KR940008909B1 - Apparatus for improving quality of image signal of sattelite transmission system - Google Patents

Abstract

The circuit for improving a screen quality of a broadcasting satellite receiver prevents a rapid drop of a carrier-to-noise (C/N) caused by a rainfall. The circuit includes a tuner for inputting a signal of a first intermediate frequency fallen to the frequency from a signal received from the satellite and executing a second detection, a second intermediate frequency amplifier, an FM demodulator, a voice/video divider, a voice signal processor, a color/luminance divider, a luminance processor, a band-pass filter, a color processor, a mixer, a C/N detector, an ADC, and a comparator.

Description

Image quality improvement circuit of satellite broadcasting receiver

1 is a circuit diagram of an image quality improvement of a satellite broadcasting receiver according to the present invention.

FIG. 2 is a block diagram of the band pass filter 9 in FIG.

3 is a detailed circuit diagram of FIG.

4 is a frequency characteristic diagram of FIG.

5 is a flowchart for calculating the C / N ratio and the S / N ratio.

* Explanation of symbols for main parts of the drawings

1: tuner 2: AGC detector

3: second intermediate frequency amplifier 4: FM demodulator

5: Audio / Video Separator 6: Luminance / Color Separator

7: luminance processing unit 8: color processing unit

9: band filter 10,12,17 amplifier

11,13: ADC (Analog To Digital Converter)

4 comparison unit 15 mixer section

16: noise detector 18: peak detector

19: C / N detection unit 21: voice signal processing unit

92: wide band band pass filter 9-3: narrow band band pass filter

9-5: Buffer part SW ₁ : Switch

The present invention relates to an image quality improvement circuit of a satellite receiver, and more particularly, to an image quality improvement circuit of a satellite broadcast receiver, which is suitable for preventing a sudden drop in C / N due to the effect of rainfall.

FIG. 1 is an arc diagram of the present invention. As shown therein, a satellite signal introduced into a parabolic antenna (not shown) is first dropped in frequency drop (not shown) to generate a first intermediate frequency amplification signal. The output signal is applied to the BS tuner 1.

The AGC (Auto Gain Control) detection stage 2 is coupled to the second intermediate frequency amplifier 3 and the output of the second intermediate frequency amplifier 3 is input to the FM demodulator 4.

The output of the FM demodulator 4 is input to the video and audio separator 5 and the C / N detector 19. In this case, the CN detector 19 is a noise detector 16, a heavy amplifier 17, a peak detector. And an output signal is input to the comparator 14 through the amplifier 12 and the analog-to-digital converter 13 (ADC).

On the other hand, the audio signal is input to the audio signal processing unit 21 through the signal separation unit 20 to obtain an audio output, and the image processing separates the video signal and then separates the luminance / color signal into the luminance processing unit 7 and The band filter 8 is output to the mixer 15, and the color processor 8 inputs the output of the Y / C separator 6 to output an image signal through the mixer 15.

At this time, the band filter 9 is controlled by the output signal of the comparator 14, the comparator 14 is the output of the AGC detector 2 through the amplifier 10 and the ADC 11 and the The output signals of the peak detector 18 of the C / N detector 19 are compared with each other to generate a control output accordingly.

FIG. 2 is a detailed circuit diagram of the band filter 9 in FIG. 1, which is composed of a wide band filter 9-2 and a narrow band filter 9-3, as shown therein. The output of the characteristic filter among the two filters through the switch 9-4 is configured to be mixed in the mixer 15 with the output signal of the color processor 8 to obtain an image output.

3A is an example of a circuit configuration of the block diagram of FIG. 2, in which an image signal is inputted to a buffer arc consisting of resistors R1-R3 and transistor Q1, and the transistor ( In the emitter of Q1), a tuning circuit composed of condensers C ₁ and C ₂ and coils L ₁ and L ₂ is connected to the switch SW1 so that the frequency of the image output due to the disease of the switch SW ₁ . The gain is configured to be as shown in FIG. 3 (b).

Referring to the circuit and the operation and effect of the present invention configured as described above in detail as follows.

First, the first intermediate frequency output from the frequency drop (not shown) is 1035 GHz to 1336 GHz, and the tuner 1 performs a second detection of the 27 MHZ band using a local oscillation of 402.78 MHz.

The input gain is controlled by the AGC detector 2 and the second intermediate frequency amplifier 3 performs the second detection and outputs the second intermediate frequency amplified signal through the FM demodulator 4. FM demodulation is performed by detecting the video audio occupied band with a 27MHz band filter.

After FM demodulation, video and audio signals are separated in order to process video and audio signals into a real-time band. In the case of Japanese satellite broadcasting, video signals are separated using a low pass filter. Separation is performed in the audio and video separator 5 using a band pass filter.

