SU1163488A1 - Colour synchronizing device - Google Patents

Abstract

1. A COLOR SYNCHRONIZATION DEVICE containing a frequency detector with a switched demodulation characteristic, the first input of which is an input of a chrominance signal, the second input is an input of gating pulses, and the third input is connected to the output of a counting trigger, which is different in order to ensure synchronization in case of identification signals dropout, between the frequency detector output and one of the installation inputs of the counting trigger are connected in series the capacitive storage device and the correction unit, countable countable input trigger is input trigger pulses of the line frequency. 2, The device according to claim 1, wherein the correction unit is made in the form of a successively connected differentiating circuit, a pulse polarity selector and a coincidence element, the second input of which is the input of the correction unit, the output is the output of the correction unit, and the input of the differentiating circuit is the input of gating pulses. 3. A device according to claim 1, characterized in that the correction unit is executed in the form of a three-input (L coincidence element, the output of which is the output of the correction block, and the first input is the input of the correction unit, while the output of the three-input coincidence element is connected through a waiting a multivibrator with a second input of a three-input element, Od the third input of which is an input of 004 gate pulses. 00 cx

Description

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..Jjfcmpov. 1 The invention relates to color television and can be used in color TV decoders and video monitoring devices. It is known a color synchronization device, which contains a series-connected resonant amplifier, an envelope detector, a switch, two integrating circuits, a co-parator, and a counter trigger P. This device has insufficient noise immunity, since, due to the high color ratio of the color synchronization signals, the constants are At the outputs of the integrating circuits, much less peak values of the signals are obtained. The closest to the invention and the technical essence is the color synchronization device. This includes a color synchronization signal detector with a switched demodulation characteristic, the output of which is connected to a trigger input, the first input of which is a chrominance input, the second input is an input of gating pulses. The trigger output is connected to the third input of the frequency detector. The frequency detector provides the ability to change the sign of the slope of the amplitude-frequency characteristic (AFC) of the device. The frequency detector input, which controls the sign of the frequency response slope, is connected to the trigger output. When receiving a protective subcarrier packet, the frequency detector generates an impulse that triggers a trigger. The trigger inverts the frequency response of the frequency detector. The trigger on the next line is triggered only if the frequency of the protective subcarrier packet changes (as in the Seckam signal). In this case, the frequency detector generates a pulse of the same polarity on each line, causing a switching trigger, at the output of which the square signal of a half-frequency frequency controls the electronic commutator of the chromaticity channel. When a sinusoidal signal is taken instead of a signal from La Sacame. Interference (signal PAL) with a constant frequency, after the first triggering of the trigger, the system stops, as the frequency detector ne 882 switches off and no longer reacts to signals with this frequency 2. However, in the known device, the counting trigger is controlled on each line directly by the demodulated busy subcarrier packet. Therefore, the coincidental coincidence of these packets (this occurs when playing a magnetic recording and as a result of signal reflections from an airplane flying by) causes the device to fail on these lines and appears on the image as narrow horizontal uncolored bands. The purpose of the invention is to ensure the stable operation of the color-synchronization device when the identification signals fall out. The goal is achieved by the fact that a color burst device containing a frequency detector with a switched demodulation characteristic, the first input of which is an input of a color signal, the second input is an input of strobe pulses; and the third input is connected to the output of a counting trigger, serially connected capacitive storage and a correction unit are connected between one of the installation inputs of the counting trigger and a correction unit, the counting input of the counting trigger is a horizontal frequency trigger input. The correction unit is made in the form of a serially connected differentiating circuit, a pulse polarity selector and a coincidence element, the second input of which is the input of the correction unit, the output is the output of the correction unit, and the input of the differentiating circuit is the input of gating pulses. The correction block is made in the form of a three-input coincidence element, the output of which is the output of the correction block, and the first input is the input of the correction block, while the output of the three-input coincidence element is connected through a waiting multivibrator to the second input of the three-input coincidence element, the third input of which is the gate pulses. Fig. 1 shows a structural electrical circuit of a color locking device} in Fig. 2 - time diagrams of signals, Fig. 3 and 4 are structural circuit diagrams of embodiments of the correction block.

