The transformation of spatial harmonics in a combined electromagnetic shield

Hybrid conductive-permeable electromagnetic shields are a key passive approach in the mitigation of undesired alternating magnetic fields. An efficient design presented in this paper is a combination of variable permeable belts and a thin conductive nonmagnetic pipe. The shield is capable of satisfying severe performance criteria, in terms of shielding factor, weight, and cost, while providing adaptive tuning for an individual inducing source inside the shield. The potential for the shield is discussed using an extended qualitative and quantitative analysis of the experimental results obtained at a magnetic test facility and shown to be promising.