JPH0670198A - Waveform equalizer - Google Patents

Abstract

PURPOSE:To improve the equalizing accuracy by storing and reading a distributed constant corresponding to each other sampling point of a VIT signal so as to correct a clipped part of the VIT signal. CONSTITUTION:An A/D converter 2 samples a MUSE signal and outputs the sampled signal and it is inputted to an adder circuit 4 by correcting with a transversal filter TF 5. The adder circuit 4 adds the output to a delayed signal to output by eliminating a waveform distortion component included in the input signal and a VIT signal fetch section 7 extracts a VIT signal from the output, control section 8 compares the VIT signal with a reference signal stores in advance to obtained and output an error and correction coefficient. A control section 11 compares the VIT signal with a distributed constant corresponding to the sampling point of the VIT signal stores in advance and obtained and outputs the error and correction coefficient. An error discrimination circuit 14 compares both the errors so as to output a correction coefficient outputted from the control section with a smaller error through a changeover device 15 and the output changes a tap gain of the TF 5.

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. 3, A / S for sampling an input signal of MUSE is used.
The D converter 2, the transversal filter 5 that corrects the output of the A / D converter 2, the output from the transversal filter 5, and the signal obtained by delaying the input signal are added to obtain a waveform or the like. The adder circuit 4 for outputting the converted MUSE signal, the circuit for branching the output from the adder circuit 4 and inputting it to the control circuit 20, the VIT signal in the MUSE signal is detected from the input, and the storage unit 21 is detected. The data is written in and read from the (RAM), compared with a predetermined reference signal stored in the reference signal storage unit 22 (ROM) in advance, calculated, and a correction coefficient is obtained and transferred to the transversal filter 5 to be transferred to the transversal filter 5. With the control circuit 20 that changes the tap gain, the waveform distortion component included in the input signal is removed, waveform equalization is performed, and the addition circuit 4 outputs the result.

In the case of the MUSE signal transmitted from the satellite, since the FM system is used, the distortion in the transmission line is small and the input signal level is kept within the input range of the A / D converter. As a result, the input signal can be prevented from being clipped. However, when transmitting a MUSE signal by CATV or the like, AM transmission is used in order to effectively use the transmission frequency band. In this case,
Similarly, the maximum value of the amplitude level of the input signal is set within the input range of the A / D converter, but if the distortion in the transmission line is large, the input will exceed the conversion window of the A / D converter. There was a case where the signal was clipped.

[0004]

Therefore, when the VIT signal superimposed on the MUSE signal is clipped, the clipped portion is not subjected to the equalization calculation, so that there is a problem that the equalization accuracy is poor. According to the present invention, the distribution constant corresponding to each sampling point of the VIT signal is stored in the distribution constant storage unit and read out to correct the clipped portion of the VIT signal to equalize the waveform, thereby increasing the equalization accuracy. The purpose is to maintain equalization speed and perform waveform equalization.

[0005]

FIG. 1 is a block diagram of an electric circuit of a waveform equalizer showing an embodiment of the present invention. As shown in FIG. The D converter 2, the transversal filter 5 that corrects the output of the A / D converter 2, the output from the transversal filter 5, and the signal obtained by delaying the output of the A / D converter 2 are added. , A waveform equalization circuit configured with an adder circuit 4 for removing and outputting a waveform distortion component included in an input signal, a VIT signal capture for extracting and outputting a VIT signal from the output from the adder circuit 4 Unit 7, a control unit 8 for comparing the VIT signal with a reference signal stored in advance and obtaining and outputting an error and a correction coefficient corresponding to the error, and sampling the VIT signal and the VIT signal stored in advance. Comparing the distributed constant corresponding to obtains and outputs a correction coefficient according to the error and the error control unit 1
1 and the error determination circuit 14 that compares the error signals output from the control unit 8 and the control unit 11 and outputs a switching signal, and the switching signal from the error determination circuit 14 controls the control unit 8 and the control unit 11. And a switching unit 15 for switching and outputting the correction coefficient signal output from the transversal filter 5, and inputting the correction coefficient signal output via the switching unit 15 to the transversal filter 5 and tapping the transversal filter 5. The gain is changed.

