JP2853246B2 - MUSE down converter - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a downconverter for converting a MUSE-type high-vision signal into an NTSC signal.

Hi-vision satellite experiment broadcasting using the MUSE system has been started.To view this broadcast on the current general TV, an adapter that converts a MUSE high-definition signal called a down converter into an NTSC signal Is required.

[Conventional technology]

The conventional downconverter uses a circuit having a configuration as shown in the electric circuit block diagram of FIG. 4, and a MUSE baseband signal demodulated by a high-vision compatible satellite broadcast receiver is supplied to the LPF1 via the input terminal 7 of the downconverter. A / D by passing only the 8.1MHz MUSE signal with the same LPF1
M input to converter 2 and input to A / D converter 2
The USE signal is converted into a digital signal and output and input to the MUSE down-conversion circuit 4. The MUSE signal input by the MUSE down-conversion circuit 4 is converted into the number of scanning lines, screen is assembled, and the audio signal is reproduced. Digital signal processing to convert to NTSC signal, output and input to D / A converter 5. The D / A converter 5 converts the signal to analog signal and outputs NTSC analog signal to down converter. The signal was output from the terminal 6 to be viewed on the display in addition to the display.

20MHz required for high definition signal transmission in MUSE system
The sub-sampling technology thins out the pixels of the band of
The band is compressed to 8.1 MHz for transmission, and the spectrum of the luminance signal is 8.1 MHz, as shown in FIG.
And transmitted within the band.

[Problems to be solved by the invention]

Therefore, when a luminance signal having a spectrum as shown in FIG. 3 is directly down-converted and converted into an NTSC signal and reproduced, the edge portion of the image projected due to the aliasing noise of the high frequency component may flicker. There was a problem.

An object of the present invention is to provide an image which is easy to view by reducing the flicker.

[Means for solving the problem]

As shown in FIG. 1, an LPF 1 that passes a MUSE signal that has been band-compressed at 8.15 MHz, an A / D converter 2 that converts the MUSE signal that has passed through the LPF 1 into a digital signal, and outputs the digital signal.
A digital filter circuit 3 for limiting the vertical and horizontal pass bands at the video sample points of the MUSE signal converted into a digital signal by the converter 2, and a signal that has passed through the digital filter circuit 3 is converted into an NTSC signal and output. And a D / A converter 5 that converts the NTSC signal into an analog signal and outputs the analog signal, and converts the MUSE baseband signal applied to the LPF 1 through the input terminal 7 to the NTS signal.
The signal is converted into an SC analog signal, output from the output terminal 6 of the down converter via the D / A converter 5, and can be viewed in addition to the display for reproducing the NTSC signal.

[Action]

FIG. 2 is a diagram showing a sampling pattern and a two-dimensional passband characteristic. According to the sampling theorem, a half of the sampling frequency is a passband width. In the MUSE decoder, an area surrounded by ◇ by the sampling pattern in FIG. In the present invention, as shown by □ in FIG. 2, in the vertical direction, about 1/2 H is set in the vertical direction, weighting is possible for each line, and output is possible, and in the horizontal direction, output is possible by passing up to about 6 MHz. Using a digital filter circuit having a pass band characteristic as described above, a 8.1 MHz bandwidth MUSE having a spectrum of a luminance signal in which a high frequency component is folded as shown in FIG.
The signal is input to the digital filter circuit, and the MUSE signal is converted into an NTSC signal by reducing the aliasing component of the high-frequency portion included in each corner of the area enclosed by the triangle.

〔Example〕

FIG. 1 is a block diagram showing an electric circuit of a down converter according to an embodiment of the present invention. A MUSE baseband signal demodulated by a high-vision compatible satellite broadcast receiver is supplied to an LPF 1 via an input terminal 7 of the down converter. Have been added.

From the MUSE baseband signal demodulated by the LPF1
A / D by passing only 8.15MHz band-compressed MUSE signal
A / D converter 2
The MUSE signal that has passed through the LPF 1 is converted into a digital signal and output, and is applied to a digital filter circuit 3. The digital filter circuit 3 has a vertical direction of about 1 / 2H as shown in FIG. Output possible, about 6M in horizontal direction
A band having a pass band characteristic of passing a frequency up to Hz and having an output enabled, and having a spectrum of a luminance signal in which a high frequency component is folded as shown in FIG.
The aliasing component contained in the high-frequency portion of the 8.1 MHz MUSE signal is reduced and output, added to the MUSE down-conversion circuit 4, and the number of scanning lines is converted for the MUSE signal input by the MUSE down-conversion circuit 4. And performs digital signal processing for screen assembly and audio signal reproduction, converts it to NTSC signal, outputs it, adds it to the D / A converter 5, converts the NTSC signal to an analog signal with the D / A converter 5, and outputs it. In addition, through the output terminal 6 of the down-converter, it is possible to view in addition to the display for NTSC signal reproduction.

〔The invention's effect〕

As described above, according to the present invention, it is possible to reduce the flicker at the edge portion of the reproduced image due to the folding of the high frequency component included in the spectrum of the luminance signal of the MUSE system, and to reproduce a video which is easy to view. Can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram of an electric circuit of a down converter showing one embodiment of the present invention, FIG. 2 is a diagram showing a two-dimensional pass band characteristic of a digital filter used in the present invention, and FIG.
FIG. 4 is a block diagram of an electric circuit of a conventional downconverter of a luminance signal of the SE system. 1 ... LPF, 2 ... A / D converter, 3 ... Digital filter circuit, 4 ... MUSE down-conversion circuit, 5 ... D / A converter, 6 ... Output terminal, 7 ... Input terminal.

Claims (2)

(57) [Claims] 1. An LPF that passes a MUSE signal that has been band-compressed at 8.15 MHz, an A / D converter that converts the MUSE signal that has passed through the LPF into a digital signal and outputs the digital signal, and an A / D converter. A digital filter circuit for limiting a pass band in the vertical and horizontal directions at a video sample point of the MUSE signal converted to a digital signal, a MUSE down-conversion circuit for converting a signal passed through the digital filter circuit to an NTSC signal and outputting the signal; And a D / A converter that converts the NTSC signal into an analog signal and outputs the analog signal. 2. The digital filter circuit is characterized in that the pass band of the digital filter circuit is about 1 / 2H in the vertical direction, weighted for each line and output is possible, and the pass band in the horizontal direction is up to about 6 MHz and output is possible. A MUSE type down converter according to claim 1.