SU1573558A1 - Corrector of high-frequency pre-distortions of secam decoder - Google Patents

Abstract

The invention relates to a color television technique. The purpose of the invention is to simplify the high-frequency predistortion corrector. The corrector contains a correction filter 1, an electronic switch 2, a delay block 3, and a gating driver 4. A full video signal SECAM is fed to the input of the corrector, which also goes to the inputs of the electronic switch 2, and to the first input directly, and to the second through the delay unit 3. The delay time is equal to the flash duration of the color subcarrier. To fill the pause in the color signal, the received signal is used twice, the main flash is demodulated without distortion. As a result, a flat area is formed, which ensures accurate fixation of the black level and reliable operation of the color lock unit. The required number of memory cells of the delay unit 3 is halved, since The flashes of the red and blue subcarriers are alternately recorded in the same memory cells, which simplifies the implementation of the equalizer. 2 Il.

Description

The invention relates to a color television technique.

The aim of the invention is to simplify the high-frequency predistortion corrector.

Figure 1 shows the electrical structure of the corrector; figure 2 - timing diagrams at the control points of the scheme.

The corrector contains a correction filter I, an electronic switch 2, a block 3 of delays and a shaper of a 4 gate pulse.

Corrector works as follows.

The input of the corrector receives the full video signal SECAM (Fig.2A). This

the same signal goes to the inputs of the electronic switch 2, and to the first input directly, and to the second through the block 3 delays. The delay time is equal to the duration of the flash color subcarrier фиг (Fig.26).

When a subcarrier color flash is present in the input signal, a gate pulse arrives at the control input of switch 2 (Figure 2B), the duration of which is also equal to the flash duration. The switch switches and the flash from the direct signal is introduced into the delayed one in the blanking interval before its flash (Figure 2d). It is known that the transition process in the correction filter, WISP

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called the inclusion of the subcarrier, takes about 2/3 of the flash duration. Therefore, by the end of the first flash introduced from the direct signal, the transient is terminated at the decoder output, and the second, main flash demodulates without distortion, resulting in a flat area that ensures accurate black level fixation and reliable color synchronization unit operation. Thus, instead of a signal from a complex oscillator, the signal received from the telecentre is used every time to fill a pause in the chroma signal. At the same time, its frequencies in the dR and dB lines are exactly equal to the frequencies of the main flashes,

With all modifications of delay unit 3, the corrector is simplified by halving the required number of memory cells of delay unit 3. This is due to the fact that the flashes of the dR and du strings are written alternately in the same memory locations. When block 3 is executed as a digital register, the addressing scheme is eliminated, which further simplifies the device.

Claims (1)

Invention Formula The SECAM decoder's high-frequency predistortion corrector containing a series-connected electronic switch, the first information input of which is the device input, and the control input connected to the output of the gating pulse generator, the first and second control inputs of which are respectively the horizontal frequency signals and clock signals frequencies, and a correction filter, the output of which is the output of the device, characterized in that, for the purpose of simplification, a delay unit is inserted, the input of which is connected to the input corrector, and the output is connected to the second information input of the electronic switch. 1 VL / DPR.1 t) f) ) 2