JPH066642A - Waveform equalizer - Google Patents

Abstract

PURPOSE:To prevent a rapid change of a screen by selecting stepwise a correction coefficient for waveform equalization. CONSTITUTION:A control circuit 7 writes a VIT signal in a MUSE signal inputted via a transversal filter(TF) 5 to a memory 8 and the signal is read therefrom and compared with a prescribed reference signal to obtain a difference. Then the difference is set to 1/n and the result is added to the VIT signal and the sum is written in a memory 9, the signal is read to obtain a correction coefficient and it is transferred to a TF 5 to change a tap gain and the TF 5 is used to correct a MUSE input signal and the difference is divided into 2/n and it is added to the VIT signal to revise the memory 9, the signal is read to obtain a correction coefficient and the result is transferred to the TF 5 to change the tap gain and the TF 5 is used to correct and outputs the MUSE input signal, then the correction coefficient is changed in n-stages for waveform equalization.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waveform equalizer for removing transmission distortion generated when transmitting a MUSE signal. Since the MUSE system adopts the sample value transmission system, if the transmission characteristic deviates from the Nyquist characteristic and the transmission signal is distorted, intersymbol interference occurs and ringing occurs on the reproduction screen. Therefore, by incorporating a waveform equalizer in the signal reproduction decoder, the occurrence of ringing is prevented.

[0002]

2. Description of the Related Art In a conventional waveform equalizer, as shown in FIG. 2, a transversal filter 5 for correcting and outputting an input signal of MUSE, an output from the transversal filter 5, and the input signal Is added to the delayed signal to output a waveform-equalized MUSE signal, a circuit for branching the output from the adder circuit 4 and inputting it to the control circuit 7, and a MUSE from the same input. V in the signal
The IT signal is detected and calculated by comparing it with a predetermined reference signal stored in the memory 10 (ROM) in advance to obtain a correction coefficient, which is written into the memory 20 (RAM), read out and transferred to the transversal filter 5. With the control circuit 7 that changes the tap gain of the transversal filter 5, the waveform distortion component included in the input signal is removed, waveform equalization is performed, and the addition circuit 4 outputs the result.

[0003]

Therefore, when there is only one adjustment mode for waveform equalization and the optimum value of the correction coefficient for waveform equalization is obtained, the correction coefficient is switched to the optimum value at a time. There was a problem that the screen changed abruptly because the change in was too large. An object of the present invention is to prevent abrupt changes in the screen by switching the correction coefficient for waveform equalization stepwise.

[0004]

FIG. 1 is an electric circuit block diagram of a waveform equalizer showing an embodiment of the present invention. As shown in FIG. 1, a MUSE input signal is corrected and output. Transversal filter 5, an adder circuit 4 for adding a signal obtained by delaying the input signal and an output from the transversal filter 5, and outputting a waveform-equalized MUSE signal, and an adder circuit 4 A circuit for branching the output from the input to the control circuit 7 and comparing the VIT signal in the MUSE signal from the input with a predetermined reference signal,
In the waveform equalization circuit in which the waveform distortion component included in the input signal is removed by the control circuit 7 that changes the tap gain of the transversal filter 5, the control circuit 7 includes a memory 8 (RAM) and a memory 9 (RAM). ) Is provided, the detected VIT signal is written into the memory 8 by the control circuit 7, read out and compared with a predetermined reference signal to obtain a difference,
The same difference is set to 1 / n, added to the detected VIT signal, written in the memory 9, read out to obtain a correction coefficient and transferred to the transversal filter 5 to change the tap gain. The MUSE input signal is corrected and output, and the difference is 2 / n.
Then, it is added to the detected VIT signal to update and write the memory 9, read out to obtain a correction coefficient and transfer it to the transversal filter 5 to change the tap gain, and the transversal filter 5 changes the MUSE The input signal is corrected and output, and the correction coefficient is changed in n steps to perform waveform equalization.

[0005]

According to the present invention, waveform equalization is performed by the above-described configuration. First, the VIT signal superimposed on the MUSE signal is detected and compared with a predetermined reference signal to calculate the difference. , The difference is set to 1 / n and added to the VIT signal to obtain a correction coefficient, and the transversal filter 5
To the MUS from the transversal filter 5 by changing the tap gain of the transversal filter 5.
The input signal of E is corrected and output, and the difference is set to 2 / n and added to the VIT signal to obtain a correction coefficient, which is transferred to the transversal filter 5 to change the tap gain, By further correcting and outputting the MUSE input signal from the transversal filter 5, the correction coefficient is changed in n steps,
Since the MUSE signal output from the transversal filter 5 can also be corrected in n steps, the correction coefficient for waveform equalization can be switched stepwise to prevent a sudden change in the screen.

