JPH04334171A - Waveform equalizing device for muse signal - Google Patents

Abstract

PURPOSE:To prevent malfunction due to noise without being affected of increase in an equalization processing time when an adaptive equalizer filter 5 is in use to apply waveform equalization to a MUSE signal. CONSTITUTION:A filter is controlled in response to a detection output of a transmission distortion detection section 7 provided in a post-stage of an adaptive equalization filter 5 receiving a MUSE signal. An addition averaging circuit 11 implementing the averaging processing of the MUSE signal is provided in a pre-stage of the filter 5 and a changeover circuit 10 is used to input an output signal of the averaging circuit 11 to the filter 5 only at the start of equalization processing and the MUSE signal is directly inputted to the filter 5 in the case of other than the start.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waveform equalization device used in a repeater or receiver in a transmission system for a MUSE signal obtained by band-compressing a high-definition signal.

0002

2. Description of the Related Art MUSE signals are transmitted by broadcasting satellites, coaxial cables, optical cables, etc., and are subject to various signal distortions due to such transmission systems. Therefore, by equalizing the signal deterioration caused by such distortion, a distortion-free MU is created.
It is necessary to convert it back into an SE signal and supply it to the decoder.

[0003] As a waveform equalizer for MUSE signals used for this purpose, for example, Japanese Patent Laid-Open No. 64-827
As shown in Publication No. 78 (H04N 7/13), etc., transmission distortion is detected using the VIT signal inserted into the first and second lines within the vertical blanking period of the MUSE signal, and the detected output is It is common to have a configuration in which the tap coefficients of the waveform equalization filter are controlled according to the waveform equalization filter.

FIG. 3 shows a schematic configuration of such a conventional MUSE signal waveform equalization device, and (1) is a device for cutting the transmission bandwidth (8.1 MHz) or more of the input analog MUSE signal. A low-pass filter, (2) is an A/C converting the MUSE signal from this filter into a digital signal.
The D conversion unit (3) is a synchronization detection unit that separates and detects the horizontal and vertical synchronization signals in the MUSE signal after the A/D conversion, (4
) is a timing pulse generator that generates various timing pulses using each synchronization signal as a time reference, and (5) is A.
This is an adaptive equalization type filter consisting of a multi-stage transversal filter into which the MUSE signal after /D conversion is input.

Further, (6) is a VIT signal that separates and extracts the VIT signal from the MUSE signal that has passed through the filter (5).
a signal acquisition section; (7) a transmission distortion detection section that detects transmission distortion such as a ghost or waveform distortion of the extracted VIT signal as an error signal with respect to the ideal VIT waveform; (5) is a tap coefficient correction section that changes the tap coefficients of each stage; (9) is a tap coefficient memory in which tap coefficients are written/read at the timing of the timing pulse generation section (4).

[0006]

[Problem to be Solved by the Invention] Now, in this waveform equalizer, as mentioned above, the VIT signal shown in FIG.
Transmission distortion is detected using the signal period, and this V
The IT signal period should originally be at a constant DC level except for the 264th sample, but in reality, various noises are mixed in. Therefore, if these noises are erroneously detected as a ghost component of the 264th sample of the VIT signal, a ghost will be added instead.

[0007] To resolve this situation, MUSE
Instead of capturing the VIT signal period from the signal only once and detecting transmission distortion, it captures it multiple times and averages it to remove the influence of noise, and uses it as the output of the VIT signal period to detect transmission distortion. Just do it. At this time, since the noise removal effect is greater as the number of times the image is captured increases, it is considered that approximately 128 times is appropriate for the number of times the image is captured.

[0008] However, the VIT signal is generated once every frame, that is, 1/30 second (actually twice, on the first line and the second line as shown in Fig. 4, but because the sampling phases are different, Since the data is actually transmitted only once), it takes more than 4 seconds to capture 128 times. This is a huge amount of time compared to the calculation time for setting the tap coefficients of the filter (5), and therefore it takes an extremely long time from the start of the waveform equalization operation to the transition to a steady state. Become.

[0009] Therefore, the present invention solves the above-mentioned drawbacks and
It is an object of the present invention to enable efficient waveform equalization processing of a USE signal.

0010

[Means for Solving the Problems] In the present invention, in a waveform equalization device that controls the filter according to the output of a transmission distortion detection section provided after the adaptive equalization filter to which the MUSE signal is input, , an averaging circuit that performs averaging processing of the MUSE signal, and a switching circuit that switches and derives the output signal of the averaging circuit and the MUSE signal are provided at a stage before the filter, and the switching circuit The output signal of the averaging circuit is input to the filter only at the start of the averaging process, and the MUSE
The signal is directly input to the filter.

Further, in the present invention, the averaging circuit is constituted by an accumulative adding circuit that sequentially cumulatively adds the input MUSE signal and its one-frame delayed output at a certain coefficient ratio; The amount of noise in the signal is detected, and the coefficient ratio is changed according to the detected output.

[0012]The detection of the amount of noise is carried out using, for example, M
It is configured to be performed during the clamp level period within the vertical blanking period of the USE signal.

[0013]

[Operation] According to the present invention, since the averaging process of the MUSE signal is performed before the start of the equalization process, transmission distortion can be detected immediately at the start of the equalization process, etc. This makes it possible to significantly reduce processing time.

