Application of spectral domain Prony´s method to the FDTD analysis of planar microstrip circuits

Residual reflection from absorbing boundaries that truncate the computational mesh in the finite-difference time-domain (FDTD) method introduces significant error in the characterization of transmission lines and discontinuities employed in microwave and millimeter-wave integrated circuits. We apply the least squares Prony´s method to accurately estimate the complex reflection coefficient (at Mur´s absorbing boundary) in the frequency domain by representing the sampled voltages along a microstrip transmission line as a plane wave superposition of incoming and outgoing transverse electromagnetic (TEM) waves at each reference port. Prony´s method is used to compute the frequency-dependent effective dielectric constant of a microstrip line and the scattering parameters of microstrip circuit elements, which corroborate well with published and measured results. A new method is discussed to reduce the computer memory required to store the temporal samples which are employed in the spectral processing of the FDTD data