Penguin

A term from radio communcations.

One of a (theoretically infinite) number of a concentric ellipsoids of revolution which define volumes in the radiation pattern of a (usually) circular aperture.

Notes:

  1. The cross section of the first FresnelZone is circular. Subsequent FresnelZones are annular in cross section, and concentric with the first.
  2. Odd-numbered FresnelZones have relatively intense field strengths, whereas even numbered FresnelZones are nulls.
  3. FresnelZones result from diffraction by the circular aperture. (188)

Interesting read at http://www.zeuswireless.com/support/fresnel-zone.php