JPH0221778A - Ghost elimination device - Google Patents

Abstract

PURPOSE:To make the operation of the system stable and to eliminate ghost early by setting a tap coefficient of a transversal filter so as to make the correction against ghost large at first and setting a tap coefficient of the transversal filter so as to make the correction against ghost small afterward. CONSTITUTION:A calculation means 5 calculating a difference between an output signal and a reference signal is provided. Then a coefficient setting means 7 is provided, which sets the tap coefficient of the transversal filter 2 so as to make the correction against ghost large at first based on the calculated value of the calculation means and sets the tap coefficient of the transversal filter 2 so as to make the correction against ghost small afterward. Thus, the constant alpha is increased so as to eliminate almost ghost at first, the constant alphais decreased to make the system stable afterward and the coefficient setting circuit sets the tap coefficient. Thus, the operation of the system is made stable to eliminate ghost quickly.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a ghost removal device for removing ghosts from a received signal of a television receiver, for example.

Conventionally, a feedback-type ghost removal device using a transversal filter to remove ghosts from received signals is configured as shown in Figure 2, where (1) is an input terminal into which the received signal is input. , (2) is a plurality of multipliers (2a, 2a,
) ~ (23N), a plurality of delay elements (2bl) ~ (2bN) that respectively delay each tap output by a unit time τ, and a plurality of adders (2c, n ~ (2bN) that respectively add each tap output)
c, l-+), and (
3) is an adder that adds the output signal from the transversal filter (2) to the signal X(iτ) input to the input terminal (1), and (4) is the adder that adds the output signal Y(iτ) from the adder (3).
The output terminal (5) outputs the output signals Y(iτ) and G from the adder (3) which are sent to the output terminal (4).
CR (Ghost Canceler Referen
ce) a subtracter (7) that calculates the difference from the reference signal R (iτ) from the signal generation circuit (6) as an error signal E (iτ);
) are the tap coefficients C, -C of the transversal filter (2) based on the error signal E(iτ) from the subtracter (5).
This is a coefficient setting circuit that sets H. Note that the OCR signal generation circuit (6) stores in advance the OCR signal that is inserted and sent to any line within the vertical blanking period of the received signal, and each time the OCR signal arrives, it is output as a reference signal R(iτ).

Therefore, the input signal X(iτ
) is added to the output signal from the transversal filter (2) in the adder (3), and then output as the output signal Y(iτ) from the output terminal (4). Further, this output signal Y(iτ) is sent to an error signal E(iτ) by a subtracter (5).
τ) [i.e., E(tτ) − Y(iτ) − R(iτ))
The coefficient setting circuit (7) sets each tap coefficient C6 to CN of the transversal filter (2) from the error signal E(iτ), and each of these tap coefficients 01 to CM is used to calculate the transversal filter (2). Versal filter (2)
The output signal Y(i
τ). Therefore, in the transversal filter (2), the multipliers (2a l) to (2aH
) are sequentially added by each adder (2c, ) to (2CM-1) (for example, the output of the previous adder (2b, l-+) delayed by unit time τ by the delay element (2bN-+) Adder (2cH-z) output and output of multiplier (2as-*)
(addition is performed in the same way as the signal sent to the next tap), and the output signal is outputted to the adder (3) as a ghost cancellation signal.

Here, for example, a signal X(iτ
) are the main signal (S+) of < (sinX)/X pulse and its ghost (S8) as shown in FIG.
), a <(sinX)/X pulse is output as shown in FIG. 3(b), and the error signal E(iτ) is as shown in FIG. Then, Z F (Zero
When using the Force) method, the coefficient Ck(j) is set at the jth tap of the first tap of the transversal filter (2) (i.e., when the reference signal is extracted the jth time).
is Ck (j) −Ck (j−1)−α(Y(kτ
)-R(kτ))=CkC3-1)-αE(kτ)
・-(1) (However, Ck (0) = 0. α is a constant). Here, the constant α in equation (1)
If you increase the value of , ghosts will be removed fewer times and
In other words, this can be done in a short time, but this results in the problem that oscillation is likely to occur.

