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Module 4.4 -Electromagnetic coupling in the far-field

Electromagnetic coupling in the far-field.
Far-field E (electric) and B (magnetic) field strength decreases inversely with distance from the source, resulting in an inverse-square law for the radiated power intensity of electromagnetic radiation. By contrast, near-field E and B strength decrease more rapidly with distance: part decreases by the inverse-distance squared, the other part by an inverse cubed law, resulting in a diminished power in the parts of the electric field by an inverse fourth-power and sixth-power, respectively. The rapid drop in power contained in the near-field ensures that effects due to the near-field essentially vanish a few wavelengths away from the radiating part of the antenna.

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