Multimodal Retrieval of the Scattering Parameters of a Coaxial-to-Waveguide Transition

In this article, a multimode characterization of coaxial-to-waveguide transition is carried out by means of inverse techniques. The multimode coaxial-to-waveguide transition is characterized by the generalized scattering matrix (GSM). A number of measured standards considering shorts are used to extract the matrices. By using optimizing techniques, such as genetic algorithms (GAs) and a gradient descent (GD)-based method, the multimodal scattering matrix is calculated with the help of a fitness function that compares the standards with analytical calculations. The same measurement setup using uniquely shorts has been simulated, and the GSM results have been retrieved, thus validating the proposed technique. This method easily allows working in the multimode range of waveguides, thus increasing considerably the bandwidth of classical applications, such as permittivity characterization. The benefits and drawbacks of the implementation are also discussed.