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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.
Fresnel used a zone construction method to find approximate values of K for the different zones, [3] which enabled him to make predictions that were in agreement with experimental results. The integral theorem of Kirchhoff includes the basic idea of Huygens–Fresnel principle. Kirchhoff showed that in many cases, the theorem can be ...
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 ...
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.
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 Fresnel number is a useful concept in physical optics. The Fresnel number establishes a coarse criterion to define the near and far field approximations. Essentially, if Fresnel number is small – less than roughly 1 – the beam is said to be in the far field. If Fresnel number is larger than 1, the beam is said to be near field. However ...
A long-range seismic sensor network was used during the Andean Seismic Project in Peru. A multi-hop span with a total length of 320 kilometres (200 miles) was crossed with some segments around 30 to 50 kilometers (19 to 31 miles). The goal was to connect to outlying stations to UCLA in order to receive seismic data in real time. [2]