JPH03226186A - Ghost elimination device - Google Patents

Abstract

PURPOSE:To attain automatic adjustment of amplitude with simple constitution by detecting the amplitude of a reference waveform in a received television signal appearing at an input terminal and adjusting the amplitude of the received television signal so that the amplitude is equal to the standard amplitude of a reference waveform stored in advance. CONSTITUTION:A reference waveform amplitude detection section 41 in a level adjustment section 4 detects an amplitude of a reference waveform based on a time mean value of regions before and after the reference waveform outputted from a waveform storage section 13 in a ghost detection section 1 and on a timing signal from a timing generating circuit 14. A division section 43 divides a standard value stored in a reference waveform amplitude standard value storage section 42 by an amplitude of the reference waveform detected by the detection section 41 and gives the result of division to a multiplier 44 as a multiple factor. The amplitude of a received digital television signal fed from an input terminal IN to the multiplier 44 is multiplied by a multiple factor fed from the division section 43 and the result is fed to one input terminal of a synthesis section 3, in which the signal is synthesized with a pseudo ghost signal fed to the other input terminal from a pseudo ghost generating section 2. Thus, the amplitude of the signal whose ghost is already eliminated is adjusted automatically with simple constitution.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a ghost removal device installed in a television receiver.

(Prior Art) With the realization of the concept of high-definition television systems such as HDTV and HDTV, there is an increasing need to install a ghost removal device within the television system receiver.

As shown in FIG. 3, a typical example of such a ghost removal device is a feedforward control type device consisting of a ghost detection section 5, a pseudo-ghost generation section 52, and a synthesis circuit 53. be.

In the ghost detection section 51, a ghost is detected using the vertical synchronization signal in the digital received television signal appearing at the input terminal IN as a reference waveform, and the tap gain is supplied to the transversal filter constituting the pseudo-ghost generation section 52. is generated. This II-like ghost generation section 52 detects ghosts contained in the received television signal based on the tap gain supplied from the ghost detection section 51 and the television signal after ghost removal supplied to the output terminal OUT. A pseudo ghost that changes in the opposite direction is generated and supplied to one input terminal of the synthesis circuit 53. In this synthesis circuit 53, the ghost contained in the received television signal supplied to the other input terminal and the pseudo ghost in the opposite direction supplied to the other input terminal are canceled by synthesis, and the ghost is removed. The signal becomes a television signal and is supplied to the output terminal OUT.

The explanation will be supplemented by the waveform diagram in FIG. The topmost waveform (A) is a waveform that shows the received television signal before the ghost occurs, including the vertical synchronization signal and its surroundings. The falling part α of this vertical synchronization signal. is used as the reference waveform for ghost detection. The waveform (B) in FIG. 4 is the waveform of the received television broadcast signal after the occurrence of a ghost. According to this waveform (B), there is a delay of time τ from the signal component, and the level is 1/3
The occurrence of a positive ghost that attenuates to a certain degree and changes in the same direction as this is illustrated. In the ghost detection section 51,
The ghost occurrence situation, which is based on the delay time (τ in this example), the level attenuation amount (approximately 173 in this example), and the forward/reverse direction of change (positive direction in this example), is determined by the reference waveform α,
Detected from a comparison with this reference waveform ghost β1,
A tap gain of the pseudo-ghost generator 52 is generated. The pseudo-ghost generation section 52 generates a pseudo-ghost shown in the waveform (C) from the tap gain and the ghost-removed reception signal waveform (D) on the output terminal OUT. This pseudo-ghost (C) is generated by delaying the waveform (D) by τ, attenuating it to about ⅓, and changing the waveform (D) in a direction opposite to that of the detected ghost. The waveform β2 in the pseudo ghost is generated by delaying the reference waveform α2 in the waveform (D) by the time τ, attenuating the waveform to about 173, and raising the reference waveform α2.

The synthesis unit 53 generates a waveform (D) by adding the waveform (B) and the waveform (C).

The ghost removal device having the configuration shown in FIG. 3 is called a feedforward control type because it detects ghosts from the received television broadcast signal before ghost removal. On the other hand, a configuration in which ghosts are detected from the received television signal after ghost removal at the subsequent stage of the synthesis circuit 53 and gradually converges to a sufficient removal state is called a feedback control type.

In this feedforward*m type ghost removal device, the amplitude of the signal waveform to be output is different before and after the ghost occurs (this is due to the amplitude of the waveform (A) and waveform (D) in Fig. 4 being different). It is clear from the comparison.Therefore, it is necessary to install an amplitude readjustment circuit after the ghost removal device to readjust the amplitude of its output to a constant value (0.286vo 1 t for the synchronization signal). .

(Problem to be Solved by the Invention) The conventional feedforward control type ghost removal device described above has a problem in that it requires the installation of a relatively complicated and expensive analog amplitude readjustment circuit such as an AGC amplifier at the subsequent stage. .

