JPH04286496A - Muse signal processing unit - Google Patents

Abstract

PURPOSE:To implement aperture correction without separate provision of an aperture correction circuit by implementing aperture correction of D/A conversion through the use of an equivalent circuit. CONSTITUTION:A tap coefficient for waveform processing is obtained by applying arithmetic processing to a data of a VIT signal in a MUSE signal. The tap coefficient is inputted to a waveform equivalent circuit 16' comprising a transversal filter to implement aperture correction for D/A conversion. An output of the circuit 16' is outputted via a D/A converter 18 and an LPF 20 without causing deterioration in a high frequency output.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a MUSE signal processing device. In particular, the present invention relates to a device, such as a MUSE signal repeater, which converts an analog MUSE signal into a digital signal, processes it, and then converts it back into an analog signal and outputs it.

0002

[Prior Art] As a technology for band compression of high-quality video signals, multiple sub-Nyquist sampling encoding method (
MUSE method) (Multiple Sub-Nyq
uistSampling Encoding) is
It was developed by NHK (Japan Broadcasting Corporation) and is broadcast regularly via satellite.

The MUSE method is a band compression method for transmitting high-quality video signals on one channel of satellite broadcasting with a bandwidth of 27 MHz. In this MUSE method, a high-quality video signal is subjected to sub-Nyquist sampling processing using a band compression encoder to convert it into a band compression signal with a bandwidth of 8.1 MHz.

[0004] The MUSE method is introduced in the following literature.

(A) NHK Technical Research, 1986, Vol. 39, No. 2, Volume 172, 18 (76-53)
(111) Page Ninomiya, Otsuka, Izumi, Koshi, Iwadate, “
``Development of MUSE method'' (B) Magazine published by Nikkei McGraw-Hill Inc. ``Nikkei Electronics, November 2, 1987 issue, No. 43
3, pp. 189-212, by Ninomiya, "Transmission system MUSE for high-definition broadcasting using satellites" The waveform equalization of this MUSE signal will be explained.

[0006] A training signal for waveform equalization is inserted into the MUSE signal in advance on the transmitting side.

This training signal is a VIT signal (V
ertical IntervalTest Si
gnal) (VITS) (VIT pulse).

On the receiving side, after converting this MUSE signal from analog to digital, the response waveform of the VIT signal is taken in, and the characteristics of the equalizing filter on the receiving side are adjusted so that the error from the ideal impulse response is reduced. This operation equalizes the characteristics of the transmission path.

The waveform equalizer for MUSE signal is “19
1989 IEICE Spring National Conference Proceedings
Separate Volume 3 3-290 Lecture No. B-584".

Referring to FIGS. 3 and 4, the conventional MUS
The E signal repeater will be explained.

(10) is a MUSE signal repeater,
Emphasis-processed MUSE signal (M in FM mode)
USE signal) and outputs an unemphasized MUSE signal (AM mode MUSE signal).

(12) is an A/D converter. (14)
is a signal processing circuit, and this signal processing circuit (14) is F
Converts an M mode input MUSE signal to an AM mode MUSE signal.

Reference numeral (16) is a well-known waveform equalization circuit, which is composed of a digital transversal filter.

(18) is a D/A converter that converts the digital MUSE signal into an analog signal.

(20) is a low-pass filter.

By the way, each part (a) of this repeater (10)
)(b)(c) The frequency characteristics (f characteristics) are shown in Fig. 4(a)(b).
) (c). As can be seen from FIG. 4(c), the output (C) of the low-pass filter (20) has a low level of high-frequency components.

This is because the sampling data has a time width equal to the clock rate, so when D/A conversion processing is performed, the f characteristic drops in the high frequency region.

[0018]

Problem to be Solved by the Invention The deterioration of the characteristics in the high frequency range can be prevented by using a well-known oversampling filter technique that increases the clock rate. However, this technique requires a high clock rate,
Increasing the clock rate of a high frequency signal such as the MUSE signal even higher is troublesome.

Therefore, it is conceivable to separately provide an aperture correction circuit that emphasizes this deterioration in advance. However, this requires additional circuitry.

[0020]

[Means for Solving the Problems] The present invention provides an equalization circuit (1
6') is used to perform aperture correction for D/A conversion.

[0021]

[Operation] Waveform equalization and aperture correction can be performed simultaneously by the waveform equalization circuit (16') consisting of a transversal filter.

[0022]

Embodiment An embodiment of the present invention will be described with reference to FIGS. 1 and 2. In addition, in FIG. 1, the same parts as in FIG. 3 are given the same reference numerals, and the description thereof will be omitted.

(16') is a waveform equalization circuit. The value of the tap coefficient of the transversal filter in this waveform equalization circuit (16') is determined as follows.

That is, as in the prior art, tap coefficients for waveform equalization processing are obtained by arithmetic processing of the data value of the VIT signal in the MUSE signal. If this tap coefficient is output as it is to the waveform equalization circuit (16') as a tap coefficient, the output f characteristic of this waveform equalization circuit (16') will be as shown in FIG.
a') As shown, it is the same as the conventional one. By the way, if the tap coefficient for D/A aperture correction is set in the transversal filter operating as this waveform equalization circuit (16'), the output of this waveform equalization circuit (16') will be as follows. As shown in 2(a''), the high frequency region (H) is raised compared to the low frequency region (L). In order to obtain the tap coefficients, these two types of tap coefficients are calculated by convolution.

If the obtained tap coefficient is used as the tap coefficient of the waveform equalization circuit (16'), the output f characteristic of the waveform equalization circuit (16') will be as shown in FIG. 2(a). The f-specifications of each part (b) and (c) in Figure 1 are also shown in Figure 2 (b) and (c).
It will be like this. In other words, the high frequency range of the output (C) of the low-pass filter (20) is output without deterioration.

[0026]

As described above, according to the present invention, aperture correction can be performed without providing a separate aperture correction circuit.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram for explaining one embodiment of the present invention.

[Figure 2] f characteristics (frequency characteristics) to explain its operation
This is a diagram.

FIG. 3 is a circuit diagram of a conventional repeater.

FIG. 4 is a special diagram for explaining its operation.

[Explanation of symbols]

16' Waveform equalization circuit 12 A/D converter 18 D/A converter 20 Low pass filter

Claims (1)

[Claims] 1. A MUSE signal processing device comprising a waveform equalization circuit (16') for MUSE signals consisting of a digital transversal filter, and outputting the output of the waveform equalization circuit as an analog signal. A MUSE signal processing device characterized by performing aperture correction for D/A conversion using a transversal filter.