Shielding effectiveness measurements for ferromagnetic shields

This paper proposes a new way to measure the shielding effectiveness of ferromagnetic shields. The procedure combines an experimental characterization of the shielding material to a forthcoming numeric simulation. Magnetic hysteresis is reduced to a series of equivalent B-H linear relations through an optimization procedure applied to a measured set of symmetric minor loops. An equivalent multilayer linear medium and a nonlinear shield are defined and adopted for calculations. The obtained results are then compared with direct measurements of shielding effectiveness at different operating frequency showing the good agreement and validity of the proposed method. Finally, a comparison and discussion on the harmonic content of the attenuated field is reported.