Arlette Fourrier-Lamer

Broad-band simultaneous measurement of complex permittivity and permeability using a coaxial discontinuity

A technique for simultaneously measuring the real and imaginary parts of both the permittivity and the permeability of a given material is discussed. A gap in a coaxial line is filled with the material under test. Complex permittivity and permeability are computed from the S-parameter (S/sub 11/ and S/sub 21/) measurement made on the gap, taking into account higher-order modes excited at the discontinuity. Measured epsilon /sub r/ and mu /sub r/ data for several materials are presented from 45 MHz up to 18 GHz. This technique shows good agreement between calculated and generally accepted values. >

Analysis of Reflection and Transmission of Electromagnetic Waves in Complex Layered Arrays

Reflective and transmitting properties of several layers of double-periodic arrays are studied. In the arrays, elements are conducting inclusions of various shapes. It is shown that in these structures all the phenomena recently found in dense wire grids with periodical defects (so called photonic band-gap structures) can be observed and explained in simple terms of inter-layer and inclusion resonances. Frequency-selective (with two and more stop bands) and polarization transformation properties of these arrays are demonstrated.

Broad-band microwave characterization of a tri-layer structure using a coaxial discontinuity with applications for magnetic liquids and films

An analytic technique is described, which allows us to determine simultaneously complex permittivity /spl epsiv/ and permeability /spl mu/ of magnetic films or magnetic liquids. The cell is a gap in a coaxial line filled with three layers (for liquid samples, the two external layers are used as windows, and for films, the middle layer constitutes the substrate). Permittivity and permeability of the unknown layer(s) are computed from the S-parameters (S/sub 11/, S/sub 21/), which are measured in the gap, taking into account higher order modes excited at the discontinuity, /spl epsiv/ and /spl mu/ measured for ethanol and a ferrofluid (with an applied magnetic static field) are presented up to 18 GHz.

Equivalent Circuit for Coaxial Discontinuities Filled With Dielectric Materials - Frequency Extension of the Marcuvitz's Circuit

An equivalent circuit for coaxial discontinuities is presented and discussed. The cell used is a circular waveguide filled with a dielectric material measured in reflection/transmission. The circuit is obtained by using two well known methods: the Marcuvitzs circuit for a cell measured in reflection and an analytical resolution using the mode-matching method. The interest of the new circuit is that it has wider frequency and geometrical ranges than the Marcuvitzs circuit and is much simpler than the mode-matching method. Using this circuit, complex permittivity can be calculated from measurements of the S-parameters (S11 and S21). Experimental results are presented up to 18 GHz. Frequency and geometrical ranges of validity are also discussed.

Microwave scattering from a broadband depolarizing array of loaded planar chiral particles

Numerical and experimental results on the scattering of an electromagnetic plane wave by an array of novel planar chiral particles are presented in this paper. The geometry of the particles are chosen in order to obtain a depolarization of the scattered wave on a broad frequency band. We also present results corresponding to arrays with the chiral particles connected to passive linear electronic loads. By varying the loads, we demonstrate, theoretically and experimentally, that the properties of depolarization can be electronically controlled. These results suggest a potential application of the studied samples in the design of agile polarization transformers.

Polarization-sensitive microwave band gaps in array structures

In this paper we explore both theoretically and experimentally the electromagnetic properties of microwave photonic band gap structures formed by several layers of doubly periodic arrays of conducting elements. The experimental results are in good agreement with the theoretical calculations. The method of the analysis of a single doubly-periodic array of conducting strips, based on Floquet theorem and the moments method, is combined with a recursive algorithm suitable to calculate the reflection and transmission operators for a system of several such layers. These structures can find practical applications in high- quality polarization-selective filters.

Microwave properties of the thermal metal-semiconductor transition of the polyaniline-VO2 composites

The purpose of this paper is to report the experimental results on polyaniline-VO2 composites in the 45MHz-18GHz frequencies range versus temperature and VO2 mass concentration. The temperature dependence studied by classical heating and courant pulse and the percolation phenomena study have been carried out in both the semi- conductor state and metallic state. The VO2 metallic oxide is remarkable through a reversible discontinuity of the electric conductivity which can reach five orders of magnitude at a transition temperature generally located at 68 degree(s)C. This transition is associated with the modification from crystal structure VO2 which passes from a quadratic structure (metal state) to a monoclinic structure (semiconductor state) at the temperature Tt. The powder of VO2 sintered in an induction oven. VO2 was dispersed in a matrix of basic polyaniline, with mass rates of 10%, 30%, 50%, 70% and 90% of vanadium oxide. The strong dynamics of the composites beyond the threshold authorizes the use of a current to induce the temperature within the sample. The simulation of multi-layer of Jauman type, with commendable reflection and transmission in the frequencies range 8-12GHz will be shown.