SU572945A1 - Device for recording and reproducing colour signal of"secam" system on magnetic tape - Google Patents

Description

The limiter 10 and the block 11 of the matched precorrection are inserted, and the series 12 of the matched decorrese and the limiter 13 are entered into the playback channel between the output of the bandpass filter 7 and the input of the low-correction block 8.

A device for recording and reproducing a chroma signal operates as follows.

The chroma input signal after decorrection by the decorrection unit 11 and spectrum limitation by the bandpass filter 2 is limited by the limiter 10, the output of which is fed to the unit 11 of the matched precorrection, then to the converter 3 and the low-pass filter 4.

In the reproduction channel, the signal from the output of the bandpass filter 7 is fed to a block 12 of matched decorrection, after which it is limited by a limiter 13 and then passed through the pre-correction block 8.

The shape of the amplitude-frequency characteristic of block 12 of matched decorrection is determined as follows.

The heaviest frequency of the chroma signal for the playback channel is the extreme upper frequency deviation of 4.7 MHz (0.3 MHz converted), therefore the block 12 of the matched decorrection provides the selection of the lower side frequency of 4.7 MHz with the maximum signal-to-noise ratio and additional suppression of the upper side frequency of 5.3 MHz. Within the mean value of the deviation from 4 to 4.7 MHz, the magnitude of the chroma signal should not decrease by more than 4 dB, as a result, the maximum excess of the signal over the combinational components is ensured.

The introduction of the block And the matched non-correction with the inverse characteristic into the recording channel leads to the frequency dependence of the recording current of the chroma signal within the deviation also by 4 dB.

A decrease in the recording current does not reduce the signal-to-noise ratio in the playback channel, since the reduction in signal is compensated for by the filtering action of block 12 of the matched decorrection.

Therefore, the maximum amplitude-frequency characteristics of block 12 matched decorrection is determined at 4.4 MHz. The upper side frequency of 5.3 MHz at the transmission of the frequency of 4.7 MHz is attenuated by an additional 8 dB, the frequency of the reference oscillator 95.0 MHz - by 4 dB.

To further reduce the combinational components in the output signal of the reproducing channel converter 6, due to the inevitable modulation amplitude, a limiter 13 is set. After the limiter, precorrection unit 8 is installed to provide standard amplitude ratios in the chromaticity deviation region.

In the recording channel, immediately after the band-pass filter 2, a limiter 10 is installed, which maintains a constant color recording current when the chroma signal oscillates. In addition, the limiter 10 "removes

spurious amplitude modulation of the signal and attenuates the effect of impulse noise.

After the limiter, a matched precorrection unit 11 is installed, the amplitude frequency and phase-frequency characteristics of which are inverse to the characteristics of the decorrection unit 12 installed in the reproduction channel.

With an increased color image quality with respect to the signal-to-noise ratio, the proposed device provides higher definition in the luminance channel (2.5 MHz band) than in foreign video recorders with a 105 mm video block diameter.

Claims (1)

Invention Formula A device for recording and reproducing the chroma signal of the SECAM system on a MUMBIT tape containing a recording channel consisting of a series-connected decorrection unit, a band-pass filter, a converter and a low-pass filter, and a playback channel consisting of a series-connected low-pass filter, converter, a bandpass filter and a precorrection unit, a reference generator, the first and second outputs of which are connected respectively to the second inputs of the transducers of each channel, characterized by for the purpose of increasing the quality of the recording and reproducing chrominance signal in the recording channel between the output of the bandpass filter and the input transducer administered sequentially the included limiter and the matched precorrection unit, and the consistently connected decorrection unit and the terminator are inserted into the playback channel between the output of the bandpass filter and the input of the precorrection unit.