(Means for Solving the Problems) The ghost removal device of the present invention includes, in addition to an existing ghost detection section, a pseudo ghost generation section, and a synthesis section, a reference waveform in a received television signal appearing at an input terminal. It has a simple configuration, and includes an amplitude adjustment section that detects the amplitude of the received television signal and supplies it to the synthesis section while adjusting the amplitude of the received television signal so that it becomes equal to the standard value of the amplitude of the reference waveform held in advance. and is configured to automatically adjust the amplitude of the deghosted signal.

Hereinafter, the operation of the present invention will be explained in detail together with examples.

(Embodiment) FIG. 1 is a block diagram showing the configuration of a ghost removal device according to an embodiment of the present invention.

This ghost removal device is composed of a ghost detection section 1, a pseudo ghost generation section 2, a synthesis section 3, and a level adjustment section 4, and removes ghosts from a digital received television signal supplied from an input terminal IN and outputs the result. Terminal OU
Output to T. This ghost removal device is configured as a feedforward control type that detects ghosts from the television signal on the input terminal side.

The ghost detection unit 1 includes an addition unit 12, a waveform holding unit 13, a timing generation unit 14, a reference area Fourier transformation unit 15, a detection area Fourier transformation unit 16, a division unit 17, and a band limiting unit 1.
8. It is composed of an inverse Fourier transform section 19 and a tap gain holding section 20, and supplies the tap gain generated by detecting a ghost to the pseudo-image ghost generation section 2.

The level adjustment section 4 installed between the input terminal IN and the synthesis section 3 includes a reference waveform amplitude detection section 41, a reference waveform amplitude standard value holding section 42, a division section 43, and a multiplication section 44.
The received television signal on the input terminal IN is supplied to one input terminal of the combining section 3 while adjusting its amplitude.

A digital received television signal supplied to the input terminal IN is supplied to a ghost detection section 1 and a level adjustment section 4. The received television signal supplied to the ghost detection section 1 is supplied to an addition section 12 and a timing generation section 14. The timing generation section 14 extracts the synchronization signal contained in the received television signal and generates a timing signal to be supplied to each section in the ghost detection section 1, such as the addition section 12 and the waveform holding section 13, and the level adjustment section 4.

The adding section 12 and the waveform holding section 13 are connected to the timing generating section 14.
Under the control of a timing signal supplied from Temporal average values over several tens to hundreds of fields are created for the preceding and succeeding regions.

The time average value of the area before and after this created reference waveform is
The tap gain is obtained through the reference domain Fourier transform circuit 15, the detection domain Fourier transform circuit 6, the division circuit 17, the band limit circuit 18, and the inverse Fourier transform circuit 19, and the tap gain is transmitted through the tap gain holding circuit 20 into the 11+1J ghost generation unit 2. to each tap of the transversal filter. Note that the reference area is an area where a reference waveform appears, and the detection area is an area behind the reference waveform where a ghost of this reference waveform appears.

Now, the reference waveform amplitude detection section 41 in the level adjustment section 4 is as follows.
The amplitude of the reference waveform is detected based on the time average value of the regions before and after the reference waveform output from the waveform holding section 13 in the ghost detection section 1 and the timing signal from the timing generation circuit 14. The dividing unit 43 includes the reference waveform amplitude standard value holding unit 42
The standard value held in is divided by the amplitude of the reference waveform detected by the detection unit 41, and the division result is supplied to the multiplier 44 as a multiplier. The amplitude of the digitally received television signal supplied from the input terminal IN to the multiplication section 44 is multiplied by the multiplier supplied from the division section 43, and then supplied to one input terminal of the synthesis section 3, and then sent to the pseudo-image ghost generation section. 2 to the other input terminal.

The output of the combining section 3 is supplied to the output terminal OUT as a received television signal from which ghosts have been removed.

The explanation will be supplemented below with reference to the waveform diagram in FIG.

The topmost waveform (A) is a waveform that shows the received television signal before the ghost occurs, including the vertical synchronization signal and its surroundings. The falling portion α0 of this vertical synchronization signal is used as a reference waveform for ghost detection.

The waveform (B) in FIG. 4 is the waveform of the received television signal after the ghost has occurred. According to this waveform (B), the signal component is delayed by time τ and the level is attenuated to about 173,
Also, the occurrence of a positive ghost that changes in the same direction as this is illustrated. Reference waveform amplitude detection section 41 of level adjustment section 4
Then, the amplitude A(α,) of the reference waveform α in the waveform (B) is detected.

On the other hand, in the amplitude standard value holding section 42 in the level adjustment section 4,
Reference waveform α in waveform (A). The amplitude A(α.) of is maintained. Therefore, from the division unit 43, A(α.)/A(
α,) is output. As a result, the received television signal supplied from the input terminal IN to the multiplier 44 is now A
The signal is multiplied by (α·)/A(α,) and supplied to the synthesis unit 3 as a waveform as shown in FIG. 2(C). The amplitude A(α,) of the reference waveform α8 included in this waveform (C) is A(αt) −A(αI)X A(α.)XA(αI)−A(α.

