SU1185651A1 - Compensator of low-frequency distortions of television signal - Google Patents

Abstract

1. COMPENSATOR OF LOW-FREQUENCY DEFAULT OF A TELEVISION SIGNAL, containing a delay element, the input of which is the device input, and the output connected to the first input of the subtractor, the output of which is the output of the device and connected to the input of the sync selector, the output of which is connected to the input of the control pulse generator, and also a low-pass filter, characterized in that, in order to increase the noise immunity of the low-frequency distortion compensator of the television signal while reducing the horizontal gain interval in the television an ion signal, an adaptive amplitude detector, as well as a capture analyzer and a logic unit connected in series, are inserted, the low-pass filter is designed as a quasi-optimal filter, and the control pulse generator is designed as an inertial synchronizer; the first input of the capture analyzer is connected to the output sync selector, and the second input - with the first output of the inertial synchronizer, the second and third outputs of which are connected respectively to the second and third inputs of the logic unit, the first input One adaptive amplitude detector is connected to the device input through a quasi-optimal filter, the second, third and fourth inputs are connected to the first, second and third outputs of the logic unit, respectively, and the output to the second subtractor input. 2. A low-frequency distortion compensator for a television signal according to claim 1, wherein the adaptive amplitude detector comprises a pulse extender, the first input of which is the first input of an adaptive amplitude detector, the second input is a second input, and the output is the output of an adaptive amplitude detector and is connected with the first inputs of the first and second current sources, the second inputs of which are the third and fourth inputs of the adaptive amplitude detector, respectively, and the outputs are connected to a common bus.

Description

The invention relates to television technology and can be used as part of receiving television equipment.

The purpose of the invention is to improve the noise immunity of the compensator for low-frequency distortion of a television signal while reducing the horizontal blanking interval in a television signal.

FIG. Figure 1 shows a structural electrical circuit for compensating the low-frequency distortion of a television signal; in fig. 2 - time diagrams that show his work.

The low-frequency distortion compensator of the television signal (Fig. 1) contains a delay element 1, a quasi-optimal filter 2, an adaptive amplitude detector 3, a subtractor 4, a synchro selector 5, an inertial synchronizer 6, a capture analyzer 7, a logic unit 8, a pulse extender 9, the first current source 10 -1 and the second current source 10-2.

The compensator for low-frequency distortion of the television signal works as follows.

The television signal of negative polarity (Fig. 2a) is fed to the input of delay element 1, which compensates for the delay in the processing channel, and to the input of the processing channel — the input of quasi-optimal filter 2, which implements the algorithm for matched filtering of a rectangular pulse, and serves to effectively suppress fluctuating noise on the top of the lowercase sync pulse (FID). The value T of the main parameter of the quasi-optimal filter 2, defined as

T 1 / F,

(where FI is the frequency of the first zero transfer function) is selected from the duration of the horizontal sync pulse t to the sum of TC of the horizontal sync pulse duration and the front horizontal blanking pad (Fig. 2a) to obtain a reasonable compromise between the accuracy and noise immunity of the device. As a result of matched filtering the output of the quasi-optimal filter 2 acts the spent signal (Fig. 26), in which the amplitude of the smoothed horizontal sync pulse is much less affected by the fluctuation GOVERNMENTAL interference than in the original signal. The processed signal through the adaptive amplitude detector 3, together with the signal from the output of the delay element 1 to the first input of the subtractor 4 (Fig. 2d), is fed to its second input (Fig. 2c). As a result of compensation in the subtractor 4, a full television signal free of low frequency distortion (Fig. 2e) is output from the full television signal of the selected low-frequency distortion (Fig. 2e), output to the device and to the control channel of the adaptive amplitude detector 4, which includes a sync selector 5, an inertial synchronizer 6, a capture analyzer 7, and a logic unit 8. Synchro selector 5 by means of amplitude and time selection selects the FID (Fig. 2e) entering the input nertsionnogo synchronizer 6 and the first input capture analyzer 7. Inertial synchronizer 6 provides noise-resistant formation of coherent

0 with a TV signal of horizontal frequency pulses with different phase relations relative to the FID. From the first output of the inertial synchronizer 6, the pulses (Fig. 2g) arrive at the second input of the capture analyzer 7, which, when the pulses coincide in time (Figs. 2e and g), forms at its output a level of a logical unit confirming the presence of the capture mode, otherwise the output of the capture analyzer 7 is formed

Q level logical zero.

