Fast evaluation of low frequency near field magnetic shielding effectiveness

In this paper, a fast approach is presented for the evaluation of near field magnetic shielding effectiveness. Generally, in the literature the near field shielding is determined from far field formulas while modifying the wave impedance. The paper shows that adding a corrective term in the generic expression of the shielding effectiveness allows predicting accurately the shielding when the source of disturbance is a magnetic dipole. In order to deduce shielding effectiveness in practical cases the approach presented in this paper relies in two steps. The first replace the real source of disturbances with a set of equivalent magnetic dipoles. In the second step the shielding effectiveness is determined with the dipoles as actual sources and using improved expressions including the corrective term. The modeling methodology is validated experimentally in case of a radiating coil located near a conducting planer shield.