JPH05122556A - Signal waveform equalizing method - Google Patents

Abstract

PURPOSE:To finish a waveform equalization within a short time at need by efficiently detecting the distortion of transmission in the case of equalizing the waveform of an input signal by using an adaptive equalizing type filter. CONSTITUTION:A front transmission distortion delay amount detection circuit 12 and a rear transmission distortion delay amount detection circuit 13 detect a period T is which the transmission distortion higher than the prescribed level of a reference signal in the input signal exists. First of all, the transmission distortion within the period T is corrected by controlling the corresponding tap coefficient of the above-mentioned filter 5 corresponding to the detected output of the transmission distortion within the period T. Afterwards, the transmission distortion out of the period T is detected and corresponding to the detecting output, the remaining tap coefficients of the filter 5 are controlled. Thus, the transmission distortion out of the period T is corrected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal waveform equalizing method used in a transmission system of MUSE signals obtained by band-compressing high-definition signals.

[0002]

2. Description of the Related Art CA for transmitting NTSC signals and MUSE signals through a transmission system such as a coaxial cable or an optical cable.
In a TV system, a so-called waveform equalizer is used to correct the waveform distortion (transmission distortion) of the signal in the above transmission system.

Among others, a waveform equalizer for MUSE signals is disclosed in, for example, Japanese Unexamined Patent Publication No. 64-82778 (H0).
4N 7/13), etc., the transmission distortion is detected by using the VIT signal inserted in the first and second lines in the vertical blanking period of the MUSE signal, and the waveform is detected according to the detected output. There is one that controls the tap coefficient of the equalization filter.

FIG. 3 shows a schematic configuration of such a conventional MUSE signal waveform equalizer. (1) is a low-pass for cutting a transmission bandwidth (8.1 MHz) or more of an input analog MUSE signal. Filter, (2) is the MU from this filter
A / D converter for converting SE signal to digital signal, (3)
Is a sync detector that separates and detects horizontal and vertical sync signals in the MUSE signal after A / D conversion, and (4) is a timing pulse generator that generates various timing pulses with each sync signal as a time reference. 5) is MUSE after A / D conversion
This is an adaptive equalization type filter consisting of multi-stage transversal filters to which signals are input.

Further, (6) is a VIT signal capturing section for separating and extracting the VIT signal from the MUSE signal passed through the filter (5), and (7) is transmission distortion such as ghost or waveform distortion of the extracted VIT signal. Is an error signal for the ideal VIT waveform, (8) is a tap coefficient correction unit that changes the tap coefficient of each stage of the filter (5) based on the error signal, and (9) is the tap coefficient correction unit. This is a tap coefficient memory in which tap coefficients are written / read at the timing of the timing pulse generator (4).

[0006]

In this waveform equalizer, the transmission distortion is generated by using the VIT signal period shown in FIG. 4 inserted in the first and second lines of the vertical blanking period of the MUSE signal as described above. Is being detected, in particular 26
216 to 263 ahead of the VIT signal of the fourth sample
The pre-transmission distortion is also calculated by using the period of the sample eye and 265
Post-transmission distortion is detected using the period up to the 316th sample.

By the way, conventionally, the transmission distortion is always detected for the entire VIT period of the 216th to 316th samples, but this is not rational. This is because the longer the transmission distortion detection period, the wider the range of transmission distortion that can be corrected, but the longer the processing time for changing the tap coefficient of the filter (5) becomes.

Therefore, it is an object of the present invention to efficiently detect transmission distortion and to end waveform equalization in a short time if necessary.

[0009]

According to the present invention, transmission distortion of a reference signal in an input signal to be waveform-equalized is detected, and an adaptive equalization type filter to which the input signal is input is controlled according to the detected output. In the waveform equalization method, the transmission distortion within the period is detected by detecting the period in which the transmission distortion of the reference signal is equal to or higher than a predetermined level, and controlling the tap coefficient of the filter corresponding to the period. And then the transmission distortion outside the above period is corrected by controlling the remaining tap coefficients of the filter.

[0010]

[Operation] According to the present invention, since waveform equalization processing is performed in at least two stages, that is, first during a period of large transmission distortion and then during a period of small transmission distortion, The equalization process can be terminated at a desired stage when the progress of the equalization is performed while confirming the progress on the display or the like.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiment of FIG. 1 showing the case of waveform equalizing a MUSE signal according to the present invention will be described below.

In FIG. 1, the same parts as those in FIG. 3 are designated by the same reference numerals and the description thereof will be omitted. In the waveform equalizer of FIG. It is composed of 10) and a control unit (11).

