SOLUTION OF MAXWELL EQUATIONS IN TIME-DOMAIN

This article presents two numerical methods used to solve 3D Maxwell's equations in the time domain. The first one is a finite difference method which has been implemented in a numerical code called ALICE. This method generally used for scatterers having an infinite conductivity, has been extended to take into account electromagnetic coupling through composite materials. The thickness of these materials can be thin or thick compared to the skin depth: the first formalism, based on the ''sheet impedance' concept, is devoted to electromagnetic sources having a low frequency content (lightning for example), the second one, more general, is however time and memory consumming. A new stability criterion has been established to calculate currents flowing on wires of arbitrary radius compared to the cell size. The second one is a time domain integral method. After a shea presentation of the method, a solution to solve numerical instability problems is proposed. New formalisms have been developed to calculate electromagnetic fields on scatterers covered with thin sheets of materials having a finite conductivity. Furthermore wire structures can be taken into account in the computer code. Results obtained by both methods are compared for modeling the Radar Cross Section (RCS) of a perfectly conducting sphere in free space and for the computation of the current flowing on a wire located inside a cavity; this current is induced by a plane wave impinging the cavity and penetrating through the walls of finite conductivity (composite material).