Depending on the type of signal at the output of the capture analyzer 7, the selection mode of the clock peak envelope changes.

If the output of the analyzer 7 capture

5 acts a single signal, then, arriving at the first input of logic unit 8, it permits the passage of pulses (Fig. 2h and 2) arriving at the second and third inputs of logic unit 8, respectively at its first and second outputs. Pulses (Fig. 2h)

 arrive at the second control input of the pulse extender 9 of the adaptive amplitude detector 3, on the first input of which a signal acts (Fig. 26) from the output of the quasi-optimal filter 2. This sets the time interval in which the maximum value of the television signal corresponding to the FID is determined.

This maximum value is stored until the next FID, before which the stored value of the television signal is reset through the first current source 10-1, activated by a pulse (Fig. 2i). The reset is performed by an amount corresponding to the a priori maximum possible change of the television signal over the period of the line due to low-frequency distortion.

In the capture mode, a logic zero level acts on the third output of the logic block, which disconnects the second current source 10-2, which at the same time has no effect on the operation of the device. If at the output of the capture analyzer 7 there is a logical zero level (no capture mode, for example, after turning on the device), then at the first

5, the output of the logical block 8 forms the level of the logical unit, at the second output the level of the logical zero, and at the third the level of the logical unit. Wherein

the pulse extender 9 determines the maximum value of the television signal over the entire line interval, the current source 10-1 is turned off, and the switched on second current source 10-2 performs a continuous reset of the voltage at the output of the pulse extender 9. Thereby, the low frequency distortion of the television signal is distinguished according to the principle of uncontrolled fixation.

In the proposed compensator for low-frequency distortion of the television signal, the inertial synchronizer 6 significantly increases the noise immunity of the processing channel and the device as a whole with respect to the prototype. In addition, since a low-frequency distortion signal is extracted from the television signal.

passing a quasi-optimal filter 2, then protection against the effects of fluctuating noise is provided. In the stationary mode, when the pulse extender 9 evaluates the amplitude only for a short interval of the control pulse, protection against impulse noise is also provided. At the same time, it is possible to work with small durations of the horizontal blanking interval, since the extension of 9 pulses is not sensitive to time errors of control pulses, and due to the presence of an uncontrolled latching mode, it is possible to effectively suppress low-frequency distortions under conditions of synchronization failure and ensures a quick entry into the stationary mode.

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Claims (2)

1. COMPENSATOR OF LOW-FREQUENCY DISTORTION OF TELEVISION SIGNAL, containing a delay element, the input of which is the input of the device, and the output is connected to the first input of the subtractor, the output of which is the output of the device and connected to the input of the sync selector, the output of which is connected to the input of the control pulse generator, as well as the lower filter frequency, characterized by the fact that the noise immunity of the frequency distortion of the cash while reducing the blanking in the television signal, introduced an adaptive amplitude detector, as well as a capture analyzer a logic block connected in series, with the aim of increasing the compensator of the low television sigintervital of the lower case into it, the low-pass filter is made in the form of a quasi-optimal filter, and the control pulse generator is made in the form of an inertial synchronizer, the first input of the capture analyzer is connected to the output of the sync selector, and the second input to the first output of the inertial synchronizer, the second and third outputs of which are connected respectively to the second and third inputs of the logic unit, the first input is adaptive of the amplitude detector through a quasi-optimal filter is connected to the input of the device, the second, third and fourth inputs are connected respectively to the first, second and third outputs of the logic unit, and the output to the second input of the subtractor. 2. Compensator of low-frequency distortion of a television signal by π. 1, characterized in that the adaptive amplitude detector contains a pulse extender, the first input of which is the first input of the adaptive amplitude detector, the second input is the second input, and the output is the output of the adaptive amplitude detector and connected to the first inputs of the first and second current sources, the second inputs of which are respectively the third and fourth inputs of the adaptive amplitude detector, and the outputs are connected to a common bus. from FIG. /