[0006]

According to the present invention, the waveform equalization is performed by the above-mentioned configuration. When the clipped VIT signal is input, the control section 11 controls the clipped portion.
The VIT signal input in step 2 is compared with the distribution constant corresponding to the sampling point of the VIT signal stored in advance, an error and a correction coefficient corresponding to the error are calculated and output, and the transversal filter 5 uses the same correction coefficient. Waveform equalization is performed by changing the tap gain, and in other cases, the VIT signal input by the control unit 8 is compared with a reference signal stored in advance, and an error and a correction coefficient according to the error are calculated. The error calculated by the control unit 11 and the error calculated by the control unit 8 are compared, and the correction coefficient signal input from the smaller error signal is output from the switcher 15. The tap gain is changed by TF5 so that the input MUSE signal is corrected, and the equalization accuracy is improved from the conventional value, and the same equalization speed as the conventional value is maintained. etc It can be.

[0007]

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. 3 are designated by the same symbols. . 1 is MU
This is an input terminal for inputting the baseband signal of the SE signal. The MUSE signal is input to the A / D converter 2 via the input terminal 1, and the A / D converter 2 samples and converts it into a digital signal. MUSE converted to signal
The signal is branched and one is input to the delay circuit 3 and the other is input to the transversal filter 5 (hereinafter abbreviated as TF5). The delay circuit 3 delays and outputs the input signal by a time equal to the time for signal processing by the TF 5.
The TF 5 is input to one end of the adder circuit 4, and the TF 5 corrects and outputs the MUSE signal input by changing the tap gain according to the correction coefficient signal input from the switcher 15.
Is input to the other end of.

In the adder circuit 4, the input from the delay circuit 3 and the input from the TF 5 are added to each other, and the waveform equalized MUS is added.
The E signal is output and input to the MUSE signal decoding processing circuit via the output terminal 6 for signal processing. Further, the output from the adder circuit 4 is branched to VIT.
The VIT signal is input to the signal capturing unit 7, and the VIT signal is extracted from the MUSE signal whose waveform is equalized by the VIT signal capturing unit 7,
It is input to the control units 8 and 11. As the control units 8 and 11, for example, a microcomputer is used, and the storage unit 9 is provided in the control unit 8.
(RAM) and reference signal storage unit 10 (ROM) are provided,
A predetermined reference signal (ideal VIT signal) is stored in advance in the reference signal storage unit 10 (ROM), and the control unit 1
1 includes a storage unit 12 (RAM) and a distribution constant storage unit 13
(ROM) is provided so that the distribution constant storage unit 13 (ROM) stores distribution constants corresponding to ideal sampling points of the VIT signal.

In the control unit 8, the input VIT signal is written and stored in the storage unit 9, read out, and stored in the reference signal storage unit 10 in advance.
Signal) to calculate and output an error and a correction coefficient corresponding to the error, the error signal is input to one end of the error determination circuit 14, and the correction coefficient signal is input to one end of the switcher 15. There is. In the control unit 11, the input VIT signal is written and stored in the storage unit 12 and read out, and the distributed constant storage unit 1
The distribution constant corresponding to each sampling point of the VIT signal stored in advance in 3 is read out, and the dispersion of the input VIT signal and the ideal dispersion of the VIT signal are compared and calculated,
An error and a correction coefficient corresponding to the error are obtained and output, the error signal is input to the other end of the error determination circuit 14, and the correction coefficient signal is input to the other end of the switcher 15. The storage unit 9 and the storage unit 12 have the same function and may be shared. The error determination circuit 14 compares the error signals input from the control units 8 and 11 and inputs the switching signal to the switching device 15,
The correction coefficient signal input from the smaller error signal is output from the switch 15, and the correction coefficient signal is output to TF.
5, the tap gain is changed by TF5, and the input MUSE signal is corrected and output.

