Addressing Numerical Challenges for Low Frequency Shielding 3D Full-Wave Simulations: FDTD and MoM

This paper addresses the challenges encountered in the 3D full-wave simulation of low-frequency shielding performance when employing two distinct solvers: Finite-Difference-Time-Domain and Method of Moments. In comparing both methods, two different cases have been considered. Firstly, the low-frequency shielding characterization of a planar material when using a loop antenna source has been explored. Secondly, the characterization of a low-frequency board-level shield, with a $50 \Omega$ matched microstrip as an electromagnetic source has been investigated. For both cases, the shielding effectiveness has been determined using the Schelkunoff Transmission Line model by using the simulated wave impedance. While doing this, the paper addresses the limitations of both methods in low-frequency simulations, followed by providing insights into achieving useful information at the lowest possible frequency. Finally, it is demonstrated that within the trustworthy frequency region, both methods yield results in a very good level of agreement.