JPH0376473A - Ghost elimination circuit - Google Patents

Abstract

PURPOSE:To preclude the possibility of the user for mis-recognizing deterioration of picture quality due to an input of a long ghost as malfunction of the elimination circuit by providing a counter means for ghost elimination range detecting a range able to eliminate ghost and a display means displaying the ghost input state based on an output of the counter means when a ghost signal in excess of the ghost elimination range is inputted. CONSTITUTION:An output signal of a counter 31 is fed to a comparator 32 together with an output signal of a counter means 35 and the quantity of the both is compared in the comparator 32. Then when the output signal of the counter 31 is smaller than the output signal of the counter means 35, since the ghost signal is within a ghost elimination range of a transversal filter 2, a display means 40 employing a display element such as an LED is light- controlled in this case. When the output signal of the counter 31 is larger than the output signal of the counter means 35, since the ghost signal is in excess of the ghost elimination range of the transversal filter 2, the display means 40 goes off.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a ghost removal circuit using a ghost removal reference signal, and particularly to a ghost removal circuit that can display a ghost signal exceeding the ghost removal range when it is input. Regarding the removal circuit.

[Prior Art] In addition to direct waves, radio waves arriving at a receiving antenna of a television receiver include reflected waves that are reflected by buildings, mountains, etc. and have different propagation paths. These reflected waves appear as ghosts on television images, causing deterioration in image quality. For this reason, various efforts have been made to remove this ghost.

FIG. 5 shows an example of a conventional ghost removal circuit in which a transversal filter is used.

In the same figure, input terminal 1 has, for example, a video detection circuit (
A video signal Sv outputted from a circuit (not shown) is supplied, and this video signal S2 is converted into a digital signal (No. 8) and then supplied to an adder 2a constituting a transversal filter 2.

The image a4Mi+sV supplied to the input terminal 1 is also supplied to the shift register group 2c via the multiplier group 2b, and the output signal of this shift register group 2c is supplied to the adder 2a. (The output signal of this adder 2a) Therefore, the output signal of the transversal filter 2 is derived to the output terminal 3.

The ghost removal circuit shown in FIG. 5 uses a step waveform (vertical synchronization signal) when moving from the third line to the fourth line during the vertical retrace period as shown in FIG. 6 as a reference signal. It will be done. Therefore, during this period, the connection switch 5 is turned on under the control of the time reference setting circuit 4, and the output signal of the transversal filter 2 is supplied to the differentiating circuit 6.

The tap coefficient correction value calculated by the differentiating circuit 6 is stored in a register group 7 constituting a tap coefficient calculation means, and is further supplied to an integrator group 9 via a switch group 8 to obtain a tap coefficient. is supplied to the multiplier group 2b.

In the above configuration, since the shift register group 2c outputs the ghost signal 43 which matches the ghost signal in time and level and whose polarity is inverted, the transversal filter 2 outputs the ghost signal removed image ( = sign SV' is output.

[Problems to be Solved by the Invention] By the way, in the ghost removal circuit shown in FIG. It detects ghost signals, and cannot respond to so-called long ghosts with long time delays.

In order to improve accuracy, we have also shifted the maximum detectable period of the ghost signal (from the falling position of the step signal when moving from the 3rd line to the 4th line to the rising position of the first cutting pulse within the vertical synchronization period). If the number of register taps is increased, the number of delay elements and multipliers will also increase, leading to problems such as higher costs.

In order to solve this problem, a system has been proposed in which ghosts are removed using a reference signal for ghost removal.

This is done by using one unused horizontal period on the broadcasting station side during the vertical retrace period of the television signal, and adding it to this part as shown in Figure 7A.
Reference signal for ghost removal (OCR signal) as shown in
is inserted and transmitted, and the receiving side detects and removes ghosts based on the OCR signal over one horizontal scanning period, thereby dealing with long ghosts.

FIG. 7A shows the OCR signal inserted in the vertical retrace period of field 1 and the signals of the lines before and after it. Figure B
1 shows a 0 pedestal signal inserted into field 5, which functions as an OCR signal, and signals on lines before and after the 0 pedestal signal. For convenience of explanation, it is assumed that the signal on the previous line of the OCR signal has a fixed waveform in both fields.

48, which is obtained by subtracting the video signal of field 5 from the video signal of field 1, and the diagram C shows the differential waveform thereof. Then, the tap coefficient (filter coefficient) of the transversal filter 2 is set based on the magnitude of the latter half of the differential output (ghost component).

