JPH07203253A - Ghost elimination device for television receiver - Google Patents

Abstract

PURPOSE:To improve picture quality considerably by implementing equalization continuously when no GCR signal is received to eliminate ghost in the television receiver mounted on a mobile object. CONSTITUTION:A received television signal for a prescribed time is stored in a TV signal memory 1, at least two GCR signals in existence before and after an equalization time period are used and a GCR signal at plural discrete times for the equalization period is obtained at a tap coefficient estimate device 13 through interpolation arithmetic operation. Then the characteristic of a transversal equalizer 2 at each discrete time is decided based on each interpolation GCR signal and a reference GCR signal. Then the television signal is read from a storage means and given to the transversal equalizer 2, and a characteristic of the transversal equalizer 2 is set to the characteristic at each discrete time corresponding to the time as the lapse of the time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ghost eliminating device for improving image quality in a television receiver mounted on a mobile body.

[0002]

2. Description of the Related Art In a television receiver, when a direct wave coming directly from a transmitting station and an indirect wave reflected by a building or a mountain and having a propagation path difference from the direct wave are received together, A ghost image appears on the screen of the machine at a position corresponding to the difference in the propagation path length, and the screen becomes very difficult to see. Therefore, in order to prevent a ghost image from being generated on the screen of the television receiver even if an indirect wave is received by the television receiver, a receiver equipped with a ghost elimination device that equalizes the received television signal is practically used. Has been converted.

This device uses a known GCR signal as shown in FIG. 1 which is already inserted in a television signal of a television broadcast wave to perform equalization. G
The CR signal has a step-like waveform and is inserted once every 1/30 seconds on average in the vertical blanking period of the television signal of the television broadcast wave. At the time of equalization, the differential waveform shown in (a) of FIG. 2 obtained by calculating the difference after sampling this television signal is used. Hereinafter, the GCR signal is defined to mean the waveform after differentiation.

The principle of the equalization operation using this GCR signal will be described below. When a direct wave and an indirect wave are received by the television receiver, G as shown in (a) of FIG.
The CR signal is a direct wave GCR as shown in Fig. 2 (b).
It has two peaks, a signal and an indirect wave GCR signal.
A television signal including an indirect wave is input to a transversal type equalizer. Then, from the output of the equalizer, GC
The R signal is detected, and the tap coefficient of the transversal equalizer is sequentially corrected so that the difference (equalization error) between the R signal and the GCR signal stored in the apparatus in advance becomes small.

When the equalization error becomes small, the characteristics of the transversal equalizer are such that the indirect wave is eventually removed, and the equalization operation is completed. However, the equalization operation described above can be easily executed in a case where the propagation path of the radio wave from the transmission station to the image receiver hardly changes, such as the reception state in a general home. When a mobile body such as an automobile receives a television broadcast wave, the propagation path of the radio wave changes as the automobile moves. Therefore, the delay time and intensity of the indirect wave fluctuate in a very fast cycle, and equalization is not easy.

A device disclosed in Japanese Patent Laid-Open No. 62-181579 has been devised so that equalization can be performed even when the delay time and intensity of the indirect wave fluctuate. FIG. 3 shows the configuration of this device. This device is
It enables the equalization operation to be executed at high speed every time an R signal is received, so that it can respond to fluctuations in the reception status compared to the conventional home-use television equalizers. is there. The calculation of the tap coefficient of the complicated transversal equalizer is simplified in order to perform the equalization operation at high speed, and the calculation is realized by the difference calculator and the memory. It is described in the above-mentioned document that this device can cope with fluctuations having a cycle of about 5 Hz.

However, in urban areas where buildings are densely packed, the delay time of indirect waves and the fluctuation range of the intensity become very large.
In such a case, no matter how fast the equalization operation is performed, the GCR signal, which is the basis of the step coefficient calculation, can be received only intermittently. Therefore, in principle, a gentle fluctuation having a cycle of about 1 Hz or less is generated. Can only respond. Here, the fluctuation cycle of the received signal being 1 Hz means that substantially the same change is repeated every second on average. However, the amplitude and phase of the signal are constantly changing during the one second, and it can be considered that these values are almost constant for about several tens of milliseconds at most. If the values of the amplitude and the phase of the signal can be regarded as substantially constant, it can be considered that the equalization effect is maintained during that period.

