Fresnel zone

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

Three Dimensional Simulation of the Radiation Field Patterns Generated by an Integrated Antenna

Abstract: Simulating the electromagnetic field patterns generated by integrated antennas used in mobile phones, for example, is fundamental to understanding their transmission characteristics and thereby engineering designs that optimise the directional properties of electromagnetic propagation. Modern integrated antennas have complex three-dimensional geometry designed to optimise their performance in terms of their multi-band and multi-modal attributes. This geometry, coupled with their close proximity to other component of the device (such as the battery and Printed Circuit Board, for example) produce complex field patterns due to the scattering of the electric (and magnetic) field within a spatial domain that is the same order of scale as the wavelength. Simulating this interaction therefore requires models that are generalised and not specific to an idealised antenna geometry. In this paper we present a threedimensional model for simulating the interaction of an electromagnetic field generated by antennas whose geometry is arbitrary with complex dielectric components in the near-field, in particular, the Fresnel zone. The resulting field pattern is then taken to be a secondary source, whose far-field intensity map is computed by application of a Fourier transform. The material properties of the dielectric are taken to include variations in the relative permittivity and conductivity which are assumed to be isotropic. The evaluation of the scattered electromagnetic field is undertaken using a new approach based on a free space Green’s function to the Poisson equation whose properties are compared to the conventional Green’s function solution to the inhomogeneous Helmholtz equation. Some example simulations are provided to illustrate the approach used which include fractal antennas based on self-similar patterns. ∗Jonathan Blackledge (jonathan.blackledge@dit.ie) is the Science Foundation Ireland Stokes Professor at Dublin Institute of Technology (DIT) and Director of the Information and Communications Security Research Group. Bazar Babajanov (a.murod@mail.ru) is Assistant Professor at the Department of Mathematical Physics, Urgench State University, Uzbekistan

Nanometer-scale machining by laser ablation with a focused extreme ultraviolet laser beam

Abstract: We report the ablation of 200 nm-top wide (130 nm FWHM) trenches on PMMA photoresist by focusing the extreme ultraviolet output from a table-top capillary discharge laser with a Fresnel zone plate lens.

Off-axis Fresnel diffraction approximation

Abstract: Diffraction is analyzed for oblique propagation of light beam under a large angle. Fresnel diffraction approximation is valid provided the beam is deflected into the direction of oblique propagation, the structure of the diffraction screen is projected onto the plane perpendicular to the propagation direction, and the diffraction pattern is observed in the plane perpendicular to the propagation. The task is illustrated by the diffraction due to a circular aperture.

Fresnel Zone Plate array fabricated by maskless lithography

Abstract: This work reports the fabrication of Fresnel Zone Plates (FZP) by employing a maskless lithography tool based on direct laser writing. The target application areas in this work are to use a micro lens array (MLA) in a wavefront sensor, for optical aberrations quantification in human eye diagnostics or adaptive optical system. This last one is essential in astronomy applications in order to correct the aberrations introduced by earth atmosphere. The fabricated FZP generates illumination points with high-contrast intensity in the focal plane, which is the purpose of the wavefront sensor. This high-contrast image suggests that the employed fabrication process is well controlled and it matches the design parameters.