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.
References in periodicals archive ?
However, the sieve is dotted with millions of holes precisely placed on silicon in a circular pattern that takes the place of conventional Fresnel zones.
As is well known, the use of reflectors or lenses based on diffractive Fresnel zones introduces a loss of gain and bandwidth when compared with parabolic reflectors.
For example, if both the jammer and the desired transmitter are beyond the Fresnel zone, the J/S equation is as follows:
This area, known as the Fresnel Zone, must be kept clear of all obstructions (see figure).
The length of the Fresnel zone from a uniform aperture of width D is [2D.
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.
Focus X-rays in this system must be carried out using diffractive optical X called Fresnel Zone Plate.
As shown in Figure 3, the determination as to which propagation model to use can be made by calculating the Fresnel Zone (FZ).
An algorithm is presented for assembling tiles into a variable spaced grating, the one-dimensional analog of a Fresnel zone plate.
The Fresnel zone plate is a planar device that produces lens-like focusing and imaging of electromagnetic waves.
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].