[0008]

Considering the normal traveling speed of an automobile, the fluctuation cycle of the received signal reaches several tens Hz. However, the in-vehicle television reception has a problem that such a daily variation cannot be coped with by the conventional equalization operation executed every time the GCR signal is received. Therefore, equalization of a vehicle-mounted television receiver is impossible only by using the conventional method, and development of a new method is indispensable.

The present invention has been made to solve the above problems, and an object of the present invention is to continuously equalize a television receiver that can be mounted on a mobile unit even when a GCR signal is not received. By doing so, it is possible to remove the ghost and significantly improve the image quality.

[0010]

The GCR signal used as a reference signal in the conventional invention is an essential signal for detecting an indirect wave and removing a ghost from a television screen. However, since the GCR signal is a reference signal for removing ghosts in a television receiving environment in a general home, it is sufficient as a reference signal when the received signal fluctuates very quickly like television reception in an automobile. is not. When receiving a television signal in a car, this is more than the interval in which the GCR signal is inserted.
This is because the fluctuation of the received signal may be faster.

Therefore, in the invention of the first aspect, the received television signal is stored for a predetermined time (for example, a signal for at least two GCR signals is included) and equalized. By using at least two GCR signals existing before and after the time interval, GCR signals at a plurality of discrete times in the equalization interval are obtained by interpolation calculation. Then, each interpolated GCR signal and the reference GCR
The characteristics of the transversal equalizer at each discrete time are determined from the signal and the television signal is read from the storage means and input to the transversal equalizer, and the characteristics of the transversal equalizer are changed with time. Accompanied by,
The feature is that the characteristic is set at each discrete time corresponding to the time.

The invention according to the second aspect is such that each received G
The characteristics of the transversal equalizer are determined corresponding to each GCR signal from the CR signal and the reference GCR signal, and the characteristics corresponding to at least two GCR signals existing before and after the time interval for equalization are also used, The characteristics of the equalization section at a plurality of discrete times are obtained by interpolation calculation. Then, the television signal is read from the storage means and input to the transversal equalizer, and the characteristics of the transversal equalizer are set to the interpolation characteristics at each discrete time corresponding to the time with the passage of time. It is characterized by doing so.

[0013]

According to the first aspect of the invention, when the GCR signal interpolating means equalizes the television signal in the target section between a certain GCR signal and the next GCR signal by the transversal equalizer, From at least two GCR signals existing before and after, the waveform of the GCR signal at a plurality of discrete times in the target section is determined by interpolation calculation, and the interpolation GCR signal is calculated. Next, the equalization characteristic determining means determines the interpolated GCR signal and the reference GC at each discrete time.
The equalization characteristic of the transversal equalizer at each time is determined based on the R signal. Then, the characteristic setting means inputs the television signal from the signal storage means to the transversal equalizer in synchronization with the passage of time, and the equalization characteristics of the discrete time corresponding to the time are transversal equalized. Is set in the bowl. As a result, GCR
Even when no signal is received, the equalization characteristic is determined based on the GCR signal determined by the interpolation calculation.
More accurate equalization of the television signal can be performed.

According to the second aspect of the invention, each time the GCR signal is received by the second equalization characteristic determining means, the GCR signal is received.
The equalization characteristic of the transversal equalizer is determined based on the signal and the reference GCR signal. Next, when equalizing characteristic interpolating means equalizes the television signal in the target section between a certain GCR signal and the next GCR signal by the transversal equalizer, at least 2 existing before and after the target section. From the equalization characteristics determined from one GCR signal, the equalization characteristics at a plurality of discrete times in the target section are determined by interpolation calculation, and the interpolation equalization characteristics are calculated. And
The second characteristic setting means inputs the television signal from the signal storage means to the transversal equalizer in synchronization with the passage of time, and the discrete time corresponding to the time determined by the equalization characteristic interpolating means. The interpolation equalization characteristic of is set in the transversal equalizer. As a result, even when the GCR signal is not received, the transversal equalizer of the transversal equalizer is changed with the passage of time based on the interpolation equalization characteristic determined by the interpolation operation from the characteristic determined based on at least two GCR signals. Since the characteristics change, more accurate equalization of the television signal can be performed.

