Full Vehicle Electromagnetic Simulation Using the Hybrid Finite Element Boundary Integral Approach

The finite element method (FEM) can be used as an analysis tool in automotive electromagnetic engineering and recently new technologies such as Domain Decomposition Method (DDM) were employed to simulate very large field structures such as a whole vehicle. A FEM solver offers numerous advantages over other numerical methods, such as method of moments (MoM) and finite difference time domain (FDTD), because it has the ability to handle complex heterogeneous and anisotropic materials which is often used inside vehicles, also providing a very precise representation of complex geometries via high order tetrahedral elements. Nevertheless, for large field problems such as the scenario of the ISO 11451-2 where an antenna radiates a vehicle in an anechoic chamber, FEM solvers requires an interface between an infinite domain to a finite domain through the use of radiating boundary conditions on artificial truncation surfaces. This causes the solver to model a great quantity of air regio. Integral equation (IE) methods, such as the Method of Moments (MoM) is a numerical approach that uses the Green's function considering Sommerfeld's radiation condition at infinity, and hence no air region needs to be modeled. Hybridization of FEM and IE solvers was accomplished as far back as 1990 and now is available on commercial codes such as Ansys HFSS. This formulation is known as the hybrid finite element and boundary integral method (FEBI), where the boundary integral, a MoM solution for Sommerfeld's radiation condition, is used as an interface boundary for the FEM solution. Thus, an exact mathematical and theoretical calculation of the far field radiation condition is satisfied. This technique presents a number of advantages for full vehicle simulation with external radiation sources, such as the ability to handle complex geometries and dielectric materials using FEM solvers without having to simulate air regions, which is now calculated through IE methods, leading to an accurate and faster simulation using less computational resources. A very complex analysis showing electromagnetic compatibility (EMC) and electromagnetic interference (EMI) on full vehicles are presented in this paper using the FEBI technique.