JP2700335B2 - Ghost removal device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a ghost removing device installed in a television receiver.

(Prior Art) A typical ghost removing device installed in a television receiver is composed of a reference waveform extracting unit 50, a ghost detecting unit 60, and a ghost removing unit 70, as shown in FIG. I have. The ghost removing unit 70 includes a transversal filter 71 for generating a pseudo ghost and an adder 72. A reference waveform extracting section 50 extracts a reference waveform for ghost detection and waveforms before and after the ghost included in a predetermined portion of the digital reception television signal to be removed from the ghost supplied to the input terminal I. The ghost detection unit 60 detects a ghost from these extracted waveforms, and
A tap coefficient group to be supplied to the transversal filter 71 in 70 is generated.

Transversal filter 71 for pseudo ghost generation
Is a cascade-connected delay device Da, Db, Dc... Dx each of which delays a digital television signal by one sampling period, and multiplies the output of each delay device by a coefficient, as shown in FIG. Kx, and adders A for adding the outputs of the respective coefficient units. The coefficient values of the coefficient units Ka to Kx are controlled by tap coefficients supplied from the ghost detection unit 60.

The tap coefficient group output from the ghost detection unit 60 is typically arranged on the time axis as a plurality of groups covering a range of about several tens of taps (sampling period) as illustrated in the waveform diagram of FIG. Distributed discretely. Therefore, if attention is paid to a certain time zone, the ghost does not appear in most of the time regions, or even if it appears, the ghost level is negligible. Therefore, the transversal filter 71 for removing ghosts has several hundred taps (a maximum of one line corresponds to 91).
If it is provided over (0 taps), the tap utilization rate in each time zone decreases, which is uneconomical.

Therefore, a configuration as shown in FIG. 10 is usually employed as a transversal filter for removing a ghost.
That is, a plurality of sub-transversal filters 81a, 81b... 81y of a limited scale of about several tens of taps are installed in parallel, and the amount of delay set in the variable delay circuits 82a, 82b. Each sub-transversal filter is dynamically converted in accordance with the appearance state, and each sub-transversal filter is delayed from the reference waveform by τa, τb... Τt from the reference waveform in the example of FIG. (Position) is selectively inserted.

The ghost elimination device using the transversal filter having such a configuration has a configuration in which a delay amount / coefficient setting unit 80 is added as shown in the block diagram of FIG. This delay amount / coefficient setting unit 80 includes a ghost removal detection unit.
The tap coefficient groups generated in 60 are grouped while being inspected, and the coefficient groups are set in each of the sub-transversal filters 81a to 81y in the transversal filter 71, and corresponding to the variable delay circuits 82a to 82y at the preceding stage. (Τa, τ
b ...) is set. When the number of coefficient groups is larger than the number of sub-transversal filters 81a to 81y, one of the sub-transversal filters is preferentially assigned to a coefficient group having a higher level.

The configuration of the transversal filter shown in FIG. 10 has the disadvantage that the amount of delay by the variable delay circuit increases and the circuit scale increases. Further, since the output of the adder 83a is distributed to a number of variable delay circuits 82a and 82y, an intermediate buffer circuit is required, and the circuit size is increased. Therefore, as shown in FIG. 12, a configuration is adopted in which the sub-transversal filters 81a to 81y are connected in cascade with variable delay devices 85a to 85y interposed. Note that the adders 84a to 84y at each stage may be integrated as one adder, or the integrated adder may be further integrated with the adder 83. According to this cascade connection configuration, only the shortage of the delay amount set up to the previous stage needs to be set in the delay circuit of the second stage shift, and the scale of the delay circuit is reduced. Further, since the output of each delay circuit is only distributed to the sub-transversal filter and the next-stage delay circuit, no intermediate buffer circuit is required and the circuit scale is reduced.

