Analysis of loaded cavity by FDTD technique combining with sum algorithm and Padé approximation

An accurate and stable method, the combination of finite-difference time-domain technique, fast Fourier transform, Pade approximation, and sum algorithm, is presented for the calculation of the quality factors of cavity. Comparing with the fast Fourier transformation/Pade technique, without missing any interesting mode, this novel method not only eliminates the sensitivity of Pade approximation but also improves the accuracy of numerical results. As a validation, two cavities are analyzed.