Time-Domain Electromagnetic Analysis of Multilayer Structures Using the Surface Equivalent Principle and Mixed-Potential Integral Equations

This paper proposes an efficient modeling technique for time-domain electromagnetic analysis of a multilayered structure, using the surface equivalent principle and mixed-potential integral equations (MPIEs). First, the surface equivalent principle is used to replace the nonmetallic parts in each layer interface of the structure by prefect electrically conductor surfaces while introducing appropriate magnetic current densities on both sides of the apertures. As a result, the problem of a multilayer structure is reduced to a cascade of parallel-plate-waveguide (PPW) regions with two half-space regions on top and bottom of the structure. A closed-form expression is then derived for the time-domain Green-function of PPWs, using the inverse Fourier transform of the existing frequency-domain counterpart. The vias inside the dielectric layers are modeled using the thin-wire approximation. Finally, the governing time-domain MPIEs for the multilayer structure are derived by enforcing the continuity of the tangential magnetic field at the interfaces and the total electric field over the vias to be zero. The algorithm is well suited for direct inclusion in the kernel of free-space time-domain computational tools based on integral equation for solving multilayer structures. The validity of the proposed method is confirmed by frequency-domain methods and CST-MWS.