Analysis of radiation patterns and feed illumination of the reflector antenna using the physical and geometrical optics

Reflector antennas are characterized by very high gains (30 dB and higher) and narrow main beams. They are widely used in satellite and line-of-sight microwave communications as well as in radar. Reflector antennas operate on principles known long ago from the theory of geometrical optics. The first reflector system was made by Hertz back in 1888 (a cylindrical reflector fed by a dipole). The radiation fields from aperture antennas, such as slots, open-ended waveguides, horns, reflector and lens antennas, are determined from the knowledge of the fields over the aperture of the antenna. In this paper, we analyzed the effects of feeds relating to the parabolic reflectors such as waveguide and horn. We show the variations of the gain in the electric and magnetic planes (E and H) according to the angle of incidence. In our case, we use the origin to be at the focus

Analysis of fractal radiation patterns from concentric-ring hexagonal arrays

These hexagonal arrays are becoming increasingly popular, especially for their applications in the area of wireless communications. The overall objective of this article has been to use the theoretical foundation developed for the analysis of radiation patterns and design of the hexagonal arrays. A technique has been developed for the analysis of radiation patterns from concentric ring arrays. A family of functions, known as generalized Weierstrass functions, has been shown to play a key role in the theory of fractal radiation pattern analysis

Radar cross section study from wave scattering structures

Radar remote sensing deals with the extraction of object information from electromagnetic wave parameters. To fully exploit the potential of acquiring quantitative information requires a detailed description of the microwaves scattering. The research on this topic was mostly centered on far-field analysis that assumes an incident plane wave, computation of its scattered field, and evaluation of the radar cross section. However, under certain practical conditions, the far-field analysis is not valid and a near-field analysis is necessary. In this paper, we have given a full analysis of the near-field of a wedge structure due to an incident wave field from a line source or a plane wave. The far-field pattern, for the case of a line source exciting the structure, is also analyzed

A Printed U-Shaped Coplanar Waveguide Feed UWB Antenna for GPR Applications

A printed U-shaped coplanar waveguide fed (CPW) ultra-wideband (UWB) antenna is designed, fabricated, and measured in this paper for ground penetrating (GPR) applications. To enhance the working bandwidth, a set of cutoffs was introduced in different parts of the antenna. The antenna was printed on the FR4-epoxy substrate in a compact size of 0.252λ0×0.3λ0×0.015λ0 at 3 GHz. The calculated results were validated by realizing and measuring a prototype. Experimental demonstrations were done with the R& S®ZNB Vector Network Analyzer, which indicates that the antenna's working bandwidth extends from 3.09 GHz to 11.07 GHz (112.71%). Additionally, the antenna's radiation patterns were measured in an isolated anechoic chamber, which shows that the proposed antenna has omni-directional radiation patterns. Moreover, acceptable gain antenna values ranging between 1.74 and 7.04 dBi and high values of radiation efficiency of more than 80% were achieved over the whole working bandwidth. Besides, the antenna presents a stable group delay with a linear phase of S21 through the UWB frequency band. To prove the efficiency of the fabricated antenna for GPR applications, the operation of the antenna was experimentally tested in a sandy soil box. The obtained results show that the proposed antenna could be a good candidate for GPR applications

State of the art: guidelines for the selection of fast precipitation devices

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Stabilization of 200 Atom Platinum Nanoparticles by Organosilane Fragments

Three's a charm: Platinum nanoparticles of 2 nm diameter and containing approximately 200 atoms covered with n-octylsilyl groups (see picture, right; Pt blue, Si red, C gray, H turquoise) form when [Pt(dba)2] (dba=dibenzylideneacetone) decomposes in the presence of n-octylsilane. The particles adopt a cuboctahedral structure with an edge length of three atoms

State of the art: guidelines for the selection of fast precipitation devices

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Regularly Distributed and Fully Accessible Pt Nanoparticles in Silica Pore Channels via the Controlled Growth of a Mesostructured Matrix around Pt Colloids

SSCI+PDEInternational audienceMerging a colloidal approach for the synthesis of Pt nanoparticles and a supramolecular pathway for generating mesostructured oxides can provide via a one-pot synthesis a well-defined, active, and stable heterogeneous catalyst. This material contains regularly distributed Pt nanoparticles along the channel pores of a highly ordered silica matrix

Highly efficient aerobic oxidation of alkenes over unsupported nanogold

Boualleg, Malika Guillois, Kevin Istria, Bertrand Burel, Laurence Veyre, Laurent Basset, Jean-Marie Thieuleux, Chloe Caps, ValerieAn octylsilane-stabilized colloidal dispersion of 2 nm crystalline gold nanoparticles is highly active and selective for the aerobic oxidations of stilbene and cyclohexene in methylcyclohexane