(Problems to be Solved by the Invention) In the above-described ghost removing apparatus, the preceding processes including extraction of the reference waveform, detection of the ghost, and delay / coefficient control can be realized mainly by software. Only the filter has to depend on the hardware configuration in order to secure the processing speed. Therefore, in order to reduce the cost of the ghost removing device, it is very important to reduce the amount of hardware of the transversal filter. For this reason, various improvements have been made such as the above-described configuration of grouping into sub-transversal filters and the configuration of cascade arrangement of these.

However, there is a problem that the cost reduction of the entire ghost removing device by reducing the hardware amount of the transversal filter is not sufficient.

(Means for Solving the Problems) The present invention has solved the above-mentioned problems, and adds the outputs of a group of sub-transversal filters connected in a ladder to a plurality of variable delay circuits each connected in cascade. ,
A ghost removing section having first and second pseudo ghost generating transversal filters for generating first and second pseudo ghosts, and extracting a reference waveform for ghost detection and waveforms before and after the ghost detection from the digital television signal A reference waveform extracting unit, a ghost detecting unit that detects a ghost from the extracted waveform, and generates a tap coefficient group of the first and second pseudo ghost generating transversal filters in the ghost removing unit; and the ghost detecting unit. Is divided into a first group having a small level and a second group having a large level, and the first group is assigned to each of the sub-transversal filters in the first transversal filter. And setting a delay amount corresponding to each of the variable delay circuits, and setting a second group to each of the sub-transformers in the second transversal filter. Is characterized in that the set transversal filter and a said delay amount and coefficient setting unit for setting a delay amount corresponding to each of the variable delay circuits. Further, the second transversal filter may be replaced with a configuration that generates the second pseudo ghost by adding the outputs of the coefficient units connected in a ladder shape to a plurality of variable delay circuits connected in cascade.

Further, the present invention provides a first transversal filter for generating the low-level pseudo ghost.
By using a single transversal filter of a predetermined number of stages without dividing into a transversal filter, it is not necessary to set a variable delay amount based on software processing in the transversal filter. In order to achieve a balance between the low cost of the device and the response speed.

(Example) Hereinafter, the operation of the present invention will be described in detail with examples.
FIG. 1 is a block diagram showing the configuration of an embodiment of the ghost removing device of the present invention.

This ghost removing device includes an input terminal 1 for a digital television signal to be removed, a reference waveform extracting unit 2, a ghost detecting unit 3, a delay / coefficient setting unit 4,
It is composed of a ghost removing section 5 and an output terminal 6 of a digital television signal from which ghost has been removed. The ghost removing unit 5 includes a transversal filter 10 for generating a low-level pseudo ghost, a transversal filter 20 for generating a high-level pseudo ghost, and adders 31 and 32.
It is composed of

FIG. 2 is a block diagram showing a configuration of the ghost removing unit of FIG. The first transversal filter for generating low-level pseudo ghosts includes variable delay circuits 11a, 11b
.. Are composed of sub-transversal filters 12a, 12b,. Similarly, the second transversal filter for generating a high-level pseudo ghost also includes variable delay circuits 21a, 11b
.. Are composed of sub-transversal filters 22a, 22b,.

In the ghost elimination device shown in FIG. 1, a ghost detection reference waveform included in a predetermined portion of a ghost removal target digital television signal supplied to an input terminal I and waveforms before and after the ghost detection are extracted by a reference waveform extraction unit 2. Is extracted. The ghost detector 2 detects a ghost from the waveform extracted in the previous stage and generates a tap coefficient group to be supplied to the transversal filter in the ghost remover 5. The delay amount / coefficient setting unit 4 divides the tap coefficient group generated by the ghost removal detection unit into a first group having a level lower than a predetermined value and a second group having a level higher than a predetermined value. Delay / coefficient setting unit 4
Is used to convert the low level first group to each of the sub-transversal filters 12a-12n in the first transversal filter 10.
And the delay amount corresponding to each of the variable delay circuits 11a to 11n. Further, the delay amount / coefficient setting unit 4 sets the high-level second group of the tap coefficient group in each of the sub-transversal filters 22a to 22b in the second transversal filter 20, and sets each variable delay Circuits 21a-21m
Set the delay amount corresponding to.

