KR970006133Y1 - Pal/ntsc mode converting circuit for satellite communication - Google Patents

Abstract

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Description

PAL / NTSC mode automatic switching circuit of satellite broadcasting

1 is a block diagram of the automatic switching circuit of the present invention.

2 is an automatic switching flowchart of the present invention.

* Description of the symbols for the main parts of the drawings *

11: 5MH _Z low pass filter 12: 4.43MH _Z band pass filter

13: first detection circuit 14: first analog switch

15: De-emphasis circuit for PAL signal 16: 3.58MH _Z band pass filter

17: 4.2MH _Z low pass filter 18: second detection circuit

19: second analog switch 20: de-emphasis circuit for NTSC signal

The present invention relates to a circuit for automatically switching the PAL or NTSC mode according to the video broadcast method of the broadcast received from the satellite.

And a 1 5MH _Z low-pass filter (11) for looking at the configuration, to remove the video signal of the audio sub-carriers at the same time the output in accordance with the selected channel from the tuner, and also a circuit for automatic switching of the subject innovation block turn, the 5MH _Z 4.43MH _Z band pass filter 12 connected to the low pass filter output for passing only the PAL type color subcarrier, and a first analog switch for passing the output of the 5MH _Z low pass filter when the color subcarrier is detected. A first detection circuit 13 for turning on 14), a de-emphasis circuit 15 for the PAL signal connected to the analog switch output, and a 3.58 for passing only NTSC color subcarriers connected to the 5MH _Z low pass filter output. MH _Z band-pass filter 16 and, with the low-pass filter 4.2MH 5MH _{Z Z} a low-pass filter 17 coupled to the output of, upon detection of the color subcarrier of the NTSC system the 4.2MH _And a second detection circuit 18 for turning on the second analog switch 19 to pass through the output of the _Z low pass filter, and a de-emphasis circuit 20 for the NTSC signal connected to the analog switch output. The output terminals of the de-emphasis circuit and the de-emphasis circuit for NTSC are connected to the video processing circuits used for PAL and NTSC.

Referring to the circuit operation and operation of the present invention configured as described above are as follows.

In the PAL method, the video signal is stretched to 5MH _Z or less, and in the NTSC mode, the video signal is stretched to 4.2MH _Z or less. The dual NTSC method and the color subcarrier exists in 3.58MH _Z, PAL method, and the color subcarrier exists in 4.3MH _Z. When the satellite signal comes from the tuner, the 5MH _Z low pass filter 11 first separates the audio signal from the video signal. At this stage, both PAL and NTSC signals of the video signal pass. The subcarrier signal passing through the filter 11 is determined by the 4.43MH _Z band pass filter 12 and the 4.43MH _Z band pass filter 12 as the signal corresponding to 4.43MH _Z. At this time, if the subcarrier is 4.43MH _Z , the first detection circuit 13 of the next stage opens the first analog switch 14 to pass the signal passing through the filter 11 through the PAL signal de-emphasis circuit to control PAL / NTSC. Send to common circuit.

Meanwhile, the signal passed through the low-pass filter 11 is not a 4.43MH _Z, unless 3.58MH _Z, it is determined 3.58MH _Z is. At this time, if the subcarrier is 3.58MH _Z, the second detection circuit 18 opens the second analog switch 19 and sends the satellite video signal passing through the 4.2MH _Z low pass filter to the NTSC signal de-emphasis circuit.

After that, the signal is processed in the PAL / NTSC common circuit like the PAL signal.

The automatic switching flow chart of each mode is shown in FIG. 2.

When the video signal comes from the tuner (201), it passes through the 5MH _Z low pass filter, at which time the video signal of both PAL and NTSC scheme is passed (202). The respective sub-carrier that is, NTSC system is when the sub-carriers of 3.58MH _Z then, PAL scheme when it is detected the sub-carriers of 4.43MH _Z. (203)

Next, the subcarrier determines whether or not the PAL method is applied to 4.43MH _{Z. If the} condition is met, the detection circuit 13 passes through the PAL de-emphasis circuit 15 (205) and is a video signal processing circuit commonly used for PAL and NTSC. (206).

If the sub-carrier is to be input is not a 4.43MH _Z, again the sub-carrier is determined whether 3.58MH _Z (207). At this time, if the condition is met, the detection circuit operates to pass the subcarrier through the 4.2MH _Z low pass filter through the NTSC de-emphasis circuit 20 (208), and sends it to the video signal processing circuit commonly used for PAL and NTSC. 206)

Since the circuit of the present invention is used as described above, the user can conveniently use the PAL / NTSC broadcasting system without knowing or adjusting the broadcasting method.

Claims (1)

In the PAL / NTSC mode automatic switching circuit of satellite broadcasting, 5MH for separating the audio sub-carrier and a video signal to be output at the same time according to the selected channel from the tuner _Z low-pass filter with the _Z 5MH low-pass filter connected to the output _Z 4.43MH band-pass filter for passing only the color subcarrier in the PAL format A first detection circuit for turning on a first analog switch for passing the output of a 5MH _Z low pass filter upon detecting the color subcarrier, a de-emphasis circuit for a PAL signal connected to the first analog switch output; _Z 5MH the low-pass filter connected to the output NTSC 3.58MH _Z bandpass filter for passing only the way of the color subcarrier and said low 5MH _Z and _Z 4.2MH low-pass filter coupled to the output of the low-pass filter, the color of the NTSC system And a second detection circuit for turning on a second analog switch for passing the output of the 4.2MH _Z low pass filter when the subcarrier is detected, and a de-emphasis circuit for NTSC signals connected to the second analog switch output. PAL / NTSC mode automatic switching circuit of satellite broadcasting.