KR930008712B1 - Multi Intermediate Frequency Processing System - Google Patents

Abstract

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Description

Multi Intermediate Frequency Processing System

1 is a block diagram of an intermediate frequency processing system of the present invention.

2 is a block diagram of a conventional intermediate frequency processing system.

The present invention relates to an intermediate frequency processing integrated circuit system for TV. In particular, the present invention relates to an intermediate frequency processing integrated circuit that can be fixedly used in only one broadcasting system so that it can be applied to all currently used TV broadcasting systems, that is, NTSC, ARM, and Secam. One is a multi-medium frequency processing system.

The color TV broadcasting system currently widely used in the world is NTSC, PAL, and SECAM. Since the NTSC system includes color signals in the same channel as a conventional black and white television, it is sent in the same standard, so it is transmitted to a black and white receiver. If you receive it, you can see it as a black and white screen. On the other hand, when you receive a black and white television radio with this color receiver, it adopts a compatible method that can be viewed as a normal black and white screen.

PAL is a broadcasting method used in West Germany, Austria, UK, Netherlands and Switzerland. The luminance signal is the same as the NTSC method, and the color signal I and Q are 90 ° like the NTSC. One side of the color signal is sent by inverting the phase. On the receiving side, if one side is inverted and applied, the phase distortion is canceled and the effect on the screen is eliminated. Compared to NTSC, even if it is compatible with black-and-white image or the price of receiver is excellent, the transmission characteristic is excellent, so the SN ratio is good even in weak electric field, and it does not receive phase distortion like SECAM. SECCAM has no concern for color change due to phase difference compared to NTSC method, but as can be seen from the operation, since two scanning lines become one color signal, the color resolution in the vertical direction is half and the compatibility of black and white television In addition, it is slightly lower and is currently used in France, the Soviet Union, Hungary, the Czech Republic, and Poland.

Since the voice carrier used in each broadcasting method is 4.5MHz for NTSC method and 5.5MHz or 6.5MHz for ARM / Secam method, it is necessary to use the conventional intermediate frequency integrated circuit to receive each broadcasting method. Since a suitable resonant circuit must be applied, there is a problem that various external components must be provided for the same integrated circuit.

In this case, the resonant circuit of the FM detection circuit for the final detection of the voice signal is different, and the inconvenience of adjusting each time, and above all, the intermediate frequency integrated circuit applied to one of the methods is different from that of the broadcast. There is a drawback that viewing is impossible because it is not applicable.

SUMMARY OF THE INVENTION An object of the present invention is to provide a multi-intermediate frequency processing system capable of viewing all broadcast methods such as NTSC, ARM, and Secam even with only one intermediate frequency integrated circuit at the user's choice.

Hereinafter, the present invention will be described with reference to the accompanying drawings. The present invention is a mode for selecting a broadcasting method according to control signals from a trap circuit 105, a filter circuit 104, and a microcomputer 100, which pass only a video signal of a specific frequency in a conventional intermediate frequency processing integrated circuit system. A trap switch 103 for passing a frequency suitable for the broadcasting method selected by the mode selection signal of the mode selection circuit 101 among the frequencies passed through the selection circuit 101, the trap circuit 105, and the filter circuit 104. And a voice switch 102.

1 is a block diagram of an intermediate frequency processing system according to the present invention, in which an intermediate frequency signal from a tuner for selecting and converting a received channel propagation into an intermediate frequency signal is input to an image intermediate frequency amplification circuit 50 of a pin 7, and is then banded. Accurately capture the characteristics of the television signal sent by the residual wave method and amplify about 70dB. In this circuit, the video signal and the audio intermediate frequency signal are amplified together. Note that when amplifying two signals of different types in one circuit, the bit signal, which is a frequency difference between the two signals generated by the FM detection circuit 61, is also amplified and displayed as a bit pattern on the screen. Therefore, the voice intermediate frequency signal is amplified by lowering to a level that does not affect the screen.

The signals sufficiently amplified by the image intermediate frequency amplification circuit 50 are input to the image detection circuit 52, the auto phase control circuit 53, and the auto frequency tuning circuit 51, respectively. The automatic phase control circuit 53 operates according to the PLL (Phase locked loop) characteristic, and the image detection circuit 52 receives an image signal which is a modulation component from the intermediate frequency signal amplified by the image intermediate frequency amplification circuit 50. Works to get The composite video signal taken out from the video detection circuit 52 includes a luminance signal, a carrier color signal, a burst signal, and a synchronization signal. The signal detected by the image detection signal 52 needs to amplify the input of the image amplifier circuit 54, that is, the image detection output voltage, to about 1-3Vp-p. Since the carrier color signal is applied to the receiving tube through a narrow color reproduction circuit, the carrier color signal generates some delay than the luminance signal.

