Field Analysis for Thin Shields in the Presence of Ferromagnetic Bodies

Application of the current sheet integral equation for an efficient analysis of the electromagnetic field in the presence of thin shields is limited to the case of nonferromagnetic and homogeneous media. An extension of this method to thin shields in the vicinity of ferromagnetic bodies is proposed in this paper for time-harmonic fields. The fixed-point polarization technique is used, where the nonlinear material is replaced by a free space and a distribution of fictitious polarization whose magnitude is corrected iteratively in terms of the magnetic induction. A Fourier decomposition of the polarization is employed and the integral equation is solved for each harmonic. The procedure has a guaranteed convergence and is more and more rapid as the number of harmonics retained decreases. In the beginning only the fundamental harmonic is considered and, afterward, higher order harmonics are added to increase the computation accuracy.