first Fresnel zone

first Fresnel zone

[¦fərst frə′nel ‚zōn]
(electromagnetism)
Circular portion of a wavefront transverse to the line between an emitter and a more distant point, where the resultant disturbance is being observed, whose center is the intersection of the front with the direct ray, and whose radius is such that the shortest path from the emitter through the periphery to the receiving point is one-half wavelength longer than the direct ray.
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References in periodicals archive ?
The essence of the near shadowing phenomenon [13] is that the line of sight (LOS) or the first Fresnel zone between transmitter (Tx) and receiver (Rx) is (partially) blocked by the user itself.
In the adjacent region of Tx, the first Fresnel zone is not large enough to touch any wall of the tunnel.
The essence of the near shadowing phenomenon is that the first Fresnel zone, especially the 60% of the first Fresnel zone is blocked by the vehicle itself.
The Dividing Point 1 locates at the distance when the Maximum first Fresnel zone first touches any one of the walls:
i](x, y, z) could be touched by the Maximum first Fresnel zone.
When the large-size vehicle is in front of the transmitter (Tx), the signal power of receiver (Rx) suffers strong attenuation because the first Fresnel zone is blocked by the vehicle itself to some extent [13].
Such effect occurs when the first Fresnel zone, especially the 60% of the first Fresnel zone is blocked by the vehicle.
v]], which means even the widest part of the first Fresnel zone (the Maximum Fresnel zone plate) is touched by the vehicle.
If this distance is larger than the radius of the Maximum first Fresnel zone plate, the first Fresnel zone can be treated as almost clear.
Figure 5 depicts the schematic diagram of an arbitrary cross-sectional tunnel, Tx, Rx, LOS, and the Maximum first Fresnel zone.
The maximum radius of the first Fresnel zone is determined by
The propagation theory indicates that the free space model can be applied if the first Fresnel zone is free of any obstacles.