JPS61242174A - Waveform equalizer - Google Patents

Abstract

PURPOSE:To shorten a waiting time for new channel selection by storing a final value of various weighing coefficients of a transversal filter to be used for waveform equalization, and also carrying out an optimum operation out of stored, weighing coefficient state at the next channel selector. CONSTITUTION:As regards a configuration of the transversal filters used herewith, D1-D7 comprise delay devices having constant delay times and M1-M6 comprise outputs of the delay devices D1-D7 which are multiplied by coefficients K1-K6 weighted in advance through memory means such as non- volatile memories. Video signals including reflected waves which are applied by a terminal G are outputted after eliminating the reflected waves out of a terminal H. Data reduced once by a ghost, that are subtraction and addition coefficients and the like, causes a receiver to store them by using non-volatile memories and so on. After then, on the occasion of new channel selection new stations at the next time, a difference between adjustment coefficients stored by the above steps and those required presently shall be adjusted.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a waveform equalizer for eliminating cost reception interference in a receiver for teletext broadcasting, television broadcasting, etc.

(Prior Art) In general, radio waves in broadcast frequency bands such as teletext or television broadcasting are reflected from the ground, buildings, or water surfaces such as lakes and oceans due to their propagation characteristics, and the reflected waves are received and boosted. This results in an undesirable received image that appears on the right side later than the original received image. This ghost significantly impairs the quality of the image received, and when the intensity of the reflected wave is strong, it becomes difficult to distinguish between the received image and the cost, making it difficult to watch, and in the case of teletext broadcasting, typographical errors may be displayed on the screen. .

Conventionally, as a method for relieving such reception,
In the video signal after demodulating the received radio waves, first (
There is a method of adding and subtracting signals that provide delay and attenuation corresponding to the delay time and intensity of reflected waves. However, even with this method, grandchild ghosts will occur, so a method similar to the above method will be used to remove them. Furthermore, there is not always only one reflected wave, but rather multiple reflected waves are usually formed in synergy. Therefore, the conventional method for removing reflected waves described above is extremely complicated to operate.

In other words, in order to optimize the weighting of the delay selection taps by using a transversal filter, the calculations in the feedback loop are performed on the reception selected band (channel).
It is necessary to readjust the channel every time the channel is changed. For example, when receiving television, a waiting time of several seconds to several seconds is required each time the channel is changed.

Figure 2 is a diagram explaining the principle of ghost removal, and shows an example of erroneous reception due to ghosts in teletext broadcasting.
) is a normal text multiplex signal, (b) is a reflected wave of this text multiplex signal reflected by buildings such as pills, mountains, etc., a so-called ghost signal, and there is a delay and attenuation compared to text multiplex signal (a). . (c) is a radio wave that actually arrives at the receiver, and the reflected waves of (a) and (b) above are superimposed. (
d) is a waveform of another character multiplex signal different from the above;
This clearly approximates the waveform of K(c), and it can therefore be seen that when there is a reflected wave, errors occur in the received characters. To eliminate this problem, it is necessary to know the delay time and reception strength of the reflected wave, and to do so, it is usually necessary to detect the waveform disturbance in the first part of the vertical synchronization signal of the received signal. There is.

Figure 3 is a model diagram of the reflected waveform to show the detection of the above delay time and reception strength. (,) is a normal vertical synchronization signal, 0.5H before and after the first part (H: horizontal synchronization) There is an equalization/matrix e. (b) is the waveform of a normal vertical synchronization signal, and (c) is the waveform on which a reflected wave is superimposed.The reflected wave has a delay time τ1. Indicates two waves of τ2, and detects their time and their respective amplitude ratios B/A and C/A (where A is the strength of the vertical synchronization signal, and B and C are the strengths of the first and second reflected waves, respectively). Then, the detection result is subjected to addition/subtraction processing that provides delay and attenuation to cancel out the reflected waves that become ghosts and obtain a normal image.

(Problem to be Solved by the Invention) In such a conventional 70-stroke removal method, each time the channel is switched as described above or the power is turned on, it takes from a few seconds to more than 10 seconds to obtain a normal image. In addition to this inconvenience, there is a problem of mental irritation while waiting, or the inability to receive information normally during that time.

In order to solve these problems, the present invention shortens the time required for channel switching or normal reception after power is turned on.

