Full-wave space-domain analysis of open microstrip discontinuitiesincluding the singular current-edge behavior

A full-wave space-domain analysis is presented for the high-frequency characterization of microstrip discontinuities. This approach solves the electric field integral equation (EFIE) for the surface current density on the microstrip using the method of moments. The current expansion functions incorporate the singular edge behavior of the surface current, yielding a very accurate current modeling. Special attention is devoted to the analytical treatment of the singular terms in the electric field Green's dyadic. The numerical results focus on the S-parameters of some simple microstrip discontinuities and the comparison with results obtained with other techniques and from measurements     

Full-wave analysis of coupled perfectly conducting wires in amultilayered medium

A full-wave analysis of coupled perfectly conducting cylindrical wires in a multilayered dielectric medium is presented. The analysis is based on a Fourier series expansion of the unknown surface currents on each wire and on an integral equation for the longitudinal field on the wires. The calculations are not restricted to the propagation constants of the different modes, but explicit results are presented for the impedances associated with each wire and each eigenmode as a function of frequency. Propagation constants, longitudinal currents on the wires, and impedances lead to a complete equivalent circuit for the structures being considered     

Synthesis and characterization of a new chiral polyurea-based catalyst

A series of chiral poly(urea)s was synthesized by solution polyaddition. The polymers are characterized by NMR, FTIR, DSC, viscosimetry, and microanalysis. After deposition of the rhodium, the insoluble chiral polymers were used as catalysts in the reduction of acetophenone by hydrogen transfer. The influence of the structure of the polymers on the catalytic activity and selectivity was investigated. The enantiomeric excesses (e.e.) obtained were up to 60%, and the polymeric catalysts were reused without loss of activity and selectivity. © 1996 John Wiley & Sons, Inc.     

Circuit parameters for single and coupled microstrip lines by arigorous full-wave space-domain analysis

A rigorous full-wave analysis is applied to determine the dispersion characteristics and the impedance matrix of coplanar microstrip lines. It is shown that the impedance definition based on the propagating power and the longitudinal current is the most appropriate one. Examples are given for the single strip, for two coupled strips, either symmetric or asymmetric, and for a three-strip configuration. Some attention is also devoted to the current profiles associated with each eigenmode     

Synthesis and thermal properties of bismaleimides with mesogen aromatic amide–ester and flexible polymethylenic group

Four bismaleimides with mesogen “amide–ester” aromatic and flexible polymethylenic group variable length (8 ≤ n ≤ 11) were synthesized in two stages, producing yields exceeding 80%. These bismaleimides (BMIs) were obtained after several purifications by dissolution—precipitation in dimethylformamide–methanol (1/4) with over 94% purity (high‐performance liquid chromatography). These pure BMIs were characterized by nuclear magnetic resonance, Fourier transform infrared spectroscopy, and elemental analysis and studied by differential scanning calorimetry, thermogravimetric analysis, polarized light microscopy, and X‐ray diffraction. Solubilities and thermal properties show effects of parity. The even BMIs are more difficult to solubilize than the odd BMI. The melting points of the even BMI (approximately, 220°C) are far higher than those of odd BMI (approximately, 160°C). Crosslinking temperatures of even BMI are close to 230°C, whereas odd BMI crosslinking temperatures are higher (approximately, 250°C). Even BMIs give rise to a liquid crystal state upon melting. Under the same conditions, odd BMIs give rise to an amorphous state; however, after crosslinking, the four bismaleimides give rise to an ordered liquid crystal state of smectic type. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

New fast and accurate line parameter calculation of generalmulticonductor transmission lines in multilayered media

An enhanced method to calculate the C, L, and R of a multiconductor bus in a multilayered medium is presented. Different board technologies, conductors of complicated shape, and conductors embedded in different layers can be handled without loss of accuracy or substantial increase in CPU time compared with existing simulation techniques. Correct determination of skin effect losses is shown to depend critically on surface charge modeling. Surface charge discontinuities are explicitly taken into account which results in reduced computation time. A further reduction of computation time is obtained by a particular treatment of the calculation of the Green's function     

Recent advances in homogeneous and heterogeneous asymmetric catalysis with nitrogen–containing ligands

Nitrogen–containing chiral ligands are being used more and more in asymmetric catalysis. This article is an overview of results published in 1993--1996 in this field and tries to open new perspectives for this type of ligand, more particularly with the purpose of heterogenization of the catalytic systems. This revised version was published online in June 2006 with corrections to the Cover Date.     

Analysis of coupled active waveguides: Comparison of different modeling techniques

A self consistent model for the analysis of phase locked array lasers is proposed and a comparison is made with the more frequently used coupled mode theory. It is shown that in most cases the coupled mode solutions are in good agreement with the self-consistent solution, but in some cases care should be taken in applying the coupled mode theory and an improvement of that theory may be useful.     

Mixed potential integral equation technique for hybridmicrostrip-slotline multilayered circuits using a mixedrectangular-triangular mesh

In this paper, a mixed potential integral equation (MPIE) formulation for hybrid microstrip-slotline multilayered circuits is presented. This integral equation is solved with the method of moments (MoM) in combination with Galerkin's method. The vector-valued rooftop functions defined over a mixed rectangular-triangular mesh are used to model the electric and magnetic currents on the microstrip and slotline structures. An efficient calculation technique for the quadruple interaction integrals between two cells in the system matrix equation is presented. Two examples of hybrid microstrip-slotline circuits are discussed. The first example compares the simulation results for a microstrip-slotline transition with measured data. The second example illustrates the use of the simulation technique in the design process of a broadband slot-coupled microstrip line transition     

Rigorous full-wave space-domain solution for dispersive microstriplines

The eigenmode problem for the open microstrip line is analyzed in the space domain starting from the calculation of a dyadic Green's function in the spectral domain. The transverse and the longitudinal current are discretized using the method of moments. A point-matching technique is used to impose the boundary condition, i.e., zero tangential electric field, on the strip. The edge conditions at the end points of the strip are explicitly incorporated and special care is taken to accurately retain the static behavior of the field on and near the strip. Special attention is given to the variation of the current distribution as a function of frequency