A technique for the characterization of a class of coaxial-line-to-waveguide adaptors, which is based on the eigenvalues and eigenvectors of their scattering matrix, is presented. The adaptor comprises a number of coaxial-line ports symmetrically distributed on the surface of the waveguide. This allows for the independent excitation and measurement of different propagating modes in a multimodal operation. The latter is required for, e.g., the simultaneous determination of both constitutive parameters in microwave, millimeter-wave, and terahertz material characterization. It is shown that the junction is fully characterized in terms of the eigenvalues of its generalized scattering matrix. The measurement of these eigenvalues through a calibration procedure enables a complete characterization of the adaptor. A four-port coaxial-line adaptor was designed and fabricated. A modified calibration technique together with both measurements and electromagnetic simulations has been used for the determination of its scattering parameters.

中文翻译：

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用于多模波导的多端口同轴线适配器的表征[-5pt]

提出了一种基于其散射矩阵的特征值和特征向量来表征一类同轴电缆到波导适配器的技术。适配器包括多个对称分布在波导表面的同轴端口。这允许在多模式操作中独立激励和测量不同的传播模式。例如，后者需要同时确定微波、毫米波和太赫兹材料表征中的两个本构参数。结果表明，根据其广义散射矩阵的特征值可以完全表征结。通过校准程序测量这些特征值可以对适配器进行完整的表征。设计并制造了一个四端口同轴线适配器。改进的校准技术连同测量和电磁模拟已被用于确定其散射参数。