Exact closed-form shielding effectiveness of planar screens with small parallel loops

The magnetic shielding effectiveness of a single planar screen of infinite extent against a parallel current loop source is evaluated through an analytic closed-form expression which is valid for arbitrarily thick screens and for any source-observation distance. The only assumption in the formulation consists in considering small loops having a constant current. The resulting formula can be expressed in terms of only elementary functions and is believed to represent the most general closed-form expression for the magnetic shielding effectiveness of a planar screen in the presence of a parallel loop. Numerical results are provided to show the generality and the validity of the proposed formula.