A model for modeling electromagnetic response in a conductor and in dielectric, a method of modeling the electromagnetic response in the conductor and dielectric and a program product therefor. Coupled supplies (delayed capacitive-current-controlled current sources or delayed inductance-voltage-controlled voltage sources) are low pass filtered in an electromagnetic model for the particular medium, e.g., a Partial Element Equivalent Circuit (PEEC) model for a conductor or dielectric. Thus, high frequency model instabilities are substantially reduced or eliminated.