Figure 1: Single resonator filter. (©2006 IEEE) (Image from "Sensitivity

analysis of scattering parameters with electromagnetic time-domain

simulators," by N.K. Nikolova, Ying Li, Yan Li, and M.H. Bakr, /IEEE

Trans. Microwave Theory Tech/., vol. 54, No. 4, April 2006, pp.

1598-1610.)

The researchers have validated their method by optimizing several example

designs with respect to shape parameters. They matched the results of their

XFDTD self-adjoint sensitivity analysis against the more traditional and

computationally intensive parameter perturbation and finite differencing of

S-parameters. The first structure that they used to validate the method was a

single resonator filter shown in Figure 1. The size of the computational

domain is 60 X 1` X 2000 cells. The excitation is a sine wave modulated by

a Gaussian pulse for a band-limited spectrum from approximately 3 to 5

GHz. Five current-density excitation points are uniformly distributed to form

a half-sine modal distribution.