Reference numerals (12) and (13) in the control unit (11) are a front transmission distortion delay amount detection unit and a rear transmission distortion delay amount detection unit added according to the present invention. Pre-transmission distortion delay amount detector (12)
Compares the VIT signal extracted by the VIT signal capturing unit (6) with an ideal VIT waveform and first determines a pre-transmission distortion (existing in 216 to 263 sample periods in FIG. 4) of a predetermined level or more of the VIT signal, Of these pre-transmission distortions, the time position (maximum delay time) of the transmission distortions farthest from the VIT signal is detected. On the other hand, the post-transmission distortion delay amount detection circuit (13) similarly performs post-transmission distortion (see FIG. 4) above a predetermined level of the VIT signal.
(Existing in 265 to 316 sample periods) of the above, and detects the maximum delay time of those post-transmission distortions.

On the other hand, the transmission distortion detection section (7) again detects the transmission distortion of the VIT signal extracted by the VIT signal acquisition section (6) by comparing it with the ideal VIT waveform. A period T sandwiched by the two maximum delay times given by the transmission distortion delay amount detection circuits (12) and (13).
(See FIG. 4). Then, an error signal indicating the magnitude of each transmission distortion detected during this period and its time position is given to the tap coefficient correction unit (8). Thereby,
The correction unit (8) sets the tap coefficient corresponding to the error signal in the filter (5) via the coefficient memory (9), and thereby the transmission distortion within the above period is equalized.

The equalizing operation is repeated until the transmission distortion within the period T becomes sufficiently small. After that, when this equalization operation is completed, the transmission distortion detector (7) detects the transmission distortion in the section outside the period T in the same manner as described above, and in accordance with the error signal obtained by this, the transmission distortion is detected. The remaining tap coefficients of the filter (5) are set similarly. This operation is also repeated until the transmission distortion outside the period T is sufficiently reduced, and as a result, all the transmission distortion to be corrected is equalized.

FIG. 2 is an operation flow chart when the control unit (11) of the above embodiment is constructed by a one-chip microcomputer,
Since its operation can be easily understood from the above description, detailed description thereof will be omitted. However, at the start of the waveform equalization processing operation, the tap coefficient of the filter (5) is in the initial state (only one in the central stage is 1, and other Note that the stage is set to 0). The delay time described above is detected as the data sample position No. (n).

Further, in the above description, the correction of the tap coefficient of the filter (5) corresponding to the section other than the period T has been described as being performed at one time, but it may be performed at a plurality of times. Good.

The calculation for changing the tap coefficient in the tap coefficient correction unit (8) is performed by the LMS (Least Mean Square) method by multiplication of the error signal and the input signal. Since it is the same, detailed description is omitted.

Although the embodiment for waveform equalizing the MUSE signal has been described above, the present invention is also applicable to waveform equalizing an NTSC television signal or the like, and in such a case, for example, a vertical synchronizing signal. The front edge of the above may be used as the reference signal.

[0020]

According to the waveform equalization method of the present invention, the waveform equalization processing is performed in at least two stages, that is, first for a period of large transmission distortion and then for a period of small transmission distortion. Therefore, you can easily check the progress of waveform equalization on the display etc.
The equalization processing time can be shortened depending on the situation.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing a main part of an operation flowchart thereof.

FIG. 3 is a block diagram showing a schematic configuration of a conventional waveform equalizer.

FIG. 4 is a signal waveform diagram of a VIT signal and a period before and after the VIT signal.

[Explanation of symbols]

 (10) Filter section (11) Control section

Claims (2)

[Claims] 1. A waveform equalization method for detecting a transmission distortion of a reference signal in an input signal to be waveform equalized, and controlling an adaptive equalization filter to which the input signal is input according to the detected output. , The front transmission distortion and the rear transmission distortion which are equal to or higher than a predetermined level of the reference signal are discriminated, and the maximum delay times from the reference signal before and after the respective transmission distortions are respectively detected, and then the maximum delay times before and after that are sandwiched. The transmission distortion within the period is detected, each transmission distortion is corrected by controlling the tap coefficient of the filter corresponding to the transmission distortion position, and then the transmission distortion of the reference signal outside the period is corrected. A signal waveform equalization method, characterized in that detection is performed and the remaining tap coefficients of the filter are controlled based on the detected output to correct transmission distortion. 2. The signal waveform equalizing method according to claim 1, wherein the input signal is a MUSE signal, and the reference signal is a VIT signal in the MUSE signal.