The color lock device (1.3 and 4) contains a frequency detector 1 with switched demodulation characteristic, capacitive drive 2, correction unit 3, counting trigger 4, coincidence element 5, differentiating circuit 6, pulse polarity selector 7, three-input. - Element B matches and standby multivibrator 9.

Frequency detector 1 can be performed by any known scheme: in the form of a resonant cascade with an amplitude detector, an analog multiplier with a phase-shifting circuit, a phase discriminator, etc. Frequency detector 1 provides for the possibility of inverting its frequency response by any known method: switching the polarity of the output signal, switching the phase-shifting circuit, etc.

Capacitive drive 2 can also be performed by any known scheme. Unlike an integrating circuit, a capacitive drive is an active circuit containing a storage capacitor and control keys opened by pulses from frequency detector 1. Since the time constant of charging the bone accumulator is significantly less than the constant time of discharge, it provides accumulation of charge even with a significant porosity of pulses.

The device works as follows.

The input of the frequency detector 1 (Fig. 1) receives a color subcarrier, extracted from the full signal to Sekaam (Fig. 2a). The strobe pulses (Fig. 26) unlock the frequency detector 1 for the duration of the passage of the identification signals. The counting input of the counting trigger 4 receives trigger pulses of the horizontal frequency (Fig. 2b), switching the counting trigger 4 and simultaneously inverting the frequency response of the frequency detector 1. In this case, two states are possible: the phase of the counting trigger 4 is correct and correction is not required: the phase of the counting Trigger 4 is incorrect and requires correction of its operation.

Since the subcarrier identification packets in the SECAM signal have two different frequency lines alternating in rows, and the frequency response of the frequency detector 1 each line is inverted, the polarity of the demodulated pulses at its output is the same on all the rows (Figure 2), and the polarity of these pulses depends on whether the phase of the counting trigger is correct or incorrect 4.

