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Shielding effectiveness (SE) of metallic rectangular enclosures with thin slots and a thin-wire antenna loaded by an impedance, illuminated by multiple electromagnetic pulses (EMPs) simultaneously, is investigated using a hybrid finite-difference time-domain (FDTD) method. In order to enhance the simulation efficiency of the FDTD algorithm, accurate formulas for handling multiple thin slots, a thin-wire antenna, and a lumped network are integrated together. Numerical results show that for real metallic enclosures, their shielding performance is very sensitive to the variations in direction and polarization angle of the incident EMPs. However, at a given frequency, the resistance and inductance loaded at the terminal of a thin-wire antenna have little effect on the SE level. For two, three, as well as more EMP incidences, common-frequency interferences will result in strong inner field resonance in the enclosure. Index Terms--Common-frequency interference, electromagnetic pulses (EMPs), finite-difference time-domain (FDTD), incident direction and polarization angles, metallic rectangular enclosures, thin slots, thin-wire antenna.

In many electrical and electronic systems, metallic enclosures are used to provide electromagnetic shielding. These enclosures normally contain thin wires, thin slots, and frequency-selective slots (FSS) that degrade the shielding effects. In this paper, integrated FDTD formulations are developed that can model both subcellular thin slots and thin wires simultaneously. The formulations are shown to be capable of accurately predicting shielding effectiveness and inner field distributious of a metallic enclosure in both the frequency- and time-domains when subject to a high-power electromagnetic pulse. Index Terms--Finite-difference time-domain (FDTD), frequency-selective slot units, high-power electromagnetic pulse (HP-EMP), inner field distribution, shielding effectiveness, thin-slot formula (TSF), thin-wire formula (TWF).

A generalized mathematical procedure is developed for investigating shielding performance and inner wideband pulse responses of metallic rectangular multistage cascaded enclosures with multiple rectangular apertures, which is illuminated by an electromagnetic pulse (EMP). The mathematical methodology is based on the integral equation technique combined with the method of moments, by which all unknown aperture fields are solved according to a set of linear algebraic equations of infinite order. Numerical computations are performed to show frequency-and geometry-dependent shielding effectiveness and inner pulse waveforms of single-and double-stage cascaded enclosures, respectively, with computational accuracy and convergence rate also checked. It is found that using appropriate metallic multistage cascaded enclosures, high shielding performance can be achieved, which can provide an effective protection for certain electronic and communication systems from the interference of an EMP. Index Terms--Electromagnetic pulse (EMP), inner pulse responses, intentional electromagnetic interference (IEMI), metallic rectangular multistage cascaded enclosures, method of moments, multiple apertures, shielding effectiveness.