radio communication

The greatest charm of radio communication is that people can transfer information by means of the fluctuation of radio waves, saving the trouble of laying wires and realizing more free, fast and barrier-free information exchange and communication. From the characteristics of radio waves, like light waves, radio waves can be reflected, refracted, diffracted and scattered. Due to the different characteristics of radio waves, some radio waves can travel on the surface of the earth, some can travel in a straight line in space, some can reflect from the atmosphere, and some can even penetrate the atmosphere and fly to distant space.

The frequency (wavelength) used for radio communication is divided into 12 frequency bands (bands), as shown in the table 1.

According to different frequencies and wavelengths, radio communication can be roughly divided into long wave communication, medium wave communication, short wave communication, ultrashort wave communication and microwave communication. Microwave communication (300 MHz ~ 300 GHz). Microwave mainly travels in a straight line, but it is greatly influenced by topography, ground objects and rain, snow and fog. Its transmission performance is stable, transmission bandwidth is wider, and the ground transmission distance is generally tens of kilometers. It can penetrate the ionosphere and spread to tens of thousands of kilometers in the air. Microwave communication is mainly used in trunk or branch wireless communication, mobile communication and satellite communication.