Antenna isotropic, what is that?

Question

i need the following answers about antenna isotropic

1. meaning

2. characteristic

3. function of each part

Answer 1

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 to/from any arbitrary direction.

In reality, a coherent isotropic radiator cannot exist, as the isotropic radiator, with a radiation pattern (as expressed in spherical coordinates) of



(note that the magnitude of this function is independent of the spherical angles  and , but it is permissible for the vector's direction, as represented by the unit vector  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 does not 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 cannot 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.