An antenna is a device for transmitting electromagnetic energy from the supply line to free space and vice versa. Antenna dares active element - the vibrator , an antenna may also contain passive components (one or more). To the active element of the antenna connected power line . When the alternating voltage supply line around the active element ( vibrator ) , a magnetic field. Passive antenna elements are needed for the formation of the magnetic field of a certain field of the structure and formation of the directional properties , impedance matching system " space - antenna power line .
The antennas can be categorized into three groups : linear antenna aperture antennas, surface-wave .
Linear antenna - is a regular cable or wiring system . Radiation is determined by the spread of linear antenna currents on its wires and their mutual orientation. This group includes the rhombic antenna vibrator . These antennas are often used in the square -wave range .
The next type of antennas is aperture antenna ( reflector antennas , parabolic ), these antennas are characterized by the presence of surface ( aperture ) , which is a transformation of energy propagating in the supply line to the radiation energy . Typically, the size of the aperture is significantly larger than the wavelength . Radiation of this antenna is determined by the structure of the electromagnetic field on the aperture .
And another group is a surface wave antenna . The emission of these antennas plays the role of a surface wave . It extends along the antenna part in the process of radiation. Antenna radiation is determined by the way of connecting to the power supply line and the condition of wave propagation along the antenna . Representative of this group is the antenna Uda - Yagi .
The antenna system is simply a collection of separate antennas. Application of the antenna system increases the possibility of the formation of the desired patterns . The antenna system provides a higher gain compared with a single antenna for enhancement (in level signal).
The antennas can be categorized into three groups : linear antenna aperture antennas, surface-wave .
Linear antenna - is a regular cable or wiring system . Radiation is determined by the spread of linear antenna currents on its wires and their mutual orientation. This group includes the rhombic antenna vibrator . These antennas are often used in the square -wave range .
The next type of antennas is aperture antenna ( reflector antennas , parabolic ), these antennas are characterized by the presence of surface ( aperture ) , which is a transformation of energy propagating in the supply line to the radiation energy . Typically, the size of the aperture is significantly larger than the wavelength . Radiation of this antenna is determined by the structure of the electromagnetic field on the aperture .
And another group is a surface wave antenna . The emission of these antennas plays the role of a surface wave . It extends along the antenna part in the process of radiation. Antenna radiation is determined by the way of connecting to the power supply line and the condition of wave propagation along the antenna . Representative of this group is the antenna Uda - Yagi .
The antenna system is simply a collection of separate antennas. Application of the antenna system increases the possibility of the formation of the desired patterns . The antenna system provides a higher gain compared with a single antenna for enhancement (in level signal).
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