JPS6310634B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic ghost removal device for a television receiver for automatically removing ghosts generated due to multiplexing of signal propagation paths, reflections, etc.

Ghosts in television receivers occur when there are multiple propagation paths for television radio waves, or when there are reflections from an antenna feeder, etc., and the time lag occurs due to differences in propagation times. This occurs because the same signals are multiplexed and received.

It is well known that when a ghost occurs in this way, the television image is projected as a double or triple horizontally shifted image, greatly reducing the quality of the image. Various types of removal devices have been proposed.

Conventionally, in order to automatically remove this ghost, it is known to use a squared sine wave pulse as a reference signal for automatic removal, or to use an equalization pulse portion within the vertical retrace period. .

By the way, if you follow the former method, square sine wave pulses are hardly used in actual television broadcasting, and the latter method can only deal with ghosts with a delay time of up to 27 μsec. Since the ghost removal correction operation is performed only once per field, the convergence speed of the ghost removal operation is slow.

This invention was made to improve the above-mentioned drawbacks, and by utilizing a plurality of horizontal synchronizing signals within the vertical retrace period existing in a television signal as a reference signal for ghost removal, the ghost removal time is reduced. It is an object of the present invention to provide an automatic ghost removal device that can widen the range and increase the convergence speed of ghost removal operations.

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, 1 is a video detection circuit, and 2 is a compensation signal generation circuit that generates a compensation signal for ghost removal. This is a so-called transversal filter type circuit, which is composed of a unit coefficient circuit and a unit delay circuit that delays the compensation signal generated by modifying the coefficient value of each coefficient circuit to match the corresponding video (luminance) signal. It is a circuit. In other words, this compensation signal generation circuit 2 is a circuit that generates a compensation signal that removes or erases the ghost component in the video detection signal on the output side of the video detection circuit 1.

3 is an adder circuit that adds the output signals from both circuits 1 and 2, and 4 is a scanning line extraction circuit that uses the horizontal synchronization signal included in the addition output signal of adder circuit 3 to add the output signals from both circuits 1 and 2. This circuit generates a gate pulse that operates the sample pulse generation circuit 5 only during a plurality of predetermined scanning line periods. Sample pulse generation circuit 5 has horizontal scanning frequency fh = 15.75MHz
Generates a sample pulse with a frequency that is an integer multiple of .

6 is a sampling circuit, and sample pulse generation circuit 5
The error signal of the output signal of the adder circuit 3, that is, the ghost component of the horizontal synchronizing signal within the vertical retrace period is sampled by the output of the adding circuit 3. 7 is a compensation signal generation control circuit which uses the error signal from the sampling circuit 6 to correct the coefficient value of the unit coefficient circuit in the compensation signal generation circuit 2 for each sample series, and adjusts the coefficient value of the unit coefficient circuit in the compensation signal generation circuit 2 into the output signal of the video detection circuit 1. It performs control operations to eliminate ghost components contained in the image.

Next, the operation of the above configuration will be explained. As shown in FIG. 2a, in several H periods after the vertical synchronizing signal 8 and the equivalent pulse 9 in the vertical retrace period, the horizontal synchronizing signal 10 and the color burst inserted into the back pouch of each horizontal synchronizing signal 10 are generated. signal,
In other words, the color synchronization signal 11 is present.

Fig. 2b shows an enlarged view of the 1H period, including the horizontal synchronizing signal 10, the burst signal 11, and the ghost signals 10a and 11a of these signals 10 and 11.
It is a depiction of In response to the horizontal synchronizing signal 9, the scanning line extracting circuit 4 generates a gate pulse for several H periods after the equivalent pulse 9, and operates the sample pulse generating circuit 5 only during that period. That is, as shown in FIG. 2c, a sample pulse 12 is generated between the trailing edge of the horizontal synchronizing signal 10 in FIG. 2b and the leading edge of the next horizontal synchronizing signal 10.

Therefore, as shown in FIG. 2d, the output signal sampled by the sampling circuit 6 includes the direct wave signal burst signal 11 shown in FIG. 2b, the horizontal synchronization ghost signal 10a, and Sampled signals 11 corresponding to the burst ghost signals 11a, respectively.
b, 10b and 11c are obtained.

