Development of a Closed-Form Expression for the Input Impedance of Power-ground Plane Structures

This paper analyzes the fundamental behavior of PCB power bus structures using the modal expansion method. The results are validated by experiments and full-wave numerical modeling. It is shown that the power bus can be modeled as a series LeC circuit below the first board resonance frequency. C is the interplane capacitance and Le is an effective inductance contributed by all the cavity nodes. The effects of the layer thickness, port location, board size and the feeding wire radius on the value of Le are discussed in this study. Le can be estimated from the geometry parameters of the test board. The goal is to obtain a simple model that can be used to analyze the power bus impedance below the first board resonance