Further, since the coefficient ratio of the cumulative addition circuit constituting the above-mentioned averaging circuit is varied according to the amount of noise, noise can be reduced without unnecessarily sacrificing followability of time fluctuations of transmission distortion. The influence of can be removed.

Furthermore, by detecting the amount of noise during the clamp level period within the vertical blanking period, the noise can be reliably detected while being distinguished from the video signal.

[0016]

[Embodiment] Fig. 1 shows an embodiment of the waveform equalization device of the present invention, and (10), (11), and (12) respectively indicate a switching circuit, an averaging section, and a newly added switching circuit according to the present invention. and a noise detection section, and the other parts are the same as the conventional device shown in FIG. 4, so the same parts are given the same reference numerals and the explanation will be omitted.

The averaging section (11) cumulatively adds and averages the MUSE signals output from the A/D converter (2) for each frame, and also averages the MUSE signals output from the A/D converter (2).
) detects the amount of noise in the MUSE signal using, for example, the clamp level section within the vertical blanking period of the MUSE signal, and the averaging section ( 12).

That is, the averaging section (11) includes a multiplier (13) with a multiplication coefficient K (0<K<1) as shown in FIG.
It consists of a multiplier (16) with a multiplication coefficient of 1-K, an adder (14), and a 1-frame delay circuit (15), and the output of the noise detection section (12) is applied to each of the multipliers (13) (16).
) (although its structure will not be described in detail here). At this time, when a large amount of noise is detected, the coefficient K is changed to become smaller so that the averaging effect, that is, the noise removal effect becomes larger, and when a small amount of noise is detected, the above-mentioned K is changed to become larger. Control is performed so that the ability to follow temporal changes in transmission distortion does not deteriorate too much.

On the other hand, the switching circuit (10) switches between the output signal of the A/D conversion section (2) and the output signal of the averaging section (11), and inputs one of them to the filter (5). The timing signal from the timing generator (4) switches to the b side only at the start of the equalization processing operation, and at other times, that is, before the start of the equalization processing and for a predetermined minute time after the start of the equalization processing. In the steady operation (equalization processing) state after the elapse of time, the switch is made to the side a.

Therefore, in the apparatus shown in FIG. 1, since the averaging process has already been performed by the adding and averaging section (11) when the power is turned on, the switching circuit (10) is used to perform the waveform equalization process after that. When switched to the b side, transmission distortion is immediately detected for the MUSE signal from which noise has been removed or reduced by the above averaging process, and the setting of the tap coefficients of the filter (5) is completed within a short time. It turns out. The operations from transmission distortion detection to tap coefficient setting are the same as in the case of FIG. 4. When the setting of the tap coefficients is completed, the switching circuit (10) returns to the a side as described above, and equalization processing is performed on the MUSE signal from the A/D converter (2).

[0021] Also, when performing waveform equalization by resetting the tap coefficient of the filter (5) from the steady operating state where equalization processing is being performed as described above, the switching circuit (10) is switched to the b side. is achieved in the same way.

[0022] In the above description, the clamp level period within the vertical blanking period is used as an example of noise amount detection, but in addition to this, for example, the VIT signal period or frame pulse period within the vertical blanking period may be used. You may also do so.

[0023]

[Effects of the Invention] According to the present invention, in a waveform equalization device that performs waveform equalization processing by detecting transmission distortion after averaging a MUSE signal a plurality of times, the above-mentioned averaging processing is performed. Since it is always performed before the start of the equalization process, the equalization process time is not unnecessarily increased due to the above-mentioned averaging process, and the waveform equalization process can be performed in the minimum necessary processing time.

Further, since the coefficient ratio of the cumulative addition circuit constituting the averaging circuit is varied according to the amount of noise, the noise can be reduced without unnecessarily sacrificing the followability of time fluctuations of transmission distortion. The effects of this can be appropriately removed.

Furthermore, if the noise amount is detected during the clamp level section of the vertical blanking period, the detection period becomes longer, so the noise amount can be detected reliably.

[Brief explanation of the drawing]

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

FIG. 2 is a block diagram showing an example of the internal configuration of its main parts.

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

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

[Explanation of symbols]

(13) Multiplier (14) Adder (16) Multiplier

Claims (3)

[Claims] 1. A waveform equalization device that includes a transmission distortion detection unit provided at a subsequent stage of an adaptive equalization filter to which a MUSE signal is input, and controls the filter according to the output of the detection unit, wherein the MUSE signal An averaging circuit that performs averaging processing, an output signal of this averaging circuit, and the above MUSE
A switching circuit for switching and deriving the signal is provided before the filter, and the switching circuit allows the output signal of the averaging circuit to be input to the filter only at the start of equalization processing, and at other times other than the start time. A waveform equalization device for a MUSE signal, characterized in that the MUSE signal is directly input to the filter. [Claim 2] The averaging circuit is connected to the input M
It is constituted by a cumulative addition circuit that sequentially cumulatively adds the USE signal and its one-frame delayed output at a certain coefficient ratio, detects the amount of noise in the MUSE signal, and adjusts the coefficient ratio according to the detected output. 2. The MUSE signal waveform equalizer according to claim 1, wherein the MUSE signal waveform equalizer is configured to change the waveform of the MUSE signal. 3. The MUSE signal waveform equalization device according to claim 3, wherein the detection of the noise amount is performed during a clamp level period within a vertical blanking period of the MUSE signal.