The principle of modern radio communication. Principles of radio and television
What is the principle of radio? To begin with, for its implementation it is necessary to have two devices: a receiver and a transmitter of electromagnetic and sound waves.
Principles of communication
Simple devices that are needed for work, created in 1886 G. Hertz. The principle of radio communication is based on the classical laws of physics. If you cut into two halves and connect a high-voltage transformer to the segments, an alternating (pulsating) current will arise between them, and an electromagnetic field will appear around it. The wire in this case is considered both as a transmitter and as a transmitting antenna.
The principle of radio communication is based on the characteristics of the electromagnetic field. Since waves are necessary for its propagation, it can be caught at a considerable distance with the help of a receiver.Two pieces of metal wire, parallel to the transmitting antenna, act in its role. Since the wave energy will propagate in different directions, and the receiver manages to capture only a part of it, in the airspace the sparks are small. But in the dark they can be seen even without optical devices.
Features of use
The principles of radio communication are based on transmitting devices developed by Hertz, but are only suitable for non-essential distances. This limitation is explained by the use of insignificant radio wave power. In order to cope with this problem, a high-frequency generator was created. With it, radio waves could spread over long distances.
Radio telephone circuit
Consider the basic principles of radio communications and examples of their practical use. In modern transmitter there is a high-frequency generator to create the necessary radiation power. It forms the carrier frequency used by the receiver for tuning. The modern transmitter has a modulator. It is a device that changes the amplitude or frequency of the wave in sync with the music or voice. An obligatory element of the transmitter is the transmitting antenna.
The easiest to read is amplitude modulation. There is a constant amplitude for the high-frequency oscillations that the generator creates. With the help of a modulator, it is changed “in the form” of a low-frequency signal coming from a microphone. The modulated signal arrives at the receiving antenna as waves with a non-constant amplitude.
The principle of radio communication is also characterized by demodulation. After capturing the receiving antenna waves, the signal is separated from one transmitter, which operates at a frequency selected as a carrier value. For carrying out such transformations applied tuning receiving circuit. The signal that is allocated from one transmitter enters the demodulator. In this device, there is a separation of low-frequency oscillations from a high-frequency signal. Then he enters the loudspeaker or headphones.
Considering the principles of radio communication, we note that the waves have different ranges. At present, medium, superlong, short, long, and also ultrashort radio waves are used.They are widely used in various fields of electronics:
- radio communication;
- radio intelligence;
The principle of modern radio communications involves the transformation of sound vibrations into electrical types using a microphone. The difficulty of transmitting such a signal is that high-frequency oscillations are required for radio communications, and sound waves have a low frequency. To solve the problem using powerful antennas. For audio frequency, the overlapping of vibrations is carried out so as to carry the signal over significant distances.
Modern principles of radio communication and television are based on a radio transmitting device. It has a high frequency generator that converts a constant voltage into high frequency harmonic oscillations. The carrier frequency must be constant.
The principles of radio communications and television suggest a certain structure of the generator. It converts the received messages into an electrical signal, which is used for the modulation process of a constant frequency. The choice of such a device is based on the physical nature of the transmitted signal. In the case of sound, a microphone is used for this,For transmission of images used transmitting television tube. A modulator is necessary for carrying out the process of converting a high frequency signal to the value that corresponds to the sound signal with the transmitted information. One or two stages are also used to amplify the modulated signal. The radiating antenna is designed to emit electromagnetic waves into the surrounding space.
A radio transmitter is used to receive information that is transmitted through electromagnetic waves emanating from a transmitting antenna of a modern radio transmitter. This device assumes the following basic elements:
- Receiving antenna, which is needed to capture electromagnetic waves. Here systematically arise modulated forced oscillations that are excited by various radio stations.
- The resonant circuit is tuned to a specific frequency, which is considered to be a useful signal.
- The detector stage is necessary for the pre-formation of the amplified modulated high-frequency signal, as well as the extraction of the modulating signal from it, which carries the transmitted information.
Detection is the opposite of modulation.The detectors are semiconductor devices and electron tubes, which have nonlinear characteristics. Modeling and detection are the main processes that contribute to the transmission and reception of sound and images, that is, they are associated with the transmission of a television image and sound signal.