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Fresnel zone: D is the distance between the transmitter and the receiver; r is the radius of the first Fresnel zone (n=1) at point P. P is d1 away from the transmitter, and d2 away from the receiver. The concept of Fresnel zone clearance may be used to analyze interference by obstacles near the path of a radio beam. The first zone must be kept ...
Schematic illustration of the first Fresnel zone for one source-receiver pair. W indicates the width of the first Fresnel zone. The banana doughnut theory [1] [2] - also sometimes known as Born-Fréchet kernel theory, or finite-frequency theory - is a model in seismic tomography that describes the shape of the Fresnel zone along the entire ray path of a body wave.
The transition zone between these near and far field regions, extending over the distance from one to two wavelengths from the antenna, [citation needed] is the intermediate region in which both near-field and far-field effects are important. In this region, near-field behavior dies out and ceases to be important, leaving far-field effects as ...
Objects within the Fresnel zone can disturb line of sight propagation even if they do not block the geometric line between antennas. Low-powered microwave transmitters can be foiled by tree branches, or even heavy rain or snow. The presence of objects not in the direct line-of-sight can cause diffraction effects that disrupt radio transmissions.
The Puget Sound faults under the heavily populated Puget Sound region (Puget Lowland) of Washington state form a regional complex of interrelated seismogenic (earthquake-causing) geologic faults. These include (from north to south, see map) the: Devils Mountain Fault; Strawberry Point and Utsalady Point faults; Southern Whidbey Island Fault (SWIF)
To map the subduction zone, researchers at sea performed active source seismic imaging, a technique that sends sound to the ocean floor and then processes the echoes that return. The method is ...
Fresnel zone antennas belong to the category of reflector and lens antennas.Unlike traditional reflector and lens antennas, however, the focusing effect in a Fresnel zone antenna is achieved by controlling the phase shifting property of the surface and allows for flat [1] [6] or arbitrary antenna shapes. [4]
The zone plate's focusing ability is an extension of the Arago spot phenomenon caused by diffraction from an opaque disc. [2] A zone plate consists of a set of concentric rings, known as Fresnel zones, which alternate between being opaque and transparent. Light hitting the zone plate will diffract around the opaque zones.