On the use of time-domain reflectometry for full-wave electromagnetic optimization of nonuniform waveguides

We present the application of an optimization technique in time domain for the design of cascaded waveguide structures. In this case, the traditional high-dimensional optimization problem can be decomposed into several one- or two-dimensional problem in the time domain. For this purpose, the time-domain response is divided into a series of small time intervals that have to be optimized successively utilizing time-domain reflectometry. A finite-difference time-domain simulator is used to obtain the time-domain response. The number of function calls (expensive full electromagnetic simulations) could be reduced up to 90% in comparison to a frequency-domain optimization. Numerical and measurement results are presented to validate the new technique.