A wireless method to obtain the impedance from scattering parameters

The coaxial wire method is a common and appreciated choice to assess the beam coupling impedance (BCI) of an accelerator element. Nevertheless, the results obtained from wire measurements could be inaccurate due to the presence of the stretched conductive. The aim of this work is to establish a solid technique to obtain the BCI from electromagnetic simulations, without modifications of the device under test. In this framework, we identified a new relation to get the resistive wall beam coupling impedance of a circular chamber directly from the scattering parameters. Furthermore, a possible generalization of the method to arbitrary cross section geometries has been studied and validated with numerical simulations.