Approximation Methods for Cylindrical Posts in Rectangular Waveguides with Mode Matching Technique

This paper analyzes the characteristics of two cylindrical posts placed in the cross section of a rectangular waveguide based on the mode matching technique. Three methods to approximate the posts are introduced: equal width method, arithmetic sequence thickness method and equal sector method. The scattering parameter convergence of these approximation methods is investigated. Meanwhile, through comparing the difference of the scattering parameters and the accurate values, the rate of convergence for each method is also explored, according to which, the most efficient approximation method is recommended. The calculated results of a symmetric two-post structure are compared with full-wave simulations using ANSYS HFSS.