Modeling and analysis of the return path discontinuity caused by vias using the 3-conductor model

Parasitics associated with the current return path discontinuity (RPD) are among the major factors affecting the signal integrity (SI) and electromagnetic compatibility (EMC) behavior of digital circuits with fast switching drivers. Vias that connect signal lines referenced to different planes cause RPD, such that the signal return current has to jump between the planes to close the current loop. In addition to the plane-vias (for planes at the same voltage level) and decoupling capacitors (for planes at different voltage levels) between the planes, the inter-plane capacitance represents a possible return path, which has to be modeled as a distributed element for plane dimensions comparable to a wavelength.