MODAL ANALYSIS OF THE EDDY CURRENT PROBLEM USING NULL-SPACE-FREE JACOBI-DAVIDSON

Electromagnetic induction sensors excel at detecting and classifying buried metallic objects. With the help of precomputed electromagnetic models, detection algorithms are able to pinpoint a target's location and orientation with high accuracy. A target's discrete spectrum of relaxation frequencies, is particularly useful for detection purposes. The discrete spectrum of relaxation frequencies is a simple pole expansion of the target's reaction to magnetic excitations. Its pole expansion coefficients can be computed by formulating differential Maxwell's equations as a generalized eigenvalue problem. When modeling arbitrary three-dimensional objects, this approach is complicated by the size of the system matrices and by a large null space that is near the eigenvalues of interest. A modified Jacobi-Davidson iteration will be described in this paper, that is capable of extracting the eigenvalues of interest without interference from the null space.