Fresnel zone

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

Formation of the Reflected and Refracted S-Polarized Electromagnetic Waves in the Fresnel Problem from the Viewpoint of Molecular Optics

Abstract: Scattering elements of the medium are point electric and magnetic dipoles. The medium consists of planeparallel electric and magnetic dipole monolayers. The fields of the dipoles are completely taken into account. The field within the medium and the reflected one are calculated. The microscopic analysis of the extinction theorem is conducted. Expressions for Fresnel coefficients are obtained. The mechanism of rotation of the magnetic field polarization vector during refraction is elucidated. A reason for the absence of the expression for the fourth wave propagating from the medium to the interface in conventionally used interface conditions is elucidated. The possibility of obtaining media with unity and zero refractive indices is substantiated.

Моделирование электромагнитного поля излучающей апертуры

Abstract: The article is devoted to the issues of numerical calculation of the characteristics of the electromagnetic field of radiating apertures. Тhe radiating aperture is a universal electrodynamic model used in the analysis of a special class of antennas, in particular, mirror and horn antennas, in the study of diffraction phenomena, in the planning of radio wave propagation paths, and when solving problems of wireless transmission of electric energy at a distance. The structure of the electromagnetic field of a radiating aperture in the intermediate and far zones is of the greatest interest according to the needs of practice. However, the theoretical solutions of these problems are usually difficult to obtain, except for some special cases related to the far zone. This leads to the development of appropriate computational models. This paper is aimed at generalization and systematization of experience in developing software for the simulation of electromagnetic field characteristics of radiating apertures in the intermediate and far zones. This paper considers an approach to developing a computational model of a radiating aperture that may be used to calculate the characteristics of electromagnetic field in the intermediate and far zones. Examples of results obtained for circular and ring apertures describing the structure of their electromagnetic field are given. Examples of flight diagrams of a circular aperture are given. The effect of “searchlight” localization of the electromagnetic field in the intermediate zone of a circular emitting aperture is demonstrated. The effect of mutual compensation of neighbouring Fresnel zones using the circular emitting aperture model is demonstrated. A program was developed for calculating the characteristics of the electromagnetic field of radiating holes in the intermediate and far zones. The results can also be used as illustration material for teaching the academic disciplines “Electrodynamics and radio wave propagation” and “Microwave devices and antennas”.

Statistical Gain Characteristics of Radar Antennas at Very Short Fresnel Zone Distances

Abstract: This paper extends the existing knowledge of statistical gain characteristics of radar antennas to include very short Fresnel zone ranges. The data indicate that the median gain and the standard deviation remain essentially the same as those observed in the Fraunhofer zone until the range begins to approach the physical dimensions of the antenna; however, as the range is decreased closer toward physical contact, the median gain decreases and the standard deviation increases. The site-effects tests which were conducted in the Fresnel zone indicate that the geometrical configuration of an object, the position of an object, and the clear-site median gain of an antenna help to determine the magnitude of the effects of objects on the clear-site statistical gain characteristics.

Application of the Common Reflection Arc Stack Method in Seismic Imaging of Volcanic Rocks

Abstract: In conventional stack methods, reflection events in a stack gather are generally assumed to come from the same reflective point under the ground. Whereas the reflective wavefield received is indistinguishable when its scope is less than the Fresnel's zone. Based on the characteristic of lava, we use arc to describe the reflective interface. Along the arc interface, reflections coming from the Fresnel zone are summed, so that the number of coverage is enhanced greatly. The aim of increasing the energy of signal and improving the quality of stack images is also attained. The relation between parameters of travel time and the interfaces of arc subsurface is presented. The steps of stacking are also given. Computational results show that the method of arc stacking can increase both the ratio of signal to noise in sections and the continuity of cophase axes in reflective events effectively.

A novel technique for high aspect ratio high resolution patterning of membranes

Abstract: This article presents a new technique for fabrication of high aspect ratio metal patterns on membranes. Two modifications of x‐ray lithographic techniques have been employed: simultaneous exposure of a photoresist coated on both sides of the membrane, and membrane exposure from back side using a negative tone photoresist. Both methods provide self‐aligned masks for pattern transfer into multiple metal layers. Those techniques have been used for fabrication of high aspect ratio Fresnel zone plates for hard x‐ray microscopy. 0.15 μm design rule Fresnel zone plates, with gold structure of 1.6 μm thickness have been fabricated.