[0006]

1 is a block diagram of an electric circuit of a waveform equalizer showing an embodiment of the present invention, in which the same components as those shown in FIG. 2 are designated by the same symbols. . 1 is MU
It is an input terminal for inputting the baseband signal of the SE signal, branches the MUSE signal input through the input terminal 1, inputs one to the delay circuit 3, and inputs the other to the transversal filter 5. . The delay circuit 3 delays the input signal by a time equal to the time for which the transversal filter 5 performs signal processing, outputs the delayed signal, inputs the delayed signal to one end of the adder circuit 4, and the transversal filter 5 receives the input signal from the control circuit 7. MU from input signal by control signal
The VIT signal superimposed on the SE signal is detected and input to the control circuit 7. Alternatively, the output from the adder circuit 4 may be branched and input to the control circuit 7, and the VIT signal superimposed on the MUSE signal may be detected from the input. A microcomputer, for example, is used as the control circuit 7, and the control circuit 7 includes a memory 8 (RAM) and a memory 9 (RAM).
And a memory 10 (ROM) are provided, and the memory 10 (RO
A predetermined reference signal (ideal VIT signal) is stored in M) in advance, the VIT signal is written to and read from the memory 8, the difference is calculated by comparing with the predetermined reference signal read from the memory 10, and the difference is 1 / N to add to the VIT signal and write it in the memory 9, read it to obtain a correction coefficient and transfer it to the transversal filter 5 to change the tap gain.
The input signal of E is corrected and output, and input to the other end of the adder circuit 4. The adder circuit 4 adds the input from the delay circuit 3 and the input from the transversal filter 5 to output a MUSE signal whose waveform is equalized at the first stage, and decodes the MUSE signal via the output terminal 6. The signal is input to the circuit for signal processing.

Further, the VI read from the memory 8
The difference obtained by comparing the T signal with a predetermined reference signal read from the memory 10 is set to 2 / n, added to the VIT signal to update and write the memory 9, and read to obtain a correction coefficient. The signal is transferred to the transversal filter 5, the tap gain is changed, and the MUSE input signal is corrected by the transversal filter 5 and is output to the adder circuit 4. In the adder circuit 4, the delay circuit 3 Input and the input from the transversal filter 5 are added to output a second-stage waveform-equalized MUSE signal, and the correction coefficient is changed to n stages in the same manner, to obtain an ideal VIT signal. Waveform equalize the MUSE signal so that

FIG. 3 is a flow chart for explaining the operation of the control circuit 7 shown in FIG. The current VIT signal is fetched from the MUSE signal input via the transversal filter 5 (hereinafter, abbreviated as TF5 in the figure) and written in the memory 8 (RAM). Memory 10 (RO
A predetermined reference signal (ideal VIT
Signal) and the VIT signal written in the memory 8 to obtain a difference (ideal VIT-current VIT),
A multiple of the difference, a = 1 in a / n, and the current V
The calculation result is added to IT, the calculation result is written and read in the memory 9, the correction coefficient is obtained and transferred to the TF 5, the tap gain is changed, and the MUSE input signal is corrected and output by the TF 5.

Next, the numerical value of a is increased by 1 at a / n, which is a multiple of the added value to the current VIT, and [current VI
T + a / n (ideal VIT-current VIT)] is calculated, the calculation result is updated and written in the memory 9, and read and read to obtain a correction coefficient, which is transferred to TF5 to change the tap gain. The TF5 corrects the MUSE input signal and outputs it. Next, it is judged whether or not the correction coefficient is switched to the n stage, and if the switching of the n stage is not completed, the process returns to step 1 and is a multiple of the addition value to the current VIT, a
It is repeated until a = n in / n, and when n stages of switching are completed, the process ends.

[0010]

As described above, according to the present invention,
By switching the correction coefficient of waveform equalization stepwise,
It is possible to prevent abrupt changes in the screen, remove the waveform distortion component of the MUSE signal, and prevent ringing or the like that appears in the reproduced image quality, which greatly contributes to improving the performance of the waveform equalizer.

[Brief description of drawings]

FIG. 1 is a block diagram of an electric circuit of a waveform equalizer showing an embodiment of the present invention.

FIG. 2 is a block diagram of an electric circuit of a waveform equalizer showing a conventional example.

FIG. 3 is a flowchart illustrating the operation of the control circuit shown in FIG.

[Explanation of symbols]

 1 Input Terminal 2 A / D Converter 3 Delay Circuit 4 Adder Circuit 5 Transversal Filter 6 Output Terminal 7 Control Circuit 8 Memory 9 Memory 10 Memory 20 Memory

Claims (1)

[Claims] 1. A MUSE signal whose waveform is equalized by adding a transversal filter that corrects and outputs an MUSE input signal, an output from the transversal filter, and a signal obtained by delaying the input signal. , A circuit for branching the output from the adder circuit and inputting it to the control circuit, a VIT signal in the MUSE signal is detected from the input and compared with a predetermined reference signal, and the transversal is performed. A control circuit that changes a tap gain of a filter and a waveform equalization circuit that removes a waveform distortion component included in an input signal. The control circuit includes a first memory and a second memory. VIT detected in the above
A signal is written in the first memory, read out, compared with a predetermined reference signal to obtain a difference, and the difference is set to 1 / n and added to the detected VIT signal, written in the second memory, read out. A correction coefficient is obtained and transferred to the transversal filter to change the tap gain, and the transversal filter corrects and outputs the MUSE input signal. Further, the difference is set to 2 / n, and the detection is performed. The second memory is updated and written by adding to the VIT signal, read out to obtain a correction coefficient, transferred to the transversal filter and changed in tap gain, and the MUSE input signal is corrected by the transversal filter. The waveform equalizer is characterized in that the waveform is equalized by changing the correction coefficient in n steps so as to be output.