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Near And Far Field





NEAR FIELD

The term near-field region (also known as the '''near field''' or '''near zone''') has the following meanings with respect to different Telecommunications technologies:
  • The close-in region of an Antenna where the angular Field distribution is dependent upon the distance from the antenna.

  • In the study of diffraction and antenna design, the near field is that part of the Radiated Field that is within a small number of wavelengths of the diffracting edge or antenna.

  • In Optical Fiber Communications , the region close to a source or Aperture .


The Diffraction pattern in the near field typically differs significantly from that observed at infinity and varies with distance from the source.


FAR FIELD

The far-field region is the region outside the near-field region, where the angular Field distribution is essentially independent of distance from the source. If the source has a maximum overall dimension ''D'' that is large compared to the wavelength, the far-field region is commonly taken to exist at distances greater than 2''D''&2/λ from the source, λ being the wavelength.

For a Beam focused at infinity, the far-field region is sometimes referred to as the Fraunhofer region. Other synonyms are '''far field''', '''far zone''', and '''radiation field'''.


SEE ALSO

;Local effects



PATENTS

  • Leydorf, G. F., , Antenna near field coupling system. 1966.



REFERENCES