That is, as illustrated in the waveform diagram of FIG. 3, if the tap coefficient group generated by the ghost detection unit 3 is as shown in FIG.
Are divided into a low level group as shown in FIG. 7B and a high level group as shown in FIG. As an example,
It is assumed that the coefficient is represented by a two's complement number having an 8-bit width including a sign bit, and the threshold Lth for distinguishing between the low level and the high level is a level of seven. The low-level coefficient group constitutes the first transversal filter 10 as 4-bit data in which the lower 3 bits are added with one sign bit (“0” for positive polarity and “1” for negative polarity). Are set in the coefficient units in the sub-transversal filters 12a to 12n. The high-level coefficient group is set as 8-bit width data in each coefficient unit in the sub-transversal filters 22a to 22m constituting the second transversal filter 20.

Further, as an example, the television signal supplied to the first and second transversal filters 10 and 20 is 8-bit data including code bits. The sub-transversal filters 12a to 12n in the first transversal filter 10 convert the 8-bit wide television signal into 1-bit signals.
Only the upper 4 bits including the sign bit of the bit are extracted, and the multiplier constituting the coefficient unit performs multiplication with a 4-bit width coefficient value to generate an 8-bit width pseudo ghost. On the other hand, in the sub-transversal filters 22a to 22n in the second transversal filter 20, in the multipliers forming the coefficient units, multiplication of the 8-bit width television signal by the coefficient value and truncation of the lower 4 bits are performed. Generates a 12-bit width pseudo ghost.

8 output from the first transversal filter 10
The pseudo ghost having the bit width is added to the pseudo ghost having the 12-bit width outputted from the second transversal filter while adding the upper 4 sign bits in the adder 31. This addition value is added to the 8-bit television signal while the lower 4 bits are discarded in the adder 32.

Thus, in the first transversal filter, 8 bits × 8 in the second transversal filter.
A 4-bit × 4-bit multiplication is performed instead of the 8-bit multiplication, and the scale of the multiplier is (4 bits / 8 bits) ² = 1/4
And the scale of the delay circuit is compressed to 4 bits / 8 bits = 1/2.

FIG. 4 shows the sub-transversal filters 22a to 22m in the second transversal filter 20 shown in FIG.
Is realized by a single-stage transversal filter including only the coefficient units 24a to 24m.

FIG. 5 shows a configuration example in which the first transversal filter shown in FIG. 2 is realized by one transversal filter 40 having a predetermined number of taps, instead of being configured by a combination of sub-transversal filters. It is. Since the level of the pseudo ghost generated by the first transversal filter 40 is small and the bit width is reduced, the scale of the hardware does not increase so much even with a continuous configuration. On the other hand, the amount of software processing to be executed by the delay amount / coefficient setting unit 4 in the preceding stage, such as the setting of the variable delay amount, is reduced as compared with the case of configuring as a combination of sub-transversal filters. Removal becomes feasible.

FIG. 6 shows the sub-transversal filters 12a to 22m in the second transversal filter 20 shown in FIG.
Is realized by a single-stage transversal filter including only the coefficient units 24a to 24m.

As described above, the configuration in which the television signal that has been converted into the digital signal is subjected to the ghost removal is exemplified. However, an A / D converter may be added to the ghost removing device to convert the analog television signal into a digital television signal, and then perform the above-described ghost removal processing.

Further, the configuration in which the digital television signal from which the ghost has been removed is output as it is has been illustrated. However,
A configuration may be adopted in which a D / A converter is added to the ghost removal device, and the ghost-removed digital television signal is converted into an analog television signal and then output.

