INVITED PAPER Hybrid Iterative Approach Combined With Domain Decomposition for the Analysis of Large Electromagnetic Problems This paper proposes a technique for electromagnetic analysis of large objects, using a ray-tracing method combined with multipole expansion of active currents over points on the radiating surface. By Carlos Delgado , Eliseo Garcı ´a, and Manuel Felipe Ca ´tedra, Fellow IEEE ABSTRACT | In this paper, we propose a technique for the electromagnetic analysis of large objects considering the interactions between separate parts of the geometry (which in this context will be referred to as domains). A number of unknowns is associated to each domain, and only the basis functions included within the same domain are considered fully coupled (i.e., a full-wave analysis is performed for every domain, isolating it from the rest of the geometry). An iterative process is then applied to determine the total currents over the object, considering the currents induced by the external sources and those due to interactions between different domains. Once a current distribution is obtained over a given domain it is essential to identify those passive domains with which the interaction active-domain–passive-domain will yield a significant contribution to the final result (scattered field, radiation pattern, S-parameters, etc.). In this work, we utilize a ray-tracing method combined with the multipole expansion of the active currents over a number of points located on the radiating surface to speed up the solution of large and realistic problems. KEYWORDS | Electromagnetic analysis; electromagnetic radia- tion; moment methods I. INTRODUCTION It is well known that, despite the fact that the method of moments (MoM) [1] is usually taken as a reference for the analysis of scattering or radiation problems where perfect electric conductor (PEC) structures or those with homo- geneous dielectric coatings are involved, its practical implementation suffers from a heavy burden imposed by the size and the density of the impedance matrix. Typical solutions for those problems that exceed the handling capabilities of the MoM resort to the use of asymptotic approaches [2], [3] in order to trade computational cost, in terms of memory and processing time, for accuracy in the results, though under some conditions these results can be notably similar to those yielded by a full-wave analysis. It is worthwhile to mention as well hybrid approaches [4], addressing electromagnetic problems that would fall Manuscript received July 16, 2011; revised May 18, 2012; accepted June 24, 2012. Date of publication August 28, 2012; date of current version January 16, 2013. This work was supported in part by the Comunidad de Madrid under Project S-2009/TIC1485, by the Castilla-La Mancha under Project PPII10-0192-0083, by the Spanish Department of Science under Technology Projects TEC 2010-15706 and CONSOLIDER-INGENIO No CSD-2008-0068. C. Delgado and M. F. Ca ´tedra are with the Computer Science Department, University of Alcala ´, 28870 Alcala ´ de Henares, Spain (e-mail: carlos.delgado@uah.es; felipe.catedra@uah.es). E. Garcı ´a is with the Automatics Department, University of Alcala ´, 28870 Alcala ´ de Henares, Spain (e-mail: eliseo.garcia@uah.es). Digital Object Identifier: 10.1109/JPROC.2012.2207934 320 Proceedings of the IEEE | Vol. 101, No. 2, February 2013 0018-9219/$31.00 Ó2012 IEEE