Comparison of FDTD and MoM for shielding effectiveness modelling of test enclosures

The FDTD (finite difference time domain) method and the MoM (method of moments) are two well known methods for the numerical solution of EMC problems. In this paper, both methods are used to calculate the shielding effectiveness (SE) of a test enclosure with one or two large apertures. For validation purposes, the simple case of an infinite screen with a single rectangular aperture or slot is considered first. The electric and magnetic near field SE is determined for a wide range of slot widths. Very good agreement (less than 2 dB difference between both methods) is obtained for frequencies up to 1 GHz. A larger discrepancy was found for more realistic shielding structures such as the test enclosure, but both methods are still within 5 dB of the experimental results for frequencies below the first resonance of the enclosure