LAUSR

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.