Suppressing linear time growth in edge element based finite element time domain solution using divergence free constraint equation

Edge elements have been a popular choice of basis functions for the solution of Maxwell's equations using the finite element method. When applied in time domain finite elements (Lee, J.-F., 1994), late time linear time growth (Hwang, C.-T. and Wu, R.-B., 1999) is observed. A method to suppress the linear time growth observed in FETD (finite element time domain) solutions is presented. The method is based on constraint equations to restrict the vector finite element solution to be divergence-free. Thus, gradient vector functions in the solution are suppressed. The method is applied to a ridged cavity and the elimination of non-physical low frequency terms is observed.