In the image amplification circuit 54, the important thing is to amplify the luminance signal with the frequency band from DC to 4MHz as faithfully as possible. In particular, if the DC signal is not transmitted to the color receiver, The color of the picture is not reproduced. Therefore, when the direct current component of the luminance signal is lost by using a coupling capacitor between the respective amplifier stages, the direct current component regeneration must be performed in the output circuit.

The signal detected by the image detector circuit 52 is buffered by the image amplifier circuit 54 and output to the pin 24. At this time, the output signal includes both a video signal and an audio signal. The signal is input to the base of the transistors Q ₁ and Q ₂ and output to the emitter of the transistor Q _{1. The} 4.5 MHz trap 33 for NTSC and the 5.5 MHz or 6.5 MHz trap 34 for ARM / Secam It is input to pins 22 and 23 via a trap circuit 105 composed of Since the signal input to the pins 22 and 23 passes the trap circuit 105 for absorbing and attenuating radio waves or signals other than the required frequency, the control signal from the mode selection circuit 101 is a video signal from which an audio carrier component is removed. That is, if the desired method is selected by the microcomputer 100, NTSC or PAL / SECAM broadcasting method, in the case of NTSC by the mode selection signal, a signal trapped at 4.5 MHz, that is, a composite video signal, is output to the pin 19 and simultaneously a transistor ( The signal output to the emitter of Q ₂ ) is a filter circuit composed of a 4.5 MHz band filter 35 in the case of NTSC, a 5.5 MHz band filter 35 in the case of Fal / Secam, or a 6.5 MHz band filter 36 ( 104 is passed through the audio carrier from which the video signal components have been removed. Therefore, the voice carrier signals described above are output to pin 18 by selecting 4.5 MHz, 5.5 MHz or 6.5 MHz according to the control signal from the mode selection circuit 101, that is, the broadcast mode selection signal, in the voice switch 102. Then, it is input to the limiter circuit 60 via the pin 28 to perform the voice intermediate frequency processing operation.

In the NTSC system, the 4.5MHz voice intermediate frequency signal is amplified by approximately 60dB by the IC differential amplifier circuit of 3-4 stages and the amplitude is constant by the limiter circuit 60. This is to remove the uneven amplitude or the mixing of the noise after the FM detection due to the mixing of pulse noise in the frequency-modulated speech intermediate frequency signal.

In addition, the trap switch 103 and the voice switch 102 are composed of a bipolar or MOS logic circuit, and the automatic discriminator 64, which adjusts to an appropriate amplitude according to the frequency and phase change, adjusts the resonance time constant to each broadcasting system. Is changed to the correct one.

On the other hand, when the broadcasting system selection signal of NTSC and PAL / SECAM is input from the microcomputer 100 to the mode selection circuit 101, it is simultaneously input to the screen display device 106 via the pins 14, 15, and 16 and the TV screen. Display the broadcast mode among NTSC, ARM, and Secam on the screen.

As described above, when the TV broadcast type NTSC, ARM, Secam, etc. adopt the intermediate frequency processing system having the structure of the present invention under any broadcasting method, each broadcasting method can be viewed by the user's selection. It is possible to solve the broadcasting system's limitation of use, solve the problem of having various external components and the trouble of adjusting the resonant circuit of the FM detection circuit every time.

Claims (2)

In an intermediate frequency processing system including an image detector circuit 52, an image amplifier circuit 54, an FM detector circuit 61, and an image intermediate frequency amplifier circuit 50, according to a control signal received from the microcomputer 100, Mode selection circuit 101 for outputting a mode selection signal for each broadcasting method via pins 14, 15, and 16, pin 24 on the base and resistor R ₁ on the emitter. And a trap circuit 105 for outputting a specific video signal to pins 22 and 23 as a transistor Q ₁ and a capacitor C ₁ and C ₂ connecting two types of traps 34 and 35. Transistor (Q ₂ ) and capacitor (C ₃ , C ₄ ) connecting resistor (R ₂ ) to emitter (24) and two kinds of band filters (35, 36), pins 20, 21 Selects a video carrier suitable for each broadcasting method by the filter circuit 104 and the video signals of the pins 22 and 23 and the mode selection signal of the mode selection circuit 101 The voice carriers corresponding to each broadcasting method are selected by the trap switch 103 output to the pin 19, the voice signals of the pins 20 and 21, and the mode selection signal of the mode selection circuit 101. 18) and the voice switch 102 outputted to the automatic discriminator 64, the process time constant for each broadcasting method is output to the pin 10 by the voice carrier signal of the voice switch 102 and the mode selection signal. Multi-median frequency processing system, characterized in that it comprises an automatic discriminator (64). The multi-intermediate frequency processing system according to claim 1, wherein the trap switch (103) and the voice switch (102) are constituted by a bipolar logic circuit or a MOS logic circuit.