Shielding of wire segments and loops in electric circuits by spherical shells

The susceptibility of an electric circuit to electromagnetic radiation incident on it is analyzed by the application of Lorentz´s reciprocity relation. An equivalent Thevenin or Norton representation of the circuit serves to determine the induced signals quantitatively. The effect of a (multilayered) spherical shield on the performance of elementary parts of the circuit, namely, a short wire segment and a loop placed at the center of the shield, is investigated. The corresponding shielding performance is expressed as the reduction of the induced source strength in the equivalent networks. Numerical results are presented in a frequency range that includes the occurrence of internal resonances in the shielding structure