Electromagnetic Characterization of Two-Layer Dielectrics Using Two Flanged Rectangular Waveguides

In this paper, a flanged waveguides technique capable of measuring both reflection and transmission coefficients is formulated to allow for the nondestructive, simultaneous extraction of complex permittivities of a two-layer lossy dielectric absorber. The technique introduced here eliminates the need for additional optimization constraints required in reflection-only based methods. Theoretical expressions for the reflection and transmission coefficients are found using a magnetic field integral equation (MFIE) formulation based on Love's Equivalence Principle and subsequently solved via the Method of Moments (MoM). In addition to these expressions, the dyadic Green's function for a magnetically excited, two-layer, parallel-plate waveguide is developed. The technique is verified experimentally and measured results for an absorber consisting of two R-cards are presented. It is discussed that the flanged waveguides technique is well suited for rapid quality control measurement of dual-layered dielectric absorber or single-layered shielding materials having both dielectric and magnetic properties.