Nonuniform coupled VLSI interconnect characterisation using genetic algorithms

Based on genetic algorithms (GA), in this paper we present a simple method to extract distributed circuit parameters of a multiple coupled nonuniform microstrip transmission lines structure from its measured or computed S-parameters. The lines may be lossless or lossy, with frequency dependent parameters. First, a sufficient amount of information about the system is measured or computed over a specified frequency range. Then, this information is used by a GA to determine the inductance and capacitance matrices of the structure. The theory used for fitness evaluation is based on the steplines approximation of the nonuniform transmission lines and quasi-TEM assumptions. Using steplines approximation, the coupled nonuniform transmission lines system structure is subdivided into arbitrary large numbers of coupled uniform lines (steplines) with different characteristics. Then, using the modal decomposition method, the system of coupled partial differential equations for each step is decomposed to a number of uncoupled ordinary wave equations which are then solved in the frequency-domain.