An efficient procedure for the analysis of shielding effectiveness can be performed by the current sheet integral equation in thin shields (CSIE). In the presence of ferromagnetic bodies and, moreover, in the periodic regime, where higher harmonics appears due to the nonlinearity of B-H characteristic, this equation can not be obtained directly. In this paper a method based on CSIE is proposed, where the nonlinear media are treated using the polarization fixed point method (PFPM). At each iteration, a Fourier analysis is performed, and CSIE is solved for each harmonic having imposed currents and the polarization harmonics as electromagnetic field sources. To speed up the iterative process the harmonic selection is progressive. The convergence of the proposed procedure is always insured.

Keywords: Thin shields, Current integral equation, Nonlinear media