SU1169198A1 - Colour synchronization device - Google Patents

Description

The invention relates to a technique of color television, in particular to the decoding devices of color TVs and video monitoring devices.

The purpose of the invention is to increase the noise immunity of the device to sinusoidal signals.

FIG. 1 shows the structural electrical circuit of the device, in FIG. 2 shows the signal plots in the circuit; FIG. 3 - minimum limit characteristic; in fig. 4 - execution of the correction circuit and switching on the color channel.

The color synchronization device contains an amplitude limiter 1, a resonant circuit 12, an amplitude detector 3, an electronic switch 4, a counting trigger 5, peak detectors 6 and 7, a limiter 8 at the minimum, a differential amplifier 9 and a block 10 for triggering the trigger and turning on the color channel.

Block 10 correction and inclusion (Fig. 4) contains two threshold blocks 11 and 12 and the Executive unit 13.

The device works as follows.

The input of the device receives a signal of the color subcarrier, taken from the point of the decoder circuit before or after the high-frequency predistortion correction circuit. To ensure the selection of color synchronization signals, the channel is unlocked with a gating pulse by any known method. In particular, in FIG. 1, the unlocking strobe pulses are applied to the amplitude detector 3. The radio pulses are allocated to the resonant circuit 2 (Fig. 2 a) with different amplitudes in lines K and B. The amplitude detector 3 highlights their envelope (Fig. 2 B), the electronic switch 4 separates them in two channels (Fig. 2 8 and g). At the outputs of the peak detectors 6 and 7, voltage increments equal to the span of 3 pulses detected in the amplitude detector are obtained (lines g and 5 in Fig. 2 V and 2). The increments of the voltage arrive at the minimum limiter 8, the amplitude characteristic of which is shown in FIG. 3. When the difference signal potentsialovvhodnyh smaller than the threshold value and the _lane exit signal

198 2

limiter 8 does not pass. The threshold voltage is chosen such that when the signal voltage difference at the SECAM limiter 8 (di _SG) outputs obtained

greater than the threshold value, the signal passes to the output of block 8 and triggers the differential amplifier 9. If the phase of the counting trigger 5 is wrong, the polarity of the voltage at the output of the differential amplifier 9 is such that the correction and switch-on circuit of the 10 produces a correction signal the input of the counting trigger 5 and changing its phase. After that, the sign of the difference signal at the input of the differential amplifier 9 changes, the voltage at its output changes the polarity and the correction and switching circuit

. forms a potential that includes a color channel.

When a sinusoidal interference is received (a PAL signal), the pulses (Fig. 2ε) on adjacent lines are equal in amplitude, since they are formed by the same circuit 2. After passing the electronic switch 4, the pulses in the two channels may differ somewhat in amplitude. for the incomplete identity of his shoulders, however, this difference is significantly less than the threshold value and _is p and does not cause the device to operate.

The threshold unit 11 is triggered when the voltage at the input of the circuit exceeds the reference value C,. Then the voltage E ^ _{pr <} is formed at the first output of the circuit _. When the sign of the input voltage changes and it exceeds the voltage ϋ ₄ , a signal appears at the output of the threshold unit 12, which through the executive unit 13 enters the installation input of the counting trigger 5 and changes its phase of operation. The execution blrk can be executed, for example, in the form of a key, when closed, the potential corresponding to a logical zero is maintained at the installation input of the counting flip-flop 5.

. Improving the resistance to sinusoidal interference in the proposed device is achieved by introducing into its composition of peak detectors and limiter

3 1169198 4

at a minimum. This ensures reliable operation of the device when the SECAM signal is received, since the difference signal, whose amplitude is determined by the frequencies of the unmodulated 5 subcarriers, passes through a minimum limiter, the threshold of which is specifically designed for this. When receiving a sinusoidal interference differential signal caused by the non-identity of the shoulders of the switch, does not pass through the limiter to a minimum,. Because g. · It does not undergo the accumulation process, and cannot exceed the difference of the amplitudes of the pulses at the inputs of the peak detectors.

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Claims (2)

1. A COLOR SYNCHRONIZATION DEVICE containing a series-connected amplitude limiter, a resonant circuit, an amplitude detector, the control input of which is the input of gating pulses, an electronic switch, the control input of which is connected to the output of the counting trigger, the counting input of which is the input of horizontal pulses, a differential amplifier, output which is connected to the input of the trigger correction block and turning on the channel Fm.1 the first output of which is connected to the installation input of the counting trigger, and the second is the output of the device, characterized in that, in order to increase the noise immunity to sinusoidal signals, two peak detectors and a minimum limiter are introduced, while the inputs of the peak detectors are connected to the corresponding outputs of the electronic switch, and the outputs are connected to the corresponding inputs of the minimum limiter, the outputs of which are connected to the inputs of the differential amplifier. 2, The device of clause .1, which is based on the fact that the trigger correction and chroma channel triggering block contains two threshold blocks, the inputs of which are connected to the outputs of the differential amplifier, and the outputs, respectively, to the control voltage output and through the execution unit counting trigger. <0 1169198 1 11