Difference between revisions of "Fresnel Zone"
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Fresnel Zone
</dt>
Any one of the array of concentric surfaces in space between transmitter
and receiver (or between radar antenna and target) over
which the increase in distance over the straight line path is equal to some
multiple of one-half wavelength. Also called half-period zone. See interference
region.
</dd>
''Outside of rather unusual multipath transmission of radio energy in the
free atmosphere, Fresnel zones are of importance primarily in studying the
interference lobes produced by the interaction of a direct and a
surface-reflected wave. Thus, for a given path, reflected radio energy
arriving at the receiver from any point along any of the surface Fresnel zones
will be some multiple of 180� out of phase with the direct wave, thereby
producing destructive or constructive interference as the multiple is odd or
even, respectively.
</dd>
References
This article is based on NASA's Dictionary of Technical Terms for Aerospace Use