Extracting R, L, G, C parameters of dispersive planar transmission lines from measured S-parameters using a genetic algorithm

Signal integrity (SI) analysis of printed circuit boards for high-speed digital design requires information on the per-unit-length R, L, G, C parameters of the transmission lines. However, these are not always available when the property of the dielectric medium used in the board is unknown. A method to extract R, L, G, and C parameters from parallel-plate and strip transmission line geometries is proposed. It is based on measured scattering parameters and analytical modeling. A genetic algorithm (GA) is used to optimize the extraction by minimizing the frequency domain discrepancy between an objective function, which is the measured scattering matrix parameter, |S21|, and a GA model based on transmission line theory. The extracted R, L, G, and C parameters are then used in a SPICE model for simulation. Good agreement has been achieved in the reported results.