SU815968A1 - Colour synchronization device - Google Patents

Description

(54) COLOR SYNCHRONIZATION DEVICE

I

The invention relates to color synchronization devices and can be used, for example, in color synchronization devices of color television decoders using line-by-line interlacing of chroma signals, in particular SECAM or PAL.

A color burst device is known that contains a processing unit of chroma signals, the output of which is connected to the first input of the first gating unit via a subcarrier detector, and the output of the first gating unit is connected to the minimum limiter and capacitive storage devices connected in series with the first and the second The first and second outputs of the switching trigger 1 are connected to the control inputs of the chrominance signal processing unit, respectively.

However, the known color burst device contains a large number of elements, some of which have a complex structure and are adjustable during device operation.

The purpose of the invention is to simplify the device.

The goal is achieved in that a color burst device containing a chrominance signal processing unit, the output of which is connected to the first input of the first gating unit via a subcarrier detector, and the output of the first gating unit is connected to the minimum limiter and capacitive storage device connected in series with the first and the first and second outputs of the switching trigger are connected to the second control inputs of the chroma signal processing unit, respectively, the second gating unit is inserted, the second the minimum signal limiter and the coincidence unit; the first input of the second gating unit is connected to the output of the capacitive storage, and the output of the second gating unit is connected to the installation input of the switching trigger via the second minimum signal limiter, while the first output of the switching trigger is simultaneously connected to the second the input of the second gating unit and with the first input of the coincidence unit, the second input of which is intended to supply gating pulses of the horizontal frequency, and the output of the matching unit with one with a second input of said first gating unit.

FIG. Figure 1 shows the structural electrical circuit of the device proposed; in fig. 2 - time diagrams that show his work.

The color burst device contains a chrominance signal processing unit 1, the output of which is connected via a subcarrier detector 2 to the first input of the first gating unit 3, the output of which is connected to the minimum stop 4 signals at minimum, the capacitive storage 5 and the first input of the second gating unit 6, another the input of which is connected to the first input of the coincidence unit 7, as well as the second limiter 8 of the minimum signal and the switching trigger 9.

The device works as follows.

At the counting input of the switching trigger 9, gating pulses of the horizontal frequency (Fig. 2a) are received and a sequence of switching square pulses (Fig. 2g) is formed at one of the outputs of the switching trigger 9, which is in the correct or wrong phase with respect to the output color signal . At the output of the subcarrier detector 2, a video signal is formed (Fig. 2s), which contains different polarity pulses (shaded) necessary for the color synchronization of the subcarrier detector, i.e., to align the operation of the chrominance signal with the input color signal. In the SECAM system, multipolar pulses are obtained by detecting subcarrier protection packets transmitted at the rear pads of horizontal sync pulses and having different frequency values on consecutive lines (4406 kHz and 4250 kHz) In the PAL system, these pulses are obtained as a result of amplitude synchronous detection of the "pods of the color subcarrier" available on consecutive phase lines differing by 90 °. These pulses have a short duration and, in the case of the SECAM system, a small amplitude, which makes the horizontal color synchronization system not sufficiently robust.

For a significant increase in noise immunity in the proposed device. synchronized color burst filtering is used.

The multipolar pulses from the output of the subcarrier detector 2 are extracted by the first gating unit 3, which is controlled by the pulses of the half-line frequency (Fig. 26). At the output of the first gating unit 3, a sequence of unipolar pulses of a semi-line frequency is formed (Fig. 2g), and their polarity depends on the position of the gating pulses according to

relation to the signal. After passing through the first signal limiter 4 at a minimum, eliminating interference caused by the detection of noise and inaccuracy of the subcarrier detector, the pulses go to capacitive storage 5, where a stepwise voltage rise occurs (Fig. 2e). Using the second gating unit 6, gating and controlling a pulse of a semi-line frequency (Fig. 2 d), a sequence of pulses of a semi-line frequency is formed, having an increasing amplitude (Fig. 2e). At some time point ti, a pulse reaching a sufficiently large amplitude occurs through the second signal limiter 8 at the minimum to the installation input of the switching trigger 9 and performs the required correction of the phase of the oscillations at its output (Fig. 2g).

By varying the charge time constant in capacitive storage 5, it is possible to change the storage parameters and select the required noise immunity and speed.

After establishing the correct phase of operation of the switching switch 9, the subcarrier detector 2 starts to transmit negative pulses, which naturally cause the recharge of capacitive storage 5 until a certain negative voltage is established at its output. Consequently, negative pulses are generated at the output of the second gating unit 6, which do not have any effect on the switching trigger 9. These pulses are used to control the shutdown of the chrominance signal processing unit 1 after the correct switching trigger 9 phase has been established.

The proposed color synchronization device has the advantage of simplicity, reliability and versatility compared with the known device and allows us to solve the problem of lowercase color synchronization in SECAM decoders, as well as SECAM PAL. In addition, it is easily implemented in an integrated design.

Claims (1)

Invention Formula A color burst device containing a chrominance signal processing unit, the output of which is connected to the first input of the first gating unit via a subcarrier detector, and the output of the first gating unit is connected to the minimum and capacitive storage devices connected in series with the first signal limiter and to the first and second control inputs The chroma signal processing unit is connected to the first and second outputs of the switching trigger, respectively, characterized in that, in order to simplify the device, the second gating lock second