Analytical and experimental techniques for the electromagnetic characterization of materials

Electromagnetic material characterization is the process of determining the permittivity and permeability of matter. This process is predominantly employed in stealth and integrated-circuit technologies with the aid of the analytical Nicolson-Ross-Weir (NRW) formulation. The increasing demands of industry have rendered the NRW technique invalid under certain conditions due to theoretical violations, leading to erroneous results. In rectangular waveguide measurements, for example, it is assumed that sample material is comprised of a single layer only, that walls are perfectly conducting and that no gaps exist between the sample and conducting boundaries. However, in the industry environment, samples are often multi-layered due to material integrity and high-temperature measurements lead to sample-to-wall gaps and involve waveguide metals that are typically poorly conducting. In addition, high-temperature strip and microstrip field applicators also involve imperfectly-conducting boundaries, leading to gross errors in the material characterization process. This dissertation provides several techniques to accommodate these errors.; Chapter 2 provides two methods, the direct and deembed techniques, for characterizing materials that are embedded in multi-layered samples. Although both formulations utilize wave-transmission matrices, it is shown that the direct method must be used if sample homogeneity is to be accurately monitored. Errors due to sample-to-wall gaps are accommodated in Chapter 3 by regarding the waveguide as inhomogeneously filled in the cross-sectional plane with LSM and LSE propagation modes supported in the sample/gap regions. This analysis leads to corrections in the scattering parameters and ideal TEJ10 propagation constant of a uniformly-filled guide. Chapter 4 investigates the effects of waveguide wall loss by using a coupled-mode perturbation theory which is based upon an impedance boundary condition at the imperfectly-conducting walls. The result is a complex correction to the ideal TE10 propagation constant.; Strip and microstrip field applicators having imperfectly-conducting boundaries are investigated in Chapters 5–7 using a spectral-domain integral-operator formulation with the aid of electric-field dyadic Green's functions. The resulting electric field integral equations, which follow from enforcement of impedance boundary conditions on the imperfect strip conductors, are solved using a non-Galerkin's Method of Moments technique employing Chebyshev basis functions of the first and second kind. The analysis in Chapters 5–6 and 7 leads to a correction in the ideal principal-mode propagation constant for the strip and microstrip transmission lines, respectively.