Shielding Effectiveness of a Lossy Metallic Enclosure

In this paper, shielding effectiveness (SE) of a perforated enclosure with imperfectly conducting walls is evaluated. To this end, first, an accurate numerical technique based on method of Moments (MoM) ispresented. In this method, lossy metallic walls of the enclosure are replaced by equivalent electric surfacecurrent sources. Then, the impedance boundary condition on the imperfectly conducting surfaces is appliedand an electric field integral equation is extracted. At the end, the integral equation is solved numerically byGalerkin method. In addition to the mentioned numerical method, an extremely fast analytical techniquebased on transmission line model(TLM) is proposed which is able to predict the SE with high level ofaccuracy over a large frequency bandwidth just in a few seconds.  For validation of both methods, othercommercial softwares (FEKO and CST) are employed and several enclosures with different conductivitiesare studied. Lossy MoM method shows accurate results for conductivities down to 10S/m, while efficientTLM method proves its accuracy for conductivities down to 250S/m.