An equivalent electric field source for wideband FDTD simulations of waveguide discontinuities

Transparent sources are often used in wideband finite-difference time-domain (FDTD) simulations of waveguide discontinuity problems. Direct implementations of transparent sources may not correspond to the original hard source spectrum, or else require auxiliary simulation steps for correction purposes. In this letter, we propose a more direct approach to construct FDTD transparent electric field source-models for waveguides. We also provide an explanation for a "spectrum distortion" phenomenon recently reported for FDTD sources in waveguide problems . The main findings are illustrated by means of FDTD simulations of waveguides operating at Ku-band.