SU1197148A1 - Device for correcting distortions of reproduced frequency-modulated signal of video tape recorder - Google Patents

Abstract

The invention can be used in the magnetic recording of television programs and provides an increase in the accuracy of the automatic correction of the reproduced FM video signal of a VCR. The reproduced FM signal is fed to a corrector with an adjustable amplitude-frequency characteristic (DIRECTION) I and then through a limiter-demodulator 2, which forms an image signal, to the device output and to the envelope selection unit of the color subcarrier 3. The output voltage of this unit is proportional to the amplitude of the unmodulated color subcarrier in the comparison unit 4 is compared with the reference voltage of the source voltage reference 5. The result of the comparison is fed to the control input BACKGROUND 1 to establish the nominal voltage plitudy unmodulated color podnesupKey. To compensate for amplitude-frequency distortion when the carrier frequency changes due to a change in luminance, KRACHH 1 also receives a signal (P formed from an input FM signal passed through limiter-demodulator 6, low-pass filter § 7, separating luminance signal, paraphase DC amplifier 8 and an adjustment block 9.2 Il.

Description

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The distortion correction device of a frequency-modulated (FM) signal belongs to the recording area of television programs, is designed to compensate for amplitude-frequency distortions that occur in the recording-reproduction channel of the video signal of a video recorder, and can be used in the technique of magnetic recording color and black-and-white television programs .

The purpose of the invention is to increase the accuracy of the automatic correction of the reproduced FM signal of a VCR.

Fig. 1 shows a structural electrical circuit of a device for correcting distortion of a reproduced FM signal of a video recorder; 2 shows timing diagrams explaining the principle of operation of the device.

The device contains an adjustable amplitude-frequency characteristic (AFC) 1 equalizer, the input of which receives the reproduced FM signal, and the output is connected to the input of the first limiter, demodulator 2, connected through the envelope selector unit of the color subcarrier 3 to the first input of the comparator unit 4, the second input of which is connected to the source of the reference voltage 5, and the output is connected to the control input of the corrector with an adjustable frequency response. The device also contains a second limiter-demodulator 6, the input of which is connected to the input of the device, and the output through a low-pass filter 7 is connected to a paraphasic DC amplifier 8 with a control unit 9 connected to its outputs, the output of which is connected to the control input of the corrector 1 The output of the first demodulator limiter is the output of the device.

The device works as follows.

The reproducible FM signal is fed to the equalizer input with adjustable frequency response 1, which compensates for the amplitude-frequency distortion of the FM signal in the recording-reproduction channel, and after correction to the input of the first limiter-demodulator 2, which converts the FM signal into an image signal. The output signal of the image, which is a complete

48.2

the television signal (Fig. 2o) is fed to the output devices in the tape recorder and to the envelope selection unit of the color subcarrier 3,

located on the rear platforms lowercase damping pulses. The output voltage (U, Fig. 2 o) of this block, proportional to the amplitude of the unmodulated color subcarrier, is compared in comparison block 4 with the reference voltage from the voltage source 5.

When the amplitude deviates from the unmodulated color subcarrier (FIG.

2 &, & from the nominal value due to the decay or rise of the total frequency response of the recording-playback channel, the voltage at the output of the comparison unit 4 (and the air current proportional to the deviation of the through frequency response from the linear one. This voltage goes to the control input of the equalizer adjustable frequency response 1 and changes its frequency response so as to establish the nominal amplitude of the unmodulated color subcarrier transmitted at black level.

To compensate for amplitude frequencies

When the carrier frequency of the FM signal changes due to a change in the brightness of the transmitted image, the second limiter modulator 6 is used, the low-pass filter 7

to extract the luminance signal and the paraphase DC amplifier 8. At the input of the second limiter, the demodulator 6, a reproducible FM signal arrives, which is converted to.

a full color television signal (Fig. 28), from which a luminance signal is extracted using a low-pass filter 7. Through the paraphase DC amplifier 8 to

The adjustment unit arcs 9 are given luminance signals of opposite polarity. The magnitude and polarity of the luminance signal supplied to the control input of the equalizer with adjustable frequency response from the output of the adjusting unit 9 depends on the position of the variable resistor's motor p and the adjusting unit, which allows you to set the required signal size,

corresponding to the change in the frequency response of the recording-reproduction channel caused by the change in the carrier frequency of the FM signal.

Claims (1)

Claim The device can also operate in manual control of the frequency response without disrupting the control loop of the correction of differential distortion, for example, when recording black and white programs. For this, a constant voltage from a manual frequency response controller can be applied to the input of the comparison unit 4. Apparatus distortion correction reproduced frequency-modulated signal recorder comprising serially coupled equalizer with adjustable amplitude-frequency characteristic (AFC) of the first limiter-demodulator and ^f block allocation envelope of the color subcarrier, wherein the equalizer input with an adjustable frequency response is the input device and the output of the first ogranichitelya- a demodulator by the output of the device, the Comparison unit, the first input of which is connected to the output of the color subcarrier envelope allocation unit, the second input d, - with a reference voltage source, and the output is connected to the control input of the corrector with adjustable frequency response, characterized in that, in order to improve the accuracy of correction of the reproduced FM signal, 25 second-connected second limiter-demodulator, low-pass filter, paraphase are introduced into it a DC amplifier and an adjustment unit, the input of the second limiter30 of the demodulator connected to the input of the device, and the output of the adjustment unit connected to the control input of the corrector with adjustable frequency response. ⁱⁿ a g o Fig2 VNIIIPI Order 7634/62 Circulation 658 Subscription Branch 1ShP Patent, Uzhgorod, Project 4,