Radio - Wave Radiation

　　Radio - wave radiation is the process by which antennas emit electromagnetic waves into the surrounding space. Understanding this process is fundamental for the design and operation of communication systems.

　　When an alternating current is applied to an antenna, it creates an oscillating electric field and a magnetic field around the antenna. These two fields are perpendicular to each other and also perpendicular to the direction of wave propagation. The combination of these fields forms an electromagnetic wave that radiates away from the antenna.

　　The radiation pattern of an antenna describes how the power is distributed in the space around the antenna. Different types of antennas have different radiation patterns. For example, an isotropic antenna, which is a theoretical antenna that radiates equally in all directions, has a spherical radiation pattern. In reality, most antennas are designed to have a non - isotropic radiation pattern to focus the radiation in a particular direction or directions. A directional antenna, such as a parabolic dish antenna, has a highly concentrated radiation pattern. The parabolic reflector of the dish antenna focuses the radio waves in a narrow beam, which is useful for long - distance communication and high - gain applications.

　　The frequency of the radio - wave radiation also affects its characteristics. Lower - frequency radio waves can travel longer distances and can penetrate through obstacles more easily. They are often used for applications such as AM radio broadcasting and long - range communication. Higher - frequency radio waves, on the other hand, have a shorter wavelength and can carry more information. They are used in applications like mobile communication, satellite communication, and Wi - Fi, but they are more easily absorbed by obstacles and have a shorter range.