Nondestructive Material Characterization of a Free-Space-Backed Magnetic Material Using a Dual-Waveguide Probe

A free-space-backed dual-waveguide probe measurement technique is introduced to determine nondestructively the complex permittivity and permeability of an unknown material. The purpose of this new measurement technique is to complement the existing PEC-backed dual-waveguide probe material-characterization method. Provided in this paper is the theoretical development of the new technique and its experimental validation. It is shown, by applying Love´s equivalence theorem, that a system of coupled magnetic field integral equations can be formulated and subsequently solved for the dominant mode reflection and transmission coefficients using the method of moments. Also included in the theoretical development of the new technique is a derivation of the dyadic Green´s function for a magnetic-current-excited two-medium grounded-slab environment. Last, experimental complex permittivity and permeability parameters extracted for two magnetic-shielding materials are presented and analyzed to validate the new technique.