Let at the wrong phase of the counting trigger 4 pulses on. the output of frequency detector 1 will be positive, and with the correct phase negative. Then, depending on the phase of operation of the counting trigger 4, the voltage produced by the capacitive drive 2 will be either positive or negative. (It is possible; such a performance of a capacitive storage device 2- when its initial voltage is equal to half the supply voltage. Then, as a result of the accumulation, the output voltage will either tend to zero or to the value of the voltage of the power source). With the wrong phase of the counting trigger 4 (fig.2d), the voltage at the output of the capacitive storage 2 (fig.2e) each line will increase by a step determined by the constant charging time of the storage capacitor. When this voltage exceeds c ... a certain trigger level (time t is in Fig. 2e), correction unit 3 will provide a correction for the phase of the counting trigger 4. In the simplest case, correction unit 3 is executed in the form of a Comparator, which is unlocked when The output of the capacitive storage device 2 exceeds a predetermined threshold. Block 3 transfers counting trigger 4 to a static state. In this case, the inversion control of the frequency response of the frequency detector is stopped, and the storage capacitor of the capacitive storage device 2 is gradually discharged. Counting trigger 4 starts up again with an arbitrary initial phase. The process repeats until the phase of operation of the counting trigger 4 becomes correct. If, instead of a signal, a SECAM is assumed to have a sinusoidal interference. 5 whose frequency is constant (for example, the signal Pal), the pulses at the output of frequency detector 1 have, by inverting its frequency response, alternating polarity (Fig. 2g). At this accumulation of voltage does not occur. The device is insensitive to sinusoidal interference. When receiving a signal from Seka and dropping individual recognition signals, the device also does not interfere due to inertia of capacitive storage 2, Since the capacitive storage device 2 has a high inertia and the output voltage cannot decrease immediately after the correction, the next false correction is possible on the next line . However, circuit solutions are possible, eliminating the possibility of false correction. In FIG. 3, the correction unit 3 is executed as a coincidence element 5, the first input of which is connected to the output of the capacitive storage device 2, and gating pulses are fed to the second input through the serially connected differentiating circuit 6 and selector 7. The selector 7 polarity of the pulses passes to the input of the element 5 matches only emissions (Fig.2z) from the differentiated decline of the gating pulses. If the correction occurs at time ij (Figure 2e}, then the phase of the counting trigger 4 changes and at time 2, the capacitive drive 2 receives a negative pulse (Figure 2d), which causes it to discharge to a level less than the response level of element 5 coincidences (Fig. 2e). Therefore, when the second input of the element 5 matches the ejection from the decay of the strobe pulse, correction cannot occur, and the counting trigger 4 continues to work with the correct phase. In Fig. 4, the correction block 3 is executed as a three-input element 8 matches, exit to The first is connected to the installation input of the counting trigger 4, the first input is connected to the output of capacitance-55. Gates of the self-consistent drive 2, gates to the third input are given, but the gates are much longer than the constant input ida coincidence element 8. Therefore, the absence of separate secondary inputs is switched on by a standby multivibrator.9 False correction is eliminated, because standby multivibrator 9 is started at the time of the phase correction of the counting trigger 4 pulses from the output of three odovogo coincidence element 8 and to move it to its original state (this interval is selected greater than the duration of one line) supports it in a locked state. In the proposed device, not only the correction of the phase of the counting trigger 4 is ensured, but also the possibility of the noise-resistant inclusion of the chromaticity channel. After the correction time (tj of Fig. 2), the pulses at the output of the frequency detector 1 become negative and the sign of the voltage accumulated in the capacitive storage device 2 changes. This voltage can be applied to the input of a color switch, made in the form of the simplest threshold amplifier stage. The chroma switch works only when the signal is received by the SECAM and the correct phase of operation of the counting trigger 4. Thus, the invention retains the advantages of the known device - high protection from sinusoidal interference, and ensures stable operation of the chromaticity channel when separate identification signals occur, unlike the well-known devices, the counting trigger is controlled by string pulses. Therefore, when the individual identification signals fall out, the trigger continues to operate. The voltage accumulation process in capacitive storage 2 is also not disturbed, it is just that the accumulation transient time is increased by the number of lines where there are no recognition signals that the viewer will not notice, since this process occurs immediately after turning on the TV. After reaching the threshold voltage in the capacitive storage, the loss of individual identification signals also does not affect the image quality and reliability of color synchronization. knowledge pulses does not change either the sign or the magnitude of the accumulated voltage, i.e. does not cause a false shutdown of the channel, and the loss of identification signals does not disrupt the operation of the counting trigger, since it is controlled by counting pulses on the counting input.

FIG. 2

Claims (3)

1. A COLOR SYNCHRONIZATION DEVICE containing a frequency detector with a switched demodulation characteristic, the first input of which is an input of a color signal, the second input is an input of strobe pulses, and the third input is connected to the output of the count. trigger, characterized in that, in order to ensure synchronization upon the occurrence of identification signals, between the output of the frequency detector and one of the installation inputs of the counting trigger are included * series-connected capacitive storage and a correction unit, and the counting input of the counting trigger is an input of line frequency triggering pulses . 2. The device according to claim 1, characterized in that the correction unit is made in the form of series-connected differentiating circuit, pulse polarity selector and coincidence element, the second input of which is the input of the correction unit, the output is the output of the correction unit, and the input of the differentiating circuit is the input of the strobe impulses. 3. The device according to claim 1, characterized in that the correction unit is made in the form of a three-input matching element, the output of which is the output of the correction unit, and the first input is the input of the correction unit, while the output of the three-input matching element is connected through the standby multivibrator to the second input of the three-input element, the third input of which is the input of the strobe pulses. figure 1