APPLICATION OF THE DISCRETE FOURIER-TRANSFORM IN THE 2D-FDTD METHOD

The discrete Fourier transform of a modal expansion in the 2D-FDTD met hod is investigated theoretically to explain the appearance of the mag nitude peaks and phase changes in the transform. It is shown that an e igenfrequency exists between two frequencies having a phase difference of 180 degrees. An algorithm using this property is proposed to impro ve the accuracy in the determination of the eigenfrequency, which is i ndependent of the frequency resolution inherent in the 2D-FDTD method. An example of a boxed anisotropic microstrip line is treated, and its result is compared with previous numerical ones. (C) 1994 John Wiley & Sons, Inc.