Abstract-This paper introduces a technique for the numerical generation of basis functions that are capable of parameterizing the frequency-variant nature of cross-sectional conductor current distributions. Hence skin and proximity effects can be captured utilizing much fewer basis functions in comparison to the prevalently-used piecewise-constant basis functions. One important characteristic of these basis functions is that they only need to be pre-computed once for a frequency range of interest per unique conductor cross-sectional geometry, and they can be stored off-line with a minimal associated cost. In addition, the robustness of these frequency-independent basis functions are enforced using an optimization routine. It has been demonstrated that the cost of solving a complex interconnect system can be reduced by a factor of 170 when compared to the use of piecewise-constant basis functions over a wide range of operating frequencies. [6] that are capable of rapid and accurate resolution of large conductor system impedance, some of which can even account for the effects invoked by the presence of a semi-conductive substrate. However, the efficiency of these solvers is being continuously challenged by the ever increasing operating frequencies which generate skin and proximity effects that need to be carefully modeled in order to provide accurate impedance solutions.
I. INTRODUCTIONSkin and proximity effects are troublesome for today's fast solvers due to the fact that most of the mixed potential integral equation (MPIE) solvers rely on piecewise-constant [7], [2], [6] or piecewise-linear basis functions to capture conductor current distributions. As frequency increases, the use of these basis functions has proven to be computationally expensive because a very fine discretization scheme must be applied in order to faithfully capture the exponential variation in crosssectional conductor current, thus generating densely-populated clusters of filaments with highly uneven aspect ratios. One might think this is not problematic if the discretized system were to be solved by a fast technique since, theoretically speaking, the computational cost only scales in a linear fashion with the total number of basis functions. However, in practice, direct computation must be used to account for the numerous near-distanced interactions generated by clusters of long and skinny filaments which takes a quadratic order of complexity to resolve.The explosive cost associated with high-frequency impedance simulations has spurred the development of methods that seek to either represent interior conductor current using surface field quantities [8]