[0015]

As described above, even when the GCR signal is not received, the equalization characteristic of the transversal equalizer can be adaptively changed with respect to the fluctuation of the received signal, and the equalization operation can be continuously performed. It can be carried out. Therefore, even when the fluctuation cycle of the received television signal is shorter than the reception interval of the GCR signal, that is, even when the fluctuation cycle of the received signal is several tens of Hz, the equalization operation is performed according to the fluctuation of the received signal. It becomes possible to significantly improve the image quality of a television in an automobile.

[0016]

Embodiments of the present invention will be described with reference to the drawings. FIG. 4 is a block diagram of a ghost removing device of a vehicle-mounted television receiver according to an embodiment of the present invention.

The received television signal is A / D converted by the A / D converter 1 and temporarily stored in the television signal memory 10 for a predetermined time period. Then, in synchronization with the synchronization signal output from the equalization operation controller 11,
The oldest television signals are read out in order, input to the transversal equalizer 2 and equalized by the equalizer 2 (ghosts are removed), and then the analog signal (original television) is output by the D / A converter 3. (John signal) and output. The tap coefficient of the equalizer 2 is
The tap coefficients stored in the tap coefficient memory 12 are sequentially set. Therefore, the television signal is equalized with the optimum tap coefficient at the time when the television signal exists. The television signal memory 10 is required to hold the signal until the tap coefficient is determined.

On the other hand, the GC used to calculate the tap coefficient
The R signal is extracted from the television signal by the GCR signal extractor 4. It is A / D converted by the A / D converter 5 and input to the tap coefficient estimator 13.

The tap coefficient estimator 13 is constructed as shown in FIG. The tap coefficient estimator 13 continuously estimates the tap coefficients to be set in the transversal equalizer 2 based on the plurality of GCR signals that have been transmitted so far and are extracted by the GCR signal extractor 4 and digitized. And output to the tap coefficient memory 12.

The relationship between the section of interest for which the tap coefficient is estimated and the received GCR signal used for it will be described with reference to FIG. In this figure, G represents a GCR signal and S represents a television signal other than that. Also, the smaller the subscript, the more the past. Here, consider a case where the tap coefficient of the transversal equalizer 2 corresponding to the television signal in the attention section Si is estimated. In this case, one or a plurality of GCR signals (Gi-n ... _, Gi, ..., Gi + m ,: n, m are non-negative integers) before and after the attention section Si are used for tap coefficient estimation. You can However, Gi + m needs to be received at the time of tap coefficient estimation. Therefore, G
In order to estimate the tap coefficient corresponding to the television signal in the attention section Si using the GCR signals up to i + m, at least the television signals in the section from Si-n to Si + m-1 are stored in the television signal memory. Must be accumulated in 10. From this, the larger the value of m, the more
The capacity of the television signal memory 10 is required, and the delay time until the received television signal is equalized and actually displayed on the television screen increases.

The tap coefficient estimation will be specifically described below. Here, a total of two GCs received immediately before and immediately after the television signal in the section of interest for which equalization is performed.
The case of using the R signal (when n = 0 and m = 1) will be described. When estimating the tap coefficient from the received GCR signal,
There are two methods shown below.

