Fresnel zone

In optics and radio communications, a Fresnel zone (pronounced "FRA-nel Zone"), named for physicist Augustin-Jean Fresnel, is one of a (theoretically infinite) number of concentric ellipsoids of revolution which define volumes in the radiation pattern of a (usually) circular aperture. Fresnel zones result from diffraction by the circular aperture. [

where,

F_n = The nth Fresnel Zone radius in metres

d₁ = The distance of P from one end in metres

d₂ = The distance of P from the other end in metres

$lambda$ = The wavelength of the transmitted signal in metres

The cross section radius of the first Fresnel zone is the highest in the center of the RF LoS which can be calculated as:

:$r\; =\; 72.05\; sqrt$D} over {4 f

where
* "r" = radius in feet
* "D" = total distance in miles
* "f" = frequency transmitted in Gigahertz.

Or even:

:$r\; =\; 17.32\; sqrt$D} over {4 f

where
* "r" = radius in metres
* "D" = total distance in kilometres
* "f" = frequency transmitted in gigahertz.

ee also

* Augustin-Jean Fresnel
* Diversity scheme
* Fresnel integral
* Fresnel number
* Fresnel diffraction
* Microwave
* Near field
* Path loss
* Rain fade
* Weissberger's Model
* Zone plate

References

External links

* [http://wisp-router.com/wirelesscalculators.php#fresnel FEN Fresnel Zone Calculator]
* [http://www.maxstream.net/support/knowledgebase/article.php?kb=90 More Fresnel Zone Details]
* [http://www.searchanddiscovery.net/documents/geophysical/sheriff/index.htm R.E. Sherriff, Understanding the Fresnel zone]
* [http://www.tapr.org/ve3jf.dcc97.html VHF/UHF/Microwave Radio Propagation: A Primer for Digital Experimenters]