Passive-assured rational function approach for compact modeling of on-chip passive components

An efficient rational function modeling approach of on-chip passive components, especially spiral inductors, is presented. In addition to the minimal number of model coefficients compared to the currently available approaches, two major features of the methodology are: 1) automatic generation of the equivalent circuit based on the rational function, and 2) guaranteed passivity of the network generated. The latter is achieved by applying a novel local-compensation technique in the frequency domain to the direct mapping of the rational function fit. The additional error incurred by this local correction is negligible in terms of the extracted component's characteristics such as effective inductance and quality factor, Q. The detailed algorithm of the technique is described and the results from the application of the method to a two-port spiral inductor are presented.