(Effects of the Invention) As described in detail above, according to the present invention, the tap coefficient group generated by the ghost detection unit is divided into a first group having a small level and a second group having a large level, The first group is set for each sub-transversal filter in the first transversal filter, the delay amount corresponding to each variable delay circuit is set, and the second group is set for the second transversal filter. Since the delay amount is set in each sub-transversal filter and the corresponding delay amount is set in each variable delay circuit, from the observation result of the ghost occurrence state, it is noted that the higher the level of the ghost, the lower the appearance frequency is. The high-level pseudo-ghost and the high-level pseudo-ghost can be generated by separate transversal filters, whereby the first pseudo-ghost for low-level pseudo-ghost generation can be generated.
, The operation bit width of the transversal filter can be reduced from the conventional operation bit width, the hardware scale can be reduced, and each of the first and second transversal filters is connected to a plurality of cascade-connected In order to generate the first and second pseudo ghosts by adding the outputs of the sub-transversal filter groups connected in a ladder shape to the variable delay circuit, a low-level pseudo ghost and a high-level pseudo ghost are grouped. An excellent effect is obtained such that the selection range of the threshold value can be widened and a wide variety of ghost environments can be handled.

Further, the second transversal filter may be replaced with a configuration in which the outputs of the coefficient units connected in a ladder shape of a plurality of cascaded variable delay circuits are added to generate a second pseudo ghost. The second transversal filter is constituted by a single sub-transversal filter instead of a plurality of sub-transversal filters, and only the highest level pseudo ghost is generated by the second transversal filter. There are effects such as simplification of the circuit configuration of the transversal filter.

Also, the present invention provides a transversal filter in which a first transversal filter for generating a low-level pseudo ghost is constituted by one transversal filter having a predetermined number of stages without being divided into sub-transversal filters. There is no need to set the variable delay amount based on software processing to the filter, and accordingly, the amount of hardware and the amount of software processing can be harmonized, and the cost of the device can be reduced and the response speed can be harmonized. To play.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a configuration of an embodiment of a ghost removing device of the present invention, and FIG. 2 is a block diagram showing a configuration of a ghost removing portion of the ghost removing device shown in FIG. 3 is a waveform diagram for explaining the operation of the ghost removing device shown in FIG. 1, and FIG. 4 is a block illustrating another configuration of the ghost removing unit shown in FIG. FIG. 5 is a block diagram showing a configuration of a ghost removing unit of another embodiment of the ghost removing device of the present invention, and FIG. 6 is a block diagram showing another configuration of the ghost removing unit shown in FIG. FIG. 7, FIG.
FIG. 8 is a block diagram showing an example of the configuration of a typical example of a conventional ghost removing apparatus. FIG. 8 is a block diagram showing an example of the configuration of the transversal filter for generating a pseudo ghost shown in FIG. 7, and FIG. FIG. 10 is a waveform diagram illustrating an example of a tap coefficient group output from the ghost detection unit illustrated in FIG. 10, FIG. 10 is a block diagram illustrating a configuration example of a conventional transversal filter for ghost removal, and FIG. FIG. 12 is a block diagram showing a configuration of a ghost removing device using the transversal filter shown in FIG. 10, and FIG. 12 is a block diagram showing another configuration example of the transversal filter of FIG. 1. Input terminal of digital television signal for ghost removal 2. Reference waveform extraction unit 3. Ghost detection unit 4. Delay / coefficient setting unit 5. Ghost removal unit 6. Digital TV with ghost removed Output terminal 10 of the john signal; a first transversal filter for generating a low-level pseudo ghost 20; a second transversal filter for generating a high-level pseudo ghost 31, 32 ... adders 11a to 11n and 21a to 21m Variable delay circuits 12a to 12n, 22a to 22m Sub-transversal filters 24a to 24m One-stage transversal filter consisting only of coefficient units 40 One transversal filter with a predetermined number of taps

Claims (6)

