Electromagnetic characterization of a magnetic material using an open-ended waveguide probe and a rigorous full-wave multimode model

In this paper a material characterization technique employing a flanged opened-ended rectangular waveguide probe is presented that now allows extraction of both permittivity and permeability from a conductor-backed lossy shielding material. As an added benefit, this non-destructive technique reduces sample preparation time leading to rapid measurement. Calculation of both material parameters is accomplished using experimental reflection measurements from two different thicknesses of a given material sample. A theoretical solution to the reflection coefficients is developed through a rigorous magnetic field integral equation (MFIE) formulation. The double integral that results from the spectral domain analysis is reduced to a single integral through careful application of Cauchy's Integral Theorem leading to improved convergence and is an additional contribution that is believed to be new for this particular structure. A comparison between the theoretical and experimental reflection coefficients allows extraction of the material parameters using a two-dimensional Newton root search algorithm. Parameter extraction results incorporating dominant and higher-order modes are presented and compared to results from traditional waveguide material characterization techniques. An uncertainty analysis is also performed to determine sensitivity to errors in sample and probe flange thickness.