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The green ball is the radiation pattern of an isotropic antenna which radiates the same total power, and is the power density it radiates. The gain of the first antenna is . Since the directive antenna radiates the same total power within a small angle along the z axis, it can have a higher signal strength in that direction than the isotropic ...
The green sphere is the radiation pattern of an ideal isotropic antenna that radiates the same maximum signal strength as the directive antenna does. The transmitter power that would have to be applied to the isotropic antenna to radiate this much power is the EIRP.
The top shows the directive pattern of a horn antenna, the bottom shows the omnidirectional pattern of a simple vertical dipole antenna. 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 ...
The term isotropic radiation is not usually used for the radiation from an isotropic radiator because it has a different meaning in physics. In thermodynamics it refers to the electromagnetic radiation pattern which would be found in a region at thermodynamic equilibrium, as in a black thermal cavity at a constant temperature. [5]
No real antenna can produce a perfectly isotropic radiation pattern, but the isotropic radiation pattern serves as a "worst possible case" reference for comparing the degree to which other antennas, regardless of type, can project some extra radiation in a preferred direction.
The antenna gain, or power gain of an antenna is defined as the ratio of the intensity (power per unit surface area) radiated by the antenna in the direction of its maximum output, at an arbitrary distance, divided by the intensity radiated at the same distance by a hypothetical isotropic antenna which radiates equal power in all directions.
Antenna directivity is the ratio of maximum radiation intensity (power per unit surface) radiated by the antenna in the maximum direction divided by the intensity radiated by a hypothetical isotropic antenna radiating the same total power as that antenna. For example, a hypothetical antenna which had a radiated pattern of a hemisphere (1/2 ...
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: =.