(Means for solving the problem) In a waveform equalizer used for a television or teletext receiver, store the final values of various weighting coefficients of the waveform equalization transversal filter. Therefore, at the time of the next channel selection, optimization calculations are performed from the above-mentioned stored various weighting coefficient states, thereby shortening the waiting time at the time of a new channel selection.

(Function) With the above-described configuration, the present invention not only provides a clear image, but also substantially eliminates the waiting time required each time a channel is changed. Apart from this, errors in receiving information during teletext broadcasting and the like will no longer occur.

(Example) Generally, the occurrence of ghosts is determined by reflected waves generated depending on the location conditions of the image receiving position and weather conditions. The present invention has been made by focusing on the fact that location conditions account for the majority of these conditions, and that they are fixed and do not change, and will be explained in detail below using examples.

FIG. 1 shows an example of the configuration of a transversal filter used for carrying out the present invention, in which C, D to D7 are delay devices having a fixed time delay, and M to M6 are the outputs of the delay devices D1 to D7. In advance, the memory means, e.g.
The non-volatile memory is multiplied by a weighted coefficient KK or 6. Σ is an adding device and 6. A video signal including reflected waves applied from terminals D and G is output from terminal H with the reflected waves removed.

First, referring to FIG. 3, the reflected wave has a delay time τ1. τ2, the optimum damping coefficient U/
, C/, and the optimal tap position τ'1. to which it should be applied.
Find τ′2. After this, the coefficient K i (i =
1 to 6) are set to the above-mentioned damping coefficients n/ and c/, respectively.

In general, these attenuation coefficients n/ and c/ are signals with opposite signs, and they are added (essentially subtracted) by the adder Σ, and the reflected waves are removed and ghosts no longer appear. By adding a new cancellation signal as described above, a so-called grandchild ghost appears, so the above-mentioned adjustment is repeated again.

Furthermore, ghosts cannot be caused by simple reflected waves, both in intensity and delay time, as shown in Figure 3(c), but in reality, many reflected waves are formed in succession without any boundaries in intensity. For this reason, the ghost removal operation cannot be accomplished by simple adjustments as described above, and requires a considerable amount of time and patient repeated adjustments. Conventionally, this adjustment required several seconds to more than 10 seconds.

The present invention aims to accomplish this in a short time.

By storing the ghost (reflected wave) removal data once performed, the subtraction coefficient, addition coefficient, etc. mentioned above in a non-volatile memory, etc., in the receiver, the same selected band, that is, channel, can be selected next time. When selected, the difference between the stored adjustment coefficient and the currently required adjustment coefficient is adjusted. The stored adjustment coefficients already cancel the almost fixed reflected waves generated by the receiver position, and also include the reflected waves caused by the weather, so the only thing to be adjusted, or canceled, is the weather. Adjustment time can be greatly shortened by adjusting only for reflected waves caused by conditions. In addition,
The most suitable storage medium is a semiconductor non-volatile memory that does not disappear even when the power is turned off, but it is also possible to use a semiconductor memory such as a CMO8) transistor that can retain memory for a long time with little power consumption.

(Effects of the Invention) As is clear from the above description of the present invention, the waveform equalizer, that is, the cost removal device according to the present invention requires the same adjustment time as the conventional one only when the device is used for the first time. However, from the second time onwards, the adjustment time and waiting time are significantly reduced, so that the practicality of the set can be greatly improved by implementing it in a receiving device or receiver for teletext broadcasting or television.

[Brief explanation of the drawing]

FIG. 1 is a circuit configuration diagram of an embodiment of the present invention, FIG. 2 is a waveform diagram showing standard cost generation, and FIG. 3 is a model diagram of cost (reflected wave). DI to D7...delay device, Ml to M6...
・Multiplication device, Σ... Addition device, K1 to 6...
(Weighted) coefficient, e...equalization, lumen, G...
- (Video) input terminal, H...output terminal. Figure 2

Claims (1)

[Claims] In a waveform equalizer for ghost removal used in combination with a television or teletext receiver, by storing the final values of the various weighting coefficients of the waveform equalization transversal filter, the next selection can be made. A waveform equalizer characterized in that, during local operation, an optimum waveform equalization calculation is performed from the stored various weighting coefficient states.