A new computationally efficient method for the analysis of planar transmission lines and complex MMIC elements

Microstrip and coplanar transmission line components have been analyzed by the finite-difference time-domain (FDTD) method. The FDTD computational mesh is truncated by imposing absorbing boundary conditions on the walls of the mesh, thus simulating outgoing waves appropriate to an open structure. The residual reflection from these boundaries introduces significant error in the frequency-domain parameters derived by Fourier transformation of the time-domain voltages and currents. In this paper, we have developed a new computationally-efficient method called the geometry rearrangement technique (GRT) to cancel the dominant contribution to such reflection. We have applied the GRT to compute the effective dielectric constant of planar transmission lines and the scattering parameters of MMIC components. The computed results have been found to be in good agreement with published data, thus indicating the effectiveness of the GRT in canceling boundary reflection. This research is applicable to efficient characterization of MMIC elements and high-density microwave and millimeter-wave packages, which are currently being investigated in aerospace research