1) Method by interpolation of GCR signal (Claim 1) FIG. 2 obtained by difference calculation of received GCR signal
A method of estimating the tap coefficient of the transversal equalizer 2 during a period in which a GCR signal is not received based on the delay profile shown in (a method based on a delay profile) 2) A method by interpolation of equalization characteristics (claim 2) A method of estimating the tap coefficient of the transversal equalizer 2 while the GCR signal is not received, based on the tap coefficient of the transversal equalizer 2 obtained at the time of receiving the GCR signal (method based on the tap coefficient)

1) Method by GCR signal interpolation (Claim 1) (Method based on delay profile) FIG. 5 shows the configuration of the tap coefficient estimator 13 for realizing this method. The received GCR signal is differentiated by the difference calculation by the difference calculator 131 to form a differential waveform as shown in FIG. Hereinafter, the signal of this differential waveform is referred to as a GCR signal. Then, this GCR signal is sequentially input to the series-connected delay device 132. Then, the output of each delay device 132 is input to the delay profile interpolator 133 and added.

The delay unit 132 of FIG. 5 has a plurality of GCR signals (Gi-n, ... _, Gi,) received before and after the target section received in the past.
, Gi + m) (n + m + 1) delay profiles are used to hold the required number in the past in time order. As described above, here, a method of estimating the tap coefficient in the attention section Si of FIG. 7 will be described. In this case, the number of delay devices 132 in FIG.
If Gi + m is the recently received GCR signal, then (n + m)
It becomes an individual.

The delay profile used when the delay profile interpolator 133 calculates the delay profile of the target section Si is a GCR signal (Gi-n, ... _, Gi, ..., G).
i + m) corresponding (n + m + 1) pieces are required. In particular, when processing with two delay profiles, that is, n = 0 and m = 1, the required delay profiles are Pi and Pi + 1, respectively. Pi
Is a numerical sequence ({Pi, 0, Pi, 1, ..., Pi, k}) obtained by sampling the delay profile as shown in FIG. 2 (c) at each predetermined delay time interval (Δτ). It is represented by. From such Pi and Pi + 1, the target section Si
Delay profile at time t, that is, a numerical sequence ({PSi, 0, PSi, 1, ..., PSi,
k}) is, for example, by linear interpolation,

[0026]

## EQU1 ## PSi, j = {(TSi-t) * Pi, j + t * Pi + 1, j} / TSi (1) Here, TSi is the time of the entire attention section Si. Since the delay device 132 in FIG. 5 has a function of delaying the signal by TSi, the signal waveform Pi + 1, j and the signal waveform Pi, j are output from the two adjacent terminals, so that the delay profile interpolation is performed. The output signal of the two terminals is calculated by the equation (1) in synchronism with the passage of time t, and the interpolated GCR signal PSi, j of the target section Si is calculated. Then, the tap coefficient calculator 134 calculates the tap coefficient based on the GCR signal PSi, j, and the value is stored in the tap coefficient memory 12 that functions as a buffer memory.

The tap coefficient calculator 134 calculates the transversal equalizer 2 from the interpolated GCR signal of the equation (1).
The tap coefficient of is determined. As a method for determining the tap coefficient, a collective control method or a sequential correction method can be used. The collective control method is a method of obtaining a transfer function of a transmission line in the frequency domain based on the received GCR signal and collectively determining tap coefficients of the equalization filter so that an inverse characteristic of the transfer function is obtained. . GCR
If the reference signal is r (t) and the impulse response of the transmission line is g (t), the received GCR signal x (t) is

[0028]

[Expression 2] x (t) = r (t) * g (t) (2) Here, * in the formula represents convolution. Fourier transform of equation (2)

[0029]

## EQU3 ## Since X (ω) = R (ω) G (ω) (3), the transfer function G (ω) of the transmission line is

[0030]

## EQU4 ## G (ω) = X (ω) / R (ω) (4) Therefore, in order to equalize the television signal, it is sufficient to use tap coefficients that can realize a transversal equalizer having an inverse characteristic of the transfer function as shown in the following equation.

[0031]

F (ω) = 1 / G (ω) = R (ω) / X (ω) (5)

On the other hand, the iterative correction method is a transversal equalizer that equalizes the received GCR signal with the transversal equalizer 2 (exists inside the tap coefficient calculator 134, and is configured by hardware or software. The tap coefficient is repeatedly corrected so as to reduce the error between the GCR reference signal and the output when the input is made. The method will be described below.

