SU572944A1 - Device for shaping discretization signals of video signals - Google Patents

Description

one

The invention relates to the field of television and can be used in analog-to-digital video signal conversion devices, in particular, in communication channel bandwidth compression systems, retracted for digital transmission of a television signal, as well as in communication systems, telemetry and signal processing.

A device for generating video signal sampling signals is known, which contains a clock signal sensor, the output of which is connected to the input of a synchronized pulse generator, the output of the latter through a frequency divider by two is connected to one of the inputs of the phase discriminator, and its output is connected to the input of a signal sampling signal generator, the output of which is connected to the key input directly, and to the second input of the phase discriminator through the frequency divider 1.

However, in the known device, the frequency multiplier does not allow to keep the original phase of the clock signal.

In order to reduce the phase instability of the sampling signals, a reversible counter and a digital-to-analog converter are added to the proposed device for forming video signal discretization devices, with two inputs of the reversing counter connected to the outputs of the frequency divider, its third input - with the output of the frequency divider by two, and the output through the digital-analog converter connected to the third input of the phase discriminator.

The drawing shows a structural electrical circuit of the proposed device. The device contains a sensor 1 clock signal, the output of which is connected to the input of the synchronized generator 2 pulses, the output

the latter through a frequency divider 3 into two connected to one of the inputs of the phase discriminator 4, and its output is connected to the input of the generator 5 of the video signal sampling signals, the output of which is connected to the input

key 6 directly, and to the second input of phase discriminator 4 through frequency divider 7, reversible counter 8 and digital-to-analog converter 9, moreover, two inputs of reversible counter 8 are connected to the outputs of frequency divider 7, its third input - to two, and the output through a digital-to-analog converter 9 is connected to the third input of the phase discriminator 4.

The device works as follows. From the output of sensor 1 of sync 1 a, the frequency pulses of the rows are fed to the input of a synchronized generator of 2 pulses operating in synchronization mode in the presence of

pulse frequency lines and in autocoa mode

oscillations in the absence of siphro1 shziruoi; their pulses. In the auto-oscillation mode, the generator 2 generates pulses with a frequency close to the line frequency, which significantly reduces the time for the generator to enter 5 video signal sampling signals.

From the output of oscillator 2, the frequency pulses of the rows arrive at divider 3, the output impulses of which are used as auto signals for video frequency sampling at the auto-tuning of the oscillator phase 5.

The automatic frequency sweep is performed using a reversible counter 8, one input of which receives impulses from the output of the divider 7, and the arcing from the output pulses from the divider 3. In the case of equal frequencies at the inputs, the reversible counter 8 is in a steady state. With the departure of the frequency of the generator 5, depending on the sign of care in the reversible counter 8, the information in the form of a binary code is either written off or recorded.

Thus, the reverse counter B generates a control sigal in a digital form, 11 re-transforming 1, with the help of a digital-to-analog converter 9 in nanometer, which controls the frequency of the generator 5 of the video signal sampling signals. The accuracy of the automatic frequency control (AFC) is determined by the resolution of the reversing counter 8, and the capture bandwidth of the AFC is determined by the dianazone and the adjustment of the generator 5 of the video signal sampling signals.

The proposed device for generating video signal discretization signals, when used in conjunction with a system of differential pulse code modulation, reduces the frequency band of a video signal by two, seven times.

Claims (1)

1. US Patent No. 3795763, cl. 178-5.6, 1974.