(57) [Claims] A first and second pseudo ghosts are generated by adding outputs of a group of sub-transversal filters connected in a ladder to a plurality of variable delay circuits connected in cascade. A ghost removing unit having a transversal filter for generating a pseudo ghost, a reference waveform extracting unit for extracting a reference waveform for ghost detection from a digital television signal and waveforms before and after the ghost detection unit, and detecting a ghost from the extracted waveform. A ghost detection unit that generates a tap coefficient group of the first and second pseudo ghost generation transversal filters in the ghost removal unit; and a first group having a small level, the tap coefficient group generated by the ghost detection unit. The sub-transversal filters in the first transversal filter are grouped into a second group having a large level. And setting a delay amount corresponding to each of the variable delay circuits, and setting a second group to each sub-transversal filter in the second transversal filter, and setting a delay amount corresponding to each of the variable delay circuits. And a delay / coefficient setting unit for setting the delay time. 2. Each of the sub-transversal filters in the first and second transversal filters includes a plurality of variable delay circuits connected in cascade, and a plurality of ladder-like connected to the plurality of variable delay circuits. 2. The ghost eliminator according to claim 1, further comprising: a coefficient unit; and an adder for adding outputs of the plurality of coefficient units. 3. A first pseudo ghost generating transversal filter for adding a ladder-like output of a group of sub-transversal filters to a plurality of cascaded variable delay circuits to generate a first pseudo ghost. A ghost removing unit having a second pseudo ghost generating transversal filter for adding a ladder-connected output of a coefficient unit to a plurality of cascaded variable delay circuits and generating a second pseudo ghost; A reference waveform extracting unit for extracting a ghost detection reference waveform and waveforms before and after the ghost detection signal from the television signal, and a first and second pseudo ghost generation transformer in the ghost removal unit detecting a ghost from the extracted waveform. A ghost detection unit that generates a tap coefficient group of a versal filter; and a tap coefficient group generated by the ghost detection unit. A first group is divided into a small first group and a second group having a large level. The first group is set for each of the sub-transversal filters in the first transversal filter, and the first group is set for each of the variable delay circuits. A delay / coefficient setting unit that sets a delay amount, sets a second group in each coefficient unit in the second transversal filter, and sets a delay amount corresponding to each of the variable delay circuits. A ghost removing device, comprising: 4. A quasi-ghost generating transversal filter for generating a first pseudo-ghost and an output of a group of sub-transversal filters connected in a ladder shape to a plurality of cascaded variable delay circuits are added. A ghost removing section having a second pseudo ghost generating transversal filter for generating a second pseudo ghost, and a reference waveform extracting section extracting a ghost detecting reference waveform from a received television signal and waveforms before and after the ghost detecting reference waveform. Ghosts are detected from these extracted waveforms,
A ghost detecting unit that generates a tap training group of a second pseudo ghost generating transversal filter; and a tap coefficient group generated by the ghost detecting unit, a first group having a small level and a second group having a large level. And the first group is set to the first transversal filter, and the second group is set to each sub-transversal filter in the second transversal filter. A ghost eliminator, comprising: a delay amount / coefficient setting unit that sets a delay amount corresponding to a circuit. 5. Each of the sub-transversal filters in the second transversal filter includes a plurality of variable delay circuits connected in cascade, and a plurality of coefficient units connected in a ladder shape to the plurality of variable delay circuits. 5. The ghost removing apparatus according to claim 4, further comprising an adder for adding outputs of said plurality of coefficient units. 6. A second pseudo-ghost-generating transversal filter for generating a first pseudo-ghost and a plurality of variable delay circuits connected in cascade add the outputs of a group of coefficient units connected in a ladder-like manner to produce a second pseudo-ghost. A ghost removing unit having a second pseudo ghost generating transversal filter for generating a pseudo ghost, a reference waveform extracting unit for extracting a reference waveform for detecting a ghost and waveforms before and after the ghost detection from a received television signal, A ghost detecting section for detecting a ghost from the obtained waveform and generating a tap teacher group of the first and second pseudo-ghost generating transversal filters in the ghost removing section; and a tap coefficient group generated by the ghost detecting section. Are divided into a first group having a small level and a second group having a large level, and the first group is provided in the first transversal filter. And a delay / coefficient setting unit that sets a second group in each coefficient unit in the second transversal filter and sets a delay amount corresponding to each of the variable delay circuits. Ghost removing device.