Analysis of a double step microstrip discontinuity in the substrate using the 3D-FDTD method

The finite-difference time-domain (FDTD) method has been applied to the analysis of a double step microstrip discontinuity having thickness changes in the longitudinal direction. The discontinuity occurs in patch antenna feeds or interconnections between microwave planar circuit modules. The simulation results are compared with those computed by HFSS to show a good agreement. An equivalent circuit for the double step discontinuity is developed from the scattering parameters computed by the FDTD method.