Frequency Characteristics of High Speed Power Distribution Grids

The variation of inductance with frequency in high performance power distribution grids is discussed in this paper. The impedance characteristics of the power grid need to be well understood for the design of efficient and robust high performance power distribution grids. The physical mechanisms underlying the dependence of inductance on frequency are discussed. The variation of inductance with frequency in three types of power grids is analyzed in terms of these mechanisms. The inductance of power distribution grids decreases with signal frequency. The decrease in inductance in non-interdigitated grids is primarily due to current redistribution in multiple forward and return current paths. In interdigitated grids, the variation of inductance with frequency is fairly small, typically less than 10% because both proximity and multi-path current redistribution effects are minimal. In paired grids, the relative decrease in inductance with frequency is larger as compared to interdigitated grids. This behavior is due to significant proximity effects. The smaller the separation between the power and ground lines and the wider the lines, the more significant proximity effects become and the greater the relative decrease in inductance with frequency.