Electromagnetic material characterization of a conductor-backed material using the two layer, two thickness, and two iris waveguide probe methods: Error analysis, simulation, and experimental results

Three material characterization techniques are investigated in this dissertation for their ability to extract the electromagnetic properties of a conductor-backed material in situ. All three techniques use a waveguide probe with a rectangular aperture placed against a conductor-backed layered material. To extract the complex material parameters, two independent complex measurements are needed. The first technique uses two thicknesses of the unknown material to obtain the two independent measurements. The second method uses a measurement of one layer of an unknown material, and a second measurement where a top layer of a known material is added. The third technique is a new method developed in this dissertation, which utilizes two irises of different sizes in the waveguide aperture to obtain the two measurements.;It is desirable in any material characterization method to understand the sensitivity of the method to errors. In this dissertation, the sensitivity of these three methods to random measurement errors is investigated. Since the fields in the waveguide aperture are approximated by using a finite number of transverse waveguide mode functions, the effect of the number of modes used in the material parameter extraction are also examined through simulation and experiment. Measurement data is used to extract the material parameters and evaluate the characterization methods.;The error sensitivity analysis, the modal analysis, and experimental results demonstrate that the two thickness method is the least sensitive to errors in the extraction process. However, this method is not practical for use as an in situ technique, since the material parameters must be known a priori. It is found that the two layer method, with a low loss dielectric material as the top layer, and the two iris method work equally well in extracting the material parameters. They are, however, more sensitive to random measurement error than the two thickness method.