The GCR signal at time k is x _k, the output of _the equalizer is y _{k, the} reference GCR signal is r _k , the number of taps of the equalizer is (N + M + 1), and the tap coefficient is C. _{If i} (i is the tap number), the error e _k is

[0034]

[Equation 6] e _k = y _k −r _k = _{i = −M} Σ ^N C _i · x _k−1 −r _k (6) Taking the sum of squares of the absolute value of e _k in the time interval (−PΔt, QΔt) (Δt: sampling time interval),

[0035]

[Equation 7] ^{_{E = k = -P Σ Q |}} e k | as ² ... Rating Scale (7), to correct the tap coefficients by the steepest gradient descent method. If the value of C _{i for} the nth time is written as C _i ⁽ⁿ⁾ , then (n + 1)
C _i for the second time is

[0036]

[Equation 8] C _i ^{(n + 1)} = C _i ⁽ⁿ⁾ −α · (δE / δC _i ) = C _i ⁽ⁿ⁾ −α · _{k = −P} Σ ^Q x _k−1 · e _k … ( 8)

(Α: convergence coefficient) Such a correction method is called an MSE (Mean Square Error) method. Also, GC
If it is assumed that the R signal is approximated by an impulse signal and all x _k other than x ₀ can be regarded as 0, the equation (8) can be expressed as follows.

[0038]

## EQU9 ## C _i ^{(n + 1)} = C _i ⁽ⁿ⁾ -αe _i (9) This is called the ZF (Zero Forcing) method. Although these are typical tap correction algorithms of the iterative correction method, various modifications and approximations are possible other than this.

2) Method by interpolation of equalization characteristics (method based on tap coefficient) FIG. 6 shows the configuration of the tap coefficient estimator 13 of FIG. 5 by this method. Unlike the method 1), the tap coefficient calculator 134 previously calculates the tap coefficient corresponding to the GCR signal based on the GCR signal by the method described above.

A differential signal of the GCR signal extracted by the difference calculator 131 (hereinafter this differential signal is referred to as a GCR signal) is obtained. That is, when the GCR signal is received, the delay profile of the GCR signal is obtained. Based on the delay profile, the tap coefficient calculator 134
The optimum tap coefficient at the time when the CR signal is received is calculated. There are two methods for calculating the tap coefficient as described above. Each tap coefficient is a series-connected delay device 13
The output signals from the terminals are input to the tap coefficient interpolator 135 after being delayed by the unit time TSi at 2, respectively.

For the calculation of the tap coefficient, the sequential correction method or the batch correction method is used as in the above. The delay device 132 of FIG. 6 receives the GCR signals (Gi-n, ...
Gi, ..., Gi + m) are used to hold a plurality of tap coefficients respectively obtained based on Gi. As described above, the tap coefficient of the attention period Si shown in FIG.
A method of estimating the tap coefficient using the CR signals Gi and Gi + 1 will be described. In this case, the number of delay devices 132 in FIG.
If it is a signal, it becomes one, and the tap coefficients at two times are used as the values at both end points of the interpolation calculation. Ci is a numerical sequence ({CSi, 0, CSi, 1, ..., C
Si, k}) is, for example, by linear interpolation,

[0042]

(10) CSi, j = {(TSi-t) .Ci, j + t.Ci + 1, j} / TSi (10) Here, TSi is the time of the target section Si.

As described above, the tap coefficient interpolator 13
From 5, the tap coefficient CSi, j defined by the equation (10) is output. In this way, the tap coefficient interpolator 135 interpolates the tap coefficient while the GCR signal is not received from the tap coefficient of the transversal equalizer 2 obtained based on the GCR signal obtained intermittently.

In the above embodiment, the equalization operation controller 11 and the tap coefficient estimator 13 are the well-known CPU,
Although it is realized by the software of the computer system using the ROM and the RAM, it may be realized by the individual digital circuits having the block configurations shown in FIGS.

