Luis Nuño

Analysis of general lossy inhomogeneous and anisotropic waveguides by the finite-element method (FEM) using edge elements

Several finite element formulations based on edge elements have been developed in recent years, avoiding the appearance of spurious modes in waveguides. However, no formulation of this kind dealing with general lossy inhomogeneous and anisotropic waveguides has been found in the literature. In this paper, a new finite element scheme for the most general linear waveguides has been derived from vector wave equations via a Galerkin procedure. In this formulation, triangular and quadrilateral edge elements have been used in order to avoid the spurious solutions. Furthermore, the final eigensystem involves only very sparse matrices, thus allowing important savings in time and memory.

New recovery error indicator for adaptive finite-element analysis on waveguiding structures

The adaptive finite-element method (FEM) is an iterative variant of the FEM where, in a first step, an initial mesh with few and low-order elements is generated, the corresponding algebraic problem is solved and the error in the solution is estimated in order to add degrees of freedom in those regions of the domain with the biggest error estimation. This process is repeated until an ending condition is reached. The two basic stages in this method are the error indication and the mesh enrichment. In this paper, within the analysis of waveguiding structures, a new error indicator based on the curl recovery is described. In addition, an overview on refinement techniques is presented, and the h-refinement employed in this study is briefly described. Results obtained with the curl-recovery indicator are discussed and compared with the classical nonadaptive FEM and two previously developed error indicators: the residual and flux continuity indicators.

SIVA UAV: A Case Study for the EMC Analysis of Composite Air Vehicles

The increased use of carbon-fiber composites in unmanned aerial vehicles is a challenge for their EMC assessment by numerical solvers. For accurate and reliable simulations, numerical procedures should be tested not only for individual components, but also within the framework of complete systems. With this aim, this paper presents a benchmark test case based on experimental measurements coming from direct-current injection tests in the SIVA unmanned air vehicle, reproduced by a numerical finite-difference-time-domain solver that employs a new subgridding scheme to treat lossy composite thin panels. Validation was undertaken by applying the feature selective validation method, which quantifies the agreement between experimental and numerical data.

Study of NiZn ferrite absorption: Effect of relative density and microstructure

A study to optimize the reflectivity of ferrite absorbers is presented. The study considers the variation of the magnetic loss factor with the evolution of fired relative density and microstructure of ferrites made from a Zn-Ni-Cu ferrite powder, and from mixture of Zn-Ni and a Cu ferrite powder. From the results, an equation which relates the magnetic loss factor to fired relative density, average grain size, and grain size distribution width, is proposed. This equation is valid for the ferrites studied, which had an average grain size below 10smm and a grain size distribution width below 30smm.

Health protection reference levels for voltages and currents in typical domestic electrical installations

Health protection reference levels were established for electric and magnetic fields. However, the corresponding reference levels for voltages and currents in cables could not be established in the general case, since they strongly depend on each particular situation. In this paper, health protection reference levels for voltages and currents are obtained for the relevant case of typical domestic electrical installations. Then, voltages and currents of most common signals in these installations are compared with these reference levels.

Shield&Reflex: A new technology for weaving shielding fabrics

A new yarn able to shield electromagnetic waves is presented. This yarn was used to manufacture different fabrics with identical texture and properties to woven fabric made with conventional yarns. The measures for check the electromagnetic waves shielding effectiveness (EMSE) have been made within a semi-anechoic chamber. The results show excellent shielding properties above 30 dB in the frequency range from 800 MHz to 4 GHz.

An improvement of the finite-element method for computing the electric field of waveguides with complex geometry

Curvilinear elements have been reported to be one of the more advantageous features of the finite-element method (FEM), since they allow fitting arbitrarily shaped geometries without staircase approximations, thus leading to more accurate results. Nevertheless, the graphical representation of the computed fields involves quite complex computations. In this paper, the homotopy continuation method has been specialized for solving the systems of polynomial equations arising when the electromagnetic field obtained through the FEM is computed at an arbitrary point within the solution domain. The results obtained with this method are satisfactorily compared with those provided by other classical widely used procedures, like the Newtons method.