Imperfect EM Shielding by Thin Conducting Sheets with PEC and SIBC

Electromagnetic compatibility of electronic based systems is increasingly gaining importance. The aim is to develop simulation tools based on the finite element method, which allow the inclusion of electromagnetic compatibility aspects of electronic based systems. The different dimensions of the involved objects are a big challenge, for example ratios higher than 1/100,000 are common. The goal is to find reasonable models to improve the performance. This paper focuses on reducing the metallic shielding to a boundary condition in the model. It is either considered as a perfectly electric conductor or as a surface impedance boundary condition. The problem arises how to apply a surface impedance boundary condition simultaneously inside and outside of the housing, which is solved by splitting the simulation domain. The open domain is truncated and replaced by either an absorbing boundary condition of first order or a perfectly matched layer. They are compared in the context of accuracy and computational cost. A representative example is a small loop antenna located in a metallic box presented here. The antenna is a substitute for more involved emitters. The simulations show that the difference between using perfectly electric conductor or a surface impedance boundary condition are small for the considered quantities. Small changes in the geometry have a greater impact on the results.