Finite element analysis of dispersion characteristics of microstrip lines lying near substrate and ground plane edges

The dispersion characteristics of microstrip lines lying near substrate and ground plane edges are examined using the finite element method (FEM). Microstrips lying near two types of edges are analyzed: a substrate edge on an infinite ground plane and a substrate/ground plane edge. The FEM formulation is based on the curl-curl vector Helmholtz equation. Mixed-order covariant projection finite elements are employed to avoid problems with spurious modes. Local absorbing boundary conditions are used to truncate the FEM mesh in the open region. An efficient sparse eigensolver, based on iterative methods, is used to solve the resulting non-linear eigenvalue equation.