Low frequency shielding effects of a conducting shell with an aperture: response of an internal wire

Finite-difference-time-domain (FD-TD) predictions have been used, with up to a million time steps, to accurately characterize wire resonances below aperture cutoff for a wire shorted at its base and located within a conducting shell pierced by an aperture. Only a modest shielding effect was observed below cutoff for perfectly conducting shells with varying size apertures. The amplitudes of the wire resonances rose as 1/ω² as frequency decreased. The Q of the wire resonances also increased rapidly with decreasing frequency. These effects were nearly offsetting, leaving the energy in each wire resonance only slightly reduced from the unshielded wire responses as the aperture size varied. This reduction only increased modestly with smaller aperture size