Analysis of scattering parameters of a stepped cylindrical horn containing inner posts using MM and 2-D FEM

This paper presents analysis of a stepped cylindrical horn containing rectangular posts using a hybrid technique consisting of mode-matching (MM) and 2-D finite-element method (FEM). Generally, presence of a post or septum inside the horn causes a problem in convergence of the numerical solution. However, accurate prediction of the eigenvalues and eigenvectors for FEM, use of a large number of modes for MM and proper numerical integration of the reaction matrix can enhance the accuracy of the result and the proposed analysis uses these techniques to overcome the convergence-related issues. The hybrid technique has been implemented in MATLAB to analyze the structure under consideration and some closed-form expressions of the reaction matrix for the cylindrical step junction have been derived to increase the computational speed and accuracy. Computed and simulated (Ansoft, HFSS-15) results have been compared and a close match is observed.