Everything about Isotropic Radiator totally explained
An
isotropic radiator is a theoretical
point source of waves which exhibits the same magnitude or properties when measured in all directions. It has no preferred direction of radiation. It radiates uniformly in all directions over a sphere centred on the source. It is a reference radiator with which other sources are compared. Isotropic radiators obey
Lambert's law.
Physics
A point radiation or sound source. At a distance, the sun is an isotropic radiator of electromagnetic radiation. The
Big Bang is another example of an isotropic radiator - the
Cosmic Microwave Background.
Antenna Theory
In antenna theory, the
isotropic radiator is a theoretical radiator having a
directivity of
0 dBi (dB relative to isotropic), which means that the radiator equally transmits (or receives) electromagnetic radiation from any arbitrary direction.
In reality, a
coherent isotropic radiator can't exist, as the isotropic radiator, with a
radiation pattern (as expressed in
spherical coordinates) of
» to be a function of
and
)
would violate the
Helmholtz Wave Equation, as derived from
Maxwell's Equations.
Although the
Sun and other
stars radiate equally in all directions, their radiation pattern doesn't violate Maxwell's equations, because radiation from a star is
incoherent. Sound waves also expand uniformly in all directions, but sound waves are
longitudinal waves and not
transverse waves.
Even though an isotropic radiator can't exist in practice, antenna directivity is usually compared to the directivity of an isotropic radiator, because the gain (which is closely related to directivity) relative to an isotropic radiator is useful in the
Friis transmission equation. The smallest directivity a radiator can have relative to an isotropic radiator, is a
Hertzian Dipole, which has 1.76 dBi.
Hairy ball theorem
Another way to explain why an isotropic radiator can't exist is by using the
hairy ball theorem, which asserts that a
continuous vector field tangent to the surface of the sphere, must fall to zero at at least one point on the sphere. This means that there's some direction for which the electric field must be zero, and hence, non-uniform.
Optics
A point source of light. The sun approximates an isotropic radiator of light. Certain munitions such as flares and chaff have isotropic radiator properties.
Sound
An isotropic radiator is a theoretical perfect speaker exhibiting equal sound volume in all directions.
Further Information
Get more info on 'Isotropic Radiator'.
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