JPH05344379A - Waveform equalizer - Google Patents

Abstract

PURPOSE:To improve the adjustment accuracy without retarding the adjustment speed by performing adjustment as providing a coarse adjustment mode and a fine adjustment mode on the waveform equalizing. CONSTITUTION:A control circuit 7 detects a VIT signal superimposed on a MUSE signal inputted through a TF 5, comparing it with the prescribed reference signal to find the coefficient for coarse adjustment to be written in a memory 9, which is sent to a transversal filter 5 to change the tap gain and to perform the coarse adjustment. Then, the distortion of the remaining VIT signal is detected to find the coefficient for fine adjustment and writes it in a memory 10, which is sent to the transversal filter 5 to change the tap gain and to perform the fine adjustment. Thus, the adjustment accuracy can be improved without retarding the adjustment speed of waveform equalizing.

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 into the signal reproduction decoder, the occurrence of ringing or the like 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 MUSE input signal, 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, and an adder circuit 4 From the input signal,
By detecting the VIT signal superimposed on the MUSE signal,
The memory 20 (R) is calculated by comparing with a predetermined reference signal stored in advance in the memory 8 (ROM) to obtain a coefficient for adjustment.
AM), read out, and transfer to the transversal filter 5 to change the tap gain of the transversal filter 5. With the control circuit 7, the waveform distortion component included in the input signal is removed to perform waveform equalization. And adder circuit 4
Output from the output terminal 6.

[0003]

Therefore, there is a problem that the adjustment mode of waveform equalization has only one step, the accuracy of the adjustment is poor, and the occurrence of ringing cannot be sufficiently prevented. It is an object of the present invention to maintain the adjustment speed of waveform equalization at the same level and improve the adjustment accuracy.

[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 an output from the transversal filter 5 and a signal obtained by delaying the input signal, and outputting a waveform-equalized MUSE signal, and an adder circuit 4 From the input signal from the adder circuit 4 for detecting the VIT signal superimposed on the MUSE signal from the input signal from the adder circuit 4 and comparing it with a predetermined reference signal, and a transversal filter In the waveform equalization circuit that removes the waveform distortion component included in the input signal with the control circuit 7 that changes the tap gain of the signal No. 5, the control circuit 7 includes the coarse adjustment memory 9 (R
AM) and a memory 10 (RAM) for fine adjustment,
The control circuit 7 compares the VIT signal with a predetermined reference signal for calculation, obtains a coefficient for coarse adjustment, writes the coefficient in the memory 9, reads the coefficient, transfers it to the transversal filter 5, and changes the tap gain to change the coarse gain. Adjustment is performed, the distortion of the remaining VIT signal is detected from the input signal from the adder circuit 4, a coefficient for fine adjustment is obtained, written in the memory 10, read out, transferred to the transversal filter 5, and tapped. Fine adjustment is performed by changing the gain.

[0005]

According to the present invention, waveform equalization is performed by the above-described structure. First, the VIT signal superimposed on the MUSE signal is detected, and the VIT signal is compared with a predetermined reference signal to perform an arithmetic operation for rough adjustment. The coefficient for waveform equalization is read from the memory 9, read out and transferred to the transversal filter 5, and the tap gain of the transversal filter 5 is changed to perform coarse adjustment, thereby adjusting the adjustment speed of waveform equalization to that of the conventional example. Maintaining the same level, then detecting the remaining distortion of the VIT signal, obtaining a coefficient for fine adjustment, and writing the coefficient into the memory 10,
It is possible to improve the adjustment accuracy of the waveform equalization by reading out and transferring to the transversal filter 5 and changing the tap gain of the transversal filter 5 to perform fine adjustment.

