Fresnel region

Fresnel region

[frā′nel ‚rē·jən]
(electromagnetism)
The region between the near field of an antenna (close to the antenna compared to a wavelength) and the Fraunhofer region.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
This distinction disappears in the Fresnel region, where the field on the positive side of the aperture plane is unidirectional ([u.sub.s] [much less tha] [u.sub.s]) and the usual definition of irradiance as the squared magnitude of the total wave function is justified.
Thereafter, a second, similar Fresnel region sees the transformation of the plane wave front at the beam waist into one diverging at angle [Theta].
For a range R, the synthetic aperture is A = R[Theta] = R[Lambda]/D and R = DA/[Lambda] But the length of the Fresnel region for aperture A is [R.sub.D] = [A.sup.2]/[Lambda].