The adder circuit 4 adds the input from the delay circuit 3 and the corrected MUSE signal from the TF 5 and outputs a waveform-equalized MUSE signal, which is waveform-equalized by the VIT signal fetching section 7. The VIT signal is extracted from the MUSE signal, input to the control units 8 and 11, and the VIT signal waveform-equalized by the control unit 8 and the predetermined reference signal stored in the reference signal storage unit 10 (ideal VIT signal) Is calculated to obtain and output an error and a correction coefficient corresponding to the error, and the control unit 11 outputs the waveform equalized VIT signal and the VIT signal stored in the distributed constant storage unit 13 in advance. The distribution constant corresponding to the sampling point is read, the variance of the waveform equalized VIT signal and the variance of the ideal VIT signal are compared and arithmetically operated, and an error and a correction coefficient corresponding to the error are obtained and output. In the error determination circuit 14, the control unit 8 and the control unit 11
If either one of the errors input from is less than or equal to the desired value, the waveform equalization is terminated, and if it exceeds the desired value, the correction coefficient signal is output from the switch 15. The waveform is further equalized based on the correction coefficient signal.

FIGS. 2A and 2B are explanatory diagrams of waveforms of the VIT signal. Normally, the VIT signal as shown in FIG. 2A is superimposed on the MUSE signal and transmitted. When AM transmission is used and the distortion in the transmission path is large, and the amplitude level of the VIT signal exceeds the conversion window of the A / D converter 2 or the like, as shown in FIG.
Alternatively, it is assumed that a VIT signal whose lower part is clipped is input. In the control unit 8, the error signal becomes large in a portion where the waveform of the VIT signal is clipped, and the correction coefficient signal output from the control unit 11 is input to the TF 5 via the switcher 15. Since the tap gain is changed to correct the input MUSE signal, the accuracy of waveform equalization can be improved. In other portions where the waveform of the VIT signal is not clipped, the error signals input from the control units 8 and 11 are compared, and the correction coefficient signal input from the smaller error signal is output from the switch 15. Then, change the tap gain with TF5,
The input MUSE signal is corrected.

[0012]

As described above, according to the present invention,
Even if a clipped VIT signal is input due to distortion of the transmission line, the clipped portion can be corrected and waveform equalization can be performed, and a waveform equalizer with improved waveform equalization accuracy and speed can be provided. It can be provided and contributes largely 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.

2A and 2B are waveform explanatory diagrams of a VIT signal.

FIG. 3 is a block diagram of an electric circuit of a waveform equalizer showing a conventional example.

[Explanation of symbols]

 1 Input Terminal 2 A / D Converter 3 Delay Circuit 4 Adder Circuit 5 Transversal Filter 6 Output Terminal 7 VIT Signal Capture Section 8 Control Section 9 Storage Section 10 Reference Signal Storage Section 11 Control Section 12 Storage Section 13 Distributed Constant Storage Section 14 Error determination circuit 15 Switching device 20 Control circuit 21 Storage unit 22 Reference signal storage unit

Claims (1)

[Claims] 1. An A / D converter for sampling an MUSE input signal, a transversal filter for correcting the output of the A / D converter, an output from the transversal filter, and the A / D converter. In the waveform equalization circuit configured by adding the delayed signal of the output of and the output signal after removing the waveform distortion component included in the input signal, A VIT signal fetching unit that fetches and outputs a VIT signal, a first control unit that compares the VIT signal with a reference signal stored in advance, and obtains and outputs an error and a correction coefficient according to the error; and the VIT signal. And a distribution constant corresponding to the sampling point of the VIT signal stored in advance to obtain an error and a correction coefficient corresponding to the error, and output the second control unit, the first control unit and the second control unit. The error determination circuit for comparing the error signals output from the control unit and outputting the switching signal, and the correction signal output from the first control unit and the second control unit by the switching signal from the error determination circuit. A switch for switching and outputting, and inputting a correction coefficient signal output from the switch to the transversal filter to change the tap gain of the transversal filter for waveform equalization. Waveform equalizer.