When using this OCR signal, the differential output of the OCR signal is such that the first half of the differential pulse is 5i.
The second half of the nX/X pulse is a 2T pulse (ghost component), and the tap coefficient of the transversal filter is set based on this differential output.
Ghosts occurring before and after the differentiated OCR waveform (sinX/X pulse) can be removed up to 44.7 μsec.

Therefore, even if OCR (No. 8 is used), 44.
Ghost signals longer than 7 μsec cannot be removed.

By the way, the propagation path of radio waves can vary depending on factors such as the location of the antenna, so some reflected waves may be short while others may be long. According to the above configuration, 4
In the case of a long ghost of 4.7 μsec or more, the ghost removal effect is naturally weakened, so the user may mistakenly think that ghost removal processing has not been performed.

Therefore, this invention solves this problem, and in particular, in the case of a long ghost that exceeds the ghost removal processing capacity, it is possible to display that such a ghost signal is input. be.

[Means for Solving the Problems] In order to solve the above-mentioned problems, in the present invention, in a ghost removal circuit using a reference signal for ghost removal, a delay time of a transversal filter to which an input signal is supplied is counted. , a ghost removal range counter means for detecting a range in which ghosts can be removed, and a display means for displaying the ghost input state based on the output of the counter unit when a ghost signal exceeding the ghost removal range is input. It is characterized by this.

[Work] A video signal is input to the transversal filter 2.

The horizontal synchronization signal in the video signal input to the transversal filter 2 and the output horizontal synchronization signal are supplied to the ghost removal range counter means 35, the delay time of the transversal filter 2 is counted, and the ghost is removed. A range that can be removed is detected.

When ghost toy No. 8 exceeding the ghost removal range is input, this ghost input state is detected by the counter means 3.
A display element 40, which is a display means, is driven based on the output of 5.

Thereby, the user can visually know that the ghost number 48 exceeding the capability of the transversal filter 2 is being input.

[Embodiment] Next, an example of a ghost removal circuit according to the present invention will be described in detail with reference to FIG. 1 and subsequent figures.

In FIG. 1, the receiving antenna 11 receives a television signal (FIG. 7 A, B) including GCR (No. 8 and O pedestal signals) for 1H period. There are direct waves emitted from the building 12 and reflected waves reflected from the building 13 and the like.

A television signal captured by the receiving antenna 11 is supplied to a tuner 14, and an intermediate frequency signal from the tuner 14 is supplied to a video detection circuit 15. Video detection circuit 1
The video signal S■ output from 5 is A/D! After being converted into a digital signal by the I converter 16, it is supplied to the transversal filter 2.

During the vertical retrace period of the video signal Sv, as described above, 5i
OCR (No. 8 is inserted) consisting of nX/X bars, etc. The 5inX/X bar is used after being differentiated and converted into a 5inX/X pulse (Fig. 7D).

The output signal of the transversal filter 2 is supplied to the GCR signal extraction circuit 17, and the extracted OCR signal (No. 8 is differentiated by the differentiation circuit 18 to form a BinX/X pulse (
After being converted into the signal shown in FIG. 2A), it is supplied to the signal comparison circuit 19.

The signal comparison circuit 19 includes a ghost removal base generated by the reference waveform generation section 20! ! Differential output S B of signal OCR' (same waveform as OCR signal, but not shown)
A sinX/X pulse (see FIG. 2B) is supplied.

A synchronization signal is supplied as a timing signal to the reference waveform generator 20, and a differentiated output of the ghost removal reference signal OCR' is generated using a ROM or the like.

Signal comparison time! From 1819, a comparison error 43 between the output signal SA of the differentiating circuit 18 and the differential output of the reference waveform generator 20 is detected.
signal, and therefore a ghost signal component e is output (second
Figure C).

The ghost signal component e from signal comparison 1 #19 is supplied to a tap coefficient (filter coefficient) calculation means 21, and a tap coefficient (negative polarity) as shown in the second diagram is calculated based on this ghost signal component. Ru. The tap coefficients are supplied to multiplier group 2b of transversal filter 2.

Here, the transversal filter 2 is configured in the same manner as described above. Therefore, as shown in FIG. 4, the adder 2a has a multiplier group 2c corresponding to each element of the shift register group 2c% shift register group. The tap coefficient calculating means 21 also includes a differentiating circuit 6, a register 7, a switch 8, and an integrator 9, as shown in FIG.
Consists of.

In the above configuration, the shift register group 2C outputs a 1f-st removal signal that matches the ghost signal included in the video signal Sv in time and level, and has its polarity inverted.

