SU951752A1 - Color synchronization device - Google Patents

Description

(54) COLOR SYNCHRONIZATION DEVICE

one

The invention relates to a color television technique and can be used in SECAM color television systems.

A color synchronization device is known for a SECAM color television receiver containing a series-connected amplitude limiter, a key whose control input is the input of gating pulses, and a band-pass filter, as well as two amplitude detectors, a subtraction unit and a capacitive storage 1.

However, the known device has a low noise immunity.

The purpose of the invention is to increase the noise immunity.

To achieve this goal, a CECAM color television receiver, containing a series-connected amplitude limiter, a key whose control input is a gate input, and a band-pass filter, as well as two amplitude detectors, a subtraction unit and a capacitive drive, has a delay unit whose input is connected to the output of the bandpass filter, the first and second outputs are connected to the corresponding amplitude detector, and the control input of the delay unit is the signal of the half-line frequency, while the amplitude outputs

 The detectors are connected to the corresponding inputs of the subtractor, the output of which is connected to the input of the entered amplitude limiter at the minimum, the output of which is connected to the input of the capacitive storage device.

10 The drawing shows a block diagram of the proposed device.

The color synchronization device of the color receiver of the SECAM system contains amplitude limiter 1, key 2, band-pass filter 3, block 4

 delays, two amplitude detectors 5, 6, block 7 subtraction, amplitude limiter 8 at the minimum, capacitive storage 9. The device works as follows. Signal input

Claims (1)

20 chromaticity SECAM. Key 2 extracts from this signal packets of unmodulated subcarriers transmitted during the return stroke in rows (the device can work with frame identification signals, if the control input K; yuch 2 is supplied with frame damping pulses). The amplitude limiter 1 ensures the independence of the amplitudes of the subcarrier packets from the amplitude-frequency characteristic of the communication channel and the variation of the AGC parameters of the TV. The subcarrier packets are passed through a bandpass filter 3. The bandpass filter is configured to provide at its output the maximum difference in amplitudes of subcarrier packets on the R-Y and B-Y lines. For this, the resonant frequency of the band pass filter 3 may, for example, be set equal to or slightly less than the frequency of the unmodulated subcarrier packets on rows B – Y (4.25 MHz). Then, at the output of the bandpass filter 3, the amplitude of the V-Y packets will be larger than the amplitude of the R-V having a frequency of 4.406 MHz. Such amplitude modulated subcarrier packets are placed on block 4 delays. Amplitude detectors 5 and 6 convert the subcarrier packets into two sequences of monopolar pulses. When receiving a SECAM signal, the amplitude of the pulses at the outputs of the amplitude detectors will be different. Two sequences of pulses are fed to the inputs of subtraction unit 7. At the output of this block, a sequence of pulses is allocated. Their amplitude is proportional to the difference of the amplitudes of the input pulses, and the sign depends on the phase of operation of the 4 delay unit. Suppose that with an incorrect switching phase, the pulses are positive. Then, after the amplitude limiter 8 at the minimum, which cuts off noise and noise with small amplitude, these pulses are sent to capacitive storage 9. A stepwise increasing potential is released at the output of capacitive storage. The time constant of the capacitive accumulator is chosen so as to exclude the effect of the loss of individual identification packets, as well as impulse noise. The potential from the output of capacitive storage 9 is used to correct the phase of a symmetric trigger in a color block. This is done by any known method. For example, the potential from capacitive storage 9, after reaching a certain threshold level, unlocks the amplitudes of the packets R-Y and B-Y. Thus, the increase in noise immunity is achieved due to the fact that the proposed device first compares the amplitudes of the detected pulse sequences in the subtraction unit 7, and only then charges the storage capacitor in the capacitive storage device 9. At the same time, the nonlinear properties of the storage capacitor do not affect the comparison accuracy pulses. Due to the fact that the channels of the device, starting from the bandpass filter 3 and up to the amplitude detectors 5 and 6, do not contain nonlinear links, and the amplitude limiter 1 is kept at the input of the bandpass filter 3 by the constant amplitude of the subcarrier packets when receiving sinusoidal interference with a constant the frequency of the amplitude of the pulses is the same and compensation of the subtracted pulses is achieved, at which the amplitude of the difference signal at the output of the subtracting unit 7 is below the threshold of the amplitude limiter 8. As a result, Co-interference, such as a PAL signal, is suppressed in subtraction unit 7 and does not affect the operation of the device. Claims. A color television color synchronization device of the SECAM system containing a series-connected amplitude limiter, a key whose control input is the input of gating pulses, and a band-pass filter, as well as two amplitude detectors, a subtraction unit and a capacitive drive, characterized in interference protection, a delay unit is introduced, the input of which is connected to the output of the bandpass filter, the first and second outputs are connected to the corresponding amplitude detector, and the input is controlled The events of the delay unit are the input of a half-line frequency signal, while the outputs of the amplitude detectors are connected to the corresponding inputs of the subtractor, the output of which is connected to the input of the input minimum amplitude limiter, the output of which is connected to the input of the capacitive storage. Sources of information taken into account in the examination 1. “Le Haut-parlevr, 1976, No. 156, p. 80-86 (prototype).