Subdomain multilevel approach with fast MBF interactions

The set of isolated solutions on the individual subsectional basis functions belonging to a given subdomain is merged into so-called macro basis functions (MBF). These are, in turn, fitted into the global MoM system, taking into account the symmetries and mutual coupling. The result is then a compressed MoM system of equations for the global problem with significantly reduced number of unknowns, which is easily solved. Finally, the solution for every single unknown is recovered by a simple expansion from the compressed solution. This powerful method can be improved, especially when the interactions between two different MBF are concerned. In a large electromagnetic problem, where the memory occupation and computational time have been already significantly reduced using the subdomain multilevel approach (SMA), the calculation of MBF reaction terms remains the most time-consuming part of the procedure. In this paper, we present an efficient way of computing MBF reaction terms.