−゛ (Amount taken by) Therefore, in conventional feedback type ghost removal devices, the constant α is made small in order to stabilize the operation of the system, and as a result, for example, as shown in Fig. 4(a), In the case of the input signal X(iτ), the output signal of the transversal filter (2) based on the tap coefficient set for the first time by the coefficient setting circuit (7) is as shown in Fig. 4(b).
(In other words, the amount of correction for the ghost is small, and the output signal Y(iτ) is as shown in Figure 4(C). It took time.

The present invention has been made in view of the above-mentioned points, and an object of the present invention is to provide a feedback-type ghost removal device in which system operation is stable and ghosts can be removed quickly.

In order to achieve the above object, the present invention provides a ghost removal device that uses a transversal filter to remove the ghost of an input signal in a feedback type and then outputs the ghost,
A calculation means for calculating the difference between the output signal and the reference signal, and a tap coefficient of the transversal filter is initially set so as to increase the amount of correction for ghosts based on the value calculated by the calculation means, and after that, the tap coefficients for the transversal filter are set to A coefficient setting means is provided for setting tap coefficients of the transversal filter so that the amount of correction is small.

According to this configuration, the coefficient setting circuit sets the tap coefficient by initially increasing the constant α so that most of the ghosts disappear, and thereafter decreasing the constant α to keep the system stable.

Back” L spot An embodiment of the present invention will be described below with reference to the drawings.

In describing this embodiment, it is assumed that the same ghost removal device and the same coefficient calculation method as the conventional example shown in FIG. 2 are used.

That is, the input signal X(rτ) input to the input terminal (1)
As shown in Fig. 1, the main signal of <(sinX)/X pulse (
31) and its ghost (So), and the reference signal R(iτ) from the GCR reference signal generation circuit (6) is (S
inX)/X pulse (where X=2πfct, fc is the cutoff frequency), according to the ZF method, the tap coefficient Ck( As mentioned above, Ck(j)=Ck(j-1)-α(Y(kτ)-R(k
τ))・(2) Therefore, if the value of the constant α is set to be large, that is, it is possible to obtain a tap coefficient of the transversal filter (2) that completely removes ghosts in one operation. For example, fc=4.2MH2,r
= 1/4 fsc 70 msec, then α 3 Σ R(iτ) i−-ω is obtained from equation (3).

Therefore, the constant α is set to the value of (4)2 at the first time (that is, when the reference signal is extracted for the first time), and the coefficient setting circuit (
When the tap coefficients of the transversal filter (2) are set in step 7), the output signal of the transversal filter (2) with the first set tap coefficients becomes as shown in Fig. 1, etc. (i.e., ghost (the amount of correction for
As shown in C), the image is output with ghosts completely removed. Then, from the second time onwards, in order to stabilize the system, the value of the constant α is reduced, for example α
By setting the tap coefficient of the transversal filter (2) to 0.05 and resetting the tap coefficient of the transversal filter (2) using the coefficient setting circuit (7), the amount of correction for the ghost becomes small and there is no possibility of oscillation occurring.

In this example, the case where the ZF method was used as the coefficient calculation method was described, but MSE (Mean 5qua
Other methods such as the reError) method may also be used.

As described above, according to the present invention, in a feedback type ghost removal device, the operation of the system is stable and ghosts can be removed quickly.

[Brief explanation of the drawing]

FIG. 1 is a signal waveform diagram according to the present invention, FIG. 2 is a block diagram showing a conventional ghost removal device suitable for implementing the present invention, and FIGS. 3 and 4 are signal waveform diagrams thereof. (1) - one input terminal, (2) - transversal filter. (6) ---OCR signal generation circuit. (7)-Coefficient setting circuit.

Claims (1)

[Claims] (1) A ghost removal device that removes the ghost of an input signal using a transversal filter in a feedback type and then outputs the result, comprising a calculation means for calculating the difference between the output signal and a reference signal, and a calculation means for calculating the difference between the output signal and a reference signal; coefficient setting means for initially setting tap coefficients of the transversal filter so that the amount of correction for ghosts is large based on the calculated value, and thereafter setting tap coefficients of the transversal filter so that the amount of correction for ghosts is small; A ghost removal device characterized by being equipped with.