Dramatic improvements in the matrix solution time for method of moment problems involving stripline interconnects

Method of moments (MoM) reaction matrices are typically thought of as being full matrices in most applications. However, in this paper, we demonstrate for the first time that sparse reaction matrices are produced when modeling stripline interconnects provided that a parallel-plate Green's function is employed in the analysis. This is demonstrated by investigating the sparse nature of the MoM reaction matrices that are produced when using the full-wave layered interconnect solver (UA-FWLIS) to model stripline interconnects. In order to explain the sparse nature of the reaction matrices, the electric fields that are excited by horizontal and vertical electric dipole sources are briefly overviewed, and the cutoff mode behavior of these electric fields is studied. Then the variations of the reaction elements with distance are studied, and this information is used to provide a cutoff criterion for the reaction element calculations. Once the reasons for the matrix sparsity have been explained, then we test various matrix solution algorithms in order to determine their efficiencies. We found that by applying sparse matrix storage techniques and a sparse matrix solver, it is possible to dramatically improve the matrix solution time when compared with a commercial MoM-based simulator.