Strongly perturbed cavity resonators as tools for non-destructive in-situ material parameter measurement

根据目前的技术状况，GHz频率下的电材料参数是通过空腔摄动方法测量的。在这样做的过程中，可以比较腔中有和没有材料样品的可测量谐振器特性，并假设样品的扰动很小，并且谐振器与测量环境之间需要耦合。例如，如果可以监控过程环境中的松散材料、流体和催化剂，那么许多过程可以更有效地运行，更节能、更环保、更经济。由于这些潜在的应用，空腔摄动法的几个假设被打破了。特别是，在工艺装置中，人们不能自由地设计几何形状和选择材料。人们更愿意面对大的、不均匀的、有损的、各向异性的和时变的填充，以及（取决于共振模式和材料参数）与测量环境的强耦合。在这些情况下，谐振器受到强烈的扰动。即使在简单的情况下（均匀的，但相当有损耗的谐振腔填充），目前也没有可行的方法从耦合谐振腔的可测量特性中提取非耦合谐振腔的特性，这些特性很有趣，因为它们反映了材料样品的特性。本项目旨在为在通常假设被违反的情况下用腔摄动法测量电材料参数奠定基础。为此，消除耦合对谐振特性的影响至关重要。

According to the state of the art, electric material parameters at GHz frequencies are measured by, amongst others, the cavity perturbation method. In doing so, one compares the measurable resonator characteristics with and without material sample in the cavity and assumes but a small perturbation by the sample and the required coupling of the resonator to the measuring environement. If one could monitor, for instance, loose materials, fluids, and catalysts in their process environments, many processes could be run more efficiently energy-wise, more environmentally friendly, and more economically. With these potential applications, several assumptions of the cavity perturbation method are violated. In particular, one cannot freely design geometries and select materials inprocess installations. One rather faces large, inhomogeneous, lossy, anisotropic, and time-varying fillings and (depending on the resonance mode and the material parameters) a strong coupling to the measuring environment. In theses cases, the resonator is stronglyperturbed. Even in simple cases (homogeneous, but quite lossy resonator filling), there is currently no feasible way of extracting the characterisctis of the uncoupled resonator, which are of interest because they mirror the properties of the material sample, from the measurable characteristics of the coupled resonator. The current project aims at laying the foundations for the measurement of electrical material parameters by the cavity perturbation method in those instances in which the usual assumptions are violated. To this end, it is vital to eliminate the effect of the coupling on the resonance characteristics.