Topic
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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02 Dec 1997
TL;DR: In this paper, a new kind of Fresnel zone plate antenna with a continuous phase structure is designed, and the authors call it a diffraction antenna, which can increase the diffraction efficiency.
Abstract: The phase Fresnel zone plate, whose diffraction efficiency is up 97%, has been made. Because of the advantages of thinner thickness, lighter weight and design flexibility, the phase Fresnel zone plate has been considered for use as a MM-wave antenna so as to increase the diffraction efficiency. However, zone plates with only four phase steps are generally made up to now, so the diffraction efficiency is only about 80%, and the highest gain is no more than 35 dB. To overcome this weakness, a new kind of Fresnel zone plate antenna with a continuous phase structure is designed, and the authors call it a diffraction antenna.
3 citations
TL;DR: In this paper, the capability of distinguishing fine details or perturbations in simple structures by means of Fresnel-domain diffraction is shown through numerical calculations, and it is shown that the greater the number of the Fresnel zones considered in the diffraction setup, the larger differentiability is reached.
3 citations
TL;DR: In this paper, the use of laser direct-write for the rapid prototyping of frequency selective Fresnel zone plate lenses is described, and a frequency selective surface which is patterned on two distinct length scales is described.
Abstract: : In this work we describe the use of laser direct-write for the rapid prototyping of frequency selective Fresnel zone plate lenses. We describe a frequency selective surface which is patterned on two distinct length scales; a smaller scale that exhibits the patterning of a traditional frequency selective surface, and a larger scale that exhibits the structure of a Fresnel zone plate. We demonstrate that laser direct-write is an ideal tool for the rapid prototyping of such spatially varying or a periodic electromagnetic structures. We present experimental results for the electromagnetic characterization of a prototype frequency selective lens fabricated using non-lithographic, laser processing.
3 citations
TL;DR: Pinhole diffraction holography has potential to generate FZP patterns that are free from aberrations and imperfections that may be present in alternative fabrication techniques, and can be used to fabricate aberration free FZPs down to a resolution of about 10 nm.
Abstract: Fresnel zone plates (FZPs) play an essential role in high spatial resolution x-ray imaging and analysis of materials in many fields. These diffractive lenses are commonly made by serial writing techniques such as electron beam or focused ion beam lithography. Here we show that pinhole diffraction holography has potential to generate FZP patterns that are free from aberrations and imperfections that may be present in alternative fabrication techniques. In this presented method, FZPs are fabricated by recording interference pattern of a spherical wave generated by diffraction through a pinhole, illuminated with coherent plane wave at extreme ultraviolet (EUV) wavelength. Fundamental and practical issues involved in formation and recording of the interference pattern are considered. It is found that resolution of the produced FZP is directly related to the diameter of the pinhole used and the pinhole size cannot be made arbitrarily small as the transmission of EUV or x-ray light through small pinholes diminishes due to poor refractive index contrast found between materials in these spectral ranges. We also find that the practical restrictions on exposure time due to the light intensity available from current sources directly imposes a limit on the number of zones that can be printed with this method. Therefore a trade-off between the resolution and the FZP diameter exists. Overall, we find that this method can be used to fabricate aberration free FZPs down to a resolution of about 10 nm.
3 citations
Patent•
24 Nov 2017
TL;DR: In this article, a locating method, a locating system and a computer readable storage medium are described. The method comprises the following steps: simultaneously receiving radio frequency signals from a sending device T by a first receiving device R1 and a second receiving deviceR2, wherein the radios frequency signals contain two or more carriers, constructing M layers of Fresnel zones of the first receiving devices, and determining the position coordinates of the target according to the intersection point of the Fresnel zone F1 and F2.
Abstract: The invention discloses a locating method, a locating system and a computer readable storage medium The method comprises the following steps: simultaneously receiving radio frequency signals from a sending device T by a first receiving device R1 and a second receiving device R2, wherein the radio frequency signals contain two or more carriers; for at least one pair of carriers in the two or more carriers, constructing M layers of Fresnel zones of the first receiving device R1; for at least one pair of carriers in the two or more carriers, constructing N layers of Fresnel zones of the second receiving device R2; determining that a target is located in a Fresnel zone F1 of the first receiving device R1 according to the radio frequency signals received by the first receiving device R1 within a period of time; determining that the target is located in a Fresnel zone F2 of the second receiving device R2 according to the radio frequency signals received by the second receiving device R2 within the corresponding period of time; determining an intersection point of the Fresnel zones F1 and F2; and determining position coordinates of the target according to the intersection point of the Fresnel zones F1 and F2
3 citations