Antenna working principle

- Nov 01, 2017 -

When the conductor through the high-frequency current, in its surrounding space will produce electric field and magnetic field. According to the distribution of electromagnetic field in space, can be divided into near, middle, far. Let R be the distance of the space from the conductor, in the region when the area near the area, in the area of the electromagnetic field and the conductor in the current and voltage are closely linked.

In the region called the far area, in which the electromagnetic field can leave the conductor to the space propagation, its change relative to the current on the conductor voltage will lag for a period of time, then the electromagnetic wave has been propagated with the current on the wire, Voltage has a direct contact, and this area of the electromagnetic field is called the radiation field.

It must be pointed out that when the length L of the conductor is much smaller than the wavelength λ, the radiation is very weak; when the length L of the wire is increased to be comparable to the wavelength, the current on the wire will be greatly increased, and thus strong radiation can be formed. 

The transmitting antenna is the use of this nature of the radiation field, so that the transmitted signal through the launch antenna can be fully to the space radiation. How can a conductor become an effective radiator system? Here we first analyze the transmission line on the situation in the parallel line of the transmission line in order to make only the energy transmission without radiation, must ensure that the two-line structure symmetry, the corresponding line on the line size and direction of the opposite, and the distance between the two lines "Π. To make the electromagnetic field can be effectively radiated out, it is necessary to destroy the transmission line of this symmetry, such as the use of the two conductors to a certain angle, or to remove one side of the method, can make the conductor symmetry damage and produce radiation.

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