[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 and outputs the input signal by a time equal to the time for which the transversal filter 5 performs signal processing, and inputs the delayed signal to one end of the adder circuit 4. The transversal filter 5 is input 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. For example, a microcomputer is used as the control circuit 7, and a predetermined reference signal (ideal VIT signal) stored in advance in the memory 8 (ROM) and V detected from the input signal are used.
The IT signal is compared and calculated to obtain a coefficient for coarse adjustment, which is written in the memory 9 (RAM), read out and transferred to the transversal filter 5, and the transversal filter 5 changes the tap gain to perform coarse adjustment. The MUSE signal is corrected and output, and is 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 waveform-equalized MUSE signal, and outputs the MUSE signal through an output terminal 6 to decode the MUSE signal. The signal is processed by inputting it to. The output of the adder circuit 4 is branched to input the waveform-equalized MUSE signal to the control circuit 7,
The control circuit 7 detects the coarsely adjusted VIT signal in the waveform-equalized MUSE signal and compares the roughly adjusted VIT signal with a predetermined reference signal stored in advance in the memory 8,
The residual VIT signal distortion is detected to obtain a coefficient for fine adjustment, which is written in the memory 10 (RAM), read out and transferred to the transversal filter 5, and the tap gain is further changed by the transversal filter 5. Fine adjustment is performed to correct and output the MUSE signal, which is input to the other end of the adder circuit 4 and is added to the input from the delay circuit 3 in the adder circuit 4 to output the waveform-equalized MUSE signal. I am trying.

FIG. 3 is a flow chart for explaining the operation of the control circuit 7 shown in FIG. The VIT signal is detected from the MUSE signal input through the transversal filter 5 (hereinafter, abbreviated as TF5 in the figure) and fetched to determine whether the coarse adjustment has been performed. If the coarse adjustment is not completed, the coarse adjustment is performed. To execute. In the coarse adjustment, a predetermined reference signal (ideal VIT signal) stored in advance in the memory 8 and a VIT signal detected from the input signal are compared and calculated to obtain a coefficient for coarse adjustment. Memory for adjustment coefficient 9
To write. Next, execute the fine adjustment, and the fine adjustment is
The coarsely adjusted VIT signal in the waveform-equalized MUSE signal input from the adder circuit 4 is detected, and the VIT signal and a predetermined reference signal (ideal VIT signal) stored in the memory 8 in advance are detected. Is calculated and the coefficient for fine adjustment is calculated, and the coefficient for fine adjustment is written in the memory 10.

It is determined whether or not the fine adjustment has been performed. If the fine adjustment has not been completed, it is further determined whether or not the coefficient for coarse adjustment written in the memory 9 has been transferred to the TF 5. If not, the memory 9 has been completed. The coefficient for coarse adjustment written in is transferred to TF5, the process returns to step 1, and if completed, the process directly returns to step 1 and the procedure for fetching the VIT signal and the following steps are repeated. At this stage, the rough adjustment has been completed,
If the coarsely adjusted VIT signal in the corrected MUSE signal input from the adder circuit 4 is detected and taken in, it is determined whether or not the coarse adjustment has been performed, and if the coarse adjustment is completed, step 2
Steps to execute the fine adjustment of 1. Repeat the following. In step 3,
It is judged whether or not the fine adjustment has been performed, and if the fine adjustment is completed, the fine adjustment coefficient written in the memory 10 is transferred to the TF 5, and the waveform equalization procedure ends.

[0010]

As described above, according to the present invention,
By providing coarse adjustment and fine adjustment modes in the waveform equalization adjustment mode and roughly adjusting the waveform equalization, the adjustment speed of the waveform equalization is maintained at the same level as in the past, and further fine adjustment is performed. The adjustment accuracy of waveform equalization can be improved, ringing that appears in the reproduced image quality can be prevented, and this greatly contributes to the performance improvement 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 an 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 a MUSE input signal, an output from the transversal filter, and a signal obtained by delaying the input signal. M from the input signal from the adder circuit that outputs the
The VIT signal superimposed on the USE signal is detected and compared with a predetermined reference signal, and the waveform distortion component included in the input signal is removed by the control circuit that changes the tap gain of the transversal filter. In the waveform equalizing circuit, a first memory for coarse adjustment and a second memory for fine adjustment are provided in the control circuit, and the VIT signal and a predetermined reference signal are compared in the control circuit for calculation. Coarse adjustment coefficients are obtained, written in the first memory, read out, transferred to the transversal filter, and the tap gain is changed to perform coarse adjustment, and the remaining VIT is obtained from the input signal from the adder circuit. The signal distortion is detected, the coefficient for fine adjustment is obtained, written in the second memory, read out, transferred to the transversal filter, and the tap gain is changed to perform fine adjustment. Waveform equalizer according to claim.