Simultaneous extraction of the permittivity and permeability of conductor-backed lossy materials using open-ended waveguide probes.

摘要

In this dissertation two non-destructive measurement techniques using flanged open-ended rectangular waveguide probes are developed and successfully demonstrate significant contributions in the field of material characterization. Each of these techniques provide accurate simultaneous extraction of permittivity and permeability from a conductor-backed lossy material having both magnetic and dielectric properties. The first technique is based on a single waveguide probe which employs a two-thickness method extraction. A rigorous solution to the reflection coefficient is compared with measured data from measurements of two different thicknesses of a sample material. Results show good agreement with those of traditional waveguide material characterization methods. The second technique is based on a collinear set of coupled waveguide probes. This novel dual probe configuration employs a rigorous formulation of the reflection and transmission coefficients providing exceptional accuracy. Comparison of results match the performance of well established, but destructive methods, providing a major contribution to this field. Uncertainty analysis indicates that the method is relatively insensitive to small changes in thickness and provides good results using typical material thickness tolerances.; Two secondary contributions also warrant attention. Unlike previous waveguide probe formulations which employ numerical integration over both the eta and xi spectral integrals, the approach used here provides a closed form solution to the eta-integral through complex analysis. This technique not only decreases computational time, but the complex analysis also provides physical insight into the probes. One important outcome is that the complex analysis revealed the fundamental mode of propagation through the material under test. Consequently, this led to the development and demonstration of a simple model allowing determination of the required flange dimensions to ensure sufficient decay of fringing fields, which is an important underlying assumption in the probe analysis.