Fresnel zone: Difference between revisions

In any wave-propagated transmission between a transmitter and receiver, some amount of the radiated wave propagates off-axis (not on the line-of-sight path between transmitter and receiver). This can then [[Reflection (physics)|reflectdeflect]] off of objects and then radiate to the receiver. However, the direct-path wave and the reflected-path wave may bearrive out of [[Phase (waves)|phase]], leading to [[destructive interference]] when the phase difference is a [[half-integer]] multiple of the [[frequency|period]]. The nth Fresnel zone is defined as the locus of points in 3D space such that a 2-segment path from the transmitter to the receiver that reflectsdeflects off a point on that surface will be nin half-wavelengths out of phase with the straight-line path. These will be ellipsoids with foci at the transmitter and receiver. In order to ensure limited interference, such transmission paths are designed with a certain clearance distance determined by a Fresnel-zone analysis.