Time domain electromagnetic response of a conductive and magnetic permeable sphere via exponential sums

Two different numerical methods are presented and compared to identify the radius, the magnetic permeability, and the electrical conductivity of a sphere embedded in a uniform time-varying magnetic field, starting from its time-domain electromagnetic response. The first technique, which has been already applied to this problem, is the Prony method whereas the second one, never experimented in this context, is a matrix pencil method. Numerical experiments, which show a better stability of the second approach, are given and future research prospects are presented.