Rigorous analysis of EM-wave penetration into a typical room using FDTD method: The transfer function concept

In this paper, a rigorous analysis of electromagnetic wave penetration into a complex structure (an unshielded typical room in this case) is achieved considering the effects of heterogeneousness in its geometry and construction materials. The finite-difference-time-domain (FDTD) method is used to investigate the field distribution in a room with a window installed in one wall, illuminated by an electromagnetic uniform plane wave traveling perpendicularly to the surface of the window. The concept of transfer function has been expanded to the room under consideration as a linear system assuming it contains no dispersive material in its structure and we have shown this technique can give a very good prediction of temporal responses of electromagnetic fields inside the room due to other input waveforms and thus save great amounts of memory and time. In the next step the field distribution inside the empty room due to a HEMP incident waveform has been predicted using transfer function concept and the results have been used to suggest the optimum implementation of 3 metallic enclosures representing sensitive electronic instruments inside the room with the purpose of better protection. It has been shown that by an intelligent implementation we can reduce amplitudes of penetrating fields inside the enclosures up to 60 percent.