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Fresnel zone

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Fresnel zone
[freznel′]
Etymology: Augustine J. Fresnel, French physicist, 1788-1827
the region nearest the face of an ultrasound transducer. It is characterized by a highly collimated beam with great variation in ultrasound intensity and is generally the area of best image resolution. Also called near field.

Fresnel zone
in ultrasonography, the area of the sound beam between the transducer and the focal zone in which complex diffraction patterns occur.


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As the corresponding effect at the point of observation P is attributable to the central Fresnel zone at Q acting alone, there is no need to know the nature of this aniso-tropy and hence it follows that dU(P) = (i/[lambda])U(Q) exp (ikQP)/QP.
The tech rep responds, "That's good to know, but what about proper Fresnel Zone clearance?
Although the deployment was Near-Line-of-Sight (nLoS), with a partially obstructed fresnel zone, radio and radar interference at and around the airport prevented wireless systems from reliably connecting.
 
 
 
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