For example, the output signal of the differentiating circuit 18 includes a ghost signal component e as shown in FIG. 2A, and the reference waveform generator 20 outputs a differential output SB as shown in FIG. 2B. At this time, the signal comparison circuit 19 outputs only the ghost signal component e as shown in FIG. Then, at a timing corresponding to the delay time of the ghost signal component e of the transversal filter 2, the multiplier 2b is informed by the tap coefficient calculation means 21 that the level is the same as that of the ghost signal component e as shown in the same figure, and Tap coefficients with inverted polarity are provided.

As a result, the shift register group 2C outputs a ghost-removed signal, and therefore the transversal filter 2 outputs a video signal Sv' from which the ghost signal has been removed.

Further, the video signal SV' outputted from the transversal filter 2 is converted into an analog signal by a D/As converter 26 and then supplied to the receiver 28 via a video amplification circuit 27. Therefore, a video signal containing a ghost (A in FIG. 3) is corrected into a video signal without a ghost (B in the same diagram) and supplied to the picture tube 28, so that a high-quality image without ghost interference is projected. .

In the present invention, the above-mentioned transversal filter 2 further includes a counter means 35 for setting a ghost removal range.
is provided.

This counter means 35 has a terminal 1 as shown in FIG.
In addition to the input video signal supplied to the register group 2c, the output video signal output from the register group 2c is inverted and supplied by the inverter 36, and a predetermined clock signal is also supplied.

36 indicates an inverter for inverting the output video (No. 3).

The counter means 35 has an extraction means (not shown) for extracting only the horizontal synchronization signal from these video signals, and the output horizontal synchronization signal (No. 3) delayed by the register group 2c from the time when the input horizontal synchronization signal is obtained. The delay time up to the point in time is counted.

Since this delay time represents the ghost removal range that can be removed by the transversal filter 2,
The output signal of the counter means 35 is nothing but an indication of the removal ability of the set transversal filter. The output signal of the counter means 35 is supplied to a comparator 32.

On the other hand, the output signal of the differentiating circuit 18 is waveform-shaped by a waveform shaping circuit 30 and then supplied to a counter 31, where the delay time from the time when the GCR signal is obtained until the ghost (i and e) is obtained is measured. Ru.

The output signal of the counter 31 is transmitted to the counter means 35 mentioned above.
It is supplied to the comparator 32 together with output number 8, and the magnitudes of the two are compared. When the output signal of the counter 31 is smaller than the output signal of the counter means 35,
Since that ghost signal is within the ghost removal range of transversal filter 2, in this case, LE
The lighting of the display means 40 using a display element D is controlled.

Therefore, the output signal of the counter 31 is
5, the ghost signal exceeds the ghost removal range of the transversal filter 2. In this case, the display means 40 is turned off as the ghost signal is outside the ghost removal capability of the transversal filter 2.

The blinking control may be reversed to the above.

[Effects of the Invention] As explained above, according to the configuration of the present invention, when a ghost signal exceeding the ghost removal range of the transversal filter is input, the display means is controlled. Even if the image quality deteriorates, there is no risk that the user will mistakenly perceive it as a malfunction of the removal circuit.

Therefore, user confidence in the device is improved.

[Brief explanation of drawings]

FIG. 1 is a system diagram showing an embodiment of the ghost removal circuit according to the present invention, FIG. 2 is a diagram showing signal waveforms at each point in FIG. 1,
Fig. 3 is a waveform diagram of ghost removal processing, Fig. 4 is a system diagram including a transversal filter, Fig. 5 is a system diagram showing a conventional example of a ghost removal circuit, and Fig. 6 is a conventional example of a ghost removal circuit. Reference Waveform FIG. 7 is a waveform diagram showing a part of the reference signal for ghost removal sent from the broadcast station side. 32 ・ ・ 35 ・ ・ Comparator/ghost removal range counter means 2 ・ 11 ・ 44 15 ・ 17 ・ 18 ・ 19 ・ 20 ・ 2 l ・ 27 ・ 28 ・ 30 ・ 31 ・ ◆Transversal filter, receiving antenna, tuner, video Detection circuit, ghost removal standard (No. 8 extraction circuit, differentiation circuit, signal comparison circuit, reference waveform generation section, tap coefficient calculation means, video amplification circuit, picture tube, waveform shaping circuit, delay time counter)

Claims (1)

[Claims] (1) In a ghost removal circuit using a reference signal for ghost removal, a ghost removal range counter means counts the delay time of a transversal filter to which an input signal is supplied and detects a range in which ghosts can be removed; 1. A ghost removal circuit comprising display means for displaying a ghost input state based on the output of the counter section when a ghost signal exceeding the range is input.