Dual-polarization slot-coupled printed antennas fed by stripline

This article presents recent techniques in the field of dual-polarization printed antennas for designing shielded radiating structures with high-quality performances in terms of cross-polarization level and input-port isolation. The use of gridded patches provides a natural solution to filtering surface currents and is of key importance in limiting inter-element coupling in arrays. Experimental results obtained on various designs are presented     

Wideband omnidirectional microstrip array

A compact broadband antenna having a far-field pattern similar to that of a magnetic dipole with horizontal polarisation has been designed and tested. The dimensions of this printed antenna, etched on low permittivity substrate, are 130×130 mm. The measured bandwidth, which is 52% for a VSWR of less than 2, is achieved through the utilisation of nonresonant elements     

Une approche rigoureuse pour l’étude de sources primaires. Applications aux antennes de satellites

A rigorous approach for radiating structures of revolution is presented, with applications to paraboloidal reflector antennas. Considering Maxwell’s equations in the sense of distributions, an equivalent problem appears for the exterior domain in a natural and exact way, leading to the formulation of the integral equations. The current density on the conducting surfaces and the reflection coefficient are determined. The computed radiating field shows an excellent agreement with experiment. The radiation characteristics of an offset paraboloidal antenna are then obtained from the physical optics integral and the extension to multibeam antennas with some examples of earth coverage is presented.     

Compact duplexer-polarizer with semicircular waveguide [antennafeed]

A light, compact, and high-performance duplexer-polarizer able to generate circularly polarized waves in a circular waveguide is discussed. Two prototypes were built. The standing-wave-ratio (SWR) and ellipticity performances are extremely good (less than 0.15 dB ellipticity over 15% bandwidth). The experimental development was facilitated by the computation of the dispersion curves and of the transverse field distribution associated with the two fundamental guided modes propagating in the different sections of a septum waveguide     

Additional modules for versatile and economical PCR-based gene deletion and modification in Saccharomyces cerevisiae

An important recent advance in the functional analysis of Saccharomyces cerevisiae genes is the development of the one-step PCR-mediated technique for deletion and modification of chromosomal genes. This method allows very rapid gene manipulations without requiring plasmid clones of the gene of interest. We describe here a new set of plasmids that serve as templates for the PCR synthesis of fragments that allow a variety of gene modifications. Using as selectable marker the S. cerevisiae TRP1 gene or modules containing the heterologous Schizosaccharomyces pombe his5⁺ or Escherichia coli kan^r gene, these plasmids allow gene deletion, gene overexpression (using the regulatable GAL1 promoter), C- or N-terminal protein tagging [with GFP(S65T), GST, or the 3HA or 13Myc epitope], and partial N- or C-terminal deletions (with or without concomitant protein tagging). Because of the modular nature of the plasmids, they allow efficient and economical use of a small number of PCR primers for a wide variety of gene manipulations. Thus, these plasmids should further facilitate the rapid analysis of gene function in S. cerevisiae. © 1998 John Wiley & Sons, Ltd.     

Rigorous analysis of three-dimensional structures incorporatingdielectrics

The paper presents the SR3D software (3D radiating structures), which calculates the electromagnetic characteristics of arbitrarily shaped structures incorporating dielectric material. The rigorous analysis method is based on the integral equation formulation. The authors included a variational approach using the reaction concept of Rumsey. The problem is numerically solved with a surface finite elements method. A guided mode excitation has been introduced in order to compute the reflection coefficient at the transmit port and the transmission coefficient between the different parts fed by guided modes. This software is validated by excellent agreement between simulated and measured radioelectric performances (patterns and SWR)     

Approximate formulas for step discontinuities in circular waveguides

The authors discuss approximate formulas to determine the normalised impedance for a discontinuity between two concentric circular waveguides. These formulas are used for the computation of step transformers. Experimental results validate these approximations.<>     

Influence des supports sur les rayonnements copolaire et contrapolaire d’une antenne à réflecteur

Scattering by struts of triangular or elliptical cross sections for reflector antennas is rigorously studied. Conformal mapping make easier solving integral equations deduced from boundary value problem. The effects of struts on co-polarization, crosspolarization antennas performances is emphasized.     

Some relations between the radiation patterns in the two main planes and the whole radiation pattern

In theoretical studies, the far fields radiated by antennas are derived by using a radiation integral. In many cases, only a cut in the two main planes called E- plane and H- plane, is of interest. Outside these two main planes, the behaviour of the field is generally not known. It seems that no detailed study has been made in order to determine whether a relation exists between the E, H planes and the whole radiation pattern. The aim of this paper is to try to link the far field in any direction of space to the far field which is present in the two main planes, and to analyse the conditions under which this pattern reconstruction is possible.     

Analyse de structures tridimensionnelles inhomogenes quelconques

This paper illustrates the capability of SR3D software to rigorously analyze 3D radiating structures including wires (thin or thick), dielectric parts and finite ground planes. The analysis method is within the class of bound ary element method (bem) and use integral equation formulation (combined field integral equation cfie) to solve electromagnetic scattering problems. It includes a variational approach based on Rumsey reaction concept. The problem is numerically solved with a surface finite element method : surfaces of 3D conducting object and interfaces between dielectric domains are meshed using surface triangular patches. We discuss on the numerical options chosen, the basis functions used, discretization density, and treatment of wires. The last sections emphasize the accuracy of the method on examples for which computed and measured reflection coefficient and radiation patterns are compared.