The audio signal separated and digitally modulated by such a process is processed by the audio signal processor 21 to obtain a final audio output. The video signal is obtained by mixing low frequencies in order to reduce transmission power and reduce center energy in broadcasting. The composite signal can be obtained by removing.

That is, the color / luminance separation unit 6 inputs the video signal separated by the audio / video separation unit 5 into color signals and black and white signals, and only the black and white signals classified therefrom are the luminance processing unit 7. Is processed in

The band filter 9 coupled to the output of the luminance processing unit 7 is configured to seek a change as shown in FIG. 3 (b), and outputs the full band 12 when C / N is good, When N deteriorates, only the signal f1 of a good band is transmitted and the high frequency component is controlled as much as the area | region of a hatched part.

This is because the S / N ratio of the high frequency band rapidly decreases when C / N is lowered, resulting in noise on the screen.

The signal controlled by the band filter 9 is mixed with the output of the color processor 8 and the mixer 15 to produce a final image output.

Here, the control of the band filter 9 detects the noise of the 9-10MHZ band by the C / N detector 19 by the noise detector 16, and then amplifies the signal, and then the peak detector 18 of the noise is amplified. DC output is obtained by integration.

Then, the output is amplified again by the DC amplifier 12, digitally coded by the ADC 13, the reference change amount is repeatedly sensed, and the output is supplied to the comparator 14.

The comparison unit 14 compares the output of the C / N detection unit 19 with the voltage of the ADC 11 at a reference value to perform control of the final band filter 9.

FIG. 5 is a flow chart for calculating the C / N and S / N. When the output of AGC and the value of C / N are constantly checked and the data change of ADC and AGC falls within the specified range, comparison is made with each other. And outputs a control voltage accordingly.

Therefore, in the present invention, black noise of image quality due to high frequency noise is generated when deteriorating C / N, and removing high frequency in a composite state when removing it causes color quality deterioration due to loss of color. By separating the control, only the band of the image (black and white) signal can be improved to improve image quality.

As described above, the present invention has an effect of improving image quality during image processing in a satellite broadcasting receiver.

Claims (3)

A gain is controlled through a tuner 1 and a AGC detector 2 for inputting a signal of a first intermediate frequency in which a signal received from a satellite is dropped in frequency and performing a second detection using the local oscillation. A second intermediate frequency amplifier 3 which inputs the output of the tuner 1 and generates a second intermediate frequency signal therefrom, and an output signal of the second intermediate frequency amplifier 4 which is band-filtered FM demodulator 4 for detecting the occupied band, an audio / video separator 5 for separating the FM demodulated video and audio signal into a real use band, and an output signal from the audio / video separator 5 A voice signal processor 21 for processing a digital signal modulated from the digital signal and generating a final voice signal, and a video signal separated by the voice and image separator 5 to input a color signal and a black and white signal. Color / brightness classification to classify When the C / N is satisfactory because it is coupled to the output unit 6, the luminance processing unit 7 for inputting and processing only black and white signals from the output of the color / luminance separation unit 6, and the luminance processing unit 7 Outputs a monochrome signal over the entire band, and when the C / N deteriorates, a band filter 9 for controlling only a high band component by transmitting only a signal of a good band and an output of the color / luminance processor 6 are inputted to display only a color signal. The color processing unit 8 to process, the outputs of the color signal processing unit 8 and the band pass filter 9 are input and mixed with each other, and the composite video signal of the mixer unit 15 and the FM demodulation unit 4 is mixed. Inputs an output of the C / N detector 19 for detecting a noise component from the output and generating a DC signal corresponding to the peak value, and the output of the C / N detector 19 amplified by the amplifier 12. The DC level is converted to the corresponding digital code The ADC 13 repeatedly detects and compares the output of the C / N detection unit 19 and the output of the AGC detector 2 converted into a digital code with a reference value, depending on the amount of the C / N and a bad state. And a comparator (14) for outputting a control signal to the band filter (9) so that a black and white signal having a good band is selected. 2. The filter of claim 1, wherein the band pass filter 99 is composed of a wide band filter 9-2 and a narrow band filter 9-3 so that the output signal of the luminance processing unit 17 is switched by switching SW ₁ . And a signal of a band in which C / N is not degraded is output to the mixer unit (15). 3. The broadband filter (9-2) and narrow band filter (9-3) according to claim 2, wherein the buffer portion (9-5) for inputting the output of the luminance processing portion and the buffer portion (9-5) Image quality improvement circuit of the satellite broadcasting receiver, characterized in that the tuning circuit consisting of coils (L ₁ , L ₂ ) and condensers (C ₁ , C ₂ ) is selectively coupled to the output terminal by switching the switch (SW ₁ ). .