SIMULTANEOUS EXTRACTION OF PERMITTIVITY AND PERMEABILITY FROM A CONDUCTOR-BACKED LOSSY MATERIAL

摘要

Nondestructive evaluation (NDE) of a conductor-backed lossy material plays an important role in electromagnetic shielding applications. Current NDE techniques limit such evaluation to non-magnetic materials and/or use of approximate solutions. In this paper a technique employing a flanged opened-ended rectangular waveguide and a rigorous integral equation model is presented allowing simultaneous extraction of both permittivity and permeability from a lossy magnetic shielding material. The technique reduces sample preparation time leading to rapid measurement. Calculation of both material parameters is accomplished using reflection measurements from two different thicknesses of a given material sample. A theoretical solution to the reflection coefficients is developed using a magnetic field integral equation (MFIE) formulation. The theoretical solution, along with experimental results of the reflection measurements, allows extraction of the material parameters using a two-dimensional Newton root search. Results using single-mode calculations are presented and compared to those obtained using traditional waveguide material characterization techniques. Future work will also be discussed.