Introduction to the Special Issue on Finite Elements for Microwave Engineering

This special issue is devoted to selected papers from the 9th International Workshop on Finite Elements for Microwave Engineering. The workshop was held 8–9 May 2008 in the city of Bonn, Germany. Workshops of this series take place every other year; their goal is to provide a highly focussed meeting place for researchers and practitioners active in theory and application of the finite element (FE) method in radio frequency and microwave engineering. The technical program featured excellent contributions from around the world, giving a comprehensive overview of the state-of-the-art in FE frequency-domain and FE timedomain methods, nonconforming and generalized FE approaches, adaptivity and mesh generation, hybrid methods, modelling techniques for materials, meta-materials, periodic structures, reduced-order and optimization methods, as well as advanced FE applications in such diverse areas as antennas, waveguide components, and electromagnetic compatibility. Unfortunately, only a limited number of representative articles could be included in this journal—13 in total. In this double issue, articles are included in alphabetical order according to the first author. The topics of the articles, dealing in varying degrees with theoretical matters and applications, are as follows. Alvarez, Gómez-Revuelto, Alonso, Garcia-Castillo, and Salazar-Palma couple FEs to the method of moments and physical optics to solve scattering and radiation problems. Dubcova, Solin, Cerveny, and Kus introduce a spaceand time-adaptive FE method for microwave heating. Eibert and Tzoulis discuss directly connected hybrid FE boundary-integral ray-optical models. Farle, Lösch, and Dyczij-Edlinger address nonphysical resonances in fast frequency sweeps. Frezza, Pajewski, Ponti, and Schettini apply the FE method to enhance the directivity of doubleslot antennas. Jacobsson and Rylander take an FE approach to model curved objects within a finite-difference time-domain scheme. Ledger investigates a preconditioner for high-frequency problems. Marais and Davidson propose an improved time-domain hybrid implicit/explicit FE method. Monk, Schöberl, and Sinwel discuss hybridized RaviartThomas elements for the Helmholtz equation. Nair and Webb propose an adaptive method for optimizing microwave devices over a frequency band. Otin derives an alternative