Resonance suppression of a spherical electromagnetic shielding enclosure by using conductive dielectrics

The resonance suppression for the electromagnetic shielding enclosure is theoretically investigated. A simple model of a double-layered spherical shell with a plane-wave illumination is assumed. When a spherical shell made of conductive dielectrics is covered with a thin metal layer, the conductivity of the dielectrics has an optimum value which minimizes the Q-factor at the fundamental resonant frequency. The optimum conductivity is shown to be a function of the resonant frequency and the thickness of the dielectric layer. The improvement of the shielding effectiveness by introducing the optimum conductivity is shown.