Comparison of field and circuit analysis for retrieving complex dielectric constant from dielectric material scattering coefficient

The goal is to determine spectral dielectric properties ∈ of a dielectric material (sample) machined to fit X-band rectangular waveguide (WG). Two approaches were utilized to achieve this goal, field approach (FA) and circuit approach (CA) in FA the boundary conditions at interfaces of the rectangular sample were used to address the reflection coefficient Γ at the sample input. In CA the ABCD matrices of WG sections (air-sample-air) were cascaded and transformed to obtain system transmission/reflection properties (scattering matrix[S]), in both FA and CA a deterministic equation roots were scanned using Muller's algorithm. Data fitting is carried using complex nonlinear least square (CNLS). An agreement was noticed for FA and CA at low and mid ranges of WG working band. Teflon and Polystrene results match the publishing data.