I. Introduction
The integrity of shielding enclosures is compromised by apertures and seams required for heat dissipation, cable penetration, and modular construction, among other possibilities [1]. These perforations allow energy to be radiated to the external environment from interior electronics, or energy coupled from the exterior to interfere with interior circuits [2], [3]. An understanding of energy coupling mechanisms to and from the enclosure is essential to minimize the EMI and susceptibility risk in a new design.
Some numerical methods have been applied to solve these EMI/EMC problems such as the finite difference time domain (FDTD) method [4], finite element method (FEM) [5], method of moments (MoM) [6], etc. Of these methods, the FDTD method is one of the most effective tools for the analysis of varieties electromagnetic problems, and has previously been applied for modeling apertures in shielding enclosures.
If the physical size of the aperture is on the order of, or larger than the spatial cell size, then modeling this aperture with FDTD is not a problem, however, if the aperture is narrow with respect to the spatial cell, one must either reduce the spatial cell size down to that require to resolve the aperture, or adopt an alternative method to characterize the aperture.
The reduction of the cell size is often not a feasible approach, and therefore alternative methods have been investigated [7]. Two of the more popular thin slot formalisms (TSF) have been proposed by Gilbert and Holland (C-TSF) [8] and Taflove (CP-FDTD) [9]. Utilizing these TSF, a thin slot segment can be modeled with a single cell, thereby saving computational resources while retaining accuracy. Previous results for slots in infinite or large planes show C-TSF computation results agree well with experimental data [4]. The two-dimensional (CP-FDTD) study based on contour path method by Taflove generally found superior accuracy of the TSF, but it can’t be applied in solving 3D electromagnetic problems.