Modeling of Power Planes in Printed Circuit Board Using Planar Circuit Approach

Abstract

Power distribution system in printed circuit board (PCB) in the form of conducting planes plays a critical role in ensuring proper operation of the whole PCB assembly. An effort to model the power distribution system in terms of equivalent circuit consisting of inductors and capacitors using planar circuit approach is presented in this paper. In this approach, the power planes are discretized into sub-segments. Electromagnetic fields within the planes are solved using Helmholtz wave equation. Approximating differentials with appropriate finite differences, the solutions can be interpreted as equivalent mesh of capacitors and inductors. These circuit models can be obtained in SPICE format so that simulations can be performed easily. SPICE simulation is performed for two planar circuit examples. Results from the first example of a L-patch microstrip planar circuit are compared with those from Method of Moment; while results of the second example of a rectangular stripline planar circuit are compared with those from Finite Difference Time Domain (FDTD) approach and from measurement. A third illustrative simulation example shows a possible application of the model in deriving design rules for high-speed PCB layout.