A Cartesian-cylindrical hybrid FD-TD analysis of composite microwave applicator structures

Cylindrical microwave applicators have been proven to be advantageous in industrial microwave heating applications where heating uniformity is highly desired. When the traditional Cartesian Finite Difference Time Domain (FD-TD) approach is used to analyze a cylindrical structure, staircase boundaries are introduced during the discretization of the outer cylindrical boundaries of the applicator. Computational errors, computational time, and computer memory requirements are increased accordingly. In this paper, a new formulation employing a hybrid Cartesian-cylindrical FD-TD scheme is developed to analyze the performance of cylindrical applicators with rectangular waveguide feeding structures. Numerical results show excellent agreement with those calculated by the traditional staircase FD-TD model with very fine meshes and the commercial software package MAFIA (MAxwell equation solution by Finite Integration Algorithm). Compared with the staircase FD-TD model, the hybrid FD-TD model achieved better computational accuracy with much less computational time and computer memory.