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Fresnel zone

About: Fresnel zone is a research topic. Over the lifetime, 2337 publications have been published within this topic receiving 37650 citations.


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Proceedings ArticleDOI
05 Jul 2022
TL;DR: In this article , the problem of field spreading when the focal length becomes more than the aperture size (D) in the fresnel zone wireless power transfer (WPT) is addressed at 2.45 GHz frequency of operation.
Abstract: In this article the problem of field spreading when the focal length $(z_{0}$) becomes more than the aperture size (D) in the fresnel zone wireless power transfer (WPT) is addressed at 2.45 GHz frequency of operation. One of the solution is to have the $ z_{0}\approx$D. However, the distance of WPT can be meters or Kms and building the D so large is not practically and economically feasible. This can be achieved with the use of repeater system, i.e, the lens kept at the focus of the previous lens. A comparison is made with the conventional WPT in the Fresnel zone with one lens and repeater system with more than one lens and the efficiency of power transfer is compared. The best part of this repeater system is with a very small receiver size (D RX = 3 cm), an efficiency of 19% (with 2 lens and always the authors are talking about the RF-RF efficiency) is achieved at 14.82 m. Also, with the increase in the repeaters, the efficiency can go upto 97% theoretically. For practical implementation the reflections from the ground and the losses from the fabricated lens have to be taken. The future work will be to design Fresnel lens with the unit cells tuned for the required amplitude and phase. In future the repeater system using Fresnel lens can help achieve higher efficiency with lower size of receiver antenna aperture, thus making practical implementation of Fresnel WPT more efficient replacing the overhead transmission cables for low duty machines and sensors.
Journal ArticleDOI
TL;DR: In this paper, the dispersive characteristics of a Ta film one-dimensional Fresnel zone plate (FZP) measured using synchrotron radiation as a light source were investigated.
Abstract: This paper presents the dispersive characteristics of a Ta film one-dimensional Fresnel zone plate (FZP) measured using synchrotron radiation as a light source. Spectral spatial distributions of the FZP linear monochromator output beam are recorded on an X-ray film. The observed distributions are well explained by the FZP's chromatic aberration. The spectral bandwidth of the monochromator output beam decreases proportional to the slit width and saturates at approximately the value limited by the size of the focused image of the synchrotron radiation source.
Journal ArticleDOI
TL;DR: In this article, the validity of the heuristic criteria (HC) of geometric optics and of the geometric theory of diffraction (GTD), suggested in (2-7, 13, 14) and based on identifying the physical volume occupied by the ray with the Fresnel volume (FV) introduced in these papers (i.e., the envelope of the first Fresnel zone), are analyzed.
Abstract: The heuristic criteria (HC) of validity of geometric optics (GO) and of the geometric theory of diffraction (GTD), suggested in (2-7, 13, 14) and based on identifying the physical volume occupied by the ray with the Fresnel volume (FV) introduced in these papers (i.e., the envelope of the first Fresnel zone), are analyzed. Numerous examples of HC invalidity are given, as well as the reasons. In particular, HC provide an incorrect answer for all GO problems with caustics, since in these problems there always exists a ray, whose FV is nonlocal and covers the FV of other rays. The HC are shown to be unsuitable for multiple ray GTD problems, as well as for the simplest problems of diffraction of a cylindrical wave by a half-plane and of a plane wave by a curved half-plane.
Proceedings ArticleDOI
01 Oct 1974
TL;DR: In this paper, the power transfer efficiency between two elliptical antennas in the Fresnel zone is investigated experimentally, where pyramidal horns in the foci of the ellipsoids enable an optimum phase illumination.
Abstract: The power transfer efficiency(ratio of received to transmitted power) between two elliptical antennas in the Fresnel zone is investigated experimentally. The design procedure for an optimum power transfer system is analyzed. Pyramidal horns in the foci of the ellipsoids enable an optimum phase illumination. Deviations from a Gaussian amplitude illumination (which is close to the optimum) cause a significant decrease of the efficiency, which however is still larger than it would be for a guided or a free path transmission in the far-field of two antennas.

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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202326
202249
202137
202052
201965
201878