Results 171 to 180 of about 4,282 (222)

Fresnel Zone Plate Antenna

IETE Journal of Research, 1968
ABSTRACTThe paper describes the design of a Fresnel zone plate suitable for use as an antenna in the centimetric or lower wavelength range. It has been shown that such antennas can be fabricated by using either metal or dielectric rings. Its properties have been analysed by employing the simple methods of electromagnetic diffraction.
G. S. Sanyal, Mahendra Singh
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Fresnel zones in inhomogeneous media

The Journal of the Acoustical Society of America, 2006
A simple general expression for the width of a Fresnel zone in a smooth inhomogeneous environment is derived. In a stratified environment at long range, the general expression is shown to reduce approximately to one that is proportional to √|α|r(R−r)/f, where α is the ray stability parameter, f is the acoustic frequency, r is the range to the field ...
Irina I. Rypina, Michael G. Brown
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Acoustic Fresnel zone plate transducers

Applied Physics Letters, 1974
Experimental focal plane intensity distributions are presented for a 10-zone acoustic zone plate operating at approximately 10 MHz. The results are related to the spatial frequency response of the transducer. Some initial imaging experiments with this transducer are described along with preliminary results for an acoustic phase plate.
S. A. Farnow, B. A. Auld
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Fresnel zones for broadband data

GEOPHYSICS, 1996
For monochromatic waves, the term “Fresnel zone” is well‐defined even though different authors use different terminology. Most authors use the definition originating from optics. There, the first Fresnel zone is defined as the area of a circular hole in a screen between a light source and an observation point that produces maximum light intensity in ...
Matthias Brühl, Gijs J. O. Vermeer, Michael Kiehn   +2 more
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Other Fresnel Zone Antennas

2002
In the preceding chapters, theoretical investigations and experiments on a number of Fresnel zone antennas are presented. This chapter is intended to introduce a wider range of Fresnel zone antennas. Section 7.1 presents a theory regarding the possibility of producing single printed Fresnel lens that doubles the efficiency of the simple Fresnel lens ...
Y. Jay Guo, Stephen K. Barton
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Solid immersion Fresnel zone plate

Digital Holography & 3-D Imaging Meeting, 2015
A solid immersion Fresnel zone plate (SIFZP) is designed and its near-field imaging characteristics are analyzed using the vector angular spectrum method. Results show SIFZP can generate a high intensity and subwavelength focus.
Yaoju Zhang, Xiao Qian, Xiukai Ruan, Haiyong Zhu   +3 more
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Offset Fresnel zone plate antennas

International Journal of Satellite Communications, 1994
AbstractThe theory of offset Fresnel zone plate antennas is presented. Explicit formulae for the design of the zone boundaries for the offset Fresnel zone plate are given. Theorectical equations and numerical results for the far‐field analysis are presented.
Y. J. Guo, S. K. Barton
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The Interferometric Fresnel Zone

72nd EAGE Conference and Exhibition incorporating SPE EUROPEC 2010, 2010
We present a way to implement the virtual source (VS) method in a real scenario where a summation over all the available sources in the dataset may not be the optimal solution. Because the main contributions to the interferometric data construction come from sources at stationary locations, a target-oriented source selection could reduce artefacts ...
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A cylindrical Fresnel zone antenna

IEEE Transactions on Antennas and Propagation, 1996
A cylindrical Fresnel zone antenna as a candidate for a base station in wireless indoor LAN systems is described. An arbitrary angle-tilted fan beam in azimuth can be achieved by moving the position of the strip dipole feed at the cylinder center.
Y. Ji, M. Fujita
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Defining the Fresnel zone for broadband radiation

Physical Review E, 2002
The concept of the Fresnel zone is central to many areas of imaging. In tomographic imaging, the transverse spatial resolution can be limited by the size of the first Fresnel zone, usually defined only for monochromatic radiation. With the increasing prevalence of broadband tomographic imaging systems, a generalization of this concept is required. Here,
Jeremy, Pearce, Daniel, Mittleman
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