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The dipole is the simplest type of antenna from a theoretical point of view. [1] Most commonly it consists of two conductors of equal length oriented end-to-end with the feedline connected between them. [8][9] Dipoles are frequently used as resonant antennas.
Near field: This dipole pattern shows a magnetic field B in red. The potential energy momentarily stored in this magnetic field is indicative of the reactive near field. Far field: The radiation pattern can extend into the far field, where the reactive stored energy has no significant presence.
The driven element is often a dipole. The parasitic elements act as resonators and couple electromagnetically with the driven element, and serve to modify the radiation pattern of the antenna, directing the radio waves in one direction, increasing the gain of the antenna. An antenna may have more than one driven element, although the most ...
In the field of antenna design the term radiation pattern (or antenna pattern or far-field pattern) refers to the directional (angular) dependence of the strength of the radio waves from the antenna or other source. [1][2][3] Particularly in the fields of fiber optics, lasers, and integrated optics, the term radiation pattern may also be used ...
Their effect is to modify the driven element's radiation pattern. The waves from the multiple elements superpose and interfere to enhance radiation in a single direction, increasing the antenna's gain in that direction. Also called a beam antenna [4] and parasitic array, the Yagi is widely used as a directional antenna on the HF, VHF and UHF bands.
Omnidirectional radiation patterns are produced by the simplest practical antennas, monopole and dipole antennas, consisting of one or two straight rod conductors on a common axis. Antenna gain (G) is defined as antenna efficiency (e) multiplied by antenna directivity (D) which is expressed mathematically as: G = e D {\displaystyle G=eD} .
Antennas. A ferrite loopstick antenna, a small loop used for AM reception in a portable radio, consisting of a wire wound around a ferrite core; the most common type of loop antenna today. A loop antenna is a radio antenna consisting of a loop or coil of wire, tubing, or other electrical conductor, that for transmitting is usually fed by a ...
The radiation of many antennas shows a pattern of maxima or "lobes" at various angles, separated by "nulls", angles where the radiation falls to zero. This is because the radio waves emitted by different parts of the antenna typically interfere , causing maxima at angles where the radio waves arrive at distant points in phase , and zero ...