filter, The averaged waveform is recorded as waveform data. Provided with a waveform memory means which may be, and can be set fast ghost canceling period, in the fast ghost removal period, based on the first the field the averaged waveform obtained by the calculation means 1
When the pass characteristic of the transversal filter is corrected for the second time, the averaged waveform is stored as the waveform data in the waveform memory means, and when the pass characteristic of the transversal filter is corrected for the second time and thereafter, the waveform memory means is used. The ghost elimination circuit, wherein the waveform data stored in the ghost detection circuit is configured to pass through the transversal filter and further supplied to the ghost detection means without passing through the field calculation means. 2. The ghost elimination circuit according to claim 1, wherein the high speed ghost elimination period is set at the start of the ghost elimination operation. 3. A transversal filter for the second and subsequent times is provided at least during the high speed ghost elimination period by providing signal switching means capable of switching the input signal so as to be directly supplied to the output side without passing through the transversal filter. 3. The ghost elimination circuit according to claim 1 or 2, wherein the input signal is directly supplied to the output side by the signal switching means after the passage characteristic is corrected. 4. The ghost removing circuit according to claim 1, wherein the ghost detection signal is a GCR signal inserted at a predetermined position of a video signal.