) ・　・　・　・(1) So, the reference waveform α is. is equal to the amplitude of

In the ghost detection unit 1, the above delay time (τ in this example)
, the occurrence of a ghost based on the level attenuation amount (approximately 1/3 in this example) and the forward/reverse direction of change (positive in this example) is detected from a comparison between the reference waveform α and its ghost β, The tap gain of the transversal filter in the pseudo-ghost main generator 2 is generated. Pseudo ghost generator 2
Then, a pseudo ghost shown in waveform CD) is generated from this tap gain and the ghost-removed received signal (E) on the output terminal OUT. This pseudo-ghost waveform (D) is
The waveform (E) is delayed by τ and attenuated by approximately 1/3,
The ghost is generated by being changed in a direction opposite to the direction of change of the detected ghost.

That is, if we focus on the reference waveform α in waveform 1), it is delayed by time τ, attenuated by A(βl) β, which has the same amplitude and the opposite direction of change, is generated in the pseudo ghost waveform (C).

That is, A(β,) = A(α3)XA(β, ) XA(α1)=A(α
5) XA(βz) XA(αt)=A(βz>
x CA (αz) XA (α2)] (2).

Here, as is clear from the comparison between waveforms (C) and (E), regardless of whether the relationship A(β3)=A(β2) holds or not, A(α3)=A(α2) ... The relationship (3) holds true.

If we substitute equation (3) into equation (2), we get A (β,) A (β3) ・ ・ ・ (
The relationship 4) is obtained.

In the synthesis unit 3, a waveform (E) from which ghosts have been removed is generated by applying electricity to the waveform (C) and the waveform (D). (1)
From formula and formula (3), we get A(α5)-A(α.) (5), and the amplitude of the television signal output from this ghost removal device is a constant value regardless of the presence or absence of ghost occurrence. becomes.

The configuration in which the reference waveform amplitude detection section 41 of the level adjustment section 4 detects the amplitude of the reference waveform from the output of the waveform holding section 13 in the ghost detection section 1 has been described above.

However, it is also possible to adopt a configuration in which the amplitude of the reference waveform is detected based on the DC component output from the reference area Fourier transform unit 15 in the ghost detection unit 1.

Further, a configuration has been illustrated in which the generation of tap gain by the ghost detection unit 1 is performed through Fourier transform of the reference area and the detection area. However, the tap gain generation method by the ghost detection unit l may be performed based on other appropriate methods such as time-axis difference processing instead of Fourier transformation.

Further, a configuration is illustrated in which a digital received television signal is supplied to the input terminal IN and is output as a ghosted digital television broadcast signal. However, analog input/output may be achieved by adding an A/D conversion circuit immediately after the input terminal and a D/A conversion circuit immediately before the output terminal.

(Effects of the Invention) As explained in detail above, the ghost removal device of the present invention detects the amplitude of the reference waveform in the received television broadcast signal appearing at the input terminal, and detects the amplitude of the reference waveform held in advance. Since it is equipped with an amplitude adjustment section that adjusts the amplitude of the received television signal so that it is equal to the standard value, automatic amplitude adjustment can be achieved with a simple configuration, and expensive analog AGC amplifiers can be installed in the subsequent stage. This has the advantage that there is no need to install it.

In other words, no matter what kind of gain generation section is used after the ghost detection section, the addition section 1 in FIG.
2, the waveform holding section 13, and the timing generation section 14. According to the present invention, this common reference waveform extraction system is the standard for level adjustment. This can be used to detect the amplitude of a waveform, and the configuration of the level adjustment section is simplified accordingly.

In addition, since a considerable portion of the parts that make up the ghost detection section and the level adjustment section can be configured as part of a program running on a common processor, the cost increase due to the addition of the level adjustment section can be kept to a small amount. I can do it.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a ghost removal device according to an embodiment of the present invention, FIG. 2 is a waveform diagram for explaining the operation of the ghost removal device of FIG. 1, and FIG. 3 is a conventional ghost removal device. A block diagram showing the configuration of the removal device, FIG.
FIG. 3 is a waveform diagram for explaining the operation of the ghost removal device shown in the figure. IN...Input terminal for received television signal in digital format, 1...Ghost detection section, 2...Pseudo ghost generation section, 3...Synthesizing section, 4...Level adjustment section, 4
DESCRIPTION OF SYMBOLS 1... Reference waveform amplitude detection section, 42... Reference waveform amplitude standard adjustment holding section, 43... Dividing section, 44... Multiplying section, OUT... Output terminal of TVIL signal from which ghosts have been removed .

Claims (1)

[Claims] A ghost detection section that detects a ghost using a vertical synchronization signal in a received television signal appearing at an input terminal as a reference waveform, and generates and outputs a tap gain of a pseudo-ghost generation section; a pseudo-ghost generation unit that generates a pseudo-ghost based on the output tap gain and the ghost-removed television signal supplied to the output terminal; and a reception unit that receives the pseudo-ghost generated by the pseudo-ghost generation unit and whose amplitude has been adjusted. a synthesizing unit that synthesizes a television signal and supplies the synthesized signal to the output terminal, detects the amplitude of a reference waveform in the received television signal appearing at the input terminal, and detects the amplitude standard of the reference waveform held in advance; and an amplitude adjustment unit that adjusts the amplitude of the received television signal so that it is equal to the amplitude of the received television signal and supplies the amplitude-adjusted received television signal to the synthesis unit.