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Antenna is a type of converter that converts a guided wave propagating on a transmission line into an electromagnetic wave propagating in free space or vice versa. In terms of propagation, antennas can be divided into omnidirectional antennas and directional antennas. Commonly used antennas include: indoor omni-directional ceiling antennas, directional ceiling antennas, wall-mounted antennas, and log-periodic antennas.
The indoor ceiling antenna is generally an omnidirectional antenna and must have the advantages of light weight, beautiful appearance, and easy installation. The indoor ceiling antenna seen on the market today has a lot of appearance and color, but its inner core is almost the same. Indoor ceiling antenna is a commonly used antenna.
The appearance of the indoor directional ceiling antenna is the same as that of the indoor omnidirectional ceiling antenna, which is different from the direction of the antenna's lobe. In some scenarios, it is often used for control signal leakage or unilateral coverage.
The indoor wall-mounted antenna also has the advantages of light weight, beautiful appearance, and easy installation. The internal structure of the wall-mounted antenna belongs to the air dielectric type microstrip antenna. It is mainly used for scenes that require orientation coverage, such as gymnasiums, elevators, and large conference rooms.
Several cycles of antennas are commonly used in scenes where the coverage and directionality of elevators are high, such as tunnels, subways, etc.
The gain in the antenna is an indicator of the antenna's ability to send and receive signals in a particular direction. Theoretically speaking, the gain represents the ratio of the power density of the actual antenna and the ideal radiating element at the same point in space under the condition of equal input power, and quantitatively describes the extent to which an antenna concentrates the input power. Units dBi and dBd.
The so-called polarization of the antenna means that the antenna radiation is the direction of the electric field strength formed. When the direction of the electric field intensity is perpendicular to the ground, this electric wave is called vertical polarization; when the electric field intensity is parallel to the ground, the electric wave becomes horizontal polarization.
The antenna pattern usually has two or more lobes, and the one with the largest radiation intensity is called the main lobe, and the rest of the lobes are called side lobes or side lobes. On both sides of the maximum radiation direction of the main lobe, the angle between two points where the radiation intensity is reduced by 3 dB (the power density is reduced by half) is defined as the lobe width (also called the beam width or the main lobe width or the half power angle). The narrower the lobe width, the better the directionality, and the longer the action distance, the stronger the anti-interference ability.
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