[0045]

Relationship with Claim 1. In claim 1, the signal storage means is composed of a television signal memory 10, and the GCR signal interpolation means is a difference between a GCR signal extractor 4, an A / D converter 5 and a tap coefficient estimator 13. Arithmetic unit 131, delay circuit 132,
The delay profile interpolator 133 is included, the equalization characteristic determining means is comprised of the tap coefficient calculator 134 and the tap coefficient memory 12, and the characteristic setting means is the equalization operation controller 11.
Composed of.

In the second aspect, the signal storage means is composed of the television signal memory 10, and the second equalization characteristic determination means is the difference calculation of the GCR signal extractor 4, the A / D converter 5 and the tap coefficient estimator 13. 131, tap coefficient calculator 13
4 (FIG. 6), the equalization characteristic interpolating means is the delay circuit 132 of the tap coefficient estimator 13 and the tap coefficient interpolator 13.
5 and the tap coefficient memory 12, and the second characteristic setting means is composed of the equalization operation controller 11.

[Brief description of drawings]

FIG. 1 is a waveform diagram of a television signal for one line of a television broadcast wave.

FIG. 2 is a GC obtained from a differential waveform of a television signal.
The waveform diagram of R signal and its sampling signal.

FIG. 3 is a block diagram of a conventional device.

FIG. 4 is a block diagram showing a configuration of an apparatus according to a specific embodiment of the present invention.

FIG. 5 is a block diagram showing a specific configuration of a tap coefficient estimator used in the apparatus of the embodiment.

FIG. 6 is a block diagram showing another specific configuration of the tap coefficient estimator used in the apparatus of the embodiment.

FIG. 7 is an explanatory diagram showing a GCR signal and a video signal included in a television signal.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... A / D converter 2 ... Transversal equalizer 4 ... GCR signal extractor 11 ... Equalization operation controller 13 ... Tap coefficient estimator

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[Procedure amendment]

[Submission date] June 29, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Title of invention

[Correction method] Added

[Correction content]

Title: Ghost receiver for television receiver

Claims (2)

[Claims] 1. Based on a GCR signal included in a television signal in a received wave of television broadcasting,
In a ghost eliminating device of a television receiver which reproduces an original television signal from which ghost has been eliminated by changing the characteristics of a transversal equalizer, a signal for storing the television signal within a predetermined time. Storage means and at least two GCR signals existing before and after the attention section when equalizing the television signal in the attention section between one GCR signal and the next GCR signal by the transversal equalizer From the above, a GCR signal interpolating means for deciding the waveform of the GCR signal at a plurality of discrete times of the attention section by interpolation calculation and computing the interpolated GCR signal, and the interpolated GCR signal and the reference GCR at each discrete time. Equalization characteristic determination for determining the equalization characteristic of the transversal equalizer at each time based on the signal And the television signal from the signal storage means is input to the transversal equalizer in synchronization with the passage of time, and the discrete signal corresponding to the time determined by the equalization characteristic determining means is input. A ghost elimination device having a characteristic setting means for setting the equalization characteristic of time in the transversal equalizer. 2. Based on a GCR signal included in a television signal in a received wave of television broadcasting,
In a ghost eliminating device of a television receiver which reproduces an original television signal from which ghost has been eliminated by changing the characteristics of a transversal equalizer, a signal for storing the television signal within a predetermined time. Storage means, and every time a GCR signal is received, the GCR signal and the reference GC
Second equalization characteristic determining means for determining the equalization characteristic of the transversal equalizer based on the R signal, and the television signal in the attention section between a certain GCR signal and the next GCR signal. When equalizing with a transversal equalizer, from the equalization characteristics determined from at least two GCR signals existing before and after the target section,
Equalization characteristic interpolating means for determining the equalization characteristics at a plurality of discrete times of the attention section by interpolation calculation and calculating the interpolation equalization characteristics; and, in synchronization with the passage of time, from the signal storage means to the television set. A John signal is input to the transversal equalizer, and the interpolation equalization characteristic at the discrete time corresponding to the time determined by the equalization characteristic interpolation means is set in the transversal equalizer. A ghost removing device having two characteristic setting means.