SU152249A1 - The method of transmission and reception of television signals - Google Patents

Description

METHOD OF TRANSMITTING AND RECEIVING TELEVISION

It was submitted on September 11, 1961 for AI 744214 / 26-9 to the Committee for Inventions and Discoveries under the Council of Ministers of the USSR

Published in the Bulletin of inventions number 24 for 1962

The known method of transmitting television signals, based on the amplitude modulation of the carrier frequency, is ineffective and allows to obtain a satisfactory quality of the transmitted image only with a high signal-to-noise ratio in the communication channel.

Other known methods of transmitting television signals, using, for example, frequency or pulse code modulation (PCM), provide enhanced noise immunity with a significant expansion of the frequency band. At the same time, the practical implementation of the aforementioned methods of transmitting television signals is very difficult and leads to the complication of transmitting and receiving equipment.

In the proposed method of transmitting and receiving television signals, the high-frequency components of the image signal are transmitted with a constant level corresponding to the maximum brightness of the image areas, and the information about the brightness of individual image areas is transmitted using pulses occupying the entire dynamic range of the transmission channel. These pulses always have a constant amplitude and frequency, equal to the odd harmonic of half the line frequency. When playing or recording images, the received signal directly affects the playback or recording device. This increases the noise immunity of the equipment and simplifies it.

FIG. 1 shows a block diagram of an apparatus for transmitting television signals according to the proposed method; in fig. 2 is a block diagram of an apparatus for receiving television signals by the proposed method.

SIGNALS

No. 152249

When reproducing television signals received by a device according to the proposed method, a television image formed by alternating dark and light dots is obtained, in a manner similar to how a tone image is reproduced on paper by typographical method (autotype).

With such a stroke-based image reproduction method, the size of the light and dark dots should vary depending on the brightness of the individual areas, while the distance between their centers is constant. If the gaps between points are small enough, when viewed from an optimal distance, individual points will not be visible and the image will be perceived as a tone formed from homogeneous surfaces of different brightness.

The frequency of the gating pulses that form the hatching image of the television image must be selected taking into account the required resolution, decomposition parameters and reproduction methods. For fast television systems (F ddr 50 Hz), the jFctp gating frequency should be chosen close to the pixel frequency. For small-frame television systems, the gating frequency should be approximately twice as high as the frequency / di. In both cases, the gating frequency / gating frequency is necessary. multiple odd harmonics of half of the line frequency so that in adjacent lines and in adjacent frames the points forming the image are shifted by the distance occupied on the line by a half of the frequency period of the strobe pulses. When these conditions are met, these points will no longer be distinguished from the normal viewing distance, and the eye of the observer will respond to the integrated brightness of individual image areas depending on the gate ratio of the gating pulses.

The principle of transmission of television signals by the proposed method is as follows. A television signal received by a conventional sensor / passes through a low-pass filter 2, where all frequencies above 0.5 e are limited. At the same time, a band-pass filter 3 separates frequency components from the TV signal in the range from 0.5 F to / d These signals are limited to a certain level by the limiter 4 and ne {: 1) through the subsequent elements of the path with a maximum amplitude given by the dynamic range of the communication channel. The frequency-limited television signal from the output of the filter 2 is fed to the transducer stage 5, where simultaneously from the generator 6 pulses are supplied, the frequency of which corresponds to the gating frequency p. , i.e., with a change in the luminance of the transmitted portion of the image. The high-frequency components of the image signal and the duration modulated gating pulses are mixed in the mixing stage 7, after which the resulting sum signal E (.yyyy is used to modulate the radio transmitter 8. In the receiver, the sum signal sum, formed by high-frequency components and gating pulses is allocated to the load of a conventional amplitude detector 9. After appropriate amplification by amplifier 10 and limiting by the limiter, a // sum signal is applied to the control electro do cathode ray tube 12, on the screen which reproduces the bar-shaped television image.

In small-frame bar-type television systems, a relaxation generator in which the pulse ratio is controlled by the television signal can be directly used to convert the television signal into a series of gates of varying duration. Low-frequency gating pulses can also be formed from triangular-shaped pulses using a restrictive device, in which the level of the limitation varies with the span of the television signal.

In fast bar television systems, in which the frequency of the image elements is several megahertz, the required gating, and the pulses can be obtained by means of a special cathode ray tube.

Subject invention

The method of transmitting and receiving television signals, characterized in that, in order to improve noise immunity and simplify the equipment, the high-frequency components of the image signal are transmitted with a constant level corresponding to the maximum brightness of the image areas, and information about all the gradations of the brightness of large parts of the image (except for levels The "black and white" is transmitted by modulating the duration of a series of high-frequency pulses with the same amplitude and a constant frequency equal to an odd harmonic field. fault line frequency, whereupon a receiver receives the signals used for modulation of the kinescope without prior decoding.

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