First, for convenience of explanation, the removal of the horizontal synchronization ghost signal 10a in FIG. 2b will be described.

Assuming that the sampled signal ^10b in FIG _. , in the compensation signal generation circuit 2, the coefficient value at the n-th scanning line of the unit coefficient circuit corresponding to the sample point (m) is expressed as C ⁿ _n
Then, the coefficient value C ⁿ⁺¹ _n of the unit coefficient circuit corresponding to the m-th sample point in the (n+1)-th horizontal scanning line shown in FIG. 2e is as shown in the following equation. That is, C ⁿ⁺¹ _n =C ⁿ _n +A·X ⁿ _n (1) where m is an integer (1, 2, . . .).

Now, the sampled signal 10b as shown in FIG.
If does not occur, then X ⁿ _n = 0, so (1)
The equation becomes C ⁿ⁺¹ _n = C ⁿ _n , and the coefficient value correction operation of the unit coefficient circuit is not performed, and the compensation signal generation circuit 2
There is no compensation signal generated.

However, the horizontal synchronization ghost signal 1 in Fig. 2b
When a sampled signal 10b based on 0a is generated,
In equation (1), X ⁿ _n ≠0, and the coefficient value of the unit coefficient circuit at the m-th sample point is corrected. At this time, in the case of a simple signal such as the horizontal synchronization ghost signal 10b, if the proportionality constant A is appropriately selected, X ⁿ _n = 0 in equation (1), that is,
It is possible to converge to a coefficient value such that C ⁿ⁺¹ _n =C ⁿ _n . A state in which X ⁿ _n =0 for all sampling points (m) is a state in which the ghost signal component is zero, that is, a state in which the ghost component in the video signal has been removed.

A scanning line in which the coefficient value C _n of the compensation signal generation circuit 2 based on the sampling circuit 6 is not corrected;
In other words, since no correction operation is performed on the remaining scanning lines that make up the field of the television signal, the coefficient values of each unit coefficient circuit are in the state where the ghost has been removed, regardless of the video signal included in this part. Fixed. Therefore, ghosts can be removed over the entire field. Since there are at least five scanning lines that include only the horizontal synchronizing signal 10 and the burst signal 11 within the vertical retrace period, the coefficient correction operation described above can be performed at least five times for one field. Therefore, by using the horizontal synchronization signal 10 within the vertical retrace period to detect residual ghosts, the convergence speed can be improved by at least five times compared to, for example, the conventional method of using equalization pulses for ghost detection. There is an advantage.

By the way, in the above coefficient value correction operation, the direct wave burst signal 11 of FIG. 2b, the sampled signal 11b based on the burst ghost signal 11a,
11c is generated as shown in FIG. 2d, and these signals 11b and 11c change the coefficient values of the respective coefficient circuits described above, and as a result, the video signal is disturbed. However, this disturbance does not substantially change the respective coefficient values, as described below.

To explain this with reference to FIG. 3, FIG. 3a is a spectral distribution diagram of the frequency band of a color television signal. In this figure, 13 is the luminance signal spectrum, and the horizontal scanning frequency fh = 15.75MH
It is distributed as a high frequency. 14 is a color burst signal spectrum, and luminance signal spectrum 13
The chrominance subcarrier frequency interpolated by 1/2 line offset is distributed at intervals fh around the frequency fc = 3.58MHz, and 8 to 12 Hz of this chrominance subcarrier is inserted, and the chrominance subcarrier Frequency fc=3.58MHz
and has a phase difference of 180°.

Here, the luminance signals of adjacent horizontal scanning lines are almost the same due to their correlation, and their phases are considered to be in the same direction, so for example, the spectrum of the luminance signal of the n-th horizontal scanning line is The relationship with the spectrum of the luminance signal of the th horizontal scanning line is as shown by the solid lines in FIGS. 3b and 3c. However, the frequency of the color burst signal is selected to be an odd multiple of 1/2 of the horizontal scanning frequency fh, so even though the burst signals of adjacent horizontal scanning lines have the same magnitude, their phases differ from each other. Since it is inverted, the spectral relationship is as shown by the dotted lines in FIG. 3b and c. Furthermore, the sample pulse 12 from the sample pulse generation circuit 4 is configured to have a frequency that is an integral multiple of the horizontal scanning frequency fh and to be in phase with the horizontal synchronizing signal 10.

Therefore, the sampled signals 11b and 11c of the burst signals 11 and 11a obtained from the nth scanning line and the (n+1)th scanning line have the same magnitude and phase, as shown in FIG. 2d and e. is inverted, so in the correction operation performed according to equation (1), the amount of correction of the coefficient by the burst signals 11b and 11c is canceled out for the nth scanning line and the (n+1)th scanning line. That will happen. Therefore, the sampling signals 11b, 11c based on the burst signals 11, 11a can be prevented from affecting the coefficient value correction operation of the unit coefficient circuit in the compensation signal generating circuit 2.

In addition, in the final operation in one field, the coefficient circuit has a coefficient value selected by the burst signal, and the video signal of the next field is affected by it, but the number of corrections performed in one field is an odd number. By doing so, when viewed as a frame, the influence of the modified coefficient values of the coefficient circuit on the video signal in each field is canceled out, so there is no visual problem.

In the above embodiment, the sampled signals 11b and 11c of the burst signal shown in FIG. 2d and the sampled signals 11b and 11c shown in FIG.
The coefficient value of the coefficient circuit in the compensation signal generation circuit 2 may be increased or decreased by a certain amount depending on the positive or negative sign of the sampled signals 11b, 11c shown in FIG. Of course, the above coefficient values may be corrected using the average value or its sign.

Further, in the above embodiment, the video detection circuit 1
Although we have described the so-called feed-forward configuration in which the adder 3 adds the output signal of the output signal and the compensation signal obtained by applying this output signal to the compensation signal generation circuit 2, this part is also referred to as the so-called feedback configuration. can do.

As described in detail above, the present invention eliminates the ghost signal component of the television signal in the horizontal blanking period during a plurality of scanning line periods including only the horizontal synchronizing signal and the color burst signal within the vertical blanking period of the standard television signal. Sampling is performed using a sample pulse signal having a frequency that is an integral multiple of the scanning frequency, and the goose signal component generated by the sampling circuit is removed in accordance with the sampling signal.
It is possible to expand the time span of ghost removal, and it is also possible to perform correction operations for ghost removal multiple times for one field.
It is possible to significantly improve the convergence speed of the ghost removal operation, and even when the signal-to-noise ratio (S/N) of the television reception signal is poor and the video detection output contains random noise, one field Since the number of corrections per hit can be increased, there is also the advantage that each coefficient value of the compensation signal generation circuit after convergence can be less affected by the random noise.

[Brief explanation of the drawing]

FIG. 1 is a block circuit diagram of the automatic ghost removal device according to the present invention, FIGS. 2 a to e are waveform diagrams of each part thereof, FIG. 3 a is a spectral distribution diagram of a color television signal, and FIGS. 3 b and c are FIG. 3 is a spectral distribution diagram of adjacent horizontal scanning lines. DESCRIPTION OF SYMBOLS 1... Video detection circuit, 2... Compensation signal generation circuit, 3... Addition circuit, 5... Sample pulse generation circuit, 4... Horizontal scanning line extraction circuit, 6... Sampling circuit, 7... Control circuit .

Claims (1)

[Claims] 1 Automatic ghost removal comprising a video detection circuit, a compensation signal generation circuit including a plurality of unit delay circuits and unit coefficient circuits corresponding to each of these delay circuits, and an addition circuit that adds the output signals of both of these circuits. The apparatus includes: a horizontal scanning line sampling circuit that generates a gate pulse signal in response to a plurality of scanning lines containing only a horizontal synchronization signal and a color burst signal within a vertical retrace period; a sample pulse generation circuit that samples the addition output signal of the circuit and whose sampling signal has a frequency that is an integral multiple of the horizontal scanning frequency; a sampling circuit that uses the sampling signal to convert the addition output signal into a sampling signal; An automatic ghost removal device comprising: a control circuit that applies a sampling signal to a unit coefficient circuit of the compensation signal generation circuit for each sample point to perform a coefficient correction operation.