Combining finite element method and Fourier transform to analyze waveguide transients

A numerical technique combining the finite element method (FEM) and Fourier transform is applied to calculate transients on 3-D microwave waveguide structures. The structures are modeled using a higher order FEM that can efficiently render frequency-domain responses at a large number of frequency samples, which are processed by the inverse discrete Fourier transform (IDFT) to obtain time-domain solutions. The FEM-IDFT approach is illustrated and its numerical properties are discussed in detail in the transient analysis of an E-plane ridge waveguide discontinuity.