Simulation and Measurement of the $S$ -Parameters of Obstacles in Periodic Waveguides

In recent years, because of the increasing interest in the analysis and design of devices that include obstacles in periodic waveguiding structures, the need for a rigorous and accurate procedure to characterize these obstacles in terms of their scattering parameters has arisen. This paper deals with both the simulation and the measurement of the S-parameters of an obstacle (iris, post, slot, etc.) in a periodic waveguide. The proposed simulation approach makes use of a commercial electromagnetic simulator to extract the S-parameters and removes the need to resort to any kind of equivalent model for the periodic waveguide. As regards the measurements, a quick and simple technique has been developed as an alternative to the costly manufacture of calibration standards. With the purpose of verifying both procedures, two different practical problems have been addressed, namely, the characterization of a single post in a post-wall waveguide and the computation of the admittance of a slot in a waveguide with dielectric-filled corrugations. Good agreement is found between simulations and measurements, which confirms the reliability and accuracy of the proposed procedures.