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

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