Application of the FDTD for the optimization of broad-band transitions between different types of transmission lines

We present the application of an optimizer-coupled finite-difference time-domain (FDTD) simulator for the optimal design of waveguide transitions. The software package contains a standard FDTD algorithm and common optimization routines. The illustrated approach is a very efficient way for various design problems of wave-guide discontinuities. Several types of transitions in an unusual aligned geometry were investigated. A broad-band minimization of reflection losses up to 14 GHz was achieved. Close